Fiberglass Resin vs. Epoxy Resis

[seven up]

Re: Fiberglass Resin vs. Epoxy Resis

shadetree,

When using the epoxy/polyester products on wood you may have noticed from this thread that sealing the wood and keeping it sealed is a priority.

Reading threads like this one and many others has literally saved my project boat from the woodpile.

One especially helpful thread was about using epoxy as a sealer. Well...the epoxy mix of resin + hardener is "watered" with laquer thinner and then brushed/poured/rolled onto the bare wood. In my experience using marine grade woods I have found that this thinned epoxy disappears into the prepared wood. This is, however, a low-priced alternative to commercially produced products made exclusively for this purpose.

I have tried diluting up to 100% and it is truely the consistency of water. There are many types of epoxies and polyesters. I have no experience with polyesters.

And shadetree, if you are putting in chopped strand mat, I have recently heard several times that epoxy will not work.

custombycrunch,

the company i use for epoxy and etc. is US Composites. was surprised when looking at the site yesterday that gelcoat/dump guns are like 120.00. maybe my next project will be fiberglass.
this latest order was for gallon 14-17. no delaminations or failures. always has kicked and cured as it should. the pumps were a waste of my time and caused some mixing screwups with the 3:1.

Enjoy

 

[ondarvr]

Re: Fiberglass Resin vs. Epoxy Resis

SU

The thinned epoxies don't protect the wood as well as straight epoxy does, nor do they cure as well. Testing shows that wood sealed with thinned epoxy absorbs more water than the same wood using straight epoxy. Both epoxy and polyester resins are greatly affected by adding solvents, the more you add, the less water, chemical and heat resistant they will be, and they will also be weaker.

 

[seven up]

Re: Fiberglass Resin vs. Epoxy Resis

ondarvr

as i wrote...diluting as a sealer. not for laminating or glueing. like an undercoating or pre-treating before the regular epoxy is applied. the diluted mix penetrates.

Enjoy

 

[strizzy]

Re: Fiberglass Resin vs. Epoxy Resis

I am happy to see the post by ondarvr. I do believe poly resin is perfectly fine for almost all the application that are seen on this forum. I don't believe that the fact of saying how all these boats need work because poly was used. I have seen many rotted boats and what I have noticed is that if there was a problem with say a transom or stinger(s) (and even some floors), there usually was a good explanation that lead to the MAIN reason they needed replacing. Whether it was lack of sealant, to just saturation of water (bad cover, drain plug left in, or the owner just didn't take care of the boat, etc). Because of that IMHO I think poly resin is fine.

 

[oncebitten]

Re: Fiberglass Resin vs. Epoxy Resis

Do the research, you can't fight the science... epoxy is better for marine applications, sheer strength, flexibility, water absorbtion, you name it. And I never said epoxy was 100% waterproof... read again please. But I object to poly being touted as bullet proof when it is simply the lesser of two products. Epoxy is more expensive, yes, but like you said, you get what you pay for. $500 For awlgrip (paint), and then go cheep with the lamination and glue materials- sounds like a pretty good indication of where the priorities are. That is mass production thinking. That's manufacturing and cost/benefit talk. Great for the company, bad for the consumer. As far as Bondo goes, it's not submerged, it's on my truck... and it's crap, and it's poly. Other fender, epoxy, looks fantastic.

Just asking for a little truth in advertising. Poly- it's cheap, and good'nuff. Epoxy- it's expensive and superior. That's all.

Don't mean to hyjack or start a fight, just defending my position. Peace.

 

[ondarvr]

Re: Fiberglass Resin vs. Epoxy Resis

OB

There is no argument, epoxy is a stronger and more water resistant product, but polyester meets the needs of most marine applications, so spending more money for little, if any improvement is not needed IMO. You said you fixed your truck with it (epoxy and poly), that means you decided not to spend the extra money and buy a new better fender, I would most likely do the same thing, but it's hard to say the new one wouldn't be better, it just may not be what's needed for the repair on your truck. It's the same thing for most boats discussed on this site.

I have no idea on what kind of repair you did on your truck, but if the repair failed, then it was either done inncorectly or you chose the wrong product(s) to do the job. I have either repaired or built most things that float or drive on the road and I almost never use epoxy ( there are some types of products that only epoxy will bond to) and the repairs don't fail.

