TOPIC: resin

what are your thoughts on polyester resin for boats. I got bondo stage 2 polyester and have read on here that is not good to use. just want to know what the draw backs are in using it is. on there web site they say it works on boats and even below the water line. please advise. thanks frog

Polyester resins have been used in fiberglass boats since the advent of fiberglass boats. In fact that's all they had until epoxy came along in the 70's. However it has some drawbacks as do most things. It is hazardous to work with, requires you be careful, don't breath it, don't get it on your skin. Works well with some glass fabrics and not so well with others. It is hard to clean up (use throw away brushes).

Epoxy is far easier, non toxic and bonds well. But has it's drawbacks too. It likes temps between 50F and 70 F. Lower than 50 it won't set up and above 70 thins out too much. It doesn't like humidity either. It is easily cleaned up with acetone. If you get it on you and you don't have acetone handy, finger nail polish remove will take it right off.

Bondo should not be used at all on boats. It gets hard and cracks. It does not bond well to fiberglass or wood. It is far from waterproof. It is fine for cars as long as the metal is cleaned thoroughly. But on boats it always has to be replaced.

If you want a good filler for boats use epoxy putty. You can buy it, or make your own. Epoxy with microballoons makes a great filler, but you can use all kinds of things for a filler. I have used saw dust, ground walnut shells, wood dust and even talc.

I think frogs refrring to Bondo 404 poly resin, not the filler.

IMO, the off the shelf resin available in most B&M stores is likely to have some age. Thats not good for the resin and worse for the MEKP. Esp old MEKP can drastically change tue cure times & quality of the resin.

The other 'problem' can be that its usually waxes resin, so layups need to be continous, wet on wet, or sand between layups.

Lastly, i've heard that it can be a varying mix of resin types, so what worked w the last gallon may or may not work the same for this gallon. Google types of polyester resin, iso is 1, there are others that i cant recall at the moment.

Peter is right about the benefits of using epoxy, but i wouldn't. Cost, once you go epoxy you have to continue to use epoxy and theres also the inability to gel coat over it.

M

thanks for the response. now I have another question. my boat is a 1958, and I understand that it was made with polyester resin and you can not use epoxy over poly. is that correct? yes I was referring to 402 or 404 resin made by bondo. I can not recall the numbers rite now. thanks again. i'm trying to make a choice if I go ahead with this boat, or find an aluminum boat. frog

frog wrote:

thanks for the response. now I have another question. my boat is a 1958, and I understand that it was made with polyester resin and you can not use epoxy over poly. is that correct? ........... i'm trying to make a choice if I go ahead with this boat, or find an aluminum boat. frog

You have it backwards. Poly resin won't adhere to epoxy, and as a poly resin, gelcoat won't adhere to epoxy either.

Glass vs aluminum is an entirely different discussion.

I've still got the Glastron FireFlite, but spend much more time working on, talking about and planning details for my aluminum boats.

Frog you're pretty close to one of the best fiberglass and resin suppliers in the country up there in Minneapolis. The gang at Express Composites has helped a BUNCH of folks I know out with advise and technical info, wouldn't hurt to give them a call;
www.expresscomposites.com/

Note: I'll probably use polyester resin again on this next build, due to cost differences. Best advise I can give if you use poly is DO wear a good respirator at all times, and change the filters as recommended!

Epoxy resin is very toxic ! Dont let the pleasant smell fool you , its whats called a "sensitizer" which means that once your body says i've had enough exposure to this stuff you're gonna get real sick , it may take years of bathing in the stuff for some or just a few uses with no PPE for others . Make sure you read and can understand the MSDS on all these materials . Polyester's stink at least tells you its not something you want to fool with irresponsibly .

Not for nothing polyester is more than fine for any repairs on these old boats , epoxy is good stuff but not worth the added expense or the minimal gains using it .

Also some people have an extreme skin reaction if they get polyester resin on themselves. Others not as bad but it still causes rashes. As was said, use a respirator, wear disposable gloves and cover up completely, no exposed skin.

bjcurt s right. If you start with epoxy you have to continue to use epoxy. It is not compatible with poly.

