This is what we're going to use to make our strongback. Well, most of it at least. Made from scap wood that has acumulated over the years. I traced the radius onto the jig base from a pattern made from 113's cabin top. The pattern was exact-so it included all the waves and woobees. Then I faired line to give a smooth arc the was the best fit at the twelve contact points of the jig knowing that some of the strongback will need to be ground away and some spots may need to be filled when jacked into place. Then I built up the two by four blocks along that line. The blocks on the ends of the arc are just stop blocks to keep the plys from running wild. They are in the same plane or angle as the sides of the coach roof but they are 3/8" wider so we can shape the ends of the strongback to a smooth edge. The greatest unsupported span of our strongback will be 24" so I'm opting for a slimmer, trimmer beam than Ebb. I'm planning for 2 3/4" wide by 3 1/2" tall. The four pieces of wood spanning the blocks are 2 3/4" off of the jig surface and are there to keep the plys from slipping off eack other when pressure is applied with the clamps. They are pre-drilled and mounted with screws so they will be removed to allow the glued plys to be introduced to the jig, then replaced and 'snugged' as needed when the cranking starts. It all sounds straight forward doesn't it? Wish us luck or send beer!
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