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PostPosted: Mon Jun 12, 2006 2:44 pm 
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I just got a used (79) H16 and while the hulls are very sound structurally, the hull bottoms are quite worn as it had been dragged a fair bit. At the very bottom I can see through the while layer to the brown in places. It still feels solid, but I'm guessing I should recoat the bottoms?

So, what exacly is gelcoat? Is it polyester or an epoxy product? The hulls are fiberglass/polyester resin I'm guessing.

Is the West marine White Gel Coar any good?

There's a few small hairline cracks here and there on the top of the hulls, what's the best way to deal with those? I've got some System Three SB112 that's a UV protected epoxy resin I use on my surfboards. Would that be acceptable?


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 Post subject: Epoxy / Polyester
PostPosted: Mon Jun 12, 2006 4:12 pm 
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Hobie boats are made of polyester. Hobie Gel Coat is Polyester

The rule of thumb?

You can repair Polyester with Polyester or Epoxy.

You can only repair Epoxy with Epoxy.

Polyester does not cure properly over epoxy.

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 Post subject: Polyester
PostPosted: Wed Jun 14, 2006 1:37 pm 
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Use the product that the boat was made of for repairs. Some Epoxies will not allow gelcoat to cure properly when put over top of them. What you're doing by introducing another product is complicating the chemical structure, so down the line if you had to make another repair you may run into compatibility issues. Case in point: I was refinishing a few H18 daggerboards. I sprayed on what I thought was my last coat of Gelcoat--walked away for a breather and to clean my gun. When I came back the substrate had bubbled up and cracked and made a huge mess out of my beautiful gelcoat job! I tried to do an emergency wipe down of the spot, catylized some new gel, and reapplied. As I shot the new gel, the cracking just spread over the whole board. I walked away in defeat. This required that I let the gel dry, sand the entire board down to the original gel and glass, and re-gel. This added 5 hours to the job!! I called the customer and he said that he coated the board 3 years prior with epoxy primer. Just keep it all the same chemical composition to save a headache down the line. Polyester is cheaper anyway.

Gelcoat is tricky stuff. To increase your chances of the gel going off. Mix your Gel with 40% Duratec clear high gloss additive. Then catylize as normal for your temp/ humidity (read the can). Gel will cure better when it oxygen is occluded, so use a product called PVA or cover the repair with plastic. It will cure faster. Hope this helps.

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 Post subject: Polyester
PostPosted: Wed Jun 14, 2006 1:43 pm 
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P.S.
If you use the West Marine Gelcoat, Do not get the stuff with wax in it. Use the Duratec as I suggested above. It works fine. Better yet, find a small, local fiberglass/plastic shop and buy a complete and compatible system from them. Again, this avoids chemical incompatibility.
Chemical incompatibility= headache for you! Believe me! :D

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 Post subject:
PostPosted: Wed Jun 14, 2006 7:19 pm 
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Cover with plastic?

Can I use something like 3mil poly? How airtight is necessary? For instance, if I apply a strip of gelcoat to just the bottom one inch of each hull, can I tape a strip of 3mil down tight over it? Will the plastic release once the resin has cured?

-jeff


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 Post subject: Cover
PostPosted: Thu Jun 15, 2006 10:18 am 
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Best to use PVA. (PolyVinyl Acetate)

This is a water based material that you spray over the gel that seals the it from oxygen and allows it to cure. Then you wash it off. Plastic is going to wrinkle the surface of the gel. Ok in small repairs where you can pull the plastic tight.

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 Post subject: pva
PostPosted: Thu Jun 15, 2006 12:31 pm 
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As Matt said it is best to use PVA, but in a pinch I just get some plastic wrap or an old ziplock out of the trash. Let the gel tack up slightly then just press it onto the gel. You won't even have to tape it too the boat the tackyness of the gel will hold it. When the gel cures it will peel right off. This method will usually add a "bag" texture to the repair that will havew to be sanded out. More so than with PVA. I'm telling you though, use the Duratec clear additive. The product claims that it will cure the gel without PVA- and it does, but it takes a while. Just occlude the O2. The Duratec is my saving grace.
Gelcoat is forgiving once you master it. You can get an invisible repair-- even if you're brushing it on-- if you're patient enough with the finish. If you mess up, just sand it out and apply another coat, fair it, buff it and you're done. Colored hulls present color match problems, white hulls are easier. The European (Tiger/FX) boats use a super bright white gelcoat that's difficult to match without using the european gel. The 16 and US boats can be matched close enough with the "base white". You'll see the repair in certain light, but it's close enough in my eyes. Hope this helps!

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