You can custom order a boat and have it made from epoxy if you have enough $$$, did you? neither did I. The cost is far to high on this type of construction for the average guy to afford, so boat manufacturers build what people can afford, that means poly. Mass production thinking is the only way we can afford most, if not all of the stuff (including toys) we buy, so is it bad that a company makes something you can fit in your budget. You can always make something out of a better more expensive product (metal, fabric, spice, plastic, fiber, etc) so where do you stop?

I didn't mean to imply that you said epoxy is water proof, and poly isn't, I just hear it so often that I put it in there for those that think it is.

 

[BillP]

Re: Fiberglass Resin vs. Epoxy Resis

The primary reasons for using epoxy on trailer boat projects like this are better tenacity, structural gluing and structural gap filling. It is virtually impossible to find rot or damage caused by water penetrating through a poly glass job applied properly. Poly or epoxy, any trailer boat you find with rotten wood is due to poor engineering, workmanship or a fracture in the glass.

On a different tack...It can be argued that "science" proves water penetrates all the way through a wood plank. In theory it also proves a planked wood boat will always leak...but in practice, planked boats have dusty bilges (unless caulked seams are leaking). "Science" makes the same argument about polyester. So much for scientific theory compared to applied science.

B.

 

[Mark42]

Re: Fiberglass Resin vs. Epoxy Resis

I agree that epoxy has superior attributes over polyester. But you will be hard pressed to convince me that polyester is the wrong material to build or repair a boat with. Especially considering that I own a boat made from polyster resin that is 42 years old and the polyester hull has yet to show signs of failing. Even the poly gelcoat just needed a polish to bring it back.

Epoxy has its place and it is a wonderful material. Its expense and incompatability with other materials puts it in the back seat (in my opinion) when compared to polyester (or vinylester) resin for boat building and repairs.

So why does a 42 year old boat made from polyester not show any water infiltration damage on the hull?

 

[shadetree]

Re: Fiberglass Resin vs. Epoxy Resis

Thanks for all the replies. I'm probably going to use the poly resin due to the price. My boat is self bailing, so any water that comes in will go right out. I ran some numbers, buying epoxy resin will cost half of what I bought the boat for. The first floor I put in my 4 winns was done with epoxy and I spent probably $2000 on materials. Poly will hold up good if I do it right. Thanks again.

 

[oncebitten]

Re: Fiberglass Resin vs. Epoxy Resis

So why does a 42 year old boat made from polyester not show any water infiltration damage on the hull?

Easy... no wood. Like I said, if your boat has wood in it... like, oh, I don't know, replacing the WOOD floor or installing a new WOOD transom, then you bet water infiltration is a factor.

If you have no wood in your boat, then all you need is a bilge pump to get the water out of your boat when it's done migrating through your polyester. d

 

[BillP]

Re: Fiberglass Resin vs. Epoxy Resis

Mark42,
There is no valid data to explain it. Water migration though trailer boat hulls is gross mis-information and hype. Anyone who has been around and cut up old glass boats knows the only problem with water "migration" and rotting wood is where a fracture or crappy glass job happened. Otherwise the bilges stay bone dry and wood perfect.

Blisters are another story and happen only on boats (a fraction of them) that spend full time in the water...and then it normally takes 10-20yrs or more to happen. Even boats that have 10,000 blisters don't leak inside, the bilges stay dry and wood structure perfect.

 

[tmh]

Re: Fiberglass Resin vs. Epoxy Resis

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.

I have wondered in several threads "why not use pressure-treated plywood?" Very few have even considered it, I have no idea why. Is there a problem with getting the poly/epoxy to coat the pressure treated ply well? What's special about "matine grade" plywood? Is it pressure treated or really just a better grade than roofing plywood or thelike?

Also, I am no boat expert - quite new to learning about this stuff - but I'd wager most floor rot in older boats is NOT from water getting through the floor, but rather the floatation foam soaking it up and the wood rotting from the inside out.

If treated, plywood just won't rot that easily, i wouldn't think.

 

[strizzy]

Re: Fiberglass Resin vs. Epoxy Resis

Well it seems like anytime I see a piece of PT lumber, it is holding water of some sort... be curious if there were some numbers out there that compared the moisture content of woods...