Epoxy or Polyester as I replace large sections of Deck Core

[coastalexplorer]

In all the boat works I worked in; They told me that Polyester resin will not adhere to epoxy resin. That epoxy resin will adhere to cured polyester. So I would think that applied logic would say; IF you have a polyester vessel to use Epoxy resin on it could be viewed as a form of pollution? Since once you use Epoxy resin on it you have committed your self to all subsequent adjacent damage and repairs will have to be completed in Epoxy also.
thus you are committed to piecemeal changing the material that your vessel is made from: with all the ensuing expense?

There are in fact some materials that Epoxy resin will not adhere to at all. There are others that an abrasion application method is used. (not sure how effective that is) So I think as a miracle cure for all situations: that Epoxy is grossly over rated. My vessel is completely made from Epoxy so I have to use it at $480 + Tax for five US Gallons trade price.

Also at the boat works I worked at; They wanted the feathered edge (otherwise called the tab) where possible ground back for one foot... not just 3 inches. Most decks are chopper gun laid up in a mould. So when ground back the surface is quite porous. Thus providing there is no water moisture present Polyester resin on a hand layup soaks into that and works quite well. Flood the area with resin. Place the glass on top and roller it...So that the resin comes up through the glass excluding the air as it does so,

So much for the many differing opinions of boat owners and boat builders?

[skipmac]

Originally Posted by toddedger

Sorry guys I've been in the industry working with epoxy for over 30 years. The 120° came directly from Gougeon brothers. Your epoxy will cure, but as soon as the sun shines on it and heats it up it will continue to shrink. Sometimes I wonder why I even bother to help you guys out.

Hi Todd,

Thought I would research this to see what is said by the epoxy makers. Found these quotes on the West System web site.

"Back in the late ’70s and early ’80s, Gougeon Brothers Inc. manufactured over 4,000 wind turbine blades and their molds using WEST SYSTEM Epoxy. It was commonplace to see a 70 foot long mold shrink 3/32” over the entire 70-foot length. That is shrinkage of .01% on a laminate consisting of fiberglass and WEST SYSTEM Epoxy."

"Three coats of epoxy followed by
three coats of varnish can achieve the
same depth and look of twelve or
more coats of varnish. Because there
are no solvents evaporating away
from the epoxy, it builds thickness
faster per layer than varnish and it
doesn’t shrink when it cures."

[FPNC]

I recommend vinyl ester resin for all repairs. It is as easy to use as polyester, however it has properties much better than polyester. It is much more heat resistant and stiffer than epoxy.

You may have to search a bit for vinyl ester but believe me, you do not want to use the easy to find polyester resin found at most marine stores.

Vinyl ester uses MEKP catalyst just like polyester.

[ArmyDaveNY]

Originally Posted by skipmac

Hi Todd,

Thought I would research this to see what is said by the epoxy makers. Found these quotes on the West System web site.

"Back in the late ’70s and early ’80s, Gougeon Brothers Inc. manufactured over 4,000 wind turbine blades and their molds using WEST SYSTEM Epoxy. It was commonplace to see a 70 foot long mold shrink 3/32” over the entire 70-foot length. That is shrinkage of .01% on a laminate consisting of fiberglass and WEST SYSTEM Epoxy."

"Three coats of epoxy followed by
three coats of varnish can achieve the
same depth and look of twelve or
more coats of varnish. Because there
are no solvents evaporating away
from the epoxy, it builds thickness
faster per layer than varnish and it
doesn’t shrink when it cures."

The shrinkage occurred in the seventies and early eighties. Is there still shrinkage (I'm NOT talking about that Seinfeld episode) today or is it no longer an issue?

[neilpride]

Cmon, if there is any shrinkage in the final layer,, guess what, you still need to sand down , priming and final topcoat...

[Souzag818]

Epoxy or vinyl ester, not polyester. Epoxy is strongest of all..

[Lepke]

I don't know where the 20% comes from, but poly doesn't bond to anything well, sanded or not. It works in construction because if additional layers are applied before the first cured, a chemical bond is achieved. You're trying to bond to existing, long cured, fiberglass. On a deck, walking over a poly repaired joint will probably cause eventually cracking at the joint and allow water to enter the new core.
Poly is cheaper and for some people easier to use. I have found over many years, epoxy does everything better that poly. You don't need to sand epoxy if you do your layup before it's cured. I had a yard that did mostly commercial boats that had tough use. We probably made a thousand hull repairs with epoxy and have never heard of a failure. I've used West Systems for a long time and is what I prefer. It's easy to get a proper mix in any temperature above 50°. I still get it here: Discount Marine Supplies offers quality boating supplies & marine supplies for boaters and sailboat owners. and get a better price than from my old suppliers.

[neilpride]

Originally Posted by Lepke

I don't know where the 20% comes from, but poly doesn't bond to anything well, sanded or not. It works in construction because if additional layers are applied before the first cured, a chemical bond is achieved. You're trying to bond to existing, long cured, fiberglass. On a deck, walking over a poly repaired joint will probably cause eventually cracking at the joint and allow water to enter the new core.
Poly is cheaper and for some people easier to use. I have found over many years, epoxy does everything better that poly. You don't need to sand epoxy if you do your layup before it's cured. I had a yard that did mostly commercial boats that had tough use. We probably made a thousand hull repairs with epoxy and have never heard of a failure. I've used West Systems for a long time and is what I prefer. It's easy to get a proper mix in any temperature above 50°. I still get it here: Discount Marine Supplies offers quality boating supplies & marine supplies for boaters and sailboat owners. and get a better price than from my old suppliers.

