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Old 09-03-2009, 06:52   #31
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The reason for not using epoxy for repairs on polyester hulls (hulls, decks) is that it would create hard spots. I think it also depends on how big the repair is.

I'm lucky enough that I never needed a hull repair so I don't have any experience with this theory but hear and read it often so guess it's "general knowledge".

cheers,
Nick.
Havent heard of that in 25 years of boatbuilding

Dave
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Old 09-03-2009, 07:14   #32
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materials polyester/ gelcoat job less than $100 Epoxy/lpu/awlgrip with awlfair over $400. polyester/gelcoat 20 minute cure, gelcoat fills and hides imperfections, (dewax) block out & buff or thin topcoat finished in 2-3 days. epoxy/lpu more prep (awlfair/545), more coats with a days wait between, slow cure, more sanding (545), fairing, 545 awlfair, day wait before next step, ADDITIONAL TRAVEL TIME (he did mention that this was for a customer), full extra cleanup (545), lpu shows every imperfection. finished in 8-9 days. It is your right to disagree with my estimates, I really don't care. cburger only asked if he should use cloth, most just told him to do it their way. I am done here on this forum...life is too short.
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Old 09-03-2009, 07:23   #33
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Originally Posted by cat man do View Post
Ahh, just saw this comment

Still not a fan of LPU, urethanes , in my experience are very easy to blend repair and buff back in compared to other breeds that can require a repaint
Dave,

But LPU is a urethane!!???

You are right about Awlgrip being expensive: a good car-paint is the same thing but those don't come with reducers/thinners for rolling and tipping, i.e.: are for spraying only.

cheers,
Nick.
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Old 09-03-2009, 07:28   #34
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Originally Posted by cat man do View Post
Havent heard of that in 25 years of boatbuilding

Dave
well, let me Google that for you:

Let me google that for you

cheers,
Nick.
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Old 09-03-2009, 07:43   #35
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Oh my goodness, hard spots. Yes, more forum misinformation. Actually, epoxy is more flexible than polyester. It is one of epoxy's great strengths. Plus the fact that it should be tapered into any repair. I'm amazed at how much crap keeps getting recycled through the forums.

Bye captjcook.
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Old 09-03-2009, 11:26   #36
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I never indicated that the plan was to gelcoat over bare plywood. I was hoping that somewhere from the forum I was going to get some information from a professional that had some real world experince with the exact application I have described. .
"I am trying to avoid laminating cloth over the plywood areas for a number of reasons". quote from cburger

I can see why people thought you were trying to gelcoat over bare ply...including myself.
Most of the posts here I felt had merit. I don't know how you can tell who has "real world experience" or not. In this cruising forum you take the information that you need and leave the rest. It is free you know. If you want "professional real world experience"...hire it.
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Old 09-03-2009, 15:53   #37
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Hi guys! I can understand the reasoning behind the "hard spots" thing. I don't really believe it though. In my experience, epoxy stiffness varies between brands. West gets alot more brittle then you would think, while MAS keeps a nice flex to it. Poly resin gets damn hard though, at least as hard as West if not more so. I have repaired alot of older fiberglass boats with epoxy, and trust me, they came out alright and have lasted. I've also responded to a lot of threads on this forum, and for offering this free advice, I felt CBurger came off kind of creepy. IMHO, which I am fully entitled to...there ARE reasons we do these repairs ourselves...
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Old 10-03-2009, 16:27   #38
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Originally Posted by s/v Jedi View Post
well, let me Google that for you:

Let me google that for you

cheers,
Nick.
Just because you saw it on the internet doesnt mean its true



Maybe I should have said
Quote:
Havent heard of that being an issue in 25 years of boatbuilding

Add: and thanks for the link

Dave
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Old 11-03-2009, 02:36   #39
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Just because you saw it on the internet doesnt mean its true
Agree, and like I wrote, I don't have the experience myself. But that "hard spot" theory is around a lot, from many sources and I can't find links that say epoxy is softer than polyester or good to use for large hull repairs. I do know that my old epoxy windsurfer is much stiffer and lighter than the exact same board in polyester so I doubt that polyester is as hard or harder. Will look for a good comparison...

