W22 Building Header Building the W22 Trimaran

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November 20, 2013

W22 Build INDEX

Building the W22—Article #6

Glassing and Finishing of the Lower Main Hull

Build Article #5 closed with the strips and centerboard case installed and finishing work underway, with filling, sanding and fairing. After a final sealing coat of epoxy has been applied, you can start with a paint primer and then, really see what sort of fairing job you did ;-) This one is starting to look pretty sharp. In Pic-3, the lower hull is ½ turned while the centerboard action and board clearance are checked. Hull supports are shaped to suit the hull form—moulded with foam in this case—and a softer sponge-foam bonded inside with supporting plywood brackets outside—though only half complete in this photo.

I think it's easier to totally finish the exterior painting of the lower hull before turning over, as the hull will be much larger once the sides and deck are all mounted. Touching up at the knuckle will be easier than turning over again, but of course, that will depend on whether you have enough height to rig overhead tackles to handle it.

Building a W22

Once over, check that the boat is levelled with the datum waterline horizontal, so that when the times comes, the bulkheads will indeed be vertical. Clean out the interior strip joints and fill-sand the surface to prepare for the interior cloth. The smoother you make it, the better the cloth will lay. With wood strips, only 1–2 FG cloth layers will be required, but with foam, it will typically need 3 (see plans and manual). See Pic-4.

Once the cloth is in, you can trial fit the bulkheads (see Pic-5). Make sure these are vertical and also square to the centerline. Between the bulkheads, there will be a centerline girder that will add significantly to the rigidity of the hull, both for sailing loads and while on the road trailer. Once the girder pieces have been fitted between the bulkheads, the top edges should all be reinforced with short battens on each side, to make sure the sole or cockpit floor has something to sit on (see Pic-6).

Building a W22

Even before the girder pieces are fitted, the two waterstay straps should be installed. These can either be stainless straps or they can be moulded in carbon fiber as shown here, Pic-8. With CF straps, there is a tube moulded into the ends that will be slotted for the waterstay itself. With either a SS or CF strap, each will require a shallow Vee block (Pic-7 & Pic-9), first securely bonded to the adjacent bulkhead and later, also bonded to the centergirder with some rugged through-fastenings to resist any lateral movement (see plans and manual).

Building a W22

Once all is secure and coated as you choose, you can start to close in with the cockpit floor and cuddy sole. First, make sure that all possible reinforcements are installed, as access is clearly much easier before floor goes in. One such reinforcement will be some vertical stiffening under the mast, shown here in Pic-10. And perhaps an extra 150mm strip of glass down the centerline inside, could be worth its weight when you find yourself sitting on the bottom in some uncharted region! (Although it's the exterior surface of a composite boat that takes all the local damage, it's the interior tension surface of the sandwich that ultimately has to fail for the boat to be crushed or pierced.)

With all-foam structure, the floor panel undersides can readily be stiffened by simply doubling the thickness, clear of the supporting structure … as shown in Pic-11. Make sure all fiberglass is sanded off and overcoated with at least 2 coats of epoxy. It's your personal choice if you decide to paint the inner bilge areas before closing up. As the enclosed epoxy is not subject to UV light, it should be fine without a paint overcoat – but a white painted interior might be easier to keep clean. Each owner can plan his own lockers and access to the inner-bottom, but finally, the interior will start to look like Pic-12.

Building a W22

Build Article #7 will cover more interior parts and also preparation of the side panels.

See W22 Build INDEX for earlier articles.

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