glassing new transom

[dcobbett]

I’d like comments and opinions on my proposed glass layup for the new transom I’m installing in my 1976, 20’ SeaCraft SF.

I’m doing the job from the outside and I’ve raised the transom from 20” to 25”. The new core is 2 layers of ¾”, 24# Penske Board. I’m using epoxy throughout, and I have 1708 (45x45) and 1808 (90x90), and some 1208 as well.

I took all of the old plywood transom and discovered bonding issues with the inner layer of matt and WR and the ends of the stringers and the bottom and sides of the hull, so I removed the old matt and WR to a line about 2” below the bottom of the inner liner. That means the lower portions of the inside layer of Penske is exposed and can be ‘glassed directly to the stringers and the bottom and portions of the sides of the hull. I’ll also install knees while I’m working in that area.

My plan is to lay on 4 or 5 layers of 1708 and 1808 (alternating) on the outside face of the transom (not carrying over the top of the transom), largest layer first, in accordance with the West booklet on repairing glass hulls. That should be close to duplicating the old skin and will let me add a layer of 6oz cloth as a finishing layer. I’ll do the same on the inside face, again, not covering the top 1-1/2” wide cut out line. Note that the exposed portion of Penkse on the inside face

SeaCraft tells me that their current transoms are 2 5/8” thick, with a 1-1/2” Coosa core, and I’d like to get more thickness of glass on my project, but I don’t want to go past the edges of the transom and on to the sides of the hull. I’m thinking about another 4 or 5 layers of glass up and over the transom cutout, feathered into the existing glass on the inside just above the splashwell drain holes, and into the outside of the new transom glass, roughly out to (between) the red lines I’ve added to one of the attached pic’s. That should give me ½”+ of new glass on each side of the main portion of the transom, plus I’ll get a box beam effect along the line of the engine cut out. I did a test with 4 layers of glass over poly over a scrap piece of 2”x6” on edge, and I was amazed at how strong the piece was when I took it off the 2”x6”.


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