Anyway, we're vinylester and I would need some good documentation or the same story from a number of experts before deciding on what to use for a big hull repair.

cheers,
Nick.
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Old 11-03-2009, 07:18   #40
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As the forum's "Creepy" guy let me just say that I do not have a dog in this race. I have worked with both products epoxy based, and polylester resins and they both have specific applications. I am very leary of the term "Expert" and don't care for how long you have been at something, there is always more to learn. Regarding the Sundeer repair here goes. A properly repaired chemically bonded firberglass repair will "Generally" be stronger than a like mechanical repair. When refering to "Compatability"
I was not suggesting that epoxy would not adhere to poly based resins, it just won't bond at a molecular level. the meathod that I would use to repair a poly boat would be to first sand the area to be repaired well with an 80 grit paper, after sanding vac up the sanding dust, prior to applying a new polyester repair material acetone the repair area very well. Acetone works as a solvent on poly and this is an attemt to get the new resins to bond at the molecular level and essentially become fused together. All susequent layers of cloth and poly should be applied when the previous layup has reached a hard tack, again always striving to have the entire repair be chemically bonded together. Please don't take my word on this, give the folks at Sundeer a call and ask them what resin they reccomend to repair your vessel, good luck!
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Old 11-03-2009, 07:19   #41
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Same prochedure for vinylester
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Old 11-03-2009, 08:12   #42
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Originally Posted by s/v Jedi View Post
Agree, and like I wrote, I don't have the experience myself. But that "hard spot" theory is around a lot, from many sources and I can't find links that say epoxy is softer than polyester or good to use for large hull repairs. I do know that my old epoxy windsurfer is much stiffer and lighter than the exact same board in polyester so I doubt that polyester is as hard or harder. Will look for a good comparison...

Anyway, we're vinylester and I would need some good documentation or the same story from a number of experts before deciding on what to use for a big hull repair.

cheers,
Nick.
Have you built or worked in composites?

I have as have many of my friends and I can tell you now that we have always done repairs on poly boats in epoxy.
So called hard spots have never been an issue.
If they had been don't you think we would use an inferior cheaper resin for the job?

I repeat, in real life its not an issue.

AND

From your links

Quote:
Wet Core Repair - SailNet Community

The question is asked as he had "heard" it may be an issue, the concensus was use epoxy
Quote:
bateau2

The hard spot here is in reference to a "High Spot" on the plywood frame creating a hard spot against the hull.

Writer says not to use "inferior materials" and to use epoxy
Quote:
Bulkhead Repair

Again, in this one, "hard Spot" is in reference to a high in the bulkhead, nothing to do with resin, which, is recommended as being epoxy
Quote:
http://www.davesevs.com/honeycomb.htm

This one uses honeycomb panels, the "Hard Spot" is where they inject resin so as they can drill for through bolting.

Which resin do they use???? You guessed it EPOXY
I think this is enough to show your lack of knowledge on the subject and to give you a big

FAIL

Dave
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Old 11-03-2009, 09:19   #43
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Dave,

Ah you're overheating in a fiberglass knowledge contest but didn't notice that I indicated several times that I am no expert on the issue and thus your "FAIL" statement is not relevant.

The list of links is a Google search and shows anything within the search criteria.

Cheers,
Nick
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Old 11-03-2009, 10:56   #44
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Wow, guys. Amazing. That ought to stop people from posting. Let's just all calm down.

If you're just looking for general opinions, I have some. I like working with polyester. I would not do anything without cloth, both matting and roving. I would not know how to get more polyester into the plywood, but styrene seems to be the right diluter. I would definitely use filler or even bodyfill to make reasonable radiuses in all corners, between layers of cloth, to get rid of corners. It is a shower, and should be easy to clean.

There are a lot of people who don't like the paints, whatever they are made of. I would use gelcoat, even if it is more difficult to get a good finish.

These are my humble opinions, but I just fix small things on my on boats. People come to these sites to get more opinions. Yes, it would be nice if we all carried our credentials on our signatures, but there is a lot of value in just stimulating thought and discussion. Let's keep the lines open, shall we?
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Old 11-03-2009, 11:19   #45
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Man...I agree, I don't know why people in these forums have to get so worked up about being right and others wrong to the point of being graded. This is a Cruising forum where we share our opinions. It's one thing to say that you disagree and another to belittle someone. It reminds me to wear a chemical filter mask when mixing resins.
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