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Hot wire cutting thru glued foam

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Hot wire cutting thru glued foam

Old 06-22-2015, 12:20 PM
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TVL
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Default Hot wire cutting thru glued foam

I just tried cutting my 1st foam wing today and it didn't go well. The airfoil that I'm tring to cut is 3.25 inches thick at it's thickess point. I could not find foam that thick so I glued two 2" pieces together with gorrila glue. The 1st bad thing is the glue foamed out so bad that it ran out from between the two pieces right onto our dinning room table. No worries though my wife is not going to kill me this time, she has been after me to refinish the table because of a water mark that would not come out, so now I have to do it soon because the four big glue spots really look bad.
Back to the wing cutting when I cut the two squares to glue together and then notchted out for two spares to run thru the wing my hot wire bow seemed to cut threw the 2" thick foam and threw the 22" long cuts for the notches quite easly. When I attempted to cut the airfoil today my hot wire bow didn't seem to cut threw very fast at all. And when it got to the glue it didn't get threw it ervy easily. I had too force it thur the glued area and the wing turned out unusable. Is there an better glue to use that the hotwire will cut threw easy'er. I wont use gorrilla glue again even with a lot of wieght it it still push the foam apart leaving a 1/16 or so gap of glue that the bow could'nt cut threw. any suggestions on what glue would work the best for the hot wire to cut threw. Any help would be highly appreciated. I'm using a big battery charger for my power source and setting it on engine start at 200amps.

Last edited by TVL; 06-22-2015 at 12:42 PM.
Old 06-22-2015, 01:28 PM
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Propworn
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It doesn't seem to make much difference the glue joint is always a problem. The best results for me have been Lepage's green press tite water based contact cement http://www.lepageproducts.com/ProductDetail.aspx?pid=89 apply two thin coats both pieces and press together. I try and keep the glue line in the center where I will not be cutting if possible.

Dennis
Old 06-22-2015, 04:55 PM
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I used Elmers white wood glue and Tite Bond and even that will snag the wire and leave a bumpy spot. As Dennis pointed out trying to avoid the glued area is the best way. I did find some very thick foam sheet at a swap meet but failed to find out where the seller got it. Here in Vegas we don't use much foam insulation so just locating the good pink foam is a mail order item. I ended up using the white foam.
Old 06-22-2015, 05:13 PM
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I use 3m 77 spray adheasive to stick the foam together. spray each half ,wait 10 minutes then stick them together! 5 minutes later use ur wire cutter as normal,when the wire hits the glue section,the heat of the wire will cur right threw no problem!
Old 06-22-2015, 05:25 PM
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Originally Posted by abacro View Post
I use 3m 77 spray adheasive to stick the foam together. spray each half ,wait 10 minutes then stick them together! 5 minutes later use ur wire cutter as normal,when the wire hits the glue section,the heat of the wire will cur right threw no problem!
Don't know about the OP but I will give it a try.
Old 06-23-2015, 05:25 AM
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Originally Posted by Gray Beard View Post
Don't know about the OP but I will give it a try.
Test it first on the foam some foams are attacked with the 3M leaving the foam glue joint soft. I make a sample glue joint using the same amount of glue I intend to use then try and rip it apart. The green foam from home depot was the worst if sprayed on heavily it would actually start to dissolve the foam.

Dennis
Old 06-23-2015, 09:24 AM
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Lepage's might not be available in the US. I have some at home I have to try this out. I'm having a difficult time to find cheap foam core material to have at least 4" thick cores.

The only foam glue I used in the past was Sigbond.

Jim

Originally Posted by Propworn View Post
It doesn't seem to make much difference the glue joint is always a problem. The best results for me have been Lepage's green press tite water based contact cement http://www.lepageproducts.com/ProductDetail.aspx?pid=89 apply two thin coats both pieces and press together. I try and keep the glue line in the center where I will not be cutting if possible.

Dennis
Old 06-24-2015, 04:13 PM
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I buy my foam in 4ft x 8ft x 5inch thickness from a furniture reupholstering shop locally. I pay about 25 dollars a sheet! Check in your area for shops like that, you might be surprised!

GL Art
Old 06-24-2015, 05:18 PM
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Never thought of that. I don't do a lot of foam cutting except for small electric type of planes and I cut some stuff for club members. Gene {goirish} here on RCU made me one of his automatic feed foam cutters. Once you get it all figured out it cuts foam without any of the start and stop marks. Just get the temp set and let it do the work for you. Gene may or may not still be making and selling these machines but it really is a quality item.

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