If this is an older fiberglass boat it is almost assuredly polyester. In that case use polyester.

thanks for all your replies. now I know enough to be dangerous. greg

I use 404 Tooling Polyester Resin-Isophthalic from US Composites:
( www.uscomposites.com/polyesters.html )

"404 is an isophthalic polyester resin that is used where strength and durability is a must. Experiences lower shrinkage and a higher heat distortion temperature than orthophthalic type polyester resins. Used extensively in boat hulls and in fiberglass mold construction."

Buy a sleeve of their quart mixing cups. You'll use a lot of them and they're a hell of a lot cheaper than if you buy them at Ace hardware!

jan, thanks for the info. frog

OR...You could use VE Resin (Vinyl Ester). It's kinda like the Best of both worlds. It has a lot of the properties of Epoxy and Poly and the cost is just a bit more than Poly but a lot less than Epoxy. One of the other problems with using Retail "Bondo" type resin is that it ALL contains wax and unless you can always do "Wet on Wet" lay ups this can cause issues with bonding when you do subsequent layups due to the fact that you have to sand between them and wipe down with acetone in order to get rid of the waxy surface. This does NOT happen with a good laminating resin since it does NOT have wax added to it. If you use over the counter Bondo filler products you should be aware that they use "Talc" as their main thickening agent and therefore the product will more readily absorb water and since polyester resin already has a tendency to be less water resistant than epoxy (albeit this is very miniscule) it still is not recommended for below the waterline use. Again, I think for the cost, VE resin is a VERY GOOD resin for the Boat Restorer to consider.

I just did the curved tripple ply transom with ac grade plywood and same bondo brand resin along with the 6oz cloth..on my 59 glasspar lido..all bought at home depot..couldnt be happier i cant order any big price quantities of anything right now so at 36 bucks for a gallon of resin and 5 bucks for 8 sqft of cloth or mat works for me!! Plus its my first time working with it on a boat..have done alot of bodies for off road vehicles for the baja 1000 and have had no material fails..tomrrow i am installing a new sole i will post how it comes out! Also have called local boat builders around here and they all say poly is fine..but only prob sanding between layup kinda sux tho but hey cant beat the smell lol

dustin, I have a sister who lives in phelan, was out there a few years ago. real pretty country. frog

gil_72gt-160 wrote:

Epoxy resin is very toxic ! Dont let the pleasant smell fool you , its whats called a "sensitizer" which means that once your body says i've had enough exposure to this stuff you're gonna get real sick , it may take years of bathing in the stuff for some or just a few uses with no PPE for others . Make sure you read and can understand the MSDS on all these materials . Polyester's stink at least tells you its not something you want to fool with irresponsibly .

Not for nothing polyester is more than fine for any repairs on these old boats , epoxy is good stuff but not worth the added expense or the minimal gains using it .

Interesting. Thanks for sharing. I had a similar issue with CA glue. I was fine for 30+ years, then one day my lungs were 'saturated', and I couldn't be around it anymore without runny nose, watery eyes, etc. I've been using west systems epoxy for some time now. Never knew it was toxic!!

Google epoxy sensitivity.

Same as your CA glue, one day you just have an allergic reaction. Then even minor exposure can cause a major reaction...

A few points.
polyester or epoxy, keep it off your skin and out of you lungs as best you can. You can get sensitized to it (esp epoxy) and then you will flush every time you get the least bit of fumes up your noise. This warning is mostly for those in the industry, us hobby guys are not at much risk as long as you keep the un reacted components off your skin. After either reacts fully they are harmless.

Polyester is a crappy adhesive. Its great and cheap for new construction were you can lay wet on wet. Sucks otherwise. Don't use it for repairs on polyester/glass boats, laminating glass on wood bottoms, building wood hulls, gluing wood to glass, as in replacing stringers or transoms, the bond is just not strong enough even with good prep for a mechanical bond. Yes many have got away with it, but if you want to be safe, restore it right, and not waste your time, use epoxy. It is cheap compared to time.

