It bears repeating: steel is today’s bargain boatbuilding material. If possible, you should choose pre-shot blasted and primed materials. The terms sandblasting, grit blasting, and shot blasting have similar meanings. The process for all three involves blasting the steel plate and bar stock with a grit to remove the impurities from the surface and preparing the material to receive the prime coating (see Chapter 9, Grit blasting and Priming). If you’re building outdoors, you’ll lose some of the percolating. But the benefits of pre-prime-coating are so positive that it’s worth your consideration. Pre-primed steel not only provides a cleaner working environment, but it will encourage you to arrange a temporary cover. When you’re welding prime-coated steel, you should wear a protective mask to avoid inhaling the fumes released as the prime coating is burned off around the weld. If you use a kit that is coated with Sigmaweld MC primer, there are very few fumes; it is always advisable to wear a protective mask and other protective gear when building any boat.

   One of the main benefits of using shot blasted and primed materials is that when you have completed the hull and deck, you should not need to shot blast or grit blast the interior. This part of the blasting process is the most time consuming and expensive. If you can avoid it by using primed, painted steel, it’s worth the cost and effort of obtaining this material and keeping your project under cover. You may wish to consider using self-applied shot blasting and priming your metal before you start construction. Make sure you use weld primer that is specially formulated for use on the plate to be welded. One brand is Sigmaweld MC primer; other manufacturers should have similar products.

    We used to think that building outdoors and using unprepared steel was a good idea; the theory was that the weather removed some of the mill scale and other surface impurities. But, as you will have gathered, we’ve changed our mind. It may take longer than originally planned to build a boat with unprepared steel, and the wastage of metal through rusting could be a sizable factor in its life expectancy. Our advice: NEVER allow your boat to get rusty during construction.

When ordering the plate, make sure you specify plate-mill and not strip-mill plate. Plate-mill stock is plate that has never been coiled. Strip-mill is plate that has been rolled into large coils after manufacture; later, the steel is unrolled and sold as flat plate. But it has a “memory,” so it won’t be absolutely flat and unstressed before you start to bend it. If you’re forced to use strip-mill material, try to ascertain the natural curve of the plate, and use it to your advantage.

Our choice for steel boat building is plate with a low to medium carbon content. You’ll find there are many different grades of steel, but we recommend low-carbon steel with a carbon content of between 0.15 and 0.28 percent. The highest carbon content acceptable to most classification authorities is 0.28 percent, so we recommend you stay within the range quoted above. Low-carbon steel is available in various shapes, strips, and plate, and has good welding characteristics. As code numbers vary from country to country, you should seek advice from your steel supplier to ensure that you receive the correct materials as suggested above. Lloyd’s A-grade shipbuilding steel will be one of your preferred choices if you live in Europe, or build from a pre-cut kit that is cut from Lloyd's-approved steel.

   The plate thickness will be specified in your plans. Remember that it’s harder to avoid distortion when welding materials that are thinner than 1/8 inch (3 mm). Even this thickness should be restricted to decks and cabins, as well as to hulls on boats under 35 feet (10.66 m) in length. Your designer will specify the plate thickness recommended for your boat. When you’re building small steel boats, it’s better to reduce the amount of framing than to reduce the plate thickness. Some builders increase the plate thickness without consulting the designer, which, in a steel boat, can have disastrous results. If you are unable to obtain plating as specified in your plans, always contact the designer for advice. Changing the plating thickness may require rescheduling the spacing and sizing of the framing.

   As you may be responsible for the quality of the steel being used in your boat, you should be aware of the common defects. Check for “wavy” areas in the sheet. This defect can appear as small, uneven areas with a wavy appearance. Another defect is rolled-in mill scale, which is caused when impurities on the surface of the plate are rolled into the surface. Buckles or kinks in the plate can be caused by improper handling after manufacture. You may also find thin areas in the center and ends of pipe.

    Avoid materials such as Cor-Ten or high-tensile steels; they have limited or no boatbuilding applications. Some designers have recommended Cor-Ten in the past, but this steel contains traces of copper, which tends to encourage corrosion in salt water rather than inhibit it. Cor-Ten was developed for use in industrial applications such as water tanks on farm properties. While it resists corrosion in a salt-free atmosphere, it doesn’t have good corrosion resistance when it’s immersed in water, especially seawater.

   Cor-Ten is more expensive than mild steel and it needs to be welded using copper-clad, continuous-feed electrodes and argon-arc. We do not recommend Cor-Ten or other specialty steels for boatbuilding.

Occasionally, we’re asked about the possibility of building a boat of stainless steel; the simple answer is: Don’t! This material has no place below the waterline on most boats including those built from non-metallic materials. The problem is shielding corrosion caused by oxygen starvation, which, in turn, will promote crevice corrosion. The important factor is the amount of oxygen in contact with the surface of the steel; one part of the steel must not be starved of oxygen while another part has it available. This phenomenon is known as the oxygen differential, and it will set up an electrochemical cell that will lead to rapid deterioration of the metal.

   Stainless steel is ideal, however, for deck fittings, chainplates, and stanchions. Stainless is also required as a liner in areas where dock and anchor lines would soon wear off the paint. On items such as stanchions, always paint 2 inches (50 mm) onto the stainless area to prevent galvanic action between any defects in the painted mild steel and the uncoated stainless fitting.

   The types of stainless steel most commonly used in boatbuilding fall into the 300 series, namely 302, 304, and 316. The 316 grade is considered the best for marine use and should be used wherever ultimate strength and freedom from corrosion are required.

When the quoted number is followed by the letter “L,” it indicates a low carbon content; this feature allows welds with good corrosion resistance by avoiding loss of chromium at the grain boundaries. The free-machining grades, type 303 or 303e, should never be used in seawater because they corrode. These specialized steels contain sulphate particles that facilitate the machining operation; however, the particles create a surface with numerous built-in alloys to particle galvanic cells. (See Chapter 12, Corrosion Prevention.)

The price of steel plate varies from supplier to supplier, so shop around. Generally speaking, the more you buy, the lower the price, by weight. We recommend that you order all the plate, stringer materials, other flat bar, and angle at one time. Many designers supply a material list with the plans and it’s wise to compare this list with the drawings, so you’ll have a better understanding of the construction procedures. Use your material list to obtain quotes from as many suppliers as possible. In most cases, 20 percent should be allowed for wastage.

   Stock sizes of sheet are 8 by 4 feet (2.50 by 1.25 m) and 6 by 3 feet (2 by 1 m) but some stockists can supply sheets 10 or 12 feet (3 or 3.50 m) long. (Note that the metric sizes here are rounded out to the most likely available sizes.) Another consideration is that the steel supplier may make additional charges for larger or unusual sizes of plate, and the delivery costs may also be higher. The size of your boat and the steel-handling equipment you have available may decide the sheet sizes for your project. We cut our kits from 20-foot (6 m) sheets or longer, depending on the size of the vessel and the type of shipping used to transport the kit. Some kits are transported in 40-foot (12 m) containers so even longer sheets can be used. The big advantage of this is that it eliminates welded seams in areas such as the side of the hull. You can easily arrange a gantry arrangement to handle these longer plates so keep this in mind when ordering your kit or basic plate material.

   It’s better to tack-weld your plates into as long a length as practical before installing them on the hull—you’ll achieve a much fairer hull by following this practice. The same advice applies to stringers and other longitudinal framing

   Framing includes the transverse frames, stringers, chine bars, stem, and backbone. For small-to-medium-sized boats, you can make the framing from flat-bar stock. For the deck beams and cabin top beams, it’s preferable to use L-angle or T-bar (flange down) as this provides a suitable cavity for the insulation material and also allows the lining materials to be fastened to the inside or underside of the flange as applicable.

Hull frames may be flat bar or L-angle. Our objections to angle used to be that it was more difficult to keep the rust out of the angle. More recently, however, we recommend that all hulls be built from pre-prime-coated steel and have sprayed-in foam insulation. Where the sprayed-in foam is installed, there’s much less chance of rust forming around the frames. Because of weight considerations alone, we would not recommend angle frames in boats under 30 feet ( 9.14 m). Heavy-displacement boats and larger vessels can carry the extra weight and also will benefit from the extra strength of the angle frames. We have just completed plans for a new Spray Pilot House 40, and in this case I have suggested L-angle or T-bar frames be used throughout. The presence of the flange will assist in the lining and fitting out process. On flat-bar frames, timber strips are screwed to the frames to accept the lining materials.

   As mentioned above, the stringers, stem, and backbone will almost always be fabricated from flat-bar stock. Occasionally, solid round bar is used for the hull chines; there will be more on this subject elsewhere in this text. Web floors (also known as solid floors or gussets at the bottom of the frames) should be cut from plate that is the same thickness as the frames.

BRONZE

Bronze is an alloy of copper, tin, and varying small amounts of other elements. It’s a fine boatbuilding metal and it has been used in marine applications from time immemorial. In Roman times, bronze was a prized alloy and had many uses. The exact combination of metals used to make the bronze alloy will depend on its intended use. Copper is the main ingredient, and tin usually accounts for 5 to 10 percent of the mix. Bronze will often take its name from the third metal in the alloy; for instance, phosphor bronze contains about 5 percent tin and 0.5 percent phosphorus, and it is suitable for use in the marine environment. Alloys of aluminum bronze, or nickel-aluminum bronze, are often used for propellers.

ALUMINIUM OR ALUMINUM

Aluminum has been available for over a century, but it’s only in the past 40 years that it has been widely used for boatbuilding. Pure aluminum is a soft metal and not suitable for most commercial applications, let alone boatbuilding. There are many aluminum alloys for various applications but only a few suitable for marine use.

   Some of the metals alloyed with aluminum are chromium, copper, iron, manganese, magnesium, and zinc. Small amounts of these metals are used to improve the industrially pure aluminum. For marine use, the main addition to pure aluminum is 4 to 5 percent of magnesium.

   Because there’s no universal grading system for aluminum, you should check with your local suppliers for advice. The table shows some type numbers and their recommended usage. We have grouped them into UK and U.S. areas; most of the rest of the world follows one system or the other.

   The 5000 series and, in particular, material with the 5086 designation, is the metal most commonly used for boatbuilding. There are several different numbers in the 5000 series and it’s worth checking with the aluminum manufacturer in your country so you get firsthand advice. Don’t be fobbed off by unscrupulous suppliers or merchants who may try to sell you what they have in stock. The 5000 series has excellent resistance to salt water, is ductile, and retains its high strength when welded. In some cases, you may choose aluminum with one designation for hull plating, another for framing, and still another for decks and superstructure.

   When you’re ready to order your aluminum materials, it’s always recommended that you make one bulk purchase. As with other metals, and indeed all your boatbuilding requirements, it’s always best to buy in bulk. If you can find another builder with similar requirements, then a group order is recommended.

   At the same time as you are ordering your aluminum plate and framing materials, you should order the filler wire for your MIG welder. The most common wire is 5356, which is compatible with most aluminum alloys used in boatbuilding, including 5052, 5086, 6061, and 6063. The 5386 wire can be used to weld these alloys to themselves or to dissimilar alloys. (See notes about spool sizes in Chapter 5, Welding.) It’s most important to keep your welding wire clean and to use the spool as soon as it is opened. Store the wire in a dry area, and discard any dirty or contaminated material.

