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.