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Old Dec 12, 2003, 02:35 AM
Vertical Wake
splatman's Avatar
visalia ca
Joined Dec 2002
735 Posts
which is better for foam sheeting---3M 77 or probond?

Have a big can of the old-formula 3M 77. Should I use this or probond for sheeting a large foamie?



splatman
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Old Dec 12, 2003, 02:47 AM
EDF Head
Haldor's Avatar
Stavanger, Norway
Joined Feb 2000
7,999 Posts
ProBond is better, different. While the 3M leave no time to reposition the skin (tacks instantly) ProBond allow this as its gluey for a while. Cure time about the same.

ProBond also expand a little so you get bettet skin contact. Last plus is it wont wear of age or hot/humid conditions. 3M can delaminate if left direct in the sun for too long.
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Old Dec 12, 2003, 06:56 AM
Big gov never Works
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Skunk Water, Rhode Island
Joined Jul 2002
12,379 Posts
I whole heartedly agree with Haldor. I actually lost the washout angle on a wing panel. Was fine when built, then later relaxed to nuetral. Caused some intense moments..

Steve
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Old Dec 12, 2003, 07:05 AM
Vertical Wake
splatman's Avatar
visalia ca
Joined Dec 2002
735 Posts
Thanks for the advice, gentlemen! I will invest in a bottle of probond. Will this work without vac-bagging? I intend to put wieght on the wing blanks (lined with wax paper). Should i put the PB on the skins or foam?
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Old Dec 12, 2003, 07:08 AM
Big gov never Works
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Skunk Water, Rhode Island
Joined Jul 2002
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Apply the PB to the skins. A very thin layer is all that is necc. Spread it thin with a plastic card. You only need to wet it.

Steve
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Old Dec 12, 2003, 08:41 AM
Registered User
Parkton, MD
Joined Dec 2000
345 Posts
Do a couple of tests first

PU glue works well but I needed a little practice. I used Gorilla Glue since I've seen reported that it doesn't foam as much. My first test was a thin layer on balsa squeegied pretty well and some white beaded FOME with no added water. I didn't care for the amount of adhesion. It stuck very well to the balsa but didn't penetrate the FOME well.

Second test was a more generous layer of PU (didn't squeegie it as thin) and some water on the FOME. It stuck well but lifted the wood a bit even though it was weighted during cure.

Last test was a well squeegied layer of PU on the wood and a sponge dampening of the FOME and I got great adhesion on both.

BTW, all tests were also done at the same time with 1/64 ply. I cut the FOME down layer by layer until I got to the glue joint to see what was really going on.

Very instructive and only took a few minutes to set the tests up.

jtm
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Last edited by Jim Miller; Dec 12, 2003 at 12:23 PM.
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