Fiberglass Resin vs. Epoxy Resis

[shadetree]

I am planning on putting a new floor in my boat, and this will be my second floor project in a boat. I plan to use 3/4" Marine grade plywood for the decking. I'll coat both sides with epoxy to keep water out, then glass over the top of the floor. I want to spend the least amount of money as possible, yet still have a quality floor.
Is there much difference between Polyester Resin and Epoxy Resin? Is one stronger than the other? Does epoxy resin last longer?
The boat will stay in my garage at all times, so getting rained on and having standing water in the bilge is not a problem.

 

[Bob_VT]

Re: Fiberglass Resin vs. Epoxy Resis

Well 3/4" is costly and heavy! Depending on the spans between supports you can get by with a thinner plywood choice. Any good quality paint will seal the underside of the plywood and yes epoxy is stronger than poly resin. As far as lasting longer depends on the use and abuse. Epoxy should but, poly resin also lasts a long time. What are you putting over the top of the deck? Carpet, paint, fiberglass, truck bed liner? With minimal exposure to the weather almost anything will last.

 

[shadetree]

Re: Fiberglass Resin vs. Epoxy Resis

The decking will almost be fully supported except for a 3' space in the center. ( the boat has a 3' wide bilge running from the bow to the stern otherwise, the floor is supported by foam and composite stringers.) I was planning on slapping on some good epoxy paint and throwing some sand in it for some texture. It has a gel coat, but I've never done that before. I've been told that it is epoxy resin with pigment added.

 

[jmandss]

Re: Fiberglass Resin vs. Epoxy Resis

Shadetree,

This is what I did after talking to an old retired boat guy in Texas. I replaced my floor with 1/2 inch marine grade plywood and fiberglassed the sides where the old fiberglass was still in good shape. I then applied HERCULINER that I bought at pep boys for 69.00 a gallon and one gallon was more than enough for my 14' boat. I has no idea how to fiberglass, and I did a bit of research on herculiner and thought what the heck seemed easy enough and the price was right. I may be redoing my floor in a couple of years and maybe not, I guess we will just have to wait and see. I can tell you this that I've already had a week long gas leak on the floor and the gas ate the carpet glue, but did not touch the herculiner. Here are a couple of before and after pictures of what I did.
Remember I am very much a rookie and guys on this board might call me crazy, but I guess we can call it an experiment.
Jay

 

[andy6374]

Re: Fiberglass Resin vs. Epoxy Resis

the added physical properties of epoxy are nothing compared to how the material is worked and how it is maintained. Use poly and work it well and you will have a quality end product

 

[jaymasta]

Re: Fiberglass Resin vs. Epoxy Resis

I agree with the above post, taht 3/4inch is not neccessary and just alot of extra uneeded weight, especially if it is supported by foam almost everywhere, I would say go with a 5/8inch, and just do a really got job with the polyester, it will save you ALOT of money in the end, and as long as you maintain it and put a good final coat of whatever you do it should be fine

 

[shadetree]

Re: Fiberglass Resin vs. Epoxy Resis

Thank you for all of your replies. It sure is nice to get good advice from folks who know.

 

[crunch]

Re: Fiberglass Resin vs. Epoxy Resis

One thing not touched upon.... coat the bottom of the plywood before you lay it down to water proof it.

Edit: Oops, Bob, I reread your post... but paint?

 

[oncebitten]

Re: Fiberglass Resin vs. Epoxy Resis

I wouldn't use anything but epoxy resins. Why do it twice, when you can do it right.

 

[neat]

Re: Fiberglass Resin vs. Epoxy Resis

I would never use epoxy resin. My boat was built in 1960 with poly resin and its still strong like a horse.
Once you put epoxy, you can not go back and use poly.

 

[Chris1956]

Re: Fiberglass Resin vs. Epoxy Resis

Shadetree, A couple of other items. You are going to want to fasten the new floor to the stringers and all around the perimeter of the plywood, at least until the resin hardens. Lay some strips of saturated cloth on top of the stringers, coat the bottom and edges of the plywood with resin, and lay it on the stringers. Now screw through the plywood into the stringers with stainless steel screws. Resin and glass the top of the plywood, and you are done. You may need to brace the edges of the plywood floor against the gunwale to hold the plywood in place until the resin sets. You may need to lay some saturated cloth on the foam especially around the perimeter of the plywood, so the plywood and foam are laminated together. Cement blocks are good to weight the plywood down to get a good bond.

