Setting up the Cabin Sides
Your plans should provide measurements for the cabin sides, so that you can make a pattern of the sides and then raise the pattern into position to check the accuracy before cutting metal and welding the sides in place. In boats supplied as steel kits or cutting files, the cabin sides are already pre-cut to the exact shape. If your design includes a pilothouse, it may be part of the cabin sides or installed as a separate item.
It’s often preferable to have the sides of the pilothouse set slightly inboard of the line of the cabin-side to cabin-top intersection. This step inward or knuckle will break up the large pilothouse-cabin-side area, and reduce the apparent height of the combined structure. You can also change the paint colour at this intersection, which will further enhance the appearance by avoiding the slab-sided look. Until you’ve installed the other parts of the superstructure, and to ensure that the sides remain at the correct angle and position when they are first installed, you’ll need to use bracing from one side to the other, and to the bulkheads and other areas. If the windows are closer than, say, 4 inches (100 mm) from the edge of the cabin sides or pilothouse plating we recommend that you don’t make any cut-outs for windows or portlights at this time. If there is insufficient uncut metal between the cut-out and edges of the plate you may have a problem and the cut-out could cause the plate to buckle, and spoil the fair line of the sides. You may wish to mark out the windows and ports, as this will enable you to locate the correct position for any framing required in the sides.
CABIN-SIDE STIFFENERS
Depending on the size and type of boat, you may need some form of stiffeners installed in the sides of the cabin or pilothouse. If possible, always line up the cabin side stiffeners with deck and cabin-top beams, so you have, in effect, a “ring frame” that will always be stronger than a discontinuous framing system. When designing our kit boats we always try to have all frames, deck beams, cabin sides, and top beams line up as suggested above. You can use the same material for framing the sides of the cabin or pilothouse as you use for the deck and cabin-top beams. Assuming you’re using angle, the flange of the L or T will face inboard, and will assist in providing a ground to attach the lining. Don’t forget to arrange some form of insulation in the cabin sides, otherwise you’ll have condensation problems in the future.
ROUNDED AND BEVELED CORNERS
Rounded corners where the cabin sides meet the top, and where the cabin front meets the top and sides, are a nice touch. You can use sections of suitably sized pipe, say 3 inch (75 mm), cut into quarters, or have some plate rolled to a suitable radius. We like bevelled corners; they’re easy to install and give an attractive appearance when used at the intersection of the cabin top and cabin sides, and in similar areas. The hull-sides-transom intersection may be fairly sharp without spoiling the appearance of the vessel. Sharp corners are hard to keep painted, though, so all corners should have at least a small radius.
INSTALLING CABINTOP BEAMS
Installing the cabin-top beams will follow much the same procedure as you have used for the deck beams. Hatches can be framed in now or cut out later and framed from underneath. We recommend that you frame up the main hatchway at this stage, as you’ll need access to the interior when you plate the cabin-top. As the surface area of the tops of the cabin and pilothouse will most certainly be greater than that of the decks (except in a flush-deck boat), you’ll need Intercostal beams in the top. The intercostals can be installed before or after the top plating. If you install the intercostals from inside, after the plating is in place, you’ll have more welding to do from underneath; however, installing the intercostals after the plating will ensure that you don’t have any ridges in the cabin-top caused by improperly aligned and installed intercostals. The intercostals can be installed in the same manner as those for the decks. Your cabin top may receive considerable traffic, so make sure the framing is adequate. A relatively light, closely framed cabin-top will serve you better than a few, widely spaced, heavier beams. Follow your plans or consult the designer of your boat if you’re unsure regarding the framing.
INSTALLING THE CABIN FRONT
The front of the cabin will most likely be curved; about the same master camber as was used for the deck-beam camber will be about right. You only take a portion of the deck pattern. For instance, if the deck camber pattern is 6 inches (150 mm) in 15 feet (4.572 m) and the cabin front is, say, 6 feet (1.83 m), then the actual amount of round in the front will be about 2 inches (50 mm) in the 6-foot (1.83 m) of width. Cabin fronts on traditional craft can be flat. The problem with flat cabin fronts—or any part of a boat that is flat—is that they tend to look convex. For that reason, you should always have a slight amount of curvature in any flat area on your boat.
The cabin front will always have some lay-back. If a truly vertical cabin front were installed, it would look as though it were leaning outward (forward) at the top. Don’t forget to allow for the camber when installing the cabin front. You are dealing with many angles in this area, and overlooking sufficient camber allowance in the front is not an unheard-of occurrence.
PLATING THE CABIN TOP
By now, you should have the cabin sides, cabin front, and cabin top beams and intercostals all installed and checked for accuracy and fairness in all planes. You’ll need to decide if you’re going to let the top overhang the sides or front of the cabin. These overhangs have many advantages and are commonly seen. While overhangs on a fiberglass or timber boat may present a potential weak point in the construction, this doesn’t apply on a metal boat.
Check your plans regarding overhangs and “eyebrows,” as the forward cabin and pilothouse overhangs are sometimes called. Overhangs must have a trim to complete the edge; you can use pipe, solid round bar, or flat bar depending on the design of your superstructure. Side overhangs, especially on powerboats, can carry the rainwater or spray from the top out past the windows. You can see that a careful balance of cabin sides lay-in and top overhangs can improve the appearance and practicality of the design. Installing the deck plate will follow the same procedure as used for the decks. Plate flanges on overhangs can have about 5 degrees of outward angle at the bottom in relation to where the flange joins the top; this will tend to throw the water outboard away from the sides and windows and help avoiding dirty dust streaks on the cabin or pilothouse sides.