In this book, we’ll mainly consider welded aluminum, as this covers the method by which most boats are built from this material. There are other building methods, however, including small boats pressed out of a single sheet; these are popular in Australia, where they’re affectionately known as tinnies. Riveted construction is still used to build some smaller aluminum boats. Aluminum boats have also been formed by explosive techniques, but this and other offbeat methods are outside the scope of this book.

    For transverse frames you may choose either flat bar, L-angle bar, T-bar or flat/round-top bar. The latter is sometimes used for longitudinal stringers. For longitudinal framing, stringers, and chine bars (if fitted), we prefer flat bar, but the final choice of scantling sections should be left to the designer of your particular boat.

COPPER NICKEL

Copper, one of the most noble metals, has excellent resistance to corrosion in the atmosphere and in freshwater. When combined with nickel to form copper-nickel, it has superior resistance to saltwater corrosion. These features, coupled with its excellent antifouling properties, make it suitable for building hulls, however its huge cost and difficulty of welding will discourage most of us from seriously considering this material for boatbuilding.

BRASS

Brass, an alloy of copper and zinc, has no place as a structural member on any boat, and should never be used in place of bronze. You may have a few decorative items—lamps and the like—that are made of brass. You will know what they are because you will be continually polishing them to remove the tarnish that quickly forms in the marine environment.

   Brass made of 60 percent copper and 40 percent zinc loses all its surface zinc in saltwater, and is soon reduced to a useless mess. Beware of cheap fittings imported from the Far East. They may be sold as bronze, and look like bronze, but they often aren’t bronze. If in doubt, select only materials from known U.S. manufacturers.

MONEL METAL

The ultimate marine metal is Monel metal. It is very expensive, otherwise it would be more widely used. It’s not used for building complete boats but it’s perfect for fittings where ultimate strength and machinability are required. There are two main alloys, including the regular version that contains 67 percent nickel and 28 percent copper. This alloy is ideal for propeller shafting, where its corrosion resistance and durability are best appreciated. There may be some doubt about the use of Monel shafting in steel boats, however, and it may be better to use 316 stainless for your shafting requirements.

The variant “K” is nonmagnetic and is often used for special purposes. Often, Monel is used as the main propeller shafting on minesweepers. They can afford it. It’s also used to protect compasses on boats and aircraft. When more boats were built of timber, and before the wood/epoxy technique was developed, Monel screws were sometimes used on the finest craft, either to fasten the hull planking or in other important parts of the structure. The alloy contains aluminum and titanium as well as nickel and copper. It’s a great metal, but it’s not important to amateur builders of metal boats.

MAGNESIUM

Freshwater anodes are made from magnesium. It may surprise you to learn that protection from galvanic and other corrosion is necessary in all types of water, including salt-free environments. Anodes of zinc are not as effective as those of magnesium in fresh water. Conversely, if you move your boat from fresh water to salt water for more than two or three weeks, you will need to change to zinc anodes; the magnesium ones will rapidly disappear. Copper-nickel hulls do not require galvanic protection in fresh

ZINC

In its pure form, zinc is used for anodes. In salt water, it’s the ideal material for this use. In fresh water, as mentioned previously, magnesium is better. A small quantity of zinc is present in many metals. Zinc is also used in paint primers, paints, and other coatings.

LEAD

With its dense consistency and very low melting point, lead has many uses for the boat owner. The most obvious use for this material is for the ballast, but don’t be tempted simply to pour molten lead into the keel of your metal boat. Even heavy steel keels can buckle if lead is installed in this manner. (See Ballast and Trimming in Chapter 15.)

TOOLS AND SAFETY EQUIPMENT

Because of today’s emphasis on working safely, you’ll want to consider what tools and equipment you need to build, maintain, or repair your metal boat. One of the best and least expensive safety items is a clean work area. Avoid leaving anything lying about that is not in use or needed in the immediate future. These are the things that can trip you up, slash you, or otherwise cause bodily injury. Working with metal naturally produces hazards of varying degrees, but you can protect yourself by having the correct safety equipment. Under no circumstances sell yourself short in this area.

Protective Clothing

   Always wear a proper industrial safety helmet. You never know when something may fall, or be dropped on your head. Safety goggles are a must. They should have side guards to protect you against flying metal particles when you’re cutting, grinding, or chipping. You’ll need a face shield and the various lenses. Don’t forget your ears; remember that good earmuffs are essential. A respirator is required. Invest in good coveralls or a boiler suit. A leather apron and gloves with cuffs are definite requirements. One of our customers built a steel Roberts 38 in a Florida nudist colony. We often wondered how he dealt with the weld splatter. Wear steel-toed shoes or boots, not sneakers, around your metal boat building project.

   Protective hand cream and an adequate first-aid kit are essential. Have the first-aid kit handy because you can’t anticipate when it may be required in a hurry; its presence may save your life or at least prevent a minor injury developing into a major one. Make sure you have plenty of eyewash on hand. A good-sized fire extinguisher and an industrial vacuum cleaner are other essential items of safety equipment.

   Arc welders are relatively safe pieces of equipment, but potentially lethal alternating-current electricity powers them, so you can’t afford to treat them casually. Your alternating current (AC) supply will be 110 volts, 220 volts, 240 volts, or perhaps a larger three-phase supply. Make no mistake: all these voltages can be lethal.

   Watching the arc with the naked eye is not recommended. Even if you look at the arc for a short period with unprotected eyes, you can get arc eye, which is very uncomfortable and feels like sand around your eyeballs. Assuming that you, as the welder, always use a mask, then it must be the assistant or casual onlooker who will need protection.

Many of the tools you’ll require for building in all types of metal are those common to steel boat building, so we’ll look at this list first. Later, we’ll follow up with information on the additional tools you’ll require for building in aluminum.

   If you have more-than-adequate funds, no doubt you’ll find many exotic and expensive labor-saving devices to keep you happy. Fortunately for the rest of us, a modern metal boat can be built with relatively few inexpensive tools, most of which are readily available in all parts of the world. The metal used to build steel or aluminum boats is relatively thin, so it can be easily handled, cut, formed, and welded. Many tools are common to the three main metals. The few specialized tools required by each type are available and familiar to those who possess the necessary skills to work with that particular material.

   A check of the yellow pages of your telephone directory will provide sources for all the tools and equipment you need. Another source is the “For Sale” sections of local newspapers. Perhaps a “Wanted” advertisement in the correct classified section will bear fruit. Flea markets, jumble sales, and yard or garage sales, are all good sources of reasonably priced tools.

   In the case of radius-chine hulls, we recommend that you have the relatively small amount of radius plating rolled by a professional metal shop. This service is available in most areas.

  Our plans include details of tools that you can make yourself. Most builders make many of their metal-handling tools, often inventing new ones as required. A simple tool that you can make yourself will serve well to bend deck beams, the stem, and other smaller parts that need to be formed. This bending device is made up of a suitably powerful hydraulic jack and a simple H-frame formed from angle bar.

   Included in the list of small tools you’ll need, are a variety of metalworking hammers and mallets, (including chipping hammers), an assortment of clamps (some of which you can make yourself), bolt cutters, a metalworker’s vice and a selection of sawhorses. A good portable drill is essential and a drill press will be useful. You’ll need a large selection of high-quality metal bits, cold chisels, and metal files. Other tools include a bench grinder, a crimper, a power hacksaw, a jig saw, a straightedge, and tin snips.

There are several ways to cut steel and most other metals. Steel was traditionally cut with a gas torch, or oxyacetylene torch, and although this method is still widely used, more sophisticated and affordable methods are now available. Nevertheless, the oxyacetylene torch and its associated bottles and gauges will find many uses around a metal boat building project, although it’s not a necessity. The gas torch is quick, efficient, and low in operating costs. With this equipment you’ll need a light- to medium-duty kit with a 90-degree angle, and specialized cutting tips.

The basic oxy kit consists of the cutting torch, tips of various sizes, a set of gas regulators, a flint lighter, goggles, a special wrench, couplings for oxygen and acetylene tanks, and two lengths of hose to lead from the tanks to the torch. This package could cost less than $400 (£230) if you’re able to pick up used equipment at a favourable price. A small cart to hold the bottles would be useful; you can either buy one or make one yourself. The cylinders are usually leased from the gas supplier and you’ll only need to pay for the refills.

   The oxyacetylene torch cuts metal through a rapid oxidization process in two continuous steps. While the torch heats a small area of metal to a cherry-red colour (about 1,500 to 1,600°F), a small stream of pressurized oxygen is directed from a central tip within the torch against the hot metal. The stream of oxygen causes the metal to “burn” rapidly and the metal separates as the torch is moved along the line of the desired cut. There are many different cutting tips and they can be used to influence the size, speed, and accuracy of the cut. A special plate-cutting, drag-step tip can cut steel plate from 1/8 to 1/4 inch (3 to 6 mm) thick with precision at the rate of about 2 feet (61 cm) per minute. The resulting cut using this tip will be between 1/16 and 3/16 inch (1.5 and 4.5 mm) wide. Using this equipment is something of an art form, and considerable experience is required to achieve the type of fine cutting that is required when plating your hull.

   The main drawback is that torch cuts are rough around the edges and usually need some cleaning up before they are suitable for welding to other parts. You should avoid the disgusting habit of some low-cost builders who plate the hulls oversize and simply torch off the overlaps at the chine. The oxyacetylene torch can also be used for some specialized welding operations, but for boatbuilding it’s better to use the other equipment discussed below, such as arc (stick), metal inert gas (MIG) or tungsten inert gas (TIG) welders (see Chapter 5). Reserve the oxy equipment for cutting where precision is not required.

You can usually cut aluminum either by sawing it or by shearing it. For straight cuts of material up to 1/4 inch (6 mm) thick, you can use the same power guillotines used for cutting steel. Remember to replace the holding-down pads with plastic ones that won’t mark the softer aluminum. Pay particular attention to keeping knives sharp; blunt cutters will burr the edges of the metal. Nibblers can be used to cut aluminum up to 1/4 inch (6 mm) thick.

BAND SAW

A deep-throated band saw fitted with a narrow (say 1/2-inch or 12 mm) blade will be capable of cutting a wide range of thicknesses. The band saw should be set to run at 2,000 to 5,000 feet (600 to 1,500 m) per minute; the slower speeds will be needed for the thicker plates. A band saw with variable speeds is preferred, but the older heavy types used for cutting timber are satisfactory.

TABLE SAW

For cutting straight lines, a regular table saw fitted with carbide-tipped blades will give perfect results. Be sure to provide lubrication with a kerosene-oil mixture or suitable vegetable oil; this will make the cuts easier and also increase the life of the blade. A portable jigsaw can also be very useful for making on-the-job cuts. Remember, a spray of lubricant will make the cutting go easier for most tools.

