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Old 03-12-2015, 16:51   #1
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fixing hairline cracks in gelcoat

what is the best way to fix small cracks on deck?
Thanks
Wolfgang
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Old 03-12-2015, 17:17   #2
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Re: fixing hairline cracks in gelcoat

The best way is:
-determine the cause
-fix the cause
-if, in fixing the cause, you have not had to do major work that results in replacing the deck where the cracks were, grind down the cracks into a wider V and fill with gel coat repair. Even some of the more die hards skip to this last step.

Having done a lot of deck work already and knowing exactly what is underneath most of my hairline cracks, I am going to try the Creeping Crack Cure in an inconspicuous place. Many people start with this step. My cracks are in my beautiful basketweave non-skid, gel coat repair will no do them justice.
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Old 03-12-2015, 17:20   #3
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Re: fixing hairline cracks in gelcoat

Drink enough beer till you don't notice them anymore
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Old 03-12-2015, 17:22   #4
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Re: fixing hairline cracks in gelcoat

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Originally Posted by WolfgangSeaLife View Post
what is the best way to fix small cracks on deck?
Thanks
Wolfgang
1. Sand down until cracks are absent.
2. Re gel
3. Fair until original
4. Fine sand
5. Polish
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Old 03-12-2015, 17:30   #5
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Re: fixing hairline cracks in gelcoat

Unless the cracks are related to a specific incident or weakness that chances of permanent repair are highly unlikely. Age related stress cracks are going to come back quite quickly no matter what you do (assuming you stress the boat by actually sailing).
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Old 03-12-2015, 17:38   #6
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Re: fixing hairline cracks in gelcoat

With Gelcoat, nothing else. But,

First you need to determine if the crack is just the gelcoat or if it is in the glass. If it's in the glass under the gelcoat, you will need to grind out the void or crack and repair with glass and resin, then but apply gelcoat.

If it's just in the gelcoat. Us a dremel tool to make a v shape. Get some gelcoat with wax in it (you will need to match the color). After you match the color and hardener, mix in baby powder until you get a paste. Clean with acetone and fill with gelcoat paste. Let sit over night and wet sand it flush and buff.

Gelcoat is very easy to do because you can never screw it up, if you do, just sand it down and try again. Online, you can find a ton of info to mixing it. Just remember, you need wax on the last layer for it to cure.
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Old 03-12-2015, 17:46   #7
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Re: fixing hairline cracks in gelcoat

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Originally Posted by Adrenaline View Post
Just remember, you need wax on the last layer for it to cure.
Not so, just buy the gelcoat with the wax in the formula or buy waxed resin and add your own pigment.
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Old 03-12-2015, 17:51   #8
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Re: fixing hairline cracks in gelcoat

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Originally Posted by Adrenaline View Post
With Gelcoat, nothing else. But,

First you need to determine if the crack is just the gelcoat or if it is in the glass. If it's in the glass under the gelcoat, you will need to grind out the void or crack and repair with glass and resin, then but apply gelcoat.

If it's just in the gelcoat. Us a dremel tool to make a v shape. Get some gelcoat with wax in it (you will need to match the color). After you match the color and hardener, mix in baby powder until you get a paste. Clean with acetone and fill with gelcoat paste. Let sit over night and wet sand it flush and buff.

Gelcoat is very easy to do because you can never screw it up, if you do, just sand it down and try again. Online, you can find a ton of info to mixing it. Just remember, you need wax on the last layer for it to cure.



Fine advice. I find that about 99.99% of the time the crack goes into the laminate as well. If you don't grind and glass, it will come back. Just filling is rarely enough.
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Old 03-12-2015, 17:53   #9
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Re: fixing hairline cracks in gelcoat

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Fine advice. I find that about 99.99% of the time the crack goes into the laminate as well. If you don't grind and glass, it will come back. Just filling is rarely enough.
Definitely. I intended "step 1" to mean following the crack until it is no longer apparent. This often does mean reglassing, unfortunately.
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Old 03-12-2015, 17:56   #10
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Re: fixing hairline cracks in gelcoat

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Not so, just buy the gelcoat with the wax in the formula or buy waxed resin and add your own pigment.



Definitely not. First, gel should be sprayed in multiple coats with wax in the last coat only. Not possible with finish gel. Second, pre-waxed gel never has enough wax in it produce a surface cure, especially on a small patch. Third, wax in the gel causes it to change color both as it cures and as it ages. If it is applied only in the top coat, all waxed gel is sanded off when polishing, leaving only virgin gel which will match better and maintain that match for much longer, rather than aging at a dissimilar rate to the surrounding gel. Fourth, gelcoat is not just resin with pigment in it. If you did that, you would have zero UV inhibitor in it. Not only would it be almost impossible to get a good match, even if you did it most certainly would not stay that way for any length of time. Not the best advice.
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Old 03-12-2015, 18:00   #11
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Re: fixing hairline cracks in gelcoat

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Originally Posted by Muckle Flugga View Post
Definitely. I intended "step 1" to mean following the crack until it is no longer apparent. This often does mean reglassing, unfortunately.



Sure does. I find that if you acteone wipe every so often with a very wet rag while grinding, it makes the crack much more visible while it's wet. Many times I have seen an owner who swore the cracks were "just cosmetic" grind them out, staying just in the gel, and then claim "look, the cracks are gone". Then I 'tone wipe and their jaw drops. Soon as the 'tone evaporates, crack is invisible again. But blatantly obvious when wet.
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Old 03-12-2015, 18:01   #12
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Re: fixing hairline cracks in gelcoat

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Definitely not. First, gel should be sprayed in multiple coats with wax in the last coat only. Not possible with finish gel. Second, pre-waxed gel never has enough wax in it produce a surface cure, especially on a small patch. Third, wax in the gel causes it to change color both as it cures and as it ages. If it is applied only in the top coat, all waxed gel is sanded off when polishing, leaving only virgin gel which will match better and maintain that match for much longer, rather than aging at a dissimilar rate to the surrounding gel. Fourth, gelcoat is not just resin with pigment in it. If you did that, you would have zero UV inhibitor in it. Not only would it be almost impossible to get a good match, even if you did it most certainly would not stay that way for any length of time. Not the best advice.
we agree to disagree.
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Old 03-12-2015, 18:03   #13
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Re: fixing hairline cracks in gelcoat

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we agree to disagree.


What specifically did I say that you disagree with? Why?
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Old 03-12-2015, 18:44   #14
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Re: fixing hairline cracks in gelcoat

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Definitely not. First, gel should be sprayed in multiple coats with wax in the last coat only. Not possible with finish gel. Second, pre-waxed gel never has enough wax in it produce a surface cure, especially on a small patch. Third, wax in the gel causes it to change color both as it cures and as it ages. If it is applied only in the top coat, all waxed gel is sanded off when polishing, leaving only virgin gel which will match better and maintain that match for much longer, rather than aging at a dissimilar rate to the surrounding gel. Fourth, gelcoat is not just resin with pigment in it. If you did that, you would have zero UV inhibitor in it. Not only would it be almost impossible to get a good match, even if you did it most certainly would not stay that way for any length of time. Not the best advice.
I agree with that, but it's not the wax that makes it change color as it ages, it's the hardener that does that. I always try to use the least amount of hardener for the temp outside.
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Old 03-12-2015, 18:53   #15
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Re: fixing hairline cracks in gelcoat

Covered in great detail in most boating books, like Don Casey's This Old Boat.

I've always felt Captain Tolley's worked great. For starters. Never had to go further, but ideas here and in that book are very good.

Good luck.
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