Epoxy or fiberglass

Tom H.

Tom H.

Member
Pros and cons of each for building a small boat to fish ponds. Want to mount a bow t-motor as well. 11' max length.

I built a boat a few years back and used epoxy so I know what it can do. I want to build a very light boat so stiffness is going to be a plus. Thats what I was thinking buy the use of fiberglass resin over epoxy.
 
Tom~

I'm not sure of your question. Will you be building a wooden boat covered with 'glass - and you want to know whether to use epoxy resin or polyester resin? If so, I would use the epoxy.

The polyester is best for when you are building a hull (or deck, etc) laminated with just layers of 'glass (roving, mat, etc).

This help?

SJS
 
epoxy is a type of resin used to saturate fiberglass. Fiberglass is fabric made from glass fibers. Epoxy is the best resin in every possible way. There is also polyester and vinyl ester resin. I don't really understand your question. If you just paint wood with epoxy it will be protected from the environment. If you fiberglass it then it will also have the added strength inherent in fiberglass.
 
Using polyester is what I want to know about. It was used for many years before epoxy gained use. Epoxy is just too much $ for me right now. I can get the poly resin local.

I know it works. I just need to mainly know how to thin it to help soak into the wood more. And the epoxy will never be as stiff as the poly.
 
Using polyester is what I want to know about. It was used for many years before epoxy gained use. Epoxy is just too much $ for me right now. I can get the poly resin local.

I know it works. I just need to mainly know how to thin it to help soak into the wood more. And the epoxy will never be as stiff as the poly.
Click to expand...


I can't help you, but it sounds like you have a plan. Ask where you buy the resin how to thin it.

T
 
Using polyester is what I want to know about. It was used for many years before epoxy gained use. Epoxy is just too much $ for me right now. I can get the poly resin local.

I know it works. I just need to mainly know how to thin it to help soak into the wood more. And the epoxy will never be as stiff as the poly.
Click to expand...

A few seconds on the internet and there are hundreds/thousands of posts on this subject on various pro/am boat building forums. iBoats has lots of detailed how to and why to posts.

A few reads of these posts tell me that no matter how much you thin a resin it will only soak in as far as the wood pore space allows. Once the resin is curing its gone as far as physics will let it. If you do a thin coat of unthinned resin on the wood and let that cure before glassing you will be fine. Thinned resin may not go any deeper than normal resin. That would change if you were pulling a vacuum on the wood to get that extra few pores deeper into the material you were coating. Then there is the issue of thinning a resin makes it weaker. Poly resins don't stick to wood very well anyway, so making that material weaker does not sound like a good plan.

Most resin makers have detailed instructions on how to thin their products. Poly resins can use a variety of solvents. The container lable will state what and how to do this, or there will be a tech sheet at their website. So when you are shopping for the local material read the lable.

Since we have no idea what material you are buying we can't help you very much.
 
Tom~

Certainly thousands of duckboats have been 'glassed with polyester resin. I'll be refurbishing my Great South Bay Scooter later this spring - it was 'glassed by my Dad in 1954. The glass is still sound - just been painted too many times.

Is your boat plywood? Better chance for success if yes.

Either way, I do not think you can or want to thin the polyester resin. Key is to be sure you use laminating (unwaxed) resin, not the usual stuff you buy (boat supply, auto body) that's intended for the top coat. It has wax in it, which floats to the surface during cure and allows for the resin to harden (polyester only cures in an air-free environment). This is necessary whenever you want or need to sand/grind.

So, I would:

1) Coat entire hull with unwaxed resin.

2) Once it's reasonably hard (it will stay somewhat tacky), roll on a second coat of unwaxed resin.

3) Lay your cloth (6 ounce or 10 ounce) onto the wet resin.

4) Wet out any unsaturated (silvery) spots with unwaxed resin.

5) Once that cures, roll on a final coat of waxed resin.

Again, if you need to grind seams or darts or corners, do so only after after applying waxed resin and letting it cure (heat and/or sunlight helps). The unwaxed (laminating) resin never gets hard enough to grind - you'll just gum up lots of sanding discs.

One other thing: When I have to use polyester, I do it outside. I have heard that, if you can smell it, it's killing you. That may or may not be an overstatement, but I enjoy the "fragrance" only in low doses. It'll linger in a shop for months or years.

Hope this helps,

SJS
 
Using polyester is what I want to know about. It was used for many years before epoxy gained use. Epoxy is just too much $ for me right now. I can get the poly resin local.

I know it works. I just need to mainly know how to thin it to help soak into the wood more. And the epoxy will never be as stiff as the poly.
Click to expand...

Tom,
We use a lot of Polyester resin in our boat building. If you'd like...give me a call and I'd be happy to answer any questions you may have. Polyester is a great medium and should be used with some CSM (chopped strand mat)...that's a major "secret" to polyester resins.
Lou
give me a shout at the shop (on website): www.lockstockbarrell.com Happy to help.
 
Thanks for all the help. Now I came into something. I was talking to a friend that used to build little layout boats. He has not done anymore in about 6 years. Just got out of it.

Anyway he tells me that he has something for me. I go over and he has a box. I look inside and it is 2 gal. of resin and one gal of hardener. EPOXY! he even has new pumps! Then he hand me another box with 10yds of 4oz cloth and 100 feet of 4" tape!

Looks like I am going to be using EPOXY!

The only problem, maybe??? This stuff is about 6 years old. It has been stored in a climate controlled basement. Will it still be good? It is still all liquid and not clumps or anything like that. It is the medium from USComposites.
 
Tom,

That stuff is crap. Set it out by your mailbox and I'll swing by to get it out of your home. VERY DANGEROUS!!! Ask no questions and just place it outside!!

What is your correct address?

Mike
 
Tom,

I should be just fine. I have used epoxy that has been out in the garage for that long and no problem. If you have any concerns about it's viability just make up a couple pumps worth and check it out. Did your friend tell you what the ratio of resin to hardner is? That is important. Another piece of advice, make small batches until you gain some experience. Epoxy is great to work with but there are specific techniques that help ensure a positive outcome.
 
Opened up the box to see exactly what I have. It s Raka 350 and Raka 127. I figured it was USComposites stuff when he said he got it from a place in Florida.

Now I have to get the pencil and paper out to start designing my new boat. Looking to do a 11' with a bow mount t-motor for getting around. Going to add a transom as I might add a motor if I can find one small enough. I want this to fish small rivers here in Iowa. They get really shallow in the summer so this has to be light to drag it.
 
The ratio on RAKA epoxy is 2 resin to 1 hardener. Stiffness shouldn't be a problem depending on what weight glass cloth you use. I've used 3.25 oz cloth on a couple of boats and it makes for a very light boat but you sacrifice some durability. Of course the thickness of the plywood is also a factor with both durability as well as ultimate weight.
 
You must log in or register to reply here.
Back
Top