POWER HANDSAW

A hand power saw or Skilsaw can be a most useful cutting device when working with aluminum. Fit your saw with a special blade designed for cutting this metal. This blade will have a tooth face rake angle of zero degrees. If you use a guide clamped in position, you can make long straight cuts with this saw. For cutting sheet or framing to length, and in fact for almost all shell and frame cutting, this is a most versatile tool. Treat the hand power saw with utmost respect; the chips thrown off the sawn material are not only hot, but also sharp. Always wear a full-face mask when working with this tool. Make sure that the remainder of your body is suitably protected from flying chips. Use kneepads if you’re kneeling while operating this saw. You’ll need to take extra care when you’re cutting 3/16-inch (4 mm) or thinner plate; the blade will tend to jump out of the cut, especially at the beginning. It’s best to do a plunge start just inside the first part of the cut. This allows the blade to enter the material along the line of cut, and can avoid the kickback.

ROUTER

You’ll find a router fitted with a single-flute, carbide-tipped cutter useful for cutting uniform holes such as lightening holes. You’ll discover that this tool has many uses in the building of your aluminum boat. As with all powered equipment, though, it has to be handled with care. A small electric router, or an air-powered one, is usually used for gouging out the back of welds or removing contaminated ones.

Planes

   Planing is possible with either a carpenter’s hand plane or an electric hand planer with carbide-tipped cutters. Any edge can be planed, and this is a useful feature where a sawn edge would show on the finished boat and planing will provide a superior finish. A plane can also be most useful in bevelling the edges of plate.

Press Brake

   For forming aluminum, hand folders will handle the thinner gauges, but for serious bending you need a press brake with a bed of about 8 feet (2.4 m). The press brake is a strong, hydraulically or mechanically powered forming machine used to crease or bend metal. This machine comes in a variety of sizes and is found in most professional metal shops. The benefit of using this machine is that it can reduce the number of welds required. For instance, a cockpit bottom and sides could be formed in one piece. If you’re building a one-off aluminum boat and you don’t own a press brake, you’ll need to find a subcontractor to handle this work. Never forget that when you’re building in aluminum it makes sense to take advantage of the easier handling of this material. Forming up large multi-surfaced parts by bending sheet into various angles can save a lot of welding and grinding.

PLATE ROLLS

Bending rolls are used to form plate into a permanent curve and can be operated by hand or power. A typical roll consists of two lower power-driven rolls and one adjustable upper idler roll. As the shape suggests, this type of roll is called a pyramid roll and is widely used in building round-bilge boats. The method of operation is that the metal is inserted between the upper roll and the lower two rolls. By adjusting the pressure on the upper idler roll, you can vary the resulting amount of curvature in the plate. Although these rolls operate at slow speeds, remember that loose clothing or carelessly placed limbs can get caught. This could be extremely dangerous especially in the power-driven versions.

EXPLOSIVE FORMING

This method has been used to form various aluminum shapes including boat hulls. Briefly, the process consists of making a concrete or steel mold and using explosives to force the metal into the correct shape within the mold. This method was used in the United States as far back as the 1960s and in Australia as recently as the late 1980s. As with many other exotic building methods, government money (taxpayers’ dollars) was used to pay for these experiments. The process proved not to be cost effective, however, so explosive forming has passed into history. We include it here because occasionally a client will inquire about the viability of this method.

WELDING

It is beyond the scope of this book to teach you how to weld. I've included suggested uses of various welding equipment and actual welding techniques to show what is involved, not to teach you the art of welding. If you’re not already a proficient welder, and you intend to undertake this work yourself, you should seek instruction and advice from an appropriate local source. There are many full- and part-time teaching institutions where the craft of welding can be learned from experts.

Nevertheless, if you’re a complete beginner, you might find it easier to understand this book if you know a few basic details about welding.

   First, when metal is heated to the melting point for welding, it distorts. So most metal boats are not welded continuously. They are mostly tacked together with small, intermittent welds at intervals. The exception, of course, is the plating of the hull, decks, and superstructure, which must be absolutely watertight. Tack-welding is perfectly strong. In fact, too much welding locks in the stresses caused by distortion, which can actually make your boat weaker. Typical tacks are 2 inches long and spaced at 10-inch intervals, but your plans and/or kit assembly text will give you precise instructions. We now recommend that you tack-weld the entire hull before running any final continuous welding. When assembling kits, you should tack-weld the hull, deck, and superstructure before any final welding.

   Tack-welds are usually laid down in two ways, a chain weld or a staggered weld. If you were welding a vertical plate to a horizontal plate, you could lay down tack-welds along one side of the join, and then back them up with identical tack-welds on the exact opposite side of the join. That’s a chain weld. Alternatively, you could lay down tack-welds along one side of the join, and then space other tack-welds alternately on the other side, not backing up the original welds, but falling in between them. That’s a staggered weld.

   In boatbuilding, you’ll need two basic types of welds. Butt welds join material end-to-end. Right-angle welds, as their name implies, join two pieces of metal touching at right angles, or nearly so. The bead of weld laid down in the right angle is known as a fillet. Heavy plates are usually ground off at an angle of about 45 degrees on each side where they join, and a V-groove weld replaces the simple fillet weld.

To control distortion of the metal during welding, you have to lay down your welds in the correct sequence. For instance, if you tried to butt-join two steel plates by starting at one end and working straight across, you’d find the plates spreading apart as you did so. There would be a large gap between them by the time you reached the far end. So you have to start with a tack-weld in the middle, then alternately lay down other tack-welds to the left and right of the center. It also helps to alternate the direction of your welding each time. This is known as back-step welding. It’s a very important principle, and one that’s followed throughout the building process on a larger scale. Thus, after you’ve welded a frame to the shell on the port side, your next move would be to weld a frame to the shell on the starboard side. And, of course, you’d start in the middle of the boat and work outward toward the ends. At this stage, you don’t have to worry about what kind of weld goes where. Your plans and or building instructions will tell you where to use the various types of welds.

ARC WELDING

   You can use arc welding for steel construction. In this method, an electrode is used to create an electric arc that melts the metal to be welded. The electrode is a metal rod that simultaneously produces the arc and is melted to contribute filler metal for the joint. There are many different types of arc welders, and it’s difficult to decide which one to buy. It’s important to make sure that the welder has sufficient capacity for your project. Don’t make the mistake of buying a welder that’s too small. The difference in price between a welder of adequate capacity and one that is underpowered for your job won’t be great, but your irritation certainly will be enormous if you make a mistake and buy a lightweight machine that is not up to the job.

   If you’re building your boat on a non-industrial site, you’ll need a welder that will run off your normal domestic electricity supply. In the case of the most powerful machines, a higher input voltage will be required, but with good fortune on your side you should be able to obtain a suitable machine to run off the local power source.

WELDER AMPERAGE

You must consider the output rating of the welder, which is measured in amps. The higher the amperage, the thicker the plate that can be welded by that machine. The thickest plate you are likely to be using will be in the order of 1/4 inch (10 mm), and this thickness can be handled by an arc welder with an output rating of 140 amps. If you are using thicker plate, say for the bottom of the keel, you can manage by bevelling the edges of the thicker plate and using more than one run of weld. You may think that because your plans call for 3/16-inch (4 or 5 mm) plate that you can get away with a welder that puts out only 110 amps. Don’t be tempted. As a minimum, choose between a 140- and a 200-amp machine.

   Arc welders of greater than 140-amp capacity cannot be run from the normal 15-amp domestic supply, so you’ll need an alternative supply. If possible, you should try to arrange a 30-amp input supply. Heavy-duty supply is obtainable in the United States by way of the three-phase wiring supplied to domestic washing machines and electric dryers. No matter where you are planning to build or undertake a major refit on a metal boat, you will need to ensure an adequate power supply of the correct voltage and amperage for your particular needs.

   The maximum input required can usually be obtained from the welder instruction manual and is often quoted in kilovolt-amps (KVA), which equals 1,000 volt-amperes times a power factor of 0.8. For example, the amperage calculation for a 140-amp welder with a maximum input of 4.2 KVA at 240 volts would look like:

V x A x 0.8 = KVA

240 x A x 0.8 = 4,200 VA

A = 22

   So, in this case, a 25- or 30-amp input supply is recommended. Some better-quality welders can be run at varying input voltages; this feature may be appreciated when you consider the voltage drop resulting from a long lead. As part of your selection of the boatbuilding site, you should consider this possibility and make allowances for any deficiencies in the power supply. A voltage meter can be used to test the voltage at the actual location where you’ll be operating your welder. A 10 percent drop in voltage could put paid to a successful welding job. Input wires will need to be heavy, and a single run of cable is best because joins at outlets and sockets can result in a considerable voltage drop. As mentioned above, the alternative is to equip yourself with a welder that will accept varying voltages.

   While we’re on the subject of leads and cables, you’ll find that the output cables supplied with your welder will seldom be long enough for your type of work. You’ll most likely have to replace them with longer leads. Make sure the replacements are of good quality and thick enough to carry the loads without an accompanying and unwelcome drop in power. The earth clamps are usually spring-loaded. You may find it advantageous to replace them with the threaded-clamp type, which has a more positive grip. Also along the same lines, your electrode holder will most likely be spring-loaded; be warned that it should not be too heavy. The many hours you will spend welding can put a strain on your wrist and arm. This is especially so if this is your first major all-welded project. A little weight saved in the holder can make all the difference.

AIR OR OIL COOLED

Arc welders come in two main types, air cooled or oil cooled. Oil-cooled versions have are capable of long continuous usage without overheating, which means that they have much longer working lives than air-cooled arc welders. Even if you’re building only one boat, you may want to take your welder with you when you go cruising as a means of earning additional funds. Oil-cooled welders also have a higher resale value. Against these advantages, you’ll find that oil-cooled versions are much heavier and need to be stowed with care as the oil can drain out of the vents if the unit is not kept upright.

Air-cooled versions are about half the price of oil-cooled welders, so you’ll need to make your own value judgment. This is only one of many you will be making throughout your boatbuilding project. Make sure the unit you select has some form of automatic thermal cut-out, so that if it overheats it will shut down before it self-destructs. Summer and winter temperatures will have an effect on the amount of time you can use your air-cooled welder before you have to take a rest and let it cool down. If there’s more than one person welding and using the same unit, extra thought will have to be given to the selection of a suitable unit.

   On some of the better air-cooled models, you’ll find a dial to control the amperage setting. This works throughout the output range, and this choke control can be handy when you’re tackling a variety of welding conditions. A proficient welder can tune the output to suit the job at hand. Finally, no matter what type of arc welder you choose, don’t buy a cheap unit; it’s unlikely to remain in working condition long enough for you to complete your boat.

ELECTRODES

   Although electrodes are consumables, rather than tools, it seems practical to include them here with arc welders. There’s a wide range of electrodes in all appropriate materials. In some cases, there’s more than one type of rod available to suit a particular job. You’ll need to undertake some experimentation to find the rod that gives you the best results. The choice of electrode will be governed by the sequence of the work, your welding position, the equipment powering the electrode, and of course, the material you’re welding.

   The electrodes must be compatible with the base metal. The low-hydrogen variety is recommended for better quality and a stronger weld. This type reduces porosity and prevents hydrogen embrittlement, which causes hairline cracks. Porosity would allow water to pass through the weld and promote corrosion as would the cracks caused by hydrogen embrittlement. Although I do not feel that is necessary to dye test every weld, it is important to make sure that you don’t rely on filler to keep the elements out of your boat.

