shrinking epoxy

Topics pertaining to fibre glassing, finishing issues, concerns and tips, epoxies and epoxy problems/resolves
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northerncat
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shrinking epoxy

Post by northerncat » Sun Sep 17, 2006 1:15 am

the definition of frustration= having a few screw holes in your boat so you mix up some epoxy and qcell to fill these little holes, two days later the epoxy is good to sand so you fair off all of these holes, two months later you spray your interrior with high build epoxy primer and start sanding and what do you discover but that the epoxy in the holes has shrunk leaving you with num,erous little conical indentations all over your boat so out with the filler again, so the lesson( i think) is to leave all of these screw holes filled and unsanded till you are ready to paint

sean

has anyone else encountered this? i assume that i sanded before the epoxy fully cured is there any other reason that this might be happening?

puremajek
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shrinking epoxy

Post by puremajek » Sun Sep 17, 2006 2:15 am

Sean



Feel for you as I managed to catch this early in the piece. My indentations were a result of using gluemix to fill the holes. Once they dried, they definitely leave indentations. With a Q-cell mix, I found it OK however, have to admit that I did not sand until at least a month later and in the case of frame 7 and the bow lockers, two years later.



Even then, I located some indentations only after the undercoat went on. I must admit that the undercoat and its smoothness definitely dictates the final coat appearance, so every improvement at this stage will show once the final coat is on.
James
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cruiserbill
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Joined: Mon Jun 13, 2011 12:04 pm
Location: Indiana

Re: shrinking epoxy

Post by cruiserbill » Fri Apr 22, 2016 6:40 am

Resurrecting an incredibly old thread. :lol:

I read that using auto body filler (Bondo here in the US) can be used for covering the screw holes. Has anyone tried this?

martica
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Re: shrinking epoxy

Post by martica » Fri Apr 22, 2016 11:55 am

I used both methods and had no issues

mikeb
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Re: shrinking epoxy

Post by mikeb » Fri Apr 22, 2016 12:29 pm

I used both & HAVE had issues. It's more noticeable in winter so maybe the cooler weather plays a part. It looks awful some days when you can clearly see the row of screws...
I have almost no fairing compound on my hulls, just highbuild to fill the weave & some localised fairing. Maybe Martica can give you some advice on how he finished his hulls.
Mike

cruiserbill
Posts: 51
Joined: Mon Jun 13, 2011 12:04 pm
Location: Indiana

Re: shrinking epoxy

Post by cruiserbill » Fri Apr 22, 2016 12:36 pm

mikeb wrote:I used both & HAVE had issues. It's more noticeable in winter so maybe the cooler weather plays a part. It looks awful some days when you can clearly see the row of screws...
I have almost no fairing compound on my hulls, just highbuild to fill the weave & some localised fairing. Maybe Martica can give you some advice on how he finished his hulls.
Mike
Yes, for those of you who have figured this out, it would be appreciated if you would share.

sea_bee
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Location: Pillar Valley NSW

Re: shrinking epoxy

Post by sea_bee » Fri May 06, 2016 8:16 pm

The indentations are not the bog shrinking. It's the plywood on either side swelling from moisture soaked up out of the air. There's not much you can do about it apart from bogging at the right time of year, and even the very experienced builders have this issue.

Chris

capt.fred
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Re: shrinking epoxy

Post by capt.fred » Sat Aug 06, 2016 11:25 am

Please be advised that epoxy does not shrink. The epoxy settles into minor crevices, thus the concave appearance. After the first batch sets up, just fill the concaves...

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