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Old 10-09-2014, 06:21 PM   #21
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Brand: Thor Motor Coach
Model: 2011 Four Winds 28Z
State: Michigan
Posts: 1,274
THOR #531
I can assure you that using epoxy is an established best practice for boat structural repairs where they deal with de-laminations, wood, and cracking structures on a daily basis. Once treated I have never seen epoxy fail in a boat repair. I have used epoxy for many jobs around my boats with great success.

Epoxy is used extensively in the marine industry especially when you are dealing with wood and fiberglass repairs.

It's true that if water gets behind the epoxy, it could separate, mostly because of the deterioration of the wood. It is also true that the longer the epoxy sits before curing, the more it will penetrate the wood.

My concern for moisture behind the epoxy is why I let the wood dry out for several days. The trick is then to make sure it does not leak. However, if the wood was still wet, the epoxy would not have fully cured. Since it cured OK, the wood was sufficiently dry.

Fortunately, epoxy is quite flexible, even when cured. Even if it separates from the wood, the epoxy will still retain it's shape and be like a cup of sorts. I am very confident it will not crack as there are no stress points that could result in it doing so.

You may be thinking of polyester resins, as they are fairly brittle. With polyester, if you smash it hard enough with a hammer, it can shatter. But epoxy is not really brittle at all, and will bend a lot before breaking.

Polyester resins are typically used in boat building for the fiberglass lay-up as it is significantly less expensive than epoxy (but high-end boats use epoxy for the lay-up). Epoxy is usually reserved for structural repairs.

I once saw a boat at our marina T-bone another boat with it's anchor... right in the side. They were only going a couple of kts, but I was surprised that the polyester fiberglass indented - in about 3 inches and popped back out without any lamination damage (although it was scratched). So even in that case, the polyester did not crack, which really surprised me.

While longer cure epoxy will soak in further than the quick dry stuff, I was running out of nice weather - and time - here in Michigan. Again, since it was not structural, I used the quick cure stuff rather than the normal West System epoxy I typically use.

If you end up having to do a repair on your rig, if you are concerned about the 5 minute epoxy drying too fast, I would recommend using the West epoxy. Since you live in Florida, epoxy will cure faster anyway, and you might find the 5 minute stuff curing too fast in the Florida heat.

There is another epoxy called CPES (Clear Penetrating Epoxy System) that takes about a week to dry, and has a consistency of water. It will soak in wood - depending on it's density - anywhere from 1/2" to several inches. I have seen that stuff poured into the top of a transom that had rotted away between the inside and outside fiberglass panels, and it stiffened into a complete single piece.

My repair job was not bad enough to warrant using it though.
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