My preference is to use pressure treated 1/2" plywood, that I let dry in my garage for a few days. I also use only poly resin for this job. The high strength of epoxy is not necessary and will triple the cost. Use two layers of cloth over the plywood, to protect from abrasion. Also, FWIW, gel coat is thickened poly resin. It is tricky to get a good finish without spraying it.

 

[neat]

Re: Fiberglass Resin vs. Epoxy Resis

...also, good luck applying gelcoat over epoxy.

 

[oncebitten]

Re: Fiberglass Resin vs. Epoxy Resis

Once you put epoxy, you can not go back and use poly.

Good point...that is an issue, if you continue to use poly... you'll definately be doing it again and again.

Sisyphus comes to mind.

And gelcoat... more poly... more blisters, good times sanding. No thanks.

 

[seven up]

Re: Fiberglass Resin vs. Epoxy Resis

I can add that the higher the mix ratios with epoxy the harder the final cure will be.

Unfortunately on my wooden project there is no place for polyester resins. Also the latest 4 gallon epoxy kit from August, 2006 was 105.50 plus 20 shipping.

Another point that has not been mentioned:
I have read that some knowledge is required for selection of your polyester resins. Waxed ? Unwaxed ?

Upon information from our local lumberyard apparently the pressure treated woods now carry a higher concentration of copper since the new regulations went into effect.

Enjoy

 

[crunch]

Re: Fiberglass Resin vs. Epoxy Resis

I can add that the higher the mix ratios with epoxy the harder the final cure will be.

Unfortunately on my wooden project there is no place for polyester resins. Also the latest 4 gallon epoxy kit from August, 2006 was 105.50 plus 20 shipping.

Another point that has not been mentioned:
I have read that some knowledge is required for selection of your polyester resins. Waxed ? Unwaxed ?

Upon information from our local lumberyard apparently the pressure treated woods now carry a higher concentration of copper since the new regulations went into effect.

Enjoy

You got a 4 gal. kit of epoxy for $105.50?... from who? I just payed $153.00 for a 3 gal. kit from Mertons and thought I got a bargain.

They changed the pressure treated formula some time last year... used to be based on arsenic, now on copper sulphate (FYI... the new treated eats galv. and SS screws in about 3 years. They now recommend ceramic coated screws )

Are there any adhesion issues with pressure treated?

 

[neat]

Re: Fiberglass Resin vs. Epoxy Resis

Good point...that is an issue, if you continue to use poly... you'll definately be doing it again and again.

Sisyphus comes to mind.

And gelcoat... more poly... more blisters, good times sanding. No thanks.

Why is that? What is your experience using poly? It is being used for boat building for so many years and if done right it is bulletproof.
I'm not saying epoxy is a bad product. It is excellent - just overpriced and is a overkill. Also, difficult to work with.

Blisters on gelcoat? Yes, still better than paint. Gelcoat is good for 20 years, paint is good for 3.

Friend of mine own a store here in Phoenix (Sticky Stuff Sales) resin, epoxy, fiberglass, gelcoat you name it. He is in boat business for 48 years. He also teach classes on the subject and guess what, he never used epoxy on the boat.
He and I are in process of filming a video on the same subject, resin, epoxy, safety, boat restoration (I own a video production business) and as soon DVD is done, I will send you a copy, beleive me, your next project will be with poly 8)

 

[oncebitten]

Re: Fiberglass Resin vs. Epoxy Resis

Okay, here's a start...

http://www.netcomposites.com/education.asp?sequence=11

I can site another ten sources that will explain that polyester resins are not only not "bullet-proof", but they aren't even waterproof. If you're talking about adding additional layers and more resin, then how does that extra weight, extra expense, extra everything make up for the simple fact that they are inferior to epoxy? <editing> I'm not saying epoxy is absolutely 100% waterproof either, but it's maybe a factor of 10 times as resistent to water infiltration as poly</editing>

I disagree that it's difficult to work with too. You can get a 2:1 ratio product that couldn't be easier to work with. And the paint on my boat has been there four years, and is likely to last another four. A linear polyurethan over a high-build epoxy primer. No problems at all.

