[Terry England]

Flexpat, We recently removed a couple of sterndrives in an old 25 Bertram and need to fill in and replace the transom for outboards. (I know this is a Seacraft site) The old Bert's, like the 23' Formulas had a slightly curved transom with a flat spot in the center 1/2 for the transom housings to bolt through so the engines sat in there straight. Since we were concerned about too much flex with the transom plywood not going the full width of the boat we switched to three 1/2' marine plywood rather than two 3/4" which is still approximately the same 1-1/2". We used a 15% styrene thinned wash coat of Polyester on each face of the plywood and laminated 2 - 1.5 oz. mat layers in between the two laminates of the three laters of 1/2" marine plywood. The styrene wash coat only seems to sink in a couple of veneers of the plywood, so with the 1/2" although it doesn't penetrate any further than it does with the 3/4" it comes much closer to complete saturation because the face surfaces are 1/4" closer to each other. We drilled 1/4" holes about 6" O.C., both ways, in the "field" to let any air out that might be trapped when laminating the whole mess together. We put some plastic down on the concrete floor, wet out and stacked the three pieces on top of one another with the glass and mat layers in between then stacked and layer of cement blocks on top as the polyester squished out through the 1/4" holes. We cut some narrow (2") by deep (24") plywood "horseshoes" the next day and after having cleaned up the inside face of the transom fiberglass we squeezed the new transom toghter with two layers of 1-1/2 oz. mat and ployester in between. We shoved the horseshoes down and wedged them tight and clamped a bunch of vice-grip welding clamps everywhere else. This is what we came up with, but I'm sure there are many other theories. There are some pictures on an album on my member profile that might help you see this set up. Good luck on your project.