   There is some disagreement between various experts as to which rods, electrodes, or consumables (these terms mean the same thing) are best for a particular job. You may need to study this subject and seek local advice from suppliers and those more experienced than yourself. Running practical tests with different types of rods will often assist you in choosing the correct rods.

   Low-hydrogen electrodes require a little more skill on the part of the operator. Avoid electrodes that are promoted as high-speed, single-pass types; they produce a weld that has low ductility and should not be used in important parts of the boat. If you are building “to survey,” or to pass U.S. Coast Guard inspection, then certain rods may be required. Check this out if you are building to a classification society rule, or under similar circumstances. No matter what rods you are using, you must store them properly. Ensure that the rods are kept in their sealed packets, dry and free from all contaminants.

   As this book covers boats built all over the world, it’s difficult to recommend specific brands and part numbers of welding rods for specific purposes, so please use the rod numbers shown in the table only as guides. When you’re fabricating a steel boat you’ll be using mild-steel rods, but it may be useful to have a few gouging rods on hand. They let you cut plate with an electric welder, and although this will not, and should not, be your common cutting method, there may be times when these rods will come in handy. To use gouging rods for cutting, the plate is heated using high amperage, then the rod is pushed through the plate and drawn along the desired line, thus effecting the cut—and a surprisingly accurate one.

   If you are not already familiar with the terms slag, flat beads, fillet welds, etc., that appear in this chapter, please refer to Appendix 2 for a complete glossary explaining these and other welding and boatbuilding terms.

For North American readers, the table shows details of a few of the more popular rods and their uses. Note that each number in the letter designation has a special meaning. For instance, the E signifies electric welding; the first two numbers relate to tensile strength, and the next number shows the welding position. One equals all positions, and the final number signifies the special manufacturer’s characteristics.

You can get your boatbuilding project off to a great start by using a pre-cut steel or aluminum kit for any metal sailboat or powerboat. Modern kits contain accurate pre-cut parts that you can easily assemble into a complete hull, deck, and superstructure. The latest computer software allows the designer to model the boat so that extremely accurate computerized files can be prepared to direct the cutting machines. These files contain all the information to facilitate computer-controlled cutting of all the metal parts for your boat. It may not interest the average builder, but a huge amount of work is required to turn a boat plan into a cut-to-size boat kit. Every part has to match that of its neighbour exactly, the slots need to be in the correct locations, and everything must fit together perfectly. All this is necessary to enable you to complete the assembly of the hull, deck, and superstructure with the minimum of problems. We’re always amused when we receive a request from an uninformed customer that goes something like this: “By the way, now that I have the plans for your design, just send me the cutting files.”

DESIGNING AND CUTTING PRECUT METAL BOAT KITS

   Many of you may be surprised that it’s not possible to take a regular boat plan—even one that is already prepared using the latest computer-aided design techniques—and use it for automatic computer-controlled cutting. There are many steps between creating the original design and having the boat cut out on a computerized plasma-oxygen cutter. If a particular design is to be sold as a pre-cut steel or aluminum hull, deck, and superstructure package, then this should be decided at an early design stage. Some designs can be converted, but it is preferable to start with automatic cutting in mind.

   The main steps in preparing a new design for a boat that is destined to be cut out by a computerized plasma-oxygen cutter is as follows. It is usually the customer who gets the process started by contacting the designer with a brief outline of what they have in mind. Further correspondence quickly establishes the client’s wish list, which usually includes things such as type and style of boat, intended usage, and overall length and beam. Draft limitations should be specified at this stage.

 Accommodation requirements, including the number of regular crew versus occasional guests, should be defined. Speed requirements are important, as are the client’s attitude to fuel costs. This list may need some refining since some elements may conflict with one another. The communication ensures the client ends up with a boat that meets most if not all his or her desires and overall requirements. So far the process is very similar to what would be followed no matter which material or building method was used to construct the vessel.

   The client and designer then enter into what can be a simple agreement where the designer agrees to prepare preliminary plans for the proposed vessel for a reasonable (a relative term!) fee. In our office the preliminary plan includes lines plan, general arrangement drawings (consisting of exterior profile, deck plan, accommodation profile, and plan views), plus sufficient calculations to ensure that the final design can meet the client’s requirements.

   Before a preliminary plan is produced, the designer produces a 3-D computer-generated model of at least the hull of the vessel. Once the preliminary plans are completed and both the designer and the client are satisfied with the overall concept and layout of the vessel, complete plans for the vessel are prepared.

   Next, a comprehensive 3-D computer model is completed that includes all parts of the hull (including transom, keel, and rudder), all decks, cockpits, a complete superstructure, main interior bulkheads, and any other features such as a flybridge, radar arch, and exhaust stack. Special items such as transom steps and other similar features are included in this model. Depending on the complexity of the design, this process can take between 80 and 200 hours.

   From this model, all of the salient hydrostatics—such as detailed weight calculations to enable material requirements and final displacement—are calculated. Stability calculations are also made at this time. During this process, fine-tuning of the model can be undertaken to make sure that the finished vessel will meet all the design requirements.

   When the comprehensive 3-D model is completed and checked, copies are provided to a team of specialized designers who prepare the final model, which includes all the scantlings (such as transverse and longditunal framing, sole bearers, deck beams, and engine beds). This team separates out all the parts for the frames, stringers, engine beds, bulkheads, hull, deck and superstructure plating, etc., and add notches to the frames and bulkheads before nesting the parts on plates.

   The design team numbers each item and draws reference lines on each part to represent frame locations, etc. (the numbers help builders identify each part, and the lines are used during the assembly process to locate frames and other structural members). The designer then works out a path for the computerized plasma-oxygen cutting machine. The path is the point at which the cutter enters the plate and starts cutting the parts. It must make sure the parts are cut in the correct order. For instance, if a window has to be cut from a cabin side, then the window aperture must be cut before the larger cabin-side part is cut; otherwise any movement in the cabin side after cutting could cause the window to be cut in an incorrect location.

   Several sheets of assembly drawings are now prepared. For instance, each frame is shown separately with all parts clearly numbered, and measurements are given to assist in welding up the frames. Other drawings show how to set up the building jig supplied with the kit. The location of every part that forms the completed hull, deck, and superstructure is shown in the various assembly drawings supplied with the kit.

Finally, all the parts are listed in a spreadsheet program and checked against the drawings and cutting files. Another designer is simultaneously working on the engineering drawings for the engine room layout. Battery placement, drive train and bearing location and sizes, exhaust system, fuel tank sizes and placement are shown in these drawings.

   Of course, all of the above steps have to be carefully checked and the whole design package coordinated before the cutting files are released to the client (to have the kit cut locally) or sent to the cutting shop that produces our kits. In terms of investment we figure that each set of cutting files and associated plans for a boat of between 36 and 65 feet costs the originating design office between $35,000 and $50,000. Because this figure is too large for an individual customer, we try to group orders for similar kits as well as treat a large part of the cost as investment against future kit orders.

   The size of readily available plate varies from country to country, so sometimes it is necessary to renest the cutting files so they fit the available plate stock. Re-nesting may be also required if the size of locally available cutting tables is less than that of the equipment used to cut the first kit. Fortunately it only costs a fraction of the original expenditure to renest the plates to any convenient size. As you can see from the above, the amount of careful and intense work required to turn a existing or new plan into a set of cutting files far exceeds the expense in creating the original design. It’s only possible to justify these costs if a firm can expect to market several kits of similar design. Often, cutting files for a particular design can be made in such a way as to give several customers the custom items they desire. Some custom items are relatively easy to incorporate in the cutting files, while other more-complex changes require redesigning the basic boat and remaking all the cutting files.

   The metal-cutting shop uses the Numerical code cutting files to produce your kit. The kits are cut from pre-shot-blasted and primed steel (or aluminum) and are delivered ready for easy assembly by any competent welder. The primer used on the steel kits is especially formulated so that it doesn’t give off harmful fumes as you weld the kit together. This primer doesn’t burn off on the reverse side of the metal in welded areas. It’s truly a remarkable coating used to protect the steel until additional paint is applied.

   The parts are all nested, including all of the hull, deck, and cabin plating. You can easily assemble the hull, deck, and superstructure. All you have to do is to match each part to the special assembly plans you receive with the kit. Whether you decide to purchase cutting files and have the kit cut locally will depend on your location. For instance, due to the availability of excellent cutting facilities in the Netherlands, most customers in Europe opt to order a pre-cut kit as opposed to cutting files. Conversely in countries with high steel import duties, such as Brazil, then cutting files and plans can be purchased on a CD. The kit is then cut locally.

In our own case we have exported complete cut kits to the United States, Canada, Philippines, Russia, and many other countries, including almost all of Europe.

   The tack-and-weld method described below is in many ways similar to the stitch-and-glue procedure used with plywood. It’s a practical and economical way to get your boatbuilding project off to a great start. You can achieve a professional result, especially if you already have some welding experience. If you lack welding experience, then any local person with suitable welding knowledge can help you assemble your kit. Of course, many thousands of boats have been built from a set of plans and frame patterns, so if there isn’t a kit that meets your requirements, building from plans is the way to go. Nonetheless, if you can afford a kit, you’ll have a hull in the least time and this alone may justify the modest additional expense. The resale value of your boat will be enhanced if you can show that the hull was built from pre-shotblasted, primed, and computer-controlled pre-cut metal parts.

STEEL KITS

In high-quality kits, all steel plates are shot-blasted and primed with a zinc-rich primer before cutting. Cutting of plates is carried out with computer-aided lofted surfaces on an NC-driven plasma-oxygen cutting machine with a maximum plate size of 82 by 10 feet (14 by 3 m). The best material is Lloyd’s-approved, “A” grade, “shipbuilding quality,” or the equivalent.  The kit includes a setting-up jig as well as detailed assembly plans. All required steel profiles are also shot-blasted and primed with a zinc-rich primer. Kits are constructed from the steel product specifications mentioned above.

   Normally, all the plate material is supplied as a flat pack with marking lines engraved in the plate surface (a zinc line) and part numbers painted on the surface. The maximum size is usually 19 feet 6 inches, by 6 feet 6 inches (6 by 2 m). All steel profiles are supplied in sufficient length to ensure the minimum number of joints in the plating. All parts that require forming or bending are supplied already formed to the correct shape.

Those who prefer aluminum as their basic building material will be pleased to learn that kits are available pre-cut from marine-grade materials.

The first thing to realize is that the kit differs in many ways from the methods you would use to build a metal boat from scratch. The kit is far superior to anything you could achieve by starting with the plans and a delivery of raw steel plate and profile bars.  Most metal boats built from scratch are built upside down; boats built from cut-to-size metal kits are built upright. Not only is this a more appropriate way to assemble the kit, it also saves the cost and inconvenience of having to turn the hull. And here’s one very important piece of advice: You must tack-weld the complete hull, deck, and superstructure together before you run any final welds. If you don’t follow this advice, you’ll almost certainly end up with an un-fair boat requiring a considerable amount of filler. In any case do not over-weld or try to run long welds at one time.

