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PostPosted: Tue May 06, 2014 7:59 am 
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Joined: Tue May 06, 2014 7:47 am
Posts: 7
Hi All,

Currently fixing holes in the hulls on the '81 HC16. I wanted to use gelcoat as paint, but as sailing season is approaching fast, somebody advised me to use polyester resin w/ coloring agent/additive as paint, in order to save time and money.

Anybody has done that? Any advices?

Thanks


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PostPosted: Tue May 06, 2014 8:29 am 
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Joined: Tue Jul 19, 2005 6:29 pm
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Location: High Point, NC
Polyester resin is very hard and somewhat brittle. Most likely you'll get serious cracking and flaking in short order. Maybe others have done it with good success, I wouldn't. Epoxy would be better, although still not ideal.


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PostPosted: Tue May 06, 2014 9:54 pm 
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Joined: Mon Aug 26, 2013 7:29 pm
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In my opinion (not a pro by any means) but it would be just as easy to spray gel coat as it would be to spray polyester. I have never done color additives to the gel coat but I did do the white and it was pretty easy. Looks up the hobie cat North America online hotline magazine and they have an article on spraying gel coat. Just make sure the weather is perfect! Humidity and temp fersure. Makes a world of difference!

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1981 Hobie 16 cat fever
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PostPosted: Wed May 07, 2014 3:13 pm 
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Joined: Mon Jul 14, 2003 7:11 pm
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Location: Detroit, MI
Gel coat is polyester resin with pigment added, so you're not really gaining anything by buying them separately (resin / pigment) and mixing it yourself.

Tom's comments about polyester vs. epoxy is a bit off. The boat is made from polyester resin. There's no reason not to use polyester resin to make cosmetic repairs and is the preferred choice for structural repairs - unless the bonding surface is limited, in which case vinylester or epoxy resin can be used.

Epoxy resin forms a strong chemical bond with almost any properly prepared surface, whereas polyester resin needs a physical "tooth" (surface roughness) to achieve the same bond.

Gel coat is meant to be sprayed inside a mold and will remain tacky if left exposed to air - this facilitates the adhesion of the next layer (usually chopped strand mat) of the laminate.

If you're going to use gel coat as paint (and I recommend you do), then you need to provide an air barrier so that it will completely cure. The easiest way to do this is to post-spray the area with PVA (polyvinyl acetate) - mold release wax - that you can get at West Marine (purple liquid - comes in a plastic bottle). Despite its nasty chemical name, it's pretty benign stuff.

Paint the area with gel coat, wait a few minutes for it to start going off, then spray with PVA (use a PreVal sprayer). Come back a couple of hours later and wash the PVA off with water. Done.


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PostPosted: Fri May 09, 2014 6:43 am 
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Joined: Tue May 06, 2014 7:47 am
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Mbounds, thanks for your feedback. Since I don't have the spray and I do all the work at the beach where my hobie is parked, I'm painting with a brush.

I'm using polyester resin, as I have somewhat large amounts of it left over. I'm mixing it with cure, little bit of acetone (as thinner), and pigment. For any future users of this method, make sure to use a lot of pigment. This was my mistake within the first layer.

The stuff is usually hardens within 1.5 hours and is ready for sanding.


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