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polyester or epoxy?????

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Old 09-10-2011, 05:11 PM
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kenh3497
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Default polyester or epoxy?????

I have a cowl from a Hangar 9 Cap 232 that is in need of repair. After a hard crash come of the "gel coat' has been blown off the fabric. and there are quite a few spider cracks in the gel coat. I'm using the term "gel coat" pretty loosely as at this point I don't know what else to call it. Only a couple of tears to repair but the gel coat is in need of major reconstruction. Does anybody know for a fact the material used? If not see the next statement.

So, how do you tell the difference between epoxy and polyester resin? I thought at one time somebody told me if you sand the part, the polyester has a different smell than the epoxy does.

I have a good supply of auto body fillers and such but of course, they are all polyester based. I suppose epoxy and micro balloons could be used to make a new gel coat and the whole thing sanded smooth again.

Ken
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Old 09-10-2011, 05:22 PM
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Default RE: polyester or epoxy?????

Ken, heat up the cowl slightly with a heat gun and take a sniff. My guess is that it will have a definate odor which means it is polyester. Any of your auto fillers will work. As far as the damage, wick some thin CA in the cracks, sand the inside with 100 grit, clean and apply some new cloth with polyester resin.
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Old 09-10-2011, 07:38 PM
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Default RE: polyester or epoxy?????

The polymer used to make the part isn't that important. Polyester will have the least bonding strength and epoxy will have the greatest bonding strength....regardless of the material in the part. For this reason I always use a laminating epoxy to make a repair. It's important that the surfaces get sanded and cleaned before the repair is made.

I suspect that the surface coat on your part is a polyester gel coat. Polyester gel coats are very prone to cracking when impacted. As stated above, I would reinforce the back of the impact with some fabric and resin. The outer could be filled with laminating epoxy and MB or an autobody filler. The autobody filler will be more prone to delaminating than the epoxy.

If you don't have a laminating epoxy then use what you got.

Adam
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Old 09-12-2011, 03:17 PM
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Default RE: polyester or epoxy?????


Quote:
ORIGINAL: wyowindworks

The polymer used to make the part isn't that important. Polyester will have the least bonding strength and epoxy will have the greatest bonding strength....regardless of the material in the part. For this reason I always use a laminating epoxy to make a repair. It's important that the surfaces get sanded and cleaned before the repair is made.

I suspect that the surface coat on your part is a polyester gel coat. Polyester gel coats are very prone to cracking when impacted. As stated above, I would reinforce the back of the impact with some fabric and resin. The outer could be filled with laminating epoxy and MB or an autobody filler. The autobody filler will be more prone to delaminating than the epoxy.

If you don't have a laminating epoxy then use what you got.

Adam

I was concerned about the bonding strength, hence the question about epoxy/polyester. The plan was to fix the splits and tears from the inside and slather the filler of choice on the outside, sand and paint.

Thanks!!

Ken
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Old 09-12-2011, 04:38 PM
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Default RE: polyester or epoxy?????


Quote:
ORIGINAL: kenh3497

I was concerned about the bonding strength, hence the question about epoxy/polyester. The plan was to fix the splits and tears from the inside and slather the filler of choice on the outside, sand and paint.
The key to a good bond will the prepping of the surface. I would sand with 80 grit sanding paper and then wipe the area with acetone. If the part was fabricated with a polyester finishing resin then there could be wax on the surface.



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