   Your kit may arrive on a flatbed truck or in a container. Kits are normally packed on pallets and can be lifted off the transport by a small crane, front-end loader, or similar equipment. Provided your kit is on a pallet, you may find it more convenient to drag your kit from the truck or container, using a pair of planks as a ramp. Once you have unloaded your kit, you must keep it covered until assembly is under way.

With your kit, you should receive a packing list and large-scale assembly drawings. The drawings will show all the parts as flat surfaces grouped together as they will be assembled to make the finished hull. There will also be a number of drawings showing the assembly of the frames. Each part will be numbered, so that you can check it against the packing list and the corresponding drawing.

   One of your first jobs will be to tack-weld the frames together, so make sure you sort the parts and store them in the order you’ll need them. On larger frames, it may be easier to tack only the bottom sections of the frames together at this time.

   Once you’ve tacked all the frames together, it’s time to prepare the building jig. The transverse profile jigs will be supported by the metal “castles” that come as part of your kit. The setting-up jig is merely intended to start things off. It is not intended to support the boat during the entire building process. Usually, however, you leave the jig in place for the entire building program so you can weld a flat strip on the top of each web to spread the load of the plate where it rests on edge of the plate web. After you have both sides of the bottom plates tacked together you should consider adding extra support and bracing to the jig structure.

   Set up two parallel I beams as shown in the instructions that come with your kit. These beams must be long enough to accept the number of support jigs mentioned above. Cross-tie I beams should be installed at the same location as indicated to install the support webs. Obviously, the whole support structure must be level in all directions and well braced as it will play a part in supporting the boat during construction.

Don’t attempt to fully weld the plates into one length on the floor. The plate joins should only be tack-welded in three locations: one weld at the each of the ends of the join, and one in the center of the join. These tacks should be no more than a 1/2 inch (12 mm) long. If you weld the plates on the floor, you’ll end up with a hard spot in the hull plating. Some plates of 1/4-inch (6 mm) or heavier material may need to be bevelled before you tack them in place. You may prefer to make the bevels after you’ve tack-welded the plates and before you run the final welds. In all cases, good metal boat building practices should prevail. After you have both sides of the bottom plates tacked together, you should consider adding extra support and bracing to the structure.

   Sailboats with long keels, such as our Spray designs, as well as most powerboats, should have the keel structure assembled at the same time as the bottom plating. Take care that you don’t “squeeze in” the tops of the keel; use the webs as spacers. After you’ve positioned the bottom plates, the keel sections, and the transverse profile jigs, you may start to tack-weld the bottom plates to the keel sides. Sailboats with deep fin-style keels may have the keel installed after the hull is completed. The canoe body should be built from the bottom of the hull upward in a manner similar to that used to assemble a powerboat hull. The webs can be arranged so that they can be added along with the rest of the keel after raising the hull to the correct elevation.

   The benefit of using this method is that it allows you to work on the hull, deck, and superstructure while the boat is lower and thus more accessible. The exact method and order of assembly depends on the availability of lifting equipment and your general work environment. Details given below are valid for the general assembly of all hulls.

   With most powerboats, you can start by laying the bottom plates in the transverse profile jigs that come with your pre-cut metal kit. The frames will soon be added at the locations indicated by the transverse lines marked on the plates.

   With any hull, the first step is to set up the bottom plates and tack them along the centreline. Next, start to install the pre-tacked frames on the appropriate transverse lines marked on the plating. From now on, the whole structure will grow upward. The better equipped your workshop is with overhead lifting and handling gear, the easier and more smoothly your job will proceed.

   If you’re in doubt about your welding skills, seek the help of a suitably qualified person at the earliest stage. There is a great deal even the most inexperienced person can do to assist a qualified welder to assemble the kit. Generally, two people are required to handle the larger pieces of metal, so acting as labourer to your hired professional may be the best route for you.

If you have moderate welding skills, you’ll find that the kit comes with enough scrap material to allow you to get in some practice before tackling the assembly of the kit. Don’t try to weld aluminum or copper-nickel unless you have the proper knowledge and considerable experience in handling these materials.

   The metal kits are constructed so that the strength of the finished hull comes from the build-up of the frames and stringers in interlocking sections. Heavy and continuous welding of frames and stringers should be avoided at all times. After the hull and deck is tack-welded together, the process of finish welding can proceed without fear of distortion.

   The secret of creating a fair hull and deck is to use a welder of high enough amperage for the job. Welding with too little amperage and or too slowly, will create a lot of heat on the spot and less penetration of the weld material in the seam. This may make for a weak weld and additional grinding to remove excessive weld material. This, in turn may further weaken the weld.

For those of you who are new to this type of boatbuilding, there is an early shock in store. Having placed the bottom plates on the jig, you may think they’re not going to fit. Keep the faith! Start tack-welding in the middle of, or somewhat aft of, the middle of the plate. Make sure the marks on the plates are lined up at all times. As you work forward and backward from the tack-welded position, you can form the plates to shape with some human help or by using a trolley jack underneath the area of the plates where they are to join. When they touch, tack-weld them together and move along to the next position.

   At the bow, you’ll probably need a block and tackle to pull the sides of the plates together. Some tension will be experienced in this area. Don’t forget to secure the positions of any clamps so that they cannot unexpectedly let go.

Having finished tack-welding the bottom plates together, start placing the frames in position on the bottom plates. Lines on the plate will indicate the location of the frames.      You may use the scale drawings as a reference. Depending on the layout of the bottom stringers on your particular design, you may have to install some of them as you are installing the bottom frames. Study the layout of the bottom framing on your boat plans and it will become apparent which sequence will work best for your hull.

   Pull up the bottom plates toward the frames until they fit snugly and tack-weld them. Start with a frame where the plates are least shaped, and work backward and forward from there. If you’ve assembled the complete frames, as opposed to the bottoms only, use temporary braces, as necessary, to support the top portions of the frames. Once all the frames are installed, you may fit some of the side stringers into the slots on the frames. These stringers will assist in stiffening up the structure at this stage. Once again: 

    Use only tack-welding at this stage of the assembly process.

   The next step is to install the side plates. This is best done by using a simple overhead gantry or a forklift truck. Pick up the side plates with a plate clamp on a chain connected to a block and tackle made fast to a forklift leg. Make sure the plate is more or less in balance while it’s hanging free of the ground before you lift it into position. Use a helper to locate a matching line in the right position and tack-weld it. Continue to move the plate up or down a bit with the block and tackle until the entire side is in position and tack-welded in place. Place some tack welds on the side frames-to-plate joint as well as on the chine seam.

   The side plates near the bow and the underside of the bow will show some tension, and can be pulled into place by attaching a chain on the outside of the plates. To attach a chain or a block and tackle to a plate, tack-weld a temporary eye or similar piece to the plate. By welding only one side of the eye, you can easily remove it after use.

Next, the transom plates, bathing platform, stern plates, and all other plates that go into forming the hull are installed and tack-welded in position. Note that with radius-chine boats, the radius panels are installed later. Remember to refer to the drawings frequently.

   Now the deck plates, superstructure, and items like a flybridge are installed and tack-welded into position. Any deck stringers and cabin top intercostals in your design may need to be installed before the applicable areas of plating. In some cases, it may be possible or preferable to tack-weld the superstructure together off the boat and then install it as one unit. Some of the more recently designed kits allow for this option by providing special landing areas at each frame, which make it simple to line up the completed superstructure with the hull and deck.

Radius Chines

   After you’ve tack-welded the entire boat together, it’s time to tackle the radius chines. We’ve always maintained that radius-chine hulls should be built upside down. For one-off boats built from scratch, this advice still stands. But, because all kit boats are built upright, a special approach is required to enable the radius chines to be fitted without blemish. At first, we supplied the radius plates rolled in one direction only; this is the same rolled plate you would use in one-off radius construction. We soon discovered why we had always insisted that these radius-chine boats should be built inverted.   Fortunately, we were able to solve the problem. The radius-chine boats built from these kits are still built upright, but with one important difference: we now supply fully formed radius plates. They are rolled in all directions to ensure a perfect fit. This improved arrangement is available because it is now possible to have the plates fully formed and rolled from the information supplied in the original modelling files. The forming cannot be accurate right to the edge of the plate, however, so each section is a little oversized at the edges, which allows for exact fitting and trimming. Your kit will contain the appropriate amount of pre-rolled, numbered sections to fit the area covered by the radius chines.

   Now you can carefully place the appropriate pre-rolled section against the position on the opening in the hull. Using a helper, scribe the edges of the plate with a sharp tool or pencil and then cut, grind, or nibble the edge for a perfect fit. Tack-weld it in position and continue until you have all the radius panels in place.

Finishing the Assembly

   The first job is to complete the welding of the frame sections and then intermittently weld the frames and stringer to the hull plating using 2-inch (50 mm) weld spaced at 6 inches (150 mm). Do not over weld and do not continuously weld on one side of the hull. Weld on a reasonable amount on one side then switch to the other side, back and forth until the entire hull is welded. Constantly working from side to side will avoid the plates pulling out of shape and general distortion that can be caused by over welding or welding entirely on one side at a time.

   You should have made a 60-degree V between the plates, 30 degrees on each plate, but if you haven’t previously prepared the heavier plates in this manner, you may do so now by running an angle grinder along the appropriate seam. Now you can proceed to run the final welds on the outside of the plates. The hull below the waterline must be welded both inside and out. Again, work from one side of the hull to the other, frequently changing sides.

   You can grind off any excess weld material by first using a coarse disk and then finishing up with a softer, more flexible disk. Take advice from your materials supplier about these items. Lastly, apply a minimum of filler to the seams and apply a coat of primer to the ground areas. You’re now ready for final finishing and painting. The remainder of the painting and fitting-out work is the same whether you build from a kit or from scratch. One big difference is that by using a pre-cut kit you’ll have saved over 75 percent of the time required to build a similar hull from scratch.

To build a boat from scratch you need a set of suitable boat plans; hopefully your plans will include full-size patterns for the frames and stem. Below is a list of what our own design office supplies in this regard. With the advent of modern computer yacht design we have been able to offer the complete plans on CD. The benefit of receiving you plans and full-size patterns in this way is that you can have as many prints made of each sheet as you may need. For instance, if you are looking for quotes on either having the hull built or to purchase some piece of equipment or quotes for mast and sails; all these suppliers want to see the plans. You will find that having the ability to have the plans printed locally will offer many advantages during the building program. Also on the CD the designer can supply photos of similar boats under construction and other printed material that will assist you to better understand the plans and the boatbuilding process in hand. As most printed plans cover many large sheets of paper, it costs a considerable amount in postage, (usually about $/€50 or £35) to deliver from the designer to you. CDs can be mailed for a very modest cost.

   Using the boat plans shown below and a collection of appropriate materials you can build a boat from scratch. You make the frames from the patterns supplied and then you make patterns for each subsequent part as you continue to build the boat.

As mentioned earlier, your plans can arrive either printed on paper or as printing files on a CD. You should receive the latest updated version of your selected boat plan, which is only possible when you order your plans direct from the designer. You will receive many construction sheets, which include copious written notes as well as the detailed drawings necessary to build all parts of your boat.

   The following list is what we consider to be a complete set of plans and full-size patterns to enable you to build your boat with the minimum time spent in doubt as to how and what to do next!

