TOPIC: Fiberglass Material

I am currently in the process of replacing my transom in a '67 Crestliner Del Rio with marine plywood-1-1/2" that is ready for installation. I am using vinyl ester resin and have the following materials to use: matt, woven roving, cloth, and 1708 biaxial. I have over 5/8" of space or room for the materials.

My question is what sequence of applying fiberglass materials would provide the strongest final transom? Starting from inside of the back hull, I could use matt then 24 woven then matt, insert the plywod, then matt and finally 1708 biaxial. This would be my first time and would greatly appreciate any advice, thanks.

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Roving is not necessary in this instance. Roving is used to create fast & strong building of hull and structural members that need to be light. Transom skin must be clean, If there are imperfections like pockets in the surface, mix up resin thickened with talcum or milled fiberglass fibers. Should look like the viscocity of mayo. Slop it on and smooth it with a plastic applicator. This is sort of like "grain filler" on wood refinishing. Immediately pou 1st layer of CSM over this. Wet it out with resin use a short nap paint roller till all is saturated. Roll out air bubbles with a fiberglass roller. Stipple the edges with a chip brush. Throw up another layer of mat. Wet it out completely. Roll resin on the rear face of the transom core & install it immediately. Clamp the crap out of it & clean up your mess. Clamps should remain on the transom till the core has cured fully. Just give it overnight or longer. Come in with a disc sander ro clean up the edges areound the core if anything is poking out. Be sure face of core is clean, Wet it out with resin using a short nap roller. Lay up another layer of CSM. Apply resin to the CSM till it is saturated, then lay your pre-cut clother over that. Apply resin sparingly - use the serrated roller to work the cloth into the mat. Just use enough resin to wer out ALL of the fibers. Carefully work the edges with a chip prush - using a stippling motion. Tape the edges with an innitial layer of mat, followed by a layer of cloth. Do all face glass at one time. Go easy on the hardener, most people use too much. The instructions on the can usually spec too much as well. You need working time. Put the resin in a large shallow pan. It will have extended pot life that way. I like to do work that does not start to "kick" till it's been mixed up for a couple hours.

As you suggest using CSM on the face of the core then cloth, after that tape over edges with CSM then cloth. Can I just make the CSM overlap to the sides/bottom of the hull about 5" as well as the cloth overlay to sides/bottom of the hull, basically each sheet overlappin? For cloth, I plan on using the 1708 biaxial. Thanks for your input.

Baybopper,

IF it was me, i would use epoxy (thickened with pulverized lime to mayonaise consistency. - agricultural lime is dirt cheap & works WELL.)
rather than polyester resin for this job, as it works FAR BETTER & is MUCH stonger.
(also, i want to do such repairs ONCE & i've seen numerous "polyester/wood separations" over the last decade but NONE with epoxy.)

just my opinion, satx

In thinking about it, I would encourage to tape the edges where the transom meets the hull FIRST. There is usually a bit of a gap at the edges of the transom, and the CSM can be "worked" into the crevices before the final covering is put on. The glass can be run from the transom face around the bend and into the hull. This will give a better finish with more strength.

PS - if you decide to use epoxy, you can't use the CSM. Vinylester is actually stronger than epoxy - but expoxy sticks to "old work" better than anything. Done right - the transom will not seperate - even if severely abused. And lastly, if the boat will allow it - why not bump that transom to a finished thickness of around 2" - it would be far stronger for not a big price / time increase.