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Old Sep 05, 2011, 06:05 PM
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Oh no, not again!
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United States, LA, Carencro
Joined Dec 2005
5,976 Posts
I probably should be a little more clear. Since I crash-tested my SBD to destruction, I have some feel for how the glues held. CA + kicker (not just CA) joints never failed, the foam always tore. That was true for 95% of my epoxy joints and epoxy is much better for filling gaps. GG broke free of the foam in maybe 1/3 of the joints. I use little or no water with GG, it foams okay without it and the large bubbles you get with too much water are pretty flimsy. I find the white GG (Sumo?) works better in that it has a little more flex and doesn't expand nearly as much. I haven't had a lot of luck with hot glue, it's pretty messy. I wrap my servos with masking tape and glue them in with a blob of silicone cement. Takes an hour or two to set, but flexible and relatively easy to clean up if you have to replace a servo.

Regarding prep - besides making sure the surfaces are clean, when I use epoxy I use at least an equal volume of microballoons. They make the mix "stiffer" and they cut the weight dramatically. For an epoxy joint, I use a toothpick or bamboo skewer to punch many small holes in the mating surfaces. This increases the bonding area and as the epoxy spreads into the holes, it tends to "lock" unlike with smooth surfaces. Fahim (Wowplanes) even made a tool, a small block of wood with brads set in it so that you can make a couple dozen holes at a time.

Which glue is best depends on several factors and a lot of it is just personal preference.

Jeff
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