There we go again with the Poly Epoxy war, done 2 multihulls stern extensions in Poly, gelcoat matched with the hull , not a single crack despite years of chárter abuse, post hurricane damaged boats done in Poly to, holes, cracks, decks ripped in pieces,,,, is just how to use Poly and how to use Epoxy...

[ramblinrod]

Originally Posted by coastalexplorer

In all the boat works I worked in; They told me that Polyester resin will not adhere to epoxy resin. That epoxy resin will adhere to cured polyester. So I would think that applied logic would say; IF you have a polyester vessel to use Epoxy resin on it could be viewed as a form of pollution? Since once you use Epoxy resin on it you have committed your self to all subsequent adjacent damage and repairs will have to be completed in Epoxy also.
thus you are committed to piecemeal changing the material that your vessel is made from: with all the ensuing expense?

There are in fact some materials that Epoxy resin will not adhere to at all. There are others that an abrasion application method is used. (not sure how effective that is) So I think as a miracle cure for all situations: that Epoxy is grossly over rated. My vessel is completely made from Epoxy so I have to use it at $480 + Tax for five US Gallons trade price.

Also at the boat works I worked at; They wanted the feathered edge (otherwise called the tab) where possible ground back for one foot... not just 3 inches. Most decks are chopper gun laid up in a mould. So when ground back the surface is quite porous. Thus providing there is no water moisture present Polyester resin on a hand layup soaks into that and works quite well. Flood the area with resin. Place the glass on top and roller it...So that the resin comes up through the glass excluding the air as it does so,

So much for the many differing opinions of boat owners and boat builders?

Always repair with same. If a choice I lean toward polyester or vinylester to avoid epoxy sensitivity or contact dermatitis development.

[lateral]

Originally Posted by toddedger

Sorry guys I've been in the industry working with epoxy for over 30 years. The 120° came directly from Gougeon brothers. Your epoxy will cure, but as soon as the sun shines on it and heats it up it will continue to shrink. Sometimes I wonder why I even bother to help you guys out.

Help us out with a quote of a URL to Gougeon please.
Never heard that, in fact the opposite, lowest shrinkage out of all resins. (105)

[glhotka]

Originally Posted by toddedger

Sorry guys I've been in the industry working with epoxy for over 30 years. The 120° came directly from Gougeon brothers. Your epoxy will cure, but as soon as the sun shines on it and heats it up it will continue to shrink. Sometimes I wonder why I even bother to help you guys out.

Todd,
2 clarification requests. Is the 120 Fahrenheit? I presume so but wanted to check. Also what is the way that you would achieve that, something as simple as a heat gun, or something more complex like a cover that allows the heat from the chemical reaction of catalyst to resin to heat up the surface area?

[glhotka]

Originally Posted by neilpride

My vote for Poly, and you can always barrier coat with epoxy...

@neilpride - When you say Barrier coat, do you mean the top layer exposed to the air, (top of deck) or barrier between the core and subsequent layers of poly layout?

[neilpride]

Originally Posted by glhotka

@neilpride - When you say Barrier coat, do you mean the top layer exposed to the air, (top of deck) or barrier between the core and subsequent layers of poly layout?

Formosa 51, i mean,, i dont know the cosmetic deck condition , if is nonskid Gel? nonskid coating, Awlgrip or whatever 2 poly finish? or if is just the crap you can found after removing acres of rotten teak deck? in any case you can built with poly and finish the glass job with a neat or 2 coats of clear epoxy, and later priming and finish with a nonskid finish, if the whole deck is Gel and in good condition i skip the Epoxy coat and finish with Poly.

[Ken Z]

I have used polyester resin on plywood since the 60s, and have had good results, altho epoxy is king and more money. If you started wit epoxy continue with it. Its best to put a coat down, let it get tacky and add stranded cloth 1.75 works, wet it out then you can add woven roven, then stranded, woven etc. until you achieve your thickness, finish with 10 oz, sometimes called surfboard fiberglass. There are different brands of epoxy, west the most known and the most expensive. I ve been using raka in ft. pierce fl @ 772-489-4070.Its a 3-1 mix and for a job that large pumping will wear you out. I fill a measuring cup with water 1 cup, put a clean stick 1/2" wide in it and draw a line, then measure 3 cups and make a line , so in a mixing container put a line at that level, one to three, add hardener first, mix at least two minutes, try to keep it in the shabe. This epoxy doesnt blush unless it gets wet after it sets. I sand in a circular motion with 80 grit before i apply another coat Raka is a little thinner than west and is easy to work, and cheaper. IT sounds like you have do the right steps and i know you dont want to repeat it. Hope this helps.

[smj]

Originally Posted by ramblinrod

Always repair with same. If a choice I lean toward polyester or vinylester to avoid epoxy sensitivity or contact dermatitis development.

Wrong