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Old 26-08-2013, 02:08   #1
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Vinylester Resin or Epoxy, How To Tell

Hello I am about to undergo a pretty major refit on my CAL 35 1983 and I am going to be doing some major glass work. I want to make sure I am matching my construction materials though so I can get proper adhesion. How do I determine whether my boat was laid up using vinylester resin or epoxy resin?

Oh sweet Jesus I can't edit my misspelled title.
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Old 26-08-2013, 02:18   #2
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re: Vinylester Resin or Epoxy, How To Tell

I have no doubt your boat was made with polyester. Resin. but either of your choices will give superior bond strength
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Old 26-08-2013, 02:45   #3
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re: Vinylester Resin or Epoxy, How To Tell

When you cut or sand the actual glass it will smell like what it was originally made of. You can buy those little DIY packs of epoxy and Bondo for poly if unfamiliar with the "fragrance". Epoxy and polyester are familiar to me. Vinylester, not so much.
And BTW just about no production builder uses epoxy except the really expensive boats. Poly has it beat on price and ease of use.
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Old 26-08-2013, 04:33   #4
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Re: Vinylester Resin or Epoxy, How To Tell

As others have said not many boats are epoxy, although a lot have a bit of vinylester resin in the outer layers. I don't understand why more expensive boats don't use the much better epoxy as routine.

However polyester does not stick well to cured polyester, so epoxy would always be my preferred choice for repair. Some disagree and site the flexibility difference, but I think most repairs that use polyester do so for cost reasons. Hull repair is not an area to skimp on the best materials.

PS I changed the title for you, but with my spelling it is probably still wrong
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Old 26-08-2013, 07:49   #5
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Re: Vinylester Resin or Epoxy, How To Tell

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Originally Posted by noelex 77 View Post
Some disagree and site the flexibility difference, but I think most repairs that use polyester do so for cost reasons.



Believe me, cost is not a factor in this decision. Our yard charges top dollar, our clients can easily afford any material we choose to use, and labor makes up 95% or more of the average bill. Clients are billed for materials with the usual markup, we would actually make more money using epoxy (mostly because jobs would take much longer but also because materials would triple in price). We choose to use poly strictly because its often the better material for the job. And it allows us to get our clients out the door with pro results much faster. Ever seen a thruster tube fail? I've glassed in a great many, never done one in anything but poly. Done lots of roll stabilizers, major keel repairs/rebuilds, huge holes in boats, etc etc. All in poly, all with zero failures. Poly not bonding well to poly is a myth which is propagated on this forum far too much, and it does boaters a disservice. Just learn to prep properly and save yourself a whole lot of time and money.
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Old 26-08-2013, 09:02   #6
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Re: Vinylester Resin or Epoxy, How To Tell

Thanks for the answer.

I did not mean to imply that the marine repair business was trying to rip anyone off. I would expect, as you say, that there is greater profit for the boatyard in using epoxy.

However, with a job like installing a bow thruster tube (as an example) personally I would want the the best possible job. Cost and time (within reason) would not be a factor. I appreciate not every owner would see the job with these priorities.

Polyester may be entirely satisfactory (and you have always given great advice on the forum so I have no doubt this is correct), but I can see no drawback (other than cost and time) in using epoxy, but perhaps I missing something. I would certain listen to any suggestion of potential problems.

Unfortunately as a long distance cruising boats if there is ever a problem the person giving assurances is long gone. This means by nature I have become conservative with mission critical bits of gear (like keeping the water out ). If there is a better way its invariably the path I choose.

Overkill is often a good thing on a cruising boat.
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Old 26-08-2013, 10:22   #7
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Believe me, cost is not a factor in this decision. Our yard charges top dollar, our clients can easily afford any material we choose to use, and labor makes up 95% or more of the average bill. Clients are billed for materials with the usual markup, we would actually make more money using epoxy (mostly because jobs would take much longer but also because materials would triple in price). We choose to use poly strictly because its often the better material for the job. And it allows us to get our clients out the door with pro results much faster. Ever seen a thruster tube fail? I've glassed in a great many, never done one in anything but poly. Done lots of roll stabilizers, major keel repairs/rebuilds, huge holes in boats, etc etc. All in poly, all with zero failures. Poly not bonding well to poly is a myth which is propagated on this forum far too much, and it does boaters a disservice. Just learn to prep properly and save yourself a whole lot of time and money.
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Old 26-08-2013, 10:42   #8
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Re: Vinylester Resin or Epoxy, How To Tell

A big downside to epoxy is that it can't be used in cold weather.
It takes a lot more time to cure. With the 'esters you can adjust the catalyst
to conditions, and get a lot of work done in a single day.
I did all my jetboat transom intake work using epoxy most because of concern about adhesion, when it was 100F outside, the epoxy cured quickly!
All my molds and car parts I've done in 'ester, using gelcoat, which can't be used with epoxy.
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Old 26-08-2013, 10:57   #9
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Re: Vinylester Resin or Epoxy, How To Tell

There are both hot and cold temperature (slow and fast) hardeners available for epoxy.

