Sanding the Pre-coat

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BillB
Posts: 19
Joined: Thu Apr 07, 2005 8:17 am

Sanding the Pre-coat

Post by BillB »

Well - it's time to finish the fiberglassing of my Nomad. Last fall events conspired to cause me to suspend fiberglassing before finishing the innner hull. Not wanting to leave a fiberglassed outter hull with an unprotected inner hull (to avoid risk of warping) - I applied a epoxy pre-coat to the inner hull. Immediately I noticed several long, deep scratches on the hull bottom. How I missed them when sanding I have no idea. Very annoying. My question is - can I sand through the pre-coat to get rid of the scratches and still avoid any blotchiness in the final finish? And to achieve this will it be necessary to apply another pre-coat? Thanks for your help - Bill.
Rick
Posts: 727
Joined: Thu May 27, 2004 9:23 am
Location: Bancroft, Ontario

Post by Rick »

Without actually seeing them, it'll probably be OK to sand out the scratches as long as they're not deep, and then to recoat the bare wood with epoxy. It'll help if there's some variation in the tone of the strips in that area, just in case there's a slightly different colored patch when the sanded area's pre-coated again... the patch should "disappear" into the various tones in the strips.
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Erik, Belgium
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Location: Gierle, Belgium
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Post by Erik, Belgium »

if you sand thru the sealcoat into the wood on some areas, you 'll always notice the difference in color afterwards. The seald wood will be darker then the sanded + later coated areas. Only solution IMO is, to sand the entire inside to bare wood. I can't image you 'd wanna do that.
It 's only a boat, I 'd just finish and paddle it.

Erik, Belgium.
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mtpocket
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Joined: Wed Sep 08, 2004 2:48 pm
Location: Indiana

Post by mtpocket »

If you decide to sand your precoated interior down to the bare wood in only some spots, be very careful once you break through the epoxy. The areas with epoxy will sand differently than those without. This means that the sander will eat into the wood much faster than through the epoxy precoat. If you work your sander back and forth over areas with and without epoxy, it will be eating into the wood while trying to sand through the epoxy in another area. This is likely to cause uneven surfaces that will be even harder to hide than the scratches. You might try to sand the area lightly through the epoxy with an orbital sander then switch to a scraper or hand held sander. As far as color matching, it was no problem at all for me. Without going into a long description of how I learned this, I found it not to be a problem. I did have to resand an area on the interior of my hull after precoat. I finished out with the same sand paper, it was the same wood and the same epoxy. I have no discoloration whatsoever. Just be careful not to dig too deep once you are through the precoat and everything should be fine.
BillB
Posts: 19
Joined: Thu Apr 07, 2005 8:17 am

Post by BillB »

Thanks guys. Those scratches really bother me so I'm going to try to carefully sand them out and re-coat. Bill.
reinbilt
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Joined: Tue Aug 31, 2004 7:35 am
Location: northern michigan

Post by reinbilt »

Bill, This is why I eliminated the precoating. On three boats with a precoat there is slight blotchy areas. Two boats with no precoat no blotchy areas. It is difficult to sand the precoat evenly to avoid this problem IMO.
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