I've built four boats... three with epoxy, one of stretched canvas covered with latex paint. I've also done some body work with both resins. After a couple years, the bondo (polyester resin) is blistering, cracking and falling off. After four years, the epoxy repair looks like the day I did it.

I'm simply saying, all these boats that people are fixing up... all made with polyester. High-end boats use epoxy now, low-end boats still use poly. If there's any wood in your boat, don't use polyester, use epoxy. Water trapped in a wood part will not only reach rot levels, but the nature of polyester resins is such that water causes the bond between the glass and the wood substrait to fail, which causes delamination.

People always come down on boats that have wood in them. It's not the wood, it's the lousy resins that cause the water penetration, degredation, delamination, rot, etc. Use the right stuff, use it properly, it will outlast polyester by a large margin.

Edited...

Now I'll go away.

 

[ondarvr]

Re: Fiberglass Resin vs. Epoxy Resis

OB

Some of what you say is accurate and some, well, not so accurate.

Nothing is really waterproof, it might be more or less water resistant than something else, but that's as far as it goe's. There are good and bad epoxies just like there are good and bad polyesters, the lower the price, well, you know, typically the lower the quality, this is true for both products. Everybody buying either product is always looking for the lowest price, not the best product, so even those looking for epoxy are not normally getting a good one when it's dirt cheap.

Epoxies are great products, but it can be difficult to take advantage of their superior properties when doing a backyard project. To get the most out of epoxy, the part needs to be well engineered and use fibers other than glass, or in combination with it, like the aerospace industry does. Epoxies are also much better glues, so bonding will be better than poly, poly is a very poor glue.

Some very (very very) high end boats use epoxy, but not many, the cost is normally not worth the benefits. Most high end boats still use polyester with a VE skin coat.

Polyester boats don't typically fall apart, if the boat has no wood, then it will last a very long time with little or no care. The problem is getting a well sealed floor or transom and keeping it that way when wood is used, The boats discussed on this site do not fail because water migrated through the polyester laminate, the wood rots because of poor designs or workmanship. Unsealed screw holes, thin or poorly rolled laminates and damage from hitting something will allow water to reach the wood and the rot begins, it makes no difference whether it's epoxy or poly.

Bondo (resin) is not designed or formulated to be used underwater, but even if it is used underwater, if it's there for only short periods of time it should hold up. If you did the repair and it's above the waterline and still failed, then you did something wrong.

If you're coating a wooden boat, then epoxy is the way to go, if you are repairing a polyester boat there is no real need to spend the money on epoxy, it just won't make that big of a difference.

 

[jaymasta]

Re: Fiberglass Resin vs. Epoxy Resis

I don't know the makeup of either except for a few months of reading that I have done on here, as well as doing a little bit of fiberglass work for my own boat a while ago, but I do know that my brother made a skim board a few years ago, he did not use fiberglass, but he did use a high quality fiberglass polyester resin from an industrial chemical store and a 1/2" piece of treated plywood, anyways he uses the skim board 3-4 times a week during the summer time for 3-4 months of the year in salt water, he has never rinsed it off, or stored it properly, last year it sat outside all year against the shed, snowed on rained on for 7+ months etc... and the board shows no signs of water intrusion at all....

 

[andy6374]

Re: Fiberglass Resin vs. Epoxy Resis

ondarvr summed it up. Like I mentioned it is way more about workmenship and maintenance than it is about epoxy vs. esters.

Even boats like Buddy Davis, Hatteras, ect.... they just started using vinylester as a HUGE upgrade, not epoxy. But both products are great.

The biggest/only benefit (as I see it) with epoxy vs ester's is the limited shrinkage that epoxy undergoes over the years. If you hand block an old hull to death and get perfect lines and use a polyester filler while doing sooo then spray it $500 worth of alwgrip materials...5 years later (really it is dependent on the amount of sunlight) you are going to get print-thru, no way around it. This is especially true with a darker color. If you were to skimcoat the hull or at least the low spots and cracks with an epoxy filler (say like system 3's quick fair) you'll get zero print thru expect where the hull has no epoxy.

Spread some poly filler now and it will still be drying and shrinking 30 years from now.

Just my 2 cents.

But I'd still you poly,vinyl over epoxy.