Epoxy vs Fiberglass

[sailvayu]

Once again your source is provided by the same company selling the stuff* (more great marketing) Yes I will not argue epoxy is stronger I am saying this extra strength is not as important in most repairs as some seem to think. And ultimate shear strength is not the same as secondary bonding strength which in my mind is more a result of properly preparation as is it material strength. (methacrylate being and exception)

Sorry I was once an Epoxy zealot myself but have come to the conclusion over 30 years of using the stuff it is not really better most of the time. So I do not agree the only negative is price. As I said there are other reasons.

*Epoxyworks 22 / Winter 2004

Copyright © 2003, Gougeon Brothers, Inc. All rights reserved.
This page is maintained by Gougeon Brothers, Inc. Last modified on (11/05/03).
Reproduction in any form, in whole or in part, is expressly forbidden without the consent of the publisher. EPOXYWORKS, Gougeon Brothers, WEST SYSTEM, Episize, Scarffer and Microlight as used throughout this publication, are trademarks of Gougeon Brothers, Inc., Bay City, Michigan, USA.

[foggysail]

Very informative thread! Question--- where does Bondo fit in? Is it an epoxy?

Thanks-

[sailvayu]

Bondo is a low quality polyester filler. there are better fillers and I will usually use a vinyl-ester filler. The problem with Bondo is the solids used are not very moisture resistant and regardless of the filler binder (the resin) if the solids are not moisture resistant the filler will be poor

[minaret]

Are we really having this conversation yet again?


Poly is just fine for 99% of boat stuff. The binder in matt is starch, which is instantly dissolved by epoxy, turning into a sticky goo that's impossible to work with. Thinning your resin or anything else will not prevent this, only going to a different more expensive, hard to find binder will do that. I've been trying for some years now to convince people on this forum that the cult of epoxy is leading them astray. It's just so much more time consuming and expensive, in many cases the cons outweigh the pros. I have used thousands of gallons of both resin systems, for repair and new construction.

[sailvayu]

Wow someone who has not been sold the bill of goods by the Gougeon Brothers!

[foggysail]

Originally Posted by sailvayu

Bondo is a low quality polyester filler. there are better fillers and I will usually use a vinyl-ester filler. The problem with Bondo is the solids used are not very moisture resistant and regardless of the filler binder (the resin) if the solids are not moisture resistant the filler will be poor

Thanks for quickly explaining my question

[CharlieCobra]

We don't use West Systems very often. We use an epoxy that has a 2:1 mix ratio and contains UV inhibitors. We've used mat with this epoxy just fine.

[s/v Jedi]

Originally Posted by sailvayu

Yes I will not argue epoxy is stronger I am saying this extra strength is not as important in most repairs as some seem to think.

Agreed. And also that a polyester hull repair with epoxy gives a hard spot while a repair with the same materials provides a better (never perfect, will always be a hard spot) match.

West System is of course the manufacturer. But their lab tests are not fake like you seem to believe. There are plenty who found similar results. The document I linked showed a typical repair with 12:1 bevel where polyester restored 70% of original strength and epoxy showed 80% of original strength. I don't think you dispute that, I think you just say so because of the principle that it is the manufacturer stating it.

@all about matt: starch and cellulose are basically the same. The important thing is that epoxy immediately breaks it down while polyester gives you enough time to work with it. For once Minaret and I agree while using just slightly different words

[minaret]

Originally Posted by CharlieCobra

We don't use West Systems very often. We use an epoxy that has a 2:1 mix ratio and contains UV inhibitors. We've used mat with this epoxy just fine.

Matt by itself, or Matt sandwiched between layers of roving or in the form of stitch Matt? I doubt you've successfully done a Matt only layup with regular starch binder and epoxy.

[sailvayu]

Jedi yes I am a bit jaded by the endless "facts" reported by WEST. and I am sure there is some bias in their reports. The problem with almost all studies of this type is they by nature have to be controlled and and likewise most average boat repairs are equally UN controlled. I tend to go by real world results I see in the field. I am not dead set against epoxy per say but given a choice in most repairs I see not advantage and a few real dis advantages to it. For the armature whom I feel we are all trying to help on these forums I just like to offer an alternative and the reasons for that opinion. let the reader decide based on the information provided. But you have to admit the Gougeon Brothers have done a great job of conniving folks their goop is the best. So I prefer information from sources with no economic gain involved.