•        Sheet 1A (there may be several sheets covering various versions of the same design). These sheets cover the boat's general arrangement drawings, profile and plan views of the hull, the deck and superstructure, plus the deck plan. In the case of sailboats, the sail plan and measurements are usually included on these sheets.

•        Sheet 1AA (there may be several sheets covering various versions of the same design). These sheets show the boat accommodation laid out and shown in plan and profile views. The several versions of the design are shown on separate sheets. Also included is a list for all the materials needed to build the hull deck and superstructure. In the case where the boat can be constructed of a variety of materials, these are all listed to allow you to cost out the boat in each.

•        Sheet 2. The boat lines plan shows hull sections, profile including all water and buttock lines, and plan view including all water lines and buttock lines. All frame spacing, stern or transom detail, keel measurements, and rudder and skeg should all be included and all dimensions clearly shown.

•        Sheet 3. This sheet will be a reduced drawing, representing what you can expect to see when you lay out the full-size boat hull patterns. We call this sheet the key to full-size patterns; it acts as a key when arranging the hull patterns and will enable you to readily understand just what the patterns contain. This sheet will help you resist the temptation of trying to lay out the patterns on your living room floor.

•        Sheet 4. This sheet shows you how to manufacture and assemble the frames, plus form up the stem and other parts of the basic framework. This sheet also shows how to set up all these items on a strong back or a system of bedlogs, which forms the shape of your hull.

•        Sheet 5. This sheet shows the installation of the stringers and deck shelf plus the installation of the plating in metal boats. In the case of radius-chine boats, additional information is supplied on installing these plates. Assuming you are building upside down, this sheet will show the turning-over process.

•        Sheet 6. Now the boat is upright and this sheet covers the inside of the hull, and shows the installation of the floor webs, bulkheads, engine beds, and all interior stiffeners for your boat.

•        Sheet 7. This sheet may show detail of the various items not covered in sheet 6. Often it takes two or more sheets to cover webs and bulkheads.

•        Sheet 8. This is the engineering sheet that covers the engine installation, locating and building the fuel and water tanks, and making the rudder. Also included are details on making the stern and rudder tubes plus propeller shaft detail. Stanchions, swim platforms, and similar items may also be on this sheet.

•        You may note that much of the above work can be completed before the deck and superstructure are in place. It is far easier to install the heavier items such as the engine before the "top" goes on. Individual builders will have a preference in this regard.

•        Sheet 9. This sheet shows details the forming and installation of deck beams, side decks, foredeck, aft deck, cockpit construction and all deck framing detail of your boat design.

•        Sheet 10. This sheet shows the patterning and making of the cabin sides, cabin front, etc. In the case of the cabin sides the measurements should be adequate to enable you to make up a plywood pattern and trial fit before cutting the actual cabin side plates.

•        Sheet 11. This sheet covers such items as deck fittings, additional rudder construction, etc.

•        A detail folio showing how to build some boat fittings and tools plus other valuable boat construction tips is included with all plans. When the plans are ordered on CD it is often possible to include numerous photos showing a sample boat under construction and examples of completed versions.

•        Sheets A, B, C, D, E, F, G, and H are the full-size boat hull frame pattern sheets that are laid together like wallpaper. The full-size patterns contain details of all frame shapes, stem, deck and cabin top cambers, and the pattern for the expanded transom. Patterns are either paper or computer files (if you have plans supplied on CD), which can be printed out by your local print shop.

   This is a good time to mention that the professional who designed your boat may have spent many hours over some small detail believing that it will have an important bearing on the performance, appearance, or resale value of your boat. Respect his or her efforts, and please don’t make changes casually without consulting the designer.

Making and erecting the frames is one of the most exciting parts of building any boat. Having built a few boats myself, I know the thrill of seeing the frames erected for the first time, and of standing back and admiring the line of the hull. Of course, the addition of the chine bars (if present) and a few stringers gives a better idea of the shape of the hull, but the initial thrill of seeing the frames erected is still a most memorable occasion.

Material Lists

   You will get a better price if you order in bulk, so we recommend that you order all the basic hull materials in one combined package. Your building plans may include a material lists and, if so, it usually consists of the main items required for building the hull, deck, and superstructure. On some occasions, if you calculate the total weight of the metals, you may find that there appears to be too much material. Your list should include an allowance for off cuts and other wastage. The list may also include details of the temporary bracing required to set up the hull.

  Even if your plans include a materials list (including the lists included in our plans), go through the drawings carefully and “take off” the list for yourself. Don’t forget to allow for wastage; 15 to 20 percent is about right. Some of this wastage material will be used to make tools, including clamps and tags. The time required calculating the quantities will be a good investment, and it will prove invaluable in your better understanding of the plans. “One hour of study can save two hours of work” is an oft-quoted truism.

The shape of the boat, the metal being used to construct the hull, and the particular building method you choose may all contribute to your decision to build the hull upright or inverted. Another factor could be the space and facilities available for turning the hull. There are many simple systems for turning hulls over, so this factor shouldn’t play too big a part in your reaching a decision. You could decide to build two or more rings around your hull, thus facilitating working on the hull and other areas of your boat.

   Advocates of the upside-down method like it because most of the important hull welding can be done in the down-hand position. In any case, some of the welding must be done from inside the hull, including tacking the intermediate stringers to the hull plating. Unfortunately, this may be a bit awkward, but at least some of this welding will have to be done while the hull is still inverted. Leaving the transom off the hull until after turnover will be of some help in gaining access to the interior of the hull. There is some justification for not installing the transom until immediately before the deck is installed.

   In the case of radius-chine construction, I consider it imperative that the hull be built upside down. Building inverted makes it easier to install the radius plating. In our opinion, it’s much simpler to lay the plate onto the framework from above than it is to draw or hold the plating from below until it is tacked in place. At the risk of repetition, you must always build radius-chine hulls upside down. Our preference for building upside down extends to round-bilge hulls as well.

   To be fair to those who prefer to build the hull upright, the stated advantages of this method include the fact that the hull is already in a position to complete the deck superstructure. In other words, it doesn’t have to be turned over. Building the hull upright offers easy access during the entire welding operation. You can overcome some of the disadvantages of not being able to lay the plate on by employing the use of adequate scaffolding. There are also many tricks, such as drilling a hole in the plating and pulling it into position with chains, wedges, and threaded bolts. As mentioned earlier, whether you build upright or upside down will largely depend on your circumstances and personal preference.

The only people who decry the use of full-size patterns are those who either don’t have access to them or those with masochistic tendencies. Under no circumstances try to “improve” on the patterns by using the offsets (if available) to re-loft the boat completely. Today, most boats are designed, drafted, lofted, and provided with full-size patterns plotted from computer-generated offsets. You can’t improve on that, even by completely re-lofting the boat by hand.

   The patterns you receive will most likely contain full-size shapes for all the frames for one side. This is all you’ll need unless you are building an asymmetrical hull. In addition to the frames, other full-size shapes may include the stem, the developed transom (the full-size transom shape when the curved transom is laid out flat—the radius will be included in the plan details); and the deck and cabin top beam cambers. Also, patterns may be included for the rudder, window patterns, and other items. These extra patterns are included when the designer feels that they will ensure that you interpret his ideas as intended. If possible, use these patterns. Usually any “improvement” in the designer’s work will result in a less attractive boat.

   Paper patterns are fine, provided they are handled properly. These patterns should not be exposed to a damp atmosphere before being transferred to a more durable surface. If your plans come with paper patterns, don’t open or unroll the patterns until you’re ready to start building the boat. The patterns that come with our plans arrive in a plastic bag, which ensures they remain as printed until you are ready to lay out the patterns and make the frames.

   You’ll need a suitable surface on which to lay out the patterns. You can work either directly from the patterns (not recommended) or you can transfer them to plywood or steel plate. This working area is variously known as the loft floor, the master plate, or any one of a dozen other locally inspired names. If you are transferring the frame shapes and other patterns to plywood, you can use a dressmaker’s wheel to mark the shapes through the patterns onto the surface of the plywood. This plywood could be later used in the fitting-out process, so it won’t represent an additional expense. If you’re transferring to steel plate, you’ll need to center-punch the main points onto the steel plate and use a batten and straightedge to scribe in the shapes of the frames. In the case of shaped frames and the stem, you’ll need to center-punch several points along the curve and then join the marks with the aid of a batten and the drafting weights known as “ducks.” We find the plywood surface has many advantages.

   The advice above applies to multi-chine sailboats, single-chine powerboats, and round-bilge boats of all types. In the case of radius-chine hulls, you’ll don't need to transfer the radius sections from the patterns; transfer only the straight sections. You should have the radius-frame parts bent to the radius specified on your plans, and the length (as measured around each radius) that will be needed to match up to the straight sections of the frames. Allow a little extra for trimming.

   If the plans for the boat of your choice are not available with full-size patterns, you’ll need to arrange for the hull to be lofted by computer or by hand. To enable the hull to be lofted by computer, you’ll need to supply the lines and offsets to be entered, faired, and then plotted as full-size patterns. Computer-lofting is available from several design offices, including ours.

  Lofting by hand involves actually drawing out the entire hull of the boat full size. Don’t be trapped into drawing only the frames or stations, without actually drawing out the complete boat full size; this means you will need a lofting floor equal in size to the length and width of the half beam of your boat. You must plot out all station and waterline grid lines plus the full-size profile. The offsets are used to lay out the curved waterlines and buttock lines. You need to take great care to ensure that the frame or station measurements are correct so when you take off the full-size frame patterns and other parts including the stem, the patterns will be totally accurate. This is not a job for the in-experienced builder. Either choose a plan with full-size patterns or have the lines professionally computer-lofted. If you do decide to tackle the lofting yourself you will need a loft floor that can consist of several sheets of plywood. The sheets are laid out to form an area of say 3 feet (1 m) longer than the overall length of the boat, or longer by half the beam if you plan to develop the transom. You should paint your loft floor with flat white paint; this will enable you to see the grid and other lines more clearly.

   You’ll need at least one long timber batten of about 3/4 by 1/2 inch (20 by 12 mm). You’ll also need some smaller battens, a builder’s square, string or chalk line, and a set of loftsman’s drafting weights (ducks), plus suitable pencils. The information included here is very basic and if you haven’t lofted a boat before, you’ll need a good book containing detailed instructions.

It’s usual to assemble the frames over patterns that have been lofted by the builder or supplied with the plans. As mentioned earlier, you may prefer to use a plywood or steel area for this purpose. Make sure the area is level and that it will provide a firm base on which to assemble the frames.

   A boat has two basic types of framing: transverse framing, generally referred to as the frames, and longitudinal framing, usually known as the stringers, which also includes chine bars, deck stringers, and the like. Here we are discussing the frames.

In metal boats, transverse-framing material may be flat bar, L-angle or T-bar. Your plans will most likely stipulate which is appropriate. For many years, flat-bar frames have been favoured in steel boats. Many designers have given this advice. The reason usually quoted is that L-angle is hard to protect from corrosion, and that the angled portion adds unnecessary weight. More recently, however, we have considered angle in a more favourable light.

