Friday, May 09, 2008

Sheathing the Crossbeams

I've spent a considerable amount of time this week on a task that is quite tedious and doesn't show a lot of progress for the amount of labor involved - that task is sheathing the crossbeams with fiberglass. This is a necessary step, I believe to insure longevity in these essential structural components of the boat, but the way they are designed is certainly not conducive to covering in fiberglass.

I just returned from Florida last week where I was working on David's Tiki 30 and as I've mentioned here before, there's quite an improvement in beam design on the newer Tiki 30. The difference is all the solid stringers are inside the plywood panels, creating a closed triangular box section that is easy to 'glass. The Tiki 26 beams, on the other hand, are a fiberglass lay-up nightmare, requiring hours upon hours of prep work and sanding the fillets smooth, then applying the glass in partial segments that can wrap around all the exposed edges. In retrospect, if I had it to do over again I would build scaled down Tiki 30-style beams for the Tiki 26 just because of this issue. Nonetheless, the beams I have must be sheathed, and that is what I'm doing. Structurally, they are just as sound in design as the newer beams, so once this job is done I won't worry about them.

In the first photo you can see the aft beam with the top plate covered in wetted-out 6-oz. fiberglass. I used tape lines like the one at the top of the fairing to cut the fiberglass in straight lines. This layer slightly overlaps the previously applied layer that covers the front fairing.

In order to be able to wrap the fiberglass fabric around the corners, I used a router to cut all the corners to a 1/2" radius. The beam on the left is the aft beam again, showing how the glass wraps around the top plate to the upper part of the vertical plywood web.

Below is the aft beam again, now with all exposed surfaces sheathed. The fabric makes a lumpy mess in places - hard to avoid with so many overlaps. In the photo below this has been faired out with a skimming compound of epoxy mixed with phenolic microballoons and silica. It will take some work, but when the beams are all sheathed and all surfaces faired and sanded smooth, they will once again be smooth and beautiful and will look great when painted.

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