Saturday, August 06, 2005

Laminating Deck Beams (2)

The prototype beam worked well; so today, I bought a sheet of 5 millimetre WBP plywood for making 56 x 25mm x 1220 mm strips, to laminate all 7 deck beams for Paradox, but first I must cut out and assemble the jig from 16 mm Conti Board. That’s more than strong enough to take the loads imposed upon it when the clamps are in place. I shall use two curved pieces of Conti Board bonded together, giving a combined thickness of 32 millimetres; this curved surface will be used to form the underneath sides of the beams. A third piece of Conti Board bonded to the other pieces will provide a backing surface for the forward side of each laminated beam. This third piece will be shaped with an identical curve, which will overlap the other curved surface by 45 mm. Its edge will be in line with the uppermost surface of each beam, when the clamps have been tightened after applying epoxy.

To accurately draw the guide lines with a carpenter’s pencil on the plywood for cutting the strips, I’ll use an 8 foot skirting board, which has a straight edge. Each beam will have a fore and aft dimension of 25 mm; therefore I’ll need to allow at least 2 mm between strips to compensate for loss while cutting the plywood with a jigsaw, and for finishing the sides of beams when the epoxy has set.

I’m looking forward to making the jig, but I’m not quite so sure that I’ll enjoy laminating the beams, each consisting of 5 x 1220 mm strips of plywood, which will mean applying slightly thickened epoxy to 8 of their sides. Bundling the strips together and bending them around the jig will be a tacky business, and I’ll need to be careful not to let the epoxy come into contact with the clamps. To prevent the beams sticking to the jig, I’ll protect it with thin plastic sheeting. Ideally I’ll need to leave each laminated beam clamped to the jig for a minimum of 48 hours; that means I may be able to make 3 beams a week; therefore they should all be finished in just over a fortnight. Hooray!

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