CLOUDY GLASS

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treeations
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Joined: Wed May 09, 2007 12:24 pm

CLOUDY GLASS

Post by treeations » Sun May 13, 2007 1:25 pm

Hello,
I built a canoe back in 1992. I primarily went by the instructions in "Canoecraft" (Copyright 1983). It came out pretty nice, but there was some cloudiness in the glass. I have lived with it and have been paddling it ever since. I'm now thinking about building another (or perhaps more) boat. I've been thinking about building a kayak and have read "Kayakcraft" and "The Strip-Built Sea Kayak" by Nick Schade. I noticed that neither of these books mentioned using a hot air gun 24 hours after the the final coat of glass has been applied, as it does on page 116 of "Canoecraft". I was wondering why this step was ommitted from "Kayakcraft" and if it could have something to do with the cloudiness in my first boat. Thanks for any info that you can give me.
Dave

Rick
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Joined: Thu May 27, 2004 9:23 am
Location: Bancroft, Ontario

Post by Rick » Mon May 14, 2007 7:40 am

Dave, some brands of epoxy will turn cloudy under cold or humid conditions, or both. I've made mistakes in the past, even when the manufacturer's instructions said epoxy could be applied at 10C (50F)... so now I epoxy when the temps are 20C or warmer and the air is relatively dry (a dehumidifier in the basement helps).

Maybe overkill but I'm not taking chances with epoxy going cloudy again, since I really don't know where the line actually is in defining when temps and humidity aren't suitable (haven't done enough tests to find out).

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Joan and Ted
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Cloudy epoxy, using a heat gun etc. ( re: WEST System)

Post by Joan and Ted » Wed May 16, 2007 10:19 am

Hello Dave - Glen Smith our forum moderator forwarded your question on to me for a response - my response relates to West System® epoxy only and I assume this is what you used? We use West because it gives consistently predictable results especially where first time builders are concerned so here are my comments:
It is likely that the problem of cloudiness is a combination of three things - using too much epoxy, working it too much and perhaps the #206 hardner (West System) if that is what you used in 1992. Ted says that hardners have changed alot in the 24 years since he wrote Canoecraft and if you use the newer #207 (West System) cloudiness is just not an issue. He has not told anyone to use a heat gun in so long we had to get out an older version of Canoecraft to refresh ourselves.

Basic technique is:
First coat: the epoxy is transferred from the can to the cloth using the brush - this is not like painting - the resin is not forced into the weave with the brush (that would encourage air bubbles) - you spread the resin using the brush so the fabric absorbs the resin at its own speed - certain grains accept different amounts of resin so add fresh resin to areas that look dry - the main idea is to work aggressively keeping the resin fresh at the working edge so the colour will be consistent.
After the epoxy has soaked in for about 20 minutes squeegie off the excess.

Second coat - the purpose is to fill the weave of the cloth and achieve a level surface - you can't brush it on without causing the resin to foam up so float the resin on and squeegie to fill the weave as you remove the excess. Transfer the resin using the brush to a portion of the area - then pull it over the area with the squeegie. - after the epoxy is roughly spread - squeegie off the excess.

Third coat buries the weave of the cloth so there is no tangible texture to the surface and you won't cut into the fibres when you sand. Apply as soon as the surface is firm enough to work on - the less time between coats the better. Since the surface is now smooth it is possible to aggressively brush (or roll) the resin with less chance of creating foam. If bubbles form lighten up - the goal is to apply a thick uniform coat of resin using the painting motion - don't create runs - read Canoecraft for tips on using the brush on this coat (we do not use rollers).

Hope this helps - let us know if you have more questions.
Joan info@bearmountainboats.com

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