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Author Topic:   Spectrum Gelcoat repair - cracks appearing
Chesapeake posted 09-04-2002 12:19 PM ET (US)   Profile for Chesapeake   Send Email to Chesapeake  
Last year I repaired holes in several areas of the hull using first epoxy and second Spectrum gelcoat patch. None of the areas patched are in typical "stressed areas".

I noticed this weekend that virtually all of the repairs now have small stress cracks where the patch meets the original gelcoat.

Has anyone else noticed this in your repairs?
Could this be an application technique problem? If so, what should I do differently?



AC posted 09-04-2002 02:53 PM ET (US)     Profile for AC  Send Email to AC     
I'm a rookie at these repairs, but have done a boatload of research on this topic for the last 60 days from 4 different sources, so perhaps some of the veterans will expand upon my response. I've read from more than one instructional source that gelcoat doesn't bond well with epoxy resin. Many of these sources reccommend polyester resin. West Systems, however, claims their epoxy resin will bond with gelcoat provided you allow the resin to completely cure and then wash off the Amine Blush with clean water and an abrasive pad like a Scotch-brite 7447 general purpose hand pad. Amine Blush blush can appear as a wax-like film on cured epoxy surfaces. It is a byproduct of the curing process.
Chesapeake posted 09-04-2002 03:13 PM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
AC: Thanks for the response. The epoxy blush did occur to me. However, the cracks have also occured also in areas where no epoxy was used.

Given that no one has previously mentioned this, I can only assume that something is wrong with either my technique or the epoxy. It looked good for a year, but now has developed a fine crack along the line where the gelcoat patch meets the original gelcoat. Could my patch be too thin?

Tom W Clark posted 09-04-2002 03:36 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

Relax, this is very common. It's almost impossible to get a perfect blend.

When I first started doing these screw hole patches in the summer of 1986 I noted this was almost the norm. In some cases I attributed the problem to the holes not being reamed out enough. A sheet metal screw can lift the fiberglass up around the hole and leave a lip that will be exposed after the patch is polished out.

In other cases I think the gel coat patch paste simply shrank a tiny bit.

I have done dozens of these patches and while there may be some slight cracking I have never had a patch fall out

If it really bugs you then you could try a little acetone wash immediately before applying some more gel coat. The acetone will thin and draw the gel coat into the tiniest of cracks.

Alternatively, you could dig out the patches and try again paying very close attention to your prep.

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