fiberglass resin vs epoxy

[larky]

I am in the process of rebuilding the wood transom in an aluminum boat. I was thinking of sealing the wood with fiberglass resin becuase it is cheaper and they sell it at the local home improvment store. Does anyone have any advise wheather this is a good idea or not. They both have similar properties. Any info would be helpfull

 

[Chris1956]

Re: fiberglass resin vs epoxy

Mayo, There are several kinds of resin. Polyester, Vinylester and Epoxy to name the top three, and group them from cheapest to most expensive. Most boats are made of polyester resin and cloth, with some better boat brands made from vinylester resin and cloth. No boat is made with epoxy resin and cloth.

In your case polyester resin is a good choice. I do not believe the epoxy would provide significantly better protection, and you certainly do not need the added strength (and cost) of epoxy. I do recommend you put coat all sides of the transom wood with resin and put two layers of cloth on the exposed parts of the transom, and make sure you have it well saturated with resin. Now put more resin to fill on the texture of the cloth, sand and paint to suit.

 

[snapperbait]

Re: fiberglass resin vs epoxy

Neither are needed in my opinion....

Well dried out pressure treated plywood would probably be the most cost effective approach...

Several thin coats of epoxy would certainly be the better of the two if you were to coat the wood.....

Polyester would most likely contribute to the wood actually rotting faster because polyester is porus (water/mosture will eventually penetrate poly)

 

[larky]

Re: fiberglass resin vs epoxy

snapperbait, I had first bought and built the transom out of pressure treated plywood, but had read later that the copper that is in the plywood (to preserve it) will react with the aluminum on my boat. I'm told that two dissimilar metals will corrode much faster if not insulated from each other

 

[JasonJ]

Re: fiberglass resin vs epoxy

Poly is fine. When water passes through a poly laminate, it is because of minor fractures that can allow the fibers in the layup to wick water through the cracks in the resin. The cracks can form from an area that was struck, or the resin was mixed improperly and is brittle. Water will not pass through poly itself, if it did then every single boat would soak up water because gelcoat is tinted polyester resin.

Yes, you can treat the transom with poly. I myself would probably go with epoxy simply due to ease of mixture, and a transom for an aluminum boat is not large enough to be cost prohibitive to use epoxy on.

 

[drewpster]

Re: fiberglass resin vs epoxy

My two cents,
There are certainly better qualified people in here but here is what I know. Water penetration into Poly resin is caused by osmosis. Water penetrates the gelcoat, then reacts with the resin creating glycol. The water then wicks into the fiberglass mat causing blisters and soft spots. ok,....this happens to boats most often when they are left in the water for long periods. I assume that your boat is a trailer boat? The most I would do is coat the poly with a barrier coat before I paint, or gelcoat, just to be on the safe side. I own an old Thundercraft tri-hull circa 1977, made of polyester, no blisters or soft spots. (because it stays on a trailer when I'm not out boating)

 

[ondarvr]

Re: fiberglass resin vs epoxy

Epoxy is the best choice if you just want to brush a coat of something on it. Epoxy is much stronger and will be less likely to crack when no glass is used, polyester will tend to crack in this type of application. Poly is not not going to allow enough water to pass through as in the "it's porus or not waterproof " opinions mentioned to rot the wood, the water gets through poorly sealed areas, or cracks.
You will need to paint the epoxy to keep UV rays away from it though.

 

[tmh]

Re: fiberglass resin vs epoxy

The stuff you see at Home Depot for example labeled "fiberglass resin" is usually Polyester Resin, which is cheaper than Epoxy Resin as stated earlier.

I agree with the poster here who said epoxy resin is better if just painting some on to seal/strengthen without fiberglass.

 

[Rockchalk]

Re: fiberglass resin vs epoxy

I redid decks in my Lund a couple winters ago. West epoxy applied with a paint roller. Not the cheapest but super easy and I think my floors may outlast my hull.

 

[ManOfwar690]

Re: fiberglass resin vs epoxy

i wouldnt do anything to it but shalac it as woo needs to breath and it rots fast if u cover it and dont alow it to breath. i have done many deck s and houses on an assortment of boats. pluss aluminum flexes and the g;ass wont on the edges there by creating a crack for water to start the rot. best to leave wood wood if you can. hope this helps