BULWARKS AND TOERAILS
If you plan to have bulwarks, you’ll have fitted a deck stringer at the appropriate height. The lines plan and/or the full-size frame patterns may show exactly where this stringer is to be installed on each frame.
If this information isn’t on your plans, you can scale off the relevant measurements and use a batten to fair in the deckline on each frame from stem to stern. Before or after the hull is plated, you can taper the inside of the frame between the deckline and the sheer. Taper the frame so that it is the right width on top to accept a flat or round bar to be installed as a cap rail.
If your bulwarks are less than say 8 inches (200 mm) at the highest point, and your hull is 3/16-inch (5 mm) plate, then the frames may finish under the deckline and it will not be necessary to have the frames extend from the deck to the sheer. You should install a pipe or solid round of a minimum of 3/4-inch (20 mm) diameter or flat bar, to complete the top edge of the bulwark plate and this may also be used to accept a wooden cap rail on the top of the bulwark plating. In any case, you should stiffen up the cut-outs; see below regarding reinforcing the edges of the apertures.
WATERWAYS AND FAIRLEADS
If your hull has bulwarks, you’ll need to install waterways on the frames and freeing ports to allow water to flow between the frames as well as through the bulwarks and off the decks. The bulk of the freeing ports must be situated at the lowest point of the deck-bulwark intersection, and the apertures must be large enough to let the water out without delay. Usually, several freeing ports spread over the lowest area are better than one large hole. All openings made in the hull plating for freeing ports, fairleads, or any similar purpose must be reinforced with suitably sized solid round bar. If docking lines are used with fairleads, the reinforcing bar in a steel hull should be stainless steel. The movement of docking lines and the anchor rode would soon wear away any paint applied to mild steel reinforcing.
THE BEVEL
A bevelled section makes an attractive intersection between the cabin or pilothouse sides and the top. There are other areas of the superstructure where a bevel can be an attractive alternative to a round edge or a plain right angle. The bevel is one of our favourite architectural features and we note that a few boat manufacturers are incorporating a bevel between the cabin sides and the top. The bevel can be of any size, but it’s usually set at about 45 degrees to the vertical and could measure 3 to 6 inches (75 mm to 150 mm) depending on the size of the boat. The use of the bevel is also a good way to disguise cabin height. If your design calls for a high cabin structure, then consider the bevel. For the record, the bevel, when used in timber work, is often referred to as an arras, or small bevel taken off the corner of a post or other feature. The arras, or bevel, does soften the appearance of any area where it is used, and it’s a great way to remove sharp edges from any object in your boat.
BUILDING OR ADDING A PILOTHOUSE
Consider a pilothouse if you want to improve the liveability and comfort of your existing or future sailboat or powerboat. Pilothouses have gained in popularity over the past 30-odd years that we’ve been recommending these structures. Almost all of our sailboat designs feature at least one version that includes a pilothouse.
If you think your boat is a candidate for one, you’ll need to consider the style and design carefully before starting the actual installation. We strongly recommend that you contact the original designers of your boat and request that they check the effect on stability and prepare plans for the structure. The addition of a pilothouse can not only provide more comfort aboard your boat, but it also can enhance its appearance and value. Conversely, a poorly designed appendage can totally destroy what you have set out to achieve.
One decision you’ll need to make is whether you prefer forward- or reverse-sloping windows. Most fishing boats and workboats have reverse-sloping windows up forward; there is a good reason for this. When steering into the sun and under other difficult conditions, reverse-facing windows give you the best view. When the rain is light, the overhang at the top of the reverse-sloping windows will keep the windows clear. Reverse windows are practical, but their appearance is not to everyone’s taste. Regular forward-sloping windows have a racier appearance and do enhance the appearance of your boat. For the best vision where you need it most, keep the slope of these windows to a reasonable angle; an extreme angle will cause vision problems.
Building a pilothouse follows a procedure similar to that used to build your regular cabin structure. You must make sure that supports of adequate proportions are placed between the generous-sized windows often associated with this structure. Additional strength by way of side framing may be required, and the windows should be divided up into reasonably sized areas. If your boat is capable of offshore work, then you should make provision for shuttering that could be fitted in the event of one or more of the windows being broken. In order to keep the weight of these rarely used storm covers to manageable proportions, you could consider building them of fiberglass sandwich, fiberglass-covered plywood, or aluminum.
ADDING A FLYBRIDGE
The main thing to consider when building a flybridge on any vessel is weight: keep it light. This structure is always high above the waterline, where weight is most undesirable. If you plan one of these items on your boat, be sure that the cabin top doesn’t have excessive camber—usually the same camber as the decks is acceptable. No matter what material you used to build your hull, deck, and superstructure, you can use aluminum or fiberglass for the construction of the flybridge. Don’t make the flybridge so large as to attract too many passengers. Keep in mind the stability of the vessel under all conditions. Some restriction on the number of seats available will help in this regard.