Epoxy is a great adhesive. Also great for wet on wet layup. Stronger than epoxy in layups. Used in high tech boat building like World Cup yachts where carbon fiber and kevlar are used to complement their strength. Yes it costs more, for good reason.

I have been told to forget Vinylester by people that should know. It is hard to come by in small quantities and is not forgiving about mixing ratios and temperatures. More for laminating anyway.

The only thing to repair fiberglass boats is epoxy. NO poly and good Lord no construction adhesive (PL) The guys doing stitch and glue plywood (me) would never use poly. There is some room for polyurethanes, to mount fittings and seal joints.

Working temps can be compensated for in large measure by changing the hardener you use from faster to slower types.

There are many formulations of epoxy available. Versions for laminating to clear coating. Different strengths also, each with compromises.

I get mine and tape, cloth and other goodies from raka.com. Decent prices and good service. They also get some great prices on short rolls of material from the local industry, the are located in central FL. Lots of boat building going on there.

And now it begins....

jbcurt00 wrote:

And now it begins....

You (we) knew it was coming, right?

Like many subjects here there are different opinions, and everyone is entitled to theirs. It's one of the things that makes this site so helpful and useful to those of us still learning. Very disappointing when any one person implies their way is the only right way, and every other method "Sucks".

OK OK...I get it.

I should back up my assertions.
There are many good books on the huge topic of building and repairing boats. I have several, my favorites are by Sam Devlin and Hub Miller. CLC Lightcraft has a lot of epoxy based info also, my friend has built several of their boats.

Other resources that generally echo the points I made.
www.boatus.com/boattech/casey/polyster-epoxy.asp
www.westsystem.com/ss/west-system-epoxy-for-fiberglass-repair/
www.amtcomposites.co.za/sites/default/files/media/howto/Advantages%20of%20Epoxy%20over%20Polyester.pdf
www.uscomposites.com/resins.html
www.multihulldesigns.com/pdf/Why%20Epoxy%20is%20Preferable%20to%20Vinylester%20and%20both%20are%20Preferable%20to%20Polyester.htm

www.google.com/search?q=strength+polyester+vs+epoxy&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb

I have built two of Jacques designs. He is the real deal marine architect. He comments on his form regularly, never sparing his view of all things boat building. I have learned much from him and building his designs. forums.bateau2.com/ Many cool designs there. www.bateau.com/

Just trying to pass on what I have learned, hoping it will save someone grief.
Mark

Chip,

WELCOME ABOARD.

yours, satx

My experience has proven that epoxy is the only resin to use when it comes to
building wooden boats. No doubt about it. However, Polyester and Vinylester are perfectly
acceptable for fiberglass boats and will form MORE than acceptable bonds to the
Old glass surfaces when those surfaces have been properly prepped. Structural
stress testing has been conducted on multiple occassions by multiple mfgs and labs
to verify this. Is epoxy a better adhesive?? Yes. Will poly do the job on
fiberglass boats and yield a totally acceptable and safe end result??? Yes. Multiple
successful restorations prove this as fact. In all my years I've never seen a
catastrophic failure caused by a polyester resin lamination breaking loose from a
stringer or transom installation and I've seen some really POOR installations. The
Polyester "Glue" adhered quite well. There is absolutely NO REASON to NOT use Polyester
or Vinylester resin to repair or restore a fiberglass boat. There is not factual
evidence that it will fail to produce structurally sound repairs on fiberglass boats.
Don't be afraid to use it as long as you do so using accepted methods.

Thanks for the welcome!

For what it's worth on the subject, I build and race model wooden boats nationally and use West Systems epoxy exclusively. I know the scale is smaller and you may start to laugh, but some of our boats are capable of speeds over 70mph!! The West Systems/wood combo makes a very rigid, durable frame.

I build and race wood rc boats also. I have been using AeroMarine epoxy from jgreer.com with good results.

One thing not mentioned here is the fact polyester is hydroscopic where as epoxy is not. If there is anything where wood encapulation is involved I know what I would use.