   Against the above objections, an argument can be made for angle. The flange will provide an excellent place to attach the lining material. Corrosion problems can be overcome by using prime-coated materials and sprayed-in foam insulation, which is now common practice in metal boat hulls. Regarding the extra weight of angle, I believe that this is not a problem in larger and heavier displacement boats. All that has been said about angle can also be applied to T-bar frames. Aluminum boats will have transverse frames made of angle, T-bar, or a proprietary extrusion that has some type of bulb or flange.

   Some builders may prefer to have the deck beams included as part of the original frame construction. If you prefer this arrangement, you’ll find it’s best used when you’re building upright. Also, including the beams at this stage may interfere with the installation of the larger and heavier items (such as the engine, etc.) in the hull at a later stage of the construction. If you are building the hull inverted you will find that the deck beams interfere with access under the boat. My experience is that the deck beams are best installed after the hull is fully plated and already turned upright and the heavier items are already installed in the hull. It is easier to check for a fair sheerline before installing the beams. In some cases—for instance, if your boat has a bulwark—this last objection may not apply, To summarize, if you’re building upright, then you may consider installing the deck beams as part of the original frame, but if you’re building inverted, don’t install the beams until after the hull is upright and preferably with the engine, etc., already placed inside the hull.

   After you have established how many frames you’ll need, and which material you’ll be using—L-angle, flat bar or T-bar, it’s now time to start cutting the correct lengths of material to form each frame. An angle grinder fitted with a suitable wheel can be used for cutting the frame material to the correct length and angle. Some builders prefer to use their oxyacetylene equipment for making these cuts, and no doubt you have your own preference. Cuts made with the angle grinder are more accurate and will be preferred by many builders. A neat trick is to make up strips of cardboard as templates for the angle joins on the frames. Use cardboard that is the same width as your frame material. Lay two cardboard strips directly over the joint on your patterns, ensuring that there is sufficient overlap to allow you to cut through both layers of cardboard using a straightedge that bisects the angle. You have now created a pattern that forms the angle required for both parts of the framing material. Transfer these angles to your lengths of framing material and now you can neatly cut each angle to provide the basis for a perfect join. You may prefer to use a carpenter’s bevel-gauge or a plastic protractor to obtain the correct angles. You can always clean up your angles by using the grinder, but it’s preferable to make the correct cuts in the first place.

Next, tack-weld the frames together. After checking against the patterns, make the final welds. It’s worth noting that a very small incorrect angle at the chine can become a large error at the sheer or keel. The frames may be made up in two halves, or one half on top of another, and then opened up like a clamshell to form the frame. You must carefully check the fully assembled and welded frames against the patterns and one half against the other. Accuracy is vital at this stage. It’s not a good idea to tack the various parts of the frame to the steel master plate or loft plate. Frames assembled in this manner can have built-in tension that will cause them to change shape when released from the loft-plate floor.

   A good way to avoid distortion is to follow the same sequence for assembling each frame. For instance, place a tack-weld at the center of each angle joint and let it cool for a few seconds before tacking either ends of the angle. Several frame sections can be done in sequence, ensuring that minimum time is lost through waiting for welds to cool, before proceeding to the next step in the assembly process. The object is to keep the job moving forward, without setting up stresses in the frames, and avoiding unnecessary delays in the work schedule.

   Once you’ve tacked the frame together, you should be able to move it about and check the accuracy against the master patterns that have been scribed on the metal or plywood loft floor. When one side of the frame is tacked together, you should turn it over and tack the other side. Again, check the accuracy against the master patterns.

You’ll be installing some form of headstock across the frame. This headstock may be used to support the frame on the strongback or bedlogs (see below). Make sure you install other bracing between the headstock and the sides and bottom of the frame, otherwise it will be too flexible and impossible to set in position on the strongback.

   Mark all of the important reference points on all frames. Include such points as the load or datum waterline (LWL or DWL), the sheerline, the deck line (if this is below the sheer), and any other points indicated on your full-size patterns. Finally, please follow the designer’s specifications for making your frames; never overlap the ends of the frame bar where they join, in the misguided belief that you’re making the boat stronger.   Overlapped metal can harbour moisture and promote corrosion. It also adds unnecessary weight and looks unsightly, as well as giving your boat an amateurish appearance. On the same theme, don’t add extra reinforcing plates or permanent gussets at the frame joints; these items were necessary for frames in wooden boats but add extra unnecessary weight in a metal hull.

   There are several ways to make the various cuts in the frame to accept the stringers, deck shelf, and sheer stringer. One method is to divide each area between the chines into equal spaces and, using a square, mark in a notch for each stringer. These notches may then be cut while the frame is still on the loft floor. If you prefer this method, it may be better to cut the notches before tacking the frame together; cutting the notches will probably distort the frame part, so this is best corrected before you assemble the frame.

We recommend standing up the frames and then marking in all of the stringer locations on the frames, using a batten to simulate the fair curve of each stringer. The next step is to take the frames down and cut the slots. Finally, check each frame for accuracy before reinstalling it in its correct location. This method is time-consuming but it does ensure that you get a fair set of stringer notches and, in turn, a fair set of stringers. This method also makes sure that the final frame is still the shape intended by the designer, and in due course it will contribute to building an attractive and fair hull.

   This is a good time to think about drainage inside your hull. When the hull is in its correct position, there will be low points on the stringers. Careful observation will enable you to locate them at this stage. This is the area where moisture can collect inside the hull and cause rust.

   If you’re intending to install foam insulation, especially the sprayed-in variety, you won’t have this problem because the foam should come at least to the inner edge of the stringers. The foam will provide a flush surface and leave nowhere for moisture to collect. In foam-insulated boats, any condensation that does occur will drain into the bilge. As your boat will need insulation, this is the obvious answer to a known problem.

If you’re going to install preformed insulation, instead of the sprayed-in variety, you may wish to grind small semicircular holes in the low point of the stringers. Arrange them so they leave a drain hole between the stringer and the hull plating.

   Some frames, too, will require limber (drainage) holes, but there’s no point in cutting limber holes in the areas of the frame or keel webs where the hole will be later filled with ballast. The forward and the aft frames will need limber holes to allow water to flow to the lowest point. Check our plans and give some thought to this drainage situation.

Do not confuse this type of hull with one that simply has pipe chines. True radius-chine hulls have a radius of between 24 and 36 inches (600 and 900 mm). The radius-chine hull has many benefits, including all of those attributed to a round-bilge metal hull. The fact is that the radius-chine hull is one of the easiest hull forms to build in metal. This ease of construction applies from making the frames right through to the final plating.

   All true radius-chine hulls are designed, faired, and lofted in the computer, so you’ll have accurate full-size patterns. Naturally, it’s most important to have accurate patterns from which to make your frames, and computer lofting is the best way to achieve this end. As the radius sections are all of the same radius, it’s only the amount of arc around the curve that will vary. This means that you won’t need to transfer all of the radius curves to your loft floor. Transfer only the straight frame sections. Make sure that the ends of these lines are clearly defined. Use a check mark to give a clear definition to the ends. Next, simply cut the straight lengths of framing and place them in position. Now, cut the exact lengths of curved frame material that have been pre-bent to the correct radius.

   You can either bend the radius-frame material yourself, or have it bent by an outside metal shop. Assuming that you farm out this work, we recommend that you have the radius-frame sections, stem bar, and lengths of plate all bent to the correct radius section at the same time (see Radius-Chine Hulls in Chapter 8, Plating Your Hull). The  techniques used for assembling the frames of your radius-chine hull are virtually the same as those used for the other hull forms.

If you’re building a “frameless” boat, that is, a hull with only a few frames, or one that has no transverse frames, then you may use angle frames as a mold, and these will not remain in the boat. When you’re building the “mold” for a frameless boat, you may find it possible to eliminate every second frame when setting up the shape of the hull. When the designer prepares computer-designed lines, it’s usual to have only four to six control sections (similar to frames) and the remainder of the hull is faired through these sections. Most light-to-medium-displacement steel-chine hulls (not radius-chine) under, say, 40 feet (12.19 m), are suitable for building with the frameless technique. Contact the designer of your boat if you’re interested in using this method. Ask if some frames may be eliminated, either in the finished boat or in the setting-up mold. Some frameless hulls are built over a timber framework; this may be helpful if you’re building a metal hull under 35 feet (10.66 m) and have limited metalworking experience. You could build the timber framework yourself, and then hire an experienced welder to weld up the hull.

PREPARING TO BUILD STEM, BACKBONE AND KEEL

You’ll find that metal boats use many different sections for building the stem. Some boats feature a stem that is a flat bar on edge. This, in fact, is the material specified for many of our sailboat designs. Other designers favour solid round bar, round or rectangular tube, or rolled plate. In some sailboats and many powerboat designs, we favour stems that incorporate a rolled plate above the top chine. Your homemade bending machine will come into use for bending the flat-bar stem if part or all or the stem is to be formed from this material. As mentioned above some stems may include a conical section of rolled plate.

   The aft section of the backbone may be installed on-edge without your having to form it in a bending device. Some stems, such as those used in the Spray designs, may be constructed using a box section of similar construction to that used to fabricate the keel. You’ll need to make plywood or hardboard patterns for the sides of the box stem, and trial-fit them before cutting any metal.

   The leading edge of the keel will be flat bar, split pipe, full pipe, or rolled plate. Flat-bar leading edges for the keel are only satisfactory for very small powerboats. In most cases, a rounded leading edge—similar to the leading edge of an aircraft wing—will not only be stronger and less liable to damage, but will also offer a better passage through the water for the keel. The aft end of the keel is usually formed of flat bar on edge.

Bedlogs and Strong-backs

   For hulls built upside down, your plans should include details of preparing the base needed to set up the hull frames. This base can have one of several names including bedlog or strongback. In our plans, a set of bedlogs consists of a framework of suitably sized timber or steel I beams placed on a prepared surface. The surface can be concrete, packed earth, or other similar base. If a packed-earth floor is used, you’d be wise to install strategically placed concrete pads capable of supporting the bedlogs and the completed hull. You’re building a foundation, albeit a temporary one, and it has to support the hull until it is plated. In the case of a hull built upright, the strongback or setting-up bedlogs will be required to remain true until the boat is completed.

   The strongback is a framework that’s usually about 3 feet (910 mm) off the ground or floor. It’s used to support frames on a hull being built upside down. The idea of the strongback is to have the inverted hull set up far enough above the floor so the builder could easily climb underneath the hull to undertake the necessary tack-welding of the stringers to the inner hull plating before the turn-over stage. More recently, however, we’ve found it easier to simply extend the frames to a common headstock or upper baseline. Using this method, we ensure that the hull will be far enough off the floor to clear the stem, and allow a welder to have easy access to the interior of the hull. In all setting-up methods, a wire stretched tightly down the centreline will be an essential part of the procedure.

GANTRY

You may consider installing a gantry that can be used to erect the frames and assist in installing the plating. If you’re assembling your hull inside a commercial building, you may be fortunate in having an overhead gantry already available; otherwise you’ll have to arrange your own. The track will consist of a pair of channel rails made from some U-section steel that run full-length each side of the hull. Two sets of A-frames set to run on wheels in the channel and an I beam rigged with one or more chain blocks, chain falls, or a chain hoist (all the same device), will complete the arrangement. An even simpler gantry is a tripod with an attachment point for a chain hoist. You can use it to lift the plates and other large metal sections.

