Quote:
Originally Posted by flyingfrizzle
. . . I know the outboard bracket will need more support than the outdrives did. I may build up about a 1/4" thick of glass on the inside once it is in place. . . . I will also add some knees to the transom down to the inner stringers plus when I build the bracket I will try to align the stringers in it to match up with the ones in the hull to the knees so that it all supports off one another.
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A bracket will evenly distribute motor loads across the entire transom, so you'll actually have lower concentrated loads and stresses on your rig than you'd have on a conventional outboard or outdrive transom mount!
I think the knees and 1/4" inside thickness are overkill, but I agree that lapping the cloth around into the hull bottom and sides is a good idea. That glass between the plies may add a bit of compressive strength but it adds NO bending strength to the transom because it's at the neutral axis. (When you bend an I-beam, the compressive and tensile stresses are directly proportional to the
distance from the neutral axis, which is at the center of a symmetrical part, so there is NO bending stress
at the neutral axis. A cored panel is similar to an I-beam, so the max bending stresses are at the outer surface. This is why cored panels can be so stiff and strong with relatively weak and lightweight core materials like foam. As long as you use epoxy or vinylester resin for good bond strength, that transom will be stiff as a brick!
FYI, Don Herman uses lots of Coosa in his brackets, so if you want some for a future project, it might be worth sending him a PM. He might be able to sell you just one piece for less than the retail you'd probably pay at at most places.