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December 18, 2013

W22 Build INDEX

Building the W22—Article #7

Starting the Main Hull Topsides

Build Article #6 covered the completion of the Lower Main Hull that includes the rounded area below the waterline, up to the knuckle flange just above it. You can clearly see the 60mm flange (beige) just above the knuckle in Photo‑1.

This flange is solidly bonded to the lower part and creates a backing for readily lapping on the upper side panels. Photo‑2 shows how the bulkheads are fitted into the lower hull and attached with 100mm bias tape on both sides.

Although using a good quality foam core is generally more expensive than plywood, it's not only lighter and rot-proof, but shows another advantage to be factored in. Look closely at Photo‑3 and you'll see the possibility of also having very little waste. As the joining cement is much stronger than the foam, small pieces can be bonded together before a panel is enclosed in glass and the resulting panel will be no weaker than one using a new sheet of foam.

Building a W22

Whether you close-in the bottom volume as watertight or arrange for access panels for stowage, is really your own choice, but it's certainly advisable to make some areas very watertight, to provide emergency buoyancy in the rare event of being holed. Of course, building in wood and even more so with foam core, will provide a natural floatability of the structure, but enclosing some areas, both at the bow and stern, will ensure that a damaged structure will float higher. As a guideline, I would recommend about 30% of the below-hull volume be enclosed, and fitted with relatively small watertight hatches just for inspection access.

The panel shown in Photos‑4 and 5, could either be permanently closed or arranged to be removable for stowage.

Building a W22

UPPER SIDES

From the knuckle line up, the side panels are primarily of flat pre-sheathed ply or can optionally be of foam core as in the example shown in these photos.

The side panels are first marked off with a horizontal datum line plus vertical measuring lines (every 500 mm) – all as detailed on Sheet 4 of the Building Plans. Once these are cut to approx. size, they can be placed in position and the butting vertical edges marked off for final fitting. Ideally, the side panels should be slightly oversize in the vertical direction, as the lower edge is designed to slightly run over the knuckle flange as it's then easy to clean up and fair, once the sides are all bonded in place.

If using sheathed 6mm ply, the manual suggests to use a thin ply butt strap (with beveled edges) on the inside of the main ply, as this will much simplify the fitting. By clamping a temporary gunwale strip around the exterior at the top of the panel, the three 8ft lengths that make up each full-length side panel will be kept fair, and the inner butt straps will cover for any slight variation at the panel joints. Once in final position, the panel ends can be bonded to the butt‑straps, using temporary sheet‑metal screws to pull the surfaces together. When cured, the screws are removed and the exterior of the joint ground down by at least 4mm, with progressively wider strips of fiberglass cloth tape laid into the broad vee so formed, completing the join with what is effectively, a flush fiberglass scarf joint.

If working with a foam core, the inner side of all side panels will first be sheathed to give the panel more rigidity and fairness. This also provides an initial smooth fiberglass finish to the interior. The panel ends can be cut to butt well at their vertical joint. It would then be a good idea to remove each panel and grind down the core for 50-75 mm from the panel edge, to create a recess of say 1 mm deep on both sides. Once put back in place, a 100-150mm glass tape is placed into this recess and finished flush, before any further glass is added. One such stripe can just be seen in photo-6, seen as a grey area as the panel curves out of sight.

Building a W22

Photos 6-7 show an upper side panel being 'trial-fitted' around the vertical frames and bulkheads that were set up in earlier Articles. Once in place in a fair line, these main topside panels can be bonded to the knuckle flange and also to the permanent bulkheads, stem and transom (see Manual for details). The use of a temporary gunwale rail clamped to the exterior top edge is recommended, to ensure the topside is kept fair during this step.

In photo‑8 below, we can start to see how the main hull will look with the sides in place, although there's still about 150 mm to add to its depth via the extended gunwales and enclosing deck. In this final photo for 2013, the sides are only positioned temporarily but once bonded to the knuckle flange and bulkheads and the upper gunwale panels are attached, the false 'bumper' bow of foam and glass can then be added to make all look neat and professional.

Building a W22

Well, we now have to give this builder a break! He will be away from our northern winter doing some house building farther south, and not be available to continue with his boat until next Spring—so unless plans change, do not expect another W22 build‑article until May 2014. (Sorry guys, but this is a typical family man with other things to look after, other than his boat ;‑).

Overall though, the articles so far should give others a really great start, and even a fast worker will not be kept waiting should they even get started today!

Regardless, all required info for the 3 hulls plus beams are well documented in the Build Manual, so it's actually a good time to get started on your own W22! So, while the low introductory price is still valid (change due in 2014), write to me for the W22 Plan Package through the website form here: Questions Form

When available, Build Article #8 will cover the fitting of the upper sides and more work on the remainder of the main hull.


See W22 Build INDEX for earlier articles.


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