BUILDING UPRIGHT

Professional builders have many methods of setting up the frames, transom, and stem, to build a metal hull upright. These methods, while suitable for the professional, could in some cases cause problems for less experienced builders. For instance, they could allow errors to creep in, resulting in a twisted or otherwise less-than-fair hull structure. It’s the responsibility of the designer, especially when dealing with a less-experienced builder, to ensure that the method of setting up the hull is well detailed in the plans. This will make things easier for the first-time builder who otherwise may be unsure of how to proceed. Experienced welders, metal workers, and fitters who had no previous boatbuilding experience have built many fine metal boats but even they need some guidance when setting up the hull; so no matter how much welding knowledge you have please take care in these first steps of your boatbuilding project.

   For the less-experienced builder, the secret is to have a well-prepared building frame, strongback, or similar arrangement to allow the frames to be set up in their correct locations and to avoid errors. One method we have used is to build a framework for a shed-like structure, and support the frames from overhead rafters. Another way is to build a set of bedlogs and use pipe supports to hold the frames in position until the keel, stringers, chine bars, and stem are installed. With a hull built upright, once the keel is plated the structure can be more or less self-supporting, with the weight mostly on the keel. Additional supports should be installed under the ends and sides of the hull to avoid sagging during construction.

By now you will have constructed and assembled all of the elements of the framework. Now you can start to install the frames on the strongback or bedlogs. A tensioned wire marks the centreline of the building jig. This wire will remain in position until the hull is turned upright.

   You’ll need a carpenter’s rule, a steel measuring tape (at least as long as your boat), a plumb bob, a large carpenter’s square, a spirit level about 3 feet (1 m) long, and a line spirit level. Each frame must be square off the strongback, and must be parallel with its neighbour. Use the plumb bob to ensure the frame is vertical.

   After you’ve marked out the strongback or bedlogs with the correct station spacing, you can start with station 5 or the midsection frame (the same frame in many cases) and install it firmly in position. Work alternatively fore and aft, installing the frames until they’re all in place. Needless to say, you should check everything several times until you’re absolutely sure the whole structure is true and fair. We have seen boats with stems that are crooked and keels whose leading edges are out of line; it’s really a sad sight. Your eye will be one of your best guides to fairness; use it, and then check again by measuring and use the level, square and plumb bob to ensure you have everything set up true and fair. There is a trick to avoid having the frames cause a "starved cow" look in the final plating. The frames ahead of the midsection should have their forward edges on the spacing line and the frames aft of the midsection should be installed so their aft edges are on the spacing line. The result is that when the plating crosses the frame, only one edge of the frame touches the plating, and the plate is not fighting its way around the frame.

   Next, install the stem, the aft centreline bar, and the centreline transom bar. The transom may be left off at this stage and not installed until after the plating is completed on the remainder of the hull. Generally, you don’t install the keel sides or the bottom of the keel plate until after the hull is plated and has the strength to support the heavier plating that is usually specified for the keel. In some designs we have specified 1/2 inch (12 mm) plate for the bottom of the keel; the idea being that this forms part of the ballast. You may substitute this for 1/4 inch (6 mm) plate as this will make for easier handling of the bottom of keel plate.

   In some designs, a few of the bulkheads may be included as frames; this works fine, providing you do not change your interior plan after the bulkheads have been installed. The bulkheads at the forward and aft ends of the engine room will be metal, as will the anchor locker bulkhead (sometimes called the crash bulkhead). The aft bulkhead of the main cabin and the forward bulkhead of the aft cabin (at least above the deckline), will all be all metal structures. In our designs, we prefer to install at least some of the bulkheads after the hull is turned over. In most cases, the bulkheads will fall on a frame. It’s no problem to deal with intermediate bulkheads. Some bulkheads will be metal and others are best built of plywood. More recently, especially in powerboats, we have recommended that the sole plating above the engine room be steel as opposed to plywood.

   In our designs, the web or solid floors form part of the frame structure. It’s like a mini-bulkhead at each frame. These web floors generally extend up from the keel to the cabin sole, and can be used to contain and divide up tanks and ballast, and to support engine beds. There is no need to ring these web floors with framing bar; in fact, it’s a bad idea because corrosion can form between the bar and the web. The material for the webs should be the same thickness as that used for the flat of the framing; this way, there will be no change in thickness where the framing and the webs are butt-welded to the remainder of the frame.

Longitudinal framing plays a very important part in maintaining the strength of your hull. After you’ve set up the frames, it’s time to install the stringers and chine bars. We prefer flat bar for stringers. For chine bars, both solid round bar and flat bar have advantages and disadvantages. We don’t recommend closed pipe for chine bars. Steel pipe can rust inside, and it’s difficult, if not impossible, to paint or otherwise protect the interior of the pipe. When it’s used in the leading edge of the keel, you can fill the pipe with lead.

   At one time many designers and builders preferred to have the stringers stand proud of the frames by 1/8 inch (3 mm), thus avoiding every frame showing through the plated surface. If the frames are not touching the plating, it will be impossible to weld the plating to the frames; in our opinion this isn’t a problem, especially in boats under, say, 40 feet (12.19 m). Using this method, the stringers are welded to the frames and the plating is welded to the stringers. This ties the structure together and provides adequate overall strength. While the foregoing advice is well founded, it may run foul of some of the metal boat building rules and regulations of classification societies such as Lloyd's, the EU, or the U.S. Coast Guard. In any case, follow your plans with one eye on any rule that you may be required to follow to register or operate the finished boat in your area.

   Check your plans and—if necessary—with the designer of your particular boat before welding or not welding frames to the hull skin; his calculations may require one or the other practice. In any case, it is worth repeating that the frames should be set up in such a way so as to avoid their showing through the plating; frames 0 through 5 (midsection) are set so the forward edge is on the station mark; frames 6 to the stern are installed so the aft edge of the frame is on the mark.

   When installing the stringers, only tack-weld them into the slots. In most designs, the plating will take a fair curve and the stringers may need to be “relieved” so they’ll make contact with the plating throughout the hull. It is a fine judgment whether to pull the plate into the stringers or let the stringers out to lie neatly against the plating. By now your eye should be developed sufficiently to make it obvious which course to follow. In some places, the stringers will need to take the strain while the plating is pulled into place; again your eye will help you to make the right decision.

   The order of installing the stringers and chine bars (if present) can be as follows. First, install the sheer or deck stringer, making sure that you keep the ends of the frames equally spaced and square off the centreline. Next, in the case of a chine or radius-chine hull, install the chine stringers (chine bars). Although there is room for discussion as to whether you should fit flat bar, round bar, or have no chine stringers at all, your practical choice is limited: follow the recommendations shown in your plans.

RADIUS-CHINE STRINGERS

In a radius-chine hull, fit two stringers, one each side of the radius. They should be just a little inside or outside of the radius-flat joint; and as you’ll need to be able to weld the plates from inside as well as outside, the stringer must be a small distance from the intersection of the radius plate–flat plate line. One reason for having these two stringers, one each side of the radius-flat intersection, is to provide a fair guide for the actual radius plate–flat plate intersection. See your plans or full-size patterns, where this line should be clearly marked.

   We do not recommend having the radius-chine stringers right on the line that intersects the flat and radius section. If you choose this method, you would need to make sure that the plate-to-stringer weld attains full penetration from outside. Also this welding from one side only may contravene the appropiate classification societies' rules.

Intermediate Stringers

   After you have installed the sheer, deck stringer (if it’s present as a separate item), and chine stringers, check your hull for fairness. Again, use your eye (and perhaps the eyes of other more experienced builders) to ensure that the hull is progressing without being pulled out of line. Now install the intermediate stringers. The number of intermediate stringers in each chine panel will depend on the size of the hull and the particular metal being used. In most cases, a minimum spacing of 12 inches (305 mm) will be adequate.

Under no circumstances should you permanently weld the intermediate stringers into their slots at this time. You may want to release them later, to allow the stringers to take up the same line as the plate.

   This is a good time to give you the first warning: We strongly recommend that you tack-weld the entire hull, including the plating, before running any final welding; don't do any finish welds until the whole structure is completed. In the case of hulls built inverted, you need to complete the welding before turning the hull over; in boats built upright, you can assemble and tack-weld the hull, deck, and superstructure before running the final welds.

   When all the chine bars and stringers are in position, the next job is to check over the structure again to ensure that it’s fair in all aspects. A timber batten, sized approximately 1 by 1/2 inch (25 by 12 mm) and about 6 feet (2 m) long, can be laid diagonally across the hull at various locations, and your eye will probably give the best indication of the overall fairness up to this point. Check over the whole structure and make sure there are no unfair areas. On a round-bilge hull a longer batten will be needed to achieve the same results.

   Before you start plating you’ll need to decide if you’re going to install the stern and rudder tubes at this stage. It’s reasonable to install the rudder tube(s) before the plating is in place. The stern tube(s) for the propeller(s) are more difficult to place correctly at this stage. If your hull is upside down, you need some very accurate calculations and measurements to get the correct angle and position for the stern tube. It may be better to leave it until you’ve completed the plating and turned the hull. In hulls built upright, it’s easier to figure out where the engine beds are located and where you should install the stern tube.

   Just a note on stern bars. If your plans call for a stern bar that is, say, 2 to 4 inches (50 to 100 mm) wide, then you may be better served by using a flat bar placed in the fore-and-aft plane and cutting it to take the tube. When you plate the hull, the plating will have a half-oval shape around the stern tube, and the water flow to the propeller will be much cleaner and less turbulent than it would be with a wide stern bar.

One of the many advantages of a metal sailboat is that the keel will almost certainly be of the “envelope” type, and your ballast will be fully enclosed and protected within the hull. Needless to say, there are no keel bolts to worry about.

If you’re building upright, you may plate the keel first. We recommend that you install a percentage of the ballast during the construction of the keel. It’s much easier to install a fair proportion of the ballast in the keel now, while you simply have to lift it into the partially plated keel. This is a good time to remind you that the sides and bottom of the keel form part of the ballast. Remember to deduct the weight of the keel structure from the overall recommended ballast before proceeding further. In our designs, we recommend you install 75 percent of the total ballast (including the weight of the keel structure) before launching. The remaining 25 percent can be installed as trim ballast after preliminary sailing trials are completed.

   You can use inexpensive plywood or hardboard to make patterns for the sides of the keel. The leading and trailing edges, and the keel webs, will already be installed. It will depend on the actual type and design of your keel as to whether you can plate the sides in one piece. In a deep keel, you may have a problem reaching down far enough to weld the lower ends of the webs and the inside side-to-bottom intersection. In this case you may prefer to have a longitudinal join, say 12 inches (305 mm) above the bottom of the keel, or some other suitable distance. On occasion, you may find it necessary to cut slots in the keel side plating so you can plug-weld through to the webs. Your plans should give you some guidance in these areas. If you’re building the hull inverted, you’ll follow similar procedures for building the keel, but you’ll undertake this work after the other parts of the hull are fully plated.