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Old 19-08-2013, 13:12   #1
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Epoxy vs Polyester or Vinylester Resin

Why are so many trying to repair fiberglass hulls with epoxy resins rather than the polyester or vinyl-ester resins your boats were built with???
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Old 19-08-2013, 13:15   #2
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Re: Epoxy vs Polyester or vinylester resin

Some of it is because epoxy has been marketed well as superior for repair work and some of it is because there are legitimate repairs and projects were epoxy is the better choice.

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Old 19-08-2013, 13:18   #3
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Re: Epoxy vs Polyester or vinylester resin

The reason I choose epoxy is that I'm not allergic to it and the fibers don't make me itch as much when grinding and fairing. I believe epoxy to be more water resistant and provide better adhesion. Afterall, barrier coats are a form of epoxy.

My assumptions might be all wrong but that's the reason I use it.

kind regards,
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Old 19-08-2013, 13:20   #4
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Re: Epoxy vs Polyester or vinylester resin

Epoxy will make a chemical bond with cured polyester resin, where polyester will not bond as well with itself, once it is cured. On the other hand, once you put epoxy resin on polyester, polyester will not adhere well to the epoxy.
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Old 19-08-2013, 13:26   #5
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Re: Epoxy vs Polyester or vinylester resin

For me it's mostly that it is well marketed - and by that I don't mean being sold as "better", but because the stuff from West Marine comes in tins that have can have an easy dispenser fitted on the top that also does the measuring - plus various grades of fillers.........life all made simple for me :-) .
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Old 19-08-2013, 13:32   #6
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Re: Epoxy vs Polyester or vinylester resin

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Originally Posted by captain58sailin View Post
Epoxy will make a chemical bond with cured polyester resin, where polyester will not bond as well with itself, once it is cured. On the other hand, once you put epoxy resin on polyester, polyester will not adhere well to the epoxy.
wot he said.
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Old 19-08-2013, 13:37   #7
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Re: Epoxy vs Polyester or vinylester resin

The yards with real expertise will tell you pretty much the same. For large areas you should work in like type materials to prevent creating new stress point (at some point unless you are an engineer..what determine large area is pretty subjective).

You don't need incredible bonding if it creates a stress point that will fail before the perfect epoxy bond strength anyhow.

Small repairs that would benefit from the extra adhesion and not suffer a stress point....or for structural areas...then yes epoxy benefits from those adhesive properties.

A lot of backyard guys with business cards will debate this all day...let'em...I listen to the guys who cut out the sides of mega yachts and put them back for advice.
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Old 19-08-2013, 14:00   #8
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Re: Epoxy vs Polyester or vinylester resin

where does your question come from?

do you have an objection?

is there some other element to your post?

personally, i use epoxy when the surface is not as pristine as i might otherwise like it, for structural (tabbing in bulkheads / chain plates beds) items and if i cant tell what the original resin was because epoxy just bonds with everything and is bullet proof.

if i am laying up multiple layers of new cloth on a well prepared surface, i use laminating resin mostly because it is a lot cheaper.

-steve
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Old 19-08-2013, 14:05   #9
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Re: Epoxy vs Polyester or vinylester resin

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Originally Posted by capttman View Post
Why are so many trying to repair fiberglass hulls with epoxy resins rather than the polyester or vinyl-ester resins your boats were built with???
People seem to think epoxy is a magical cure-all. "I don't have to pay to have it fixed if I cram enough epoxy in the hole!" I'm sure that's not the case for everyone, but I've seen a lot of boats where people expected it to be the solution. ...like this boat:

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Old 19-08-2013, 14:08   #10
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Re: Epoxy vs Polyester or vinylester resin

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People seem to think epoxy is a magical cure-all. "I don't have to pay to have it fixed if I cram enough epoxy in the hole!" I'm sure that's not the case for everyone, but I've seen a lot of boats where people expected it to be the solution. ...like this boat:
Why in this case wouldn't a slightly thickened epoxy be the right solution?

Small blisters or chips...seems what most Dr's order....

Unless the crayon or pencil marking is outlining a serious delam/hydrolysis issue.
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Old 19-08-2013, 14:14   #11
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Re: Epoxy vs Polyester or vinylester resin

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Why in this case wouldn't a slightly thickened epoxy be the right solution?

Small blisters or chips...seems what most Dr's order....

Unless the crayon or pencil marking is outlining a serious delam/hydrolysis issue.
As you can see from the radiating damage, it wasn't the solution.

The holes are spots that someone just filled with epoxy. I couldn't tell you what created the holes, it was delivered to us this way. The cracks all radiate out from those holes. I suspect that moisture was trapped inside the hull when someone attempted this epoxy repair, so all they managed to do was seal water inside. Once winter came around, the water freezes and expands, forces voids in the glass and allows more water to get in. Apparently the damage wasn't this visible for a while, and when we ground open the bottom there was even more damage than you could see through the gelcoat.

The right solution is to grind out the damaged areas and glass it properly. The material doesn't particularly matter.
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Old 19-08-2013, 14:16   #12
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Re: Epoxy vs Polyester or vinylester resin

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The right solution is to grind out the damaged areas and glass it properly. The material doesn't particularly matter.
Or slap on some antifouling .
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Old 19-08-2013, 14:21   #13
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Re: Epoxy vs Polyester or vinylester resin

Yup, ready to go in the water. :P

I suppose what I'm trying to say is that it isn't so much a matter of whether you're using epoxy, polyester or vinylester, it's a matter of whether or not you've done the due diligence in actually repairing the damage - and when you've done it right, you don't need to worry about what you've used.

Though I will add, encountering vinylester and epoxy repairs has been nothing but a headache for us.
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Old 19-08-2013, 14:34   #14
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Re: Epoxy vs Polyester or vinylester resin

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Originally Posted by AbaftAndBaffled View Post
As you can see from the radiating damage, it wasn't the solution.

The holes are spots that someone just filled with epoxy. I couldn't tell you what created the holes, it was delivered to us this way. The cracks all radiate out from those holes. I suspect that moisture was trapped inside the hull when someone attempted this epoxy repair, so all they managed to do was seal water inside. Once winter came around, the water freezes and expands, forces voids in the glass and allows more water to get in. Apparently the damage wasn't this visible for a while, and when we ground open the bottom there was even more damage than you could see through the gelcoat.

The right solution is to grind out the damaged areas and glass it properly. The material doesn't particularly matter.
Wow...picture just came up in giant size and now can see the rest of the damage..knew it was either too simple or to complicated based on your post...just wanted to know which one...

Did you find out what the impact was? Did the cracks go all the way through?
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Old 19-08-2013, 14:42   #15
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Re: Epoxy vs Polyester or vinylester resin

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Wow...picture just came up in giant size and now can see the rest of the damage..knew it was either too simple or to complicated based on your post...just wanted to know which one...

Did you find out what the impact was? Did the cracks go all the way through?
I don't think it is/was an impact at all, I think it's just age and lack of care. It may have sank at some point, though that in and of itself shouldn't be enough to write a hull off. Our own boat sank down to the gunwales (long before it became ours) and the hull is still in immaculate shape.

Jeez, I've derailed this thread. D:

One thing I will say for any type of repair on a boat, if you're using a material other than what it was built with, make sure you document it somewhere as a reference so people down the road know what they're dealing with.
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