Priming Epoxy Resin Tips?

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PostPosted: Tue Mar 13, 2012 4:54 pm
Hi guys, Im planning some fibreglass repairs and was unsure about a couple of things.

Basically im using an epoxy resin filler (from west systems), and I was wondering if there was any suggestions, tips, or special advice I should heed before priming over it.

I planned to use a simple UPOL aerosol primer, but could get hold of some 2 pack if you guys say its worth it?


Someone I spoke to earlier said I didnt actually need to spray primer over it but that seems totally crazy.



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PostPosted: Tue Mar 13, 2012 5:55 pm
I used some of the West epoxy filler a long time ago on my boat, it was very hard sanding as I remember. I'm no expert, but I do think that you need to use a two-part epoxy primer.



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PostPosted: Wed Mar 14, 2012 4:03 pm
fireboat wrote:I used some of the West epoxy filler a long time ago on my boat, it was very hard sanding as I remember. I'm no expert, but I do think that you need to use a two-part epoxy primer.


I think almost all epoxies are two-part\. You need to primer the epoxy first and then paint over it use something compatible with epoxies for primer.. I don't know what that UPOL stuff is..

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PostPosted: Wed Mar 14, 2012 9:38 pm
Get some epoxy primer and seal the fiberglass with it first. No laquer or enamel spray bombing please.
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PostPosted: Thu Mar 15, 2012 2:35 pm
timbo wrote:Get some epoxy primer and seal the fiberglass with it first. No laquer or enamel spray bombing please.


Epoxy primer is meant to be applied over bare metal not over fiberglass please use either polyester or epoxy resin to spot repair where you want to.

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PostPosted: Thu Mar 15, 2012 3:30 pm
giorgos wrote:
timbo wrote:Get some epoxy primer and seal the fiberglass with it first. No laquer or enamel spray bombing please.


Epoxy primer is meant to be applied over bare metal not over fiberglass please use either polyester or epoxy resin to spot repair where you want to.

If there is a problem with the substrate epoxy should hold it down better than just plain poly. I used to think on that same line giorgos but have changed that procedure over the last year after talking to some guys on the SPI forum that do mostly fiberglass projects and kit cars.
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PostPosted: Thu Mar 15, 2012 5:45 pm
Polyester resin will only adhere mechanically to cured fiberglass, which is still sufficient for most non-structural repairs, but I have seen a lot of repairs where you could pull strips of polyester resin/cloth off because of inadequate bonding. Not something that you want when you are 20 miles offshore. Epoxy however will have a much stronger chemical bond as well and is inherently more waterproof than polyester. Vinyester resin is a good compromise on price and performance.

As a primer, most of the marine coating manufacturers (Interlux, Awlgrip, Alexseal, System 3) require an epoxy primer for their two-part paints, even over a fiberglass substrate. You could use almost any epoxy primer but many of the marine versions can be rolled if you don't want to spray.



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PostPosted: Sun Mar 18, 2012 3:08 pm
Well I should have pointed that out fireboat , epoxy resin is much stronger (and pricier....) than polyester resin. It all depends on what kind of damage you're repairing, if you want to relaminate most people use polyester resin because of the price tag (and other reasons too but I won't get too technical)..the epoxy primer should go over the repaired area after you've sanded it and flattened it out. Polyester resin is not completely hydrophobic it has pores that water seeps into and can crack a lot easier on the hull areas where static pressure is applied. Epoxy is much better but hasn't got elasticity and will deteriorate under uv rays that's why you should always cover the epoxy resin with paint.

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