sledracr

Thickening polyester resin

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I'm in the middle of removing/replacing/re-positioning some deck hardware, and will end up with a bunch of 1/4-inch (and a few 5/16") holes that need to be filled.

Normally I'd make sure the inside of the hole is clean/dry/solid, seal up the underside, mix up some epoxy with WEST-406 to about the consistency of mayonnaise, and splooge it in.

But these holes are in a very-visible area where I want to have the finished surface look nice, so I want the surface gelcoated to match, and gelcoat guy says gelcoat won't bond with epoxy.

So.... polyester it is, and I don't know what the best thickening agent is these days for use with polyester resin.

Old school, I'd get a bag of 1/16" (or 1/32") cut glass strands and mix it in.  Is that still good?  will WEST-406 (colloidal silica) work with polyster resin?  Is there something better to use?

 

 

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West 406 works fine with polyester.  A bitch to sand tho, but thats the same as epoxy.  410 works as well. 

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The notion gel coat won't bond to cured epoxy has been proven false.  It all depends on surface prep, while basically boils down to: make sure epoxy is full cured, use water and a scotch brite type pad to remove any amine blush, then sand: http://epoxyworks.com/index.php/applying-polyester-gelcoat-over-epoxy/

As for fillers.  cabosil is a much cheaper version of WEST 406.  I wouldn't consider 410 for deck hardware holes for 2 reasons: it has relatively low structural strength, and it is one of the few WEST fillers that that won't work well with Polyester resin,

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Shrinkage is another reason to go epoxy rather than poly.  I believe The PO of my boat used poly to fill some holes.  At deck level you can see where the plug has pulled away from the paint.

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Marine tex is made for this and can be tinted to match you gelcoat color. You can also use some of the newer epoxies for surfboards that do not blush and can be pigmented to match your gelcoat.  Good luck to you.

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