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Old 26-08-2013, 11:23   #10
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Re: Vinylester Resin or Epoxy, How To Tell

I think vinyl ester would be a much better materials and polyester. as it has superior secondary bond strength. when a polyester boat is built it has a chemical bonds with a repair you only have a mechanical Bond. and yes repairs have been done for years with polyester resin I'm just saying vinyl is a superior product. I do not see the downside for using vinyl ester other than an increase in cost.
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Old 26-08-2013, 11:43   #11
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Re: Vinylester Resin or Epoxy, How To Tell

While not really a "downside", vinylester resin is not as easy to work with as polyester - requiring much more careful prep work and not as accommodating of the curing environments and conditions one often finds themselves in.

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Old 26-08-2013, 11:53   #12
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Re: Vinylester Resin or Epoxy, How To Tell

Myth #1 Epoxy "chemically" bonds to polyester while polyester does not "chemically" bond. Why people think this is true is beyond me, it defies common sense and I have yet to see anything (not published buy the Gougeon Brothers) that proves this. Good preparation is all you need and is key to any repair.

Down side of epoxy, Expense it is 3 times as much, hard to work with therefore you may get a repair that is actually weaker, Has poor UV resistance and if exposed to sunlight will fail, Gelcoat does not adhere well. You need to use glass material with a special binder.

The OPs boat is built with polyester there is little doubt of that, so most experts will recommend polyester for above the waterline and vinylester for below.

Honestly I have personally seen more failed repairs done with epoxy than with poly but I am sure there are those that never will be convinced because it is a common belief the epoxy is better. The Gougeon Brothers are great at marketing!
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Old 26-08-2013, 11:53   #13
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Vinylester is icky. It looks neat though.
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Old 26-08-2013, 12:01   #14
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Re: Vinylester Resin or Epoxy, How To Tell

i have used epoxy and poly extensively (by which i mean a TON).

my general rule: epoxy for structural (tabbing in bulkheads, stringers etc) and poly for larger surfaces (re-coring decks etc).

i have used both while filling thru hulls with 403, 404 and 407.

when fairing with 410, i always use poly.

a few things...

1. surface prep is really important. sand / grind and clean (lacquer thinner) before applying either

2. epoxy bonds to poly but poly does not bond to epoxy

3. fiberglass is NOT a sponge and will not absorb more resin over time. avoid the temptation to 'pour it on there'

4. be patient... set a plan in your head... prepare (cut the glass to the correct size / place it next to the work area)...get into a rhythm... dont rush

-steve
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Old 26-08-2013, 12:47   #15
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Re: Vinylester Resin or Epoxy, How To Tell

I've done a lot of work with both epoxy and poly/vinylester. I've used epoxy almost exclusivly in boat building project's. Don't see why I'd use anything else. It is by far the strongest, most water resistant, best primary and secondary bonds. And it doesn't make me want to vomit when using it. I have a fair amount of use with poly in that I designed and build a hardtop for a factory five Shellby Cobra. I've built enough to know what my nose tells me, this **** stinks and is def not good for you. Neither is the epoxy, but one is worse than the other in my estimation. And as to money? I think its false economy to make that an issue. If I use a gallon of epoxy it cost, worst case from WM a hundred bucks, versus $25 for poly. When putting in a bulkhead I don't think $75 saved is worth the trade off. Now when you get up to using 5+g And your interested in thickness, poly is the way to go. Strength/waterproof/structural,,,epoxy. I've a friend who spent weeks getting the bottom of his 50er stripped and ready for barrior coat, he used vinylester, given that its a bit better than poly. Crazy logic to me. After all that $$$ in labor, and the same amount of labor to roll out,,,use epoxy. My Dad told me decades ago use bronze screws in boats, period. I would 'save' money and watch the damn thing fall aprt. For the sake of $25 I lost whole projects., Just my thoughts.
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