To glass or not to glass (?)

[les45]

I am enlarging my fenders as I upgrade to larger tires. I've taken the old flat sided HF fenders and covered them with 3/4" plywood and 1X3. This resulted in a bunch of countersunk bolt heads that I have filled with Dap Plastic Wood. I planned to coat all the wood with Aeromarine epoxy system, primarily to seal the wood and to smooth over the grain. My question is: should I lay a fiberglass mat over everything in the first coat to help bridge the Plastic Wood covered holes? I'm not worried about strength as much as getting a good bond all over including the bolt holes.

[les45]

Based on the overwhelming responses to this thread, I decided to lay the fiberglass mat over all the wood. I'm currently sanding my second coat of epoxy. Will post progress photos on an update to my journal when I get it all complete.
(starting to wonder if the current crowd is more interested in this site for personal chit chat than the teardrop technical stuff)

[jeff0520]

Well, I didn't notice your original posting, but I'd say glass. Epoxy without some sort of fiber to reinforce it is fairly brittle. For something as exposed and subject to banging around as a fender, I'd say the reinforcement is fairly important.

[Oldragbaggers]

I'm a little late to the thread, but why mat?? Mat adds a lot of bulk and weight. Why not fiberglass cloth?

[les45]

I'm a little late to the thread, but why mat?? Mat adds a lot of bulk and weight. Why not fiberglass cloth?

Sorry about that. Wrong choice of words. In fact, I did use fiberglass cloth. While my primary purpose was to bridge the plastic wood in the bolt holes, I also wanted it to smooth over the grain and give strength to all of the epoxy like Jeff said. Second coat is sanded and I hope to have the third and final coat of epoxy on soon if the weather cooperates (rainy and cold here in the sunny south today).

[Oldragbaggers]

Good choice. I would have done exactly the same.

[CliffinGA]

Same here Larry, how's it looking so far bud?

Cliff

[Kody]

I would glass it all over with woven cloth (not chopped strand) cut on a 45 degree angle, (Bias Cut). This makes it so much easier to form and shape of the edges. I would also paint the inside (underneath surface) with a thick bitumen paint to help protect the glass from stones hitting it. With such a symmetrical shape of guard, you could also use it as a male mold and make fiberglass guards for a lighter weight. If you go this way, use 6 layers of cloth and roll them down with a F/G specific roller. By rolling the glass out, you get an extremely dense structure that is amazingly strong. I made a paddle for my kayak by rolling the glass and ended up with a thickness of 1/8" but having about 10 layers of 4 oz cloth. The curved blades, 18" x 8" were unbreakable. Just a thought.

Kody