[s/v Jedi]

Originally Posted by sailvayu

you have to admit the Gougeon Brothers have done a great job of conniving folks their goop is the best. So I prefer information from sources with no economic gain involved.

They do so good because they came with their complete system for building wood-epoxy boat... which are great boats.

In Europe, MAS epoxy is very popular and it is also widely available in the US. It is as good but they lack the complete all-you-ever-need catalog of West System. That catalog also makes it easy for general, non-specialized retailers like chandleries: no need to go and select fiberglass tapes/cloth etc. as it is all in the catalog.

I still think the little repair kits from West System are pretty neat, deliver good results when following instructions, and are very expensive for what you get. Despite the price, they are very popular.

Where are the polyester repair kits in the chandleries? But you can get them at the NAPA

[ssanzone]

i have a follow up question...

if poly resin does not adhere well to cured poly, how does one layer (i am planning mat (2x) under cloth).

do i need to apply the next layer while the previous layer is still setting up?

i have never entertained this notion as i have, to date, always used expoxy.

other question, i want to lay up cloth on the new wood bulkheads and figured i would use poly and light cloth because of the volume. should i be using WEST as i am adhering cloth to wood?

-steve

[sailvayu]

Jedi yes I agree and WEST as a company is a very good one. they have a good product and provide great information on how to use it. they are a good example of a well run company that took a vanilla product and made it look like gold. And yes their wood epoxy boats are very nice. I just get worked up with the "it is the only thing to use" attitude you get with a lot of boat owners.

ssanzone, Poly DOES adhere well to Poly this is one of the biggest myths going. Proper preparation is key but the applies to almost any resin used. I have done some repairs and years later had to change things (like 20 years) and not been able to break the bond (ended up grinding it off) This secondary bonding thing comes from those repairs poorly made and I have seen as much epoxy peel off as poly with a poor job.

For your bulkhead repair I personally would use poly or vinyl-easter but I would put as much effort into good prep. In that application If you use epoxy I would wet the wood down with epoxy and let it set other wise the wood will wick the resin out of the material. use Epiglass not regular fiberglass as has been mentioned because of the binder problems. Use a layer of CMS (chopped strand mat) first then a couple layers of 1808 or the like over that. Use a fast cure resin as most epoxies do not have a great thixotrope and will run out of the material (another advantage to poly) on vertical surfaces. Mix small batches and work fast. would help to have some assistance. Like I say I personally would use polyester but epoxy in this application is fine.

[Searanger50]

So - to put the fox amongst the the chickens - which is best to repair the holes left in the hull when disused through hulls are removed?

Kevin.

[s/v Jedi]

Originally Posted by sailvayu

Jedi yes I agree and WEST as a company is a very good one. they have a good product and provide great information on how to use it. they are a good example of a well run company that took a vanilla product and made it look like gold. And yes their wood epoxy boats are very nice. I just get worked up with the "it is the only thing to use" attitude you get with a lot of boat owners.

ssanzone, Poly DOES adhere well to Poly this is one of the biggest myths going. Proper preparation is key but the applies to almost any resin used. I have done some repairs and years later had to change things (like 20 years) and not been able to break the bond (ended up grinding it off) This secondary bonding thing comes from those repairs poorly made and I have seen as much epoxy peel off as poly with a poor job.

For your bulkhead repair I personally would use poly or vinyl-easter but I would put as much effort into good prep. In that application If you use epoxy I would wet the wood down with epoxy and let it set other wise the wood will wick the resin out of the material. use Epiglass not regular fiberglass as has been mentioned because of the binder problems. Use a layer of CMS (chopped strand mat) first then a couple layers of 1808 or the like over that. Use a fast cure resin as most epoxies do not have a great thixotrope and will run out of the material (another advantage to poly) on vertical surfaces. Mix small batches and work fast. would help to have some assistance. Like I say I personally would use polyester but epoxy in this application is fine.

If using epoxy, replace matt with cloth or with a stitched matt. For polyester use the standard cellulose binder matt