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One more fiberglass question

AeroDog

Well Known Member
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I've used the search tool, read all of Dan's articles and lots of others but can't find this answer. Using West 105/206 epoxy, what is approximately the minimum time I need to let it cure before sanding? I saw Dan mention 24 hours in one post, but is it OK to sand sooner? The KAI says "Let it cure for a day or so." Can I sand it when it feels hard to my fingernail?

Jerre
 
I've used the search tool, read all of Dan's articles and lots of others but can't find this answer. Using West 105/206 epoxy, what is approximately the minimum time I need to let it cure before sanding? I saw Dan mention 24 hours in one post, but is it OK to sand sooner? The KAI says "Let it cure for a day or so." Can I sand it when it feels hard to my fingernail?

Jerre

You aren't going to hurt it by sanding too early. If the epoxy isn't fully cured, it'll gum up your sandpaper instead of sanding cleanly.
 
Temp

Huge variation with temperature. With a curing lamp it’s an hour. In a room temp hangar it would be a day. Just set it aside and work on something else.
 
Sanding

Agreed. Temp is the variable. You can sand it earlier, but it gums up the sandpaper. I tried to put parts in our furnace room. Sometimes it works in your favor. Sanding micro for example. If you catch it just shy of fully cured, a file will take it down really quick and the gummy stuff comes off the file with a wire brush.
 
I've had it cure in 4 hours when it's 90+ degrees and 50% humidity. I've also had to use the fast hardener to get it to set in 24 hours when it's 30 degrees overnight.
 
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