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PostPosted: Fri Nov 26, 2010 9:06 am 
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I want spray my entire H18 with new gelcoat, I've begun preping the hulls but am not exactly sure what materials I will need, here's what I was planning on buying:

Base white polyester Gelcoat w/ hardner - waxed or unwaxed?
Duratech Hi gloss additive
Laquer thinner
Polyvinyl Alcohol

-I plan on mixing Gelcoat and Duratech 1:1 and then adding about 2% hardner? (not sure how to do this accurately) Do I need to use a gelcoat that uses the same type hardner as the Duratech or is all hardner the same?

-How much do I thin it down to spray with a gravity feed HVLP gun? 10:1?

-Is a gallon of gelcoat and gallon of duratech enough to do both hulls?

-How many coats do I spray and how much time between coats? When does PVA go on?

-How much sanding should be done on the old gelcoat?


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PostPosted: Sat Nov 27, 2010 1:31 pm 
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The article in this issue of the Hotline (07-08_2008.pdf spray gel) might be of some help. It dosen't have everything you always wanted to know about spraying gelcoat, but it may answer some of your questions.


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PostPosted: Sat Nov 27, 2010 4:59 pm 
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Location: Rapid City, South Dakota
http://2010.archive.hobiecat.com/hobieclass/eHCA_Hotline07-08_2008.pdf Page 16.

Read that, its a pretty good guide.

When I sprayed Last I used a 50:50 mix of unwaxed gelcoat and duratech and 2% MEK. you wont need the pva. and use Acetone instead of lacquer thinner.

I did my measurements using a digital scale, that I got from a kitchen store.

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PostPosted: Mon Nov 29, 2010 9:34 am 
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Is the duratech absolutely necessary? If I spray a few coats of white gelcoat thinned with styrene and then a coat of PVA it will not dry to a hard glossy finish?


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PostPosted: Mon Nov 29, 2010 3:53 pm 
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Location: New Port Richey Fl.
I did my 18 first coat 100% white gel thinned with styrene kicked with MEK at 1.5%. Second coat 75% gel 25% Duratec thinned with styrene, kicked with MEK @ 2%. Third coat 50/50 gel and Duratec thinned with styrene and About 5% sanding aid added for drying and kicked @ 2% with MEK. Duratec is a great product, very hard and durable but it is clear that is why the first coat is gel only for coverage and last coat 50/50 for durability. All coats sprayed one after the other just wait for a little tackiness between coats. Sanding aid last coat only to get the gel coat to cure. I used mixing cups and mixed all my coats less MEK before starting the first coat. Not sure what the thinning ratio was, I just mixed up some gel and styrene and did practice shots adding styrene as I went to figure how much of each to use, sorry I do not remember how much of each. You what it to spray out smooth without splotches yet not so thin it runs all over the place. 24 hr dry time then sand 250 dry-350 dry-500-600-800-1000-1200 all wet then buff with 3M SUPER DUTY RUBBING COMPOUND. I finished off with 3 coats of Liquid Glass polish. For the 250 and 350 dry sanding I used a tool that looks like a plane it is long and narrow this took out all the peaks and valleys. Hope this helps, good luck.mine came out looking brand new!!! A lot of sanding work but it will last 3X longer than painting. Jim.

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PostPosted: Tue Nov 30, 2010 7:33 am 
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Thanks! I was thinking about premixing also and then adding the MEK before spraying. Appproxamitely how much mixture did you use per coat? Im not sure how much duratec and gelcoat I need to buy. Im spraying the hulls of a H18, Im still undecided what to do with the top deck. Can I spray over the non-slip surface with out sanding it down first? I'd like to maintain the non-slip look.

Is sanding aid similar to the "waxed" gelcoat? Where can I purchase sanding aid by itself?

How did you measure your 2% MEK? I will probably do it by eye.


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PostPosted: Wed Dec 01, 2010 5:14 am 
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Location: New Port Richey Fl.
Used a medicine cup to measure MEK. Mixed up all gel/duratec first in large mixing cups the size of the gravity feeder cup. I used about 1.5 gals of gel 1/2 1 gal duratec. Sanding aid purchased along with all other materials at a fiberglass coating store. I think the sanding aid is a type nof wax that comes to the surface after spraying.

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PostPosted: Mon Dec 06, 2010 10:07 am 
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Duratec contains a high percentage of Styrene.


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