This is some "old" pics of a test I did a few years back when deciding upon the right way (for me) to glue the plywood skins on Divinycell H60 & H80 (or the equivalent Airex C70.55 or C70.75). These foams (cross-linked PVC) are very good for making sponsons and they can handle normal CA glue. In fact when I did this test it showed better glue joints with CA glue then epoxy actually!
These pics have been available all the time if you would have clicked the links to the right (Kep's 21 build tips #2) ->
Glue test, Divinycell H80 to the left & H60 on the right. 0.8 mm plywood. Great Planes Pro CA kicker on foam (no glue pre-applied on the foam). Zap CA+ green on plywood. Will properly not work that good as the CA on bigger surfaces has time to sink into the plywood a little too much. Maybe could work better if an slow version of the CA is used. Left overnight to set properly (one wouldn't crash test a sponson after just a couple of minutes, right?) - it sat good after a couple of minutes though.
Glue test, Divinycell H80 to the left & H60 on the right. 0.8 mm plywood. No kicker used at all. Zap CA+ green on the foam (none on the plywood). Dont use this method - trust me. It seems the air in the foam pores makes the CA not to set at all it seems. After 3 minutes I could lift the plywood from the foam - nothing had happened. Left overnight to set "properly", well I hoped it had set by then... To my surprise it actually had. But the glue joint is no good.
Glue test, Divinycell H80 to the left & H60 on the right. 0.8 mm plywood. Z-poxy 30 minute. Left overnight to set properly. To my surprise, the glue joint was quite good... I had tested earlier with the 5 minute version and that was just a sad sight. With 5 minute epoxy it was just a "glue skin" on the plywood when bending it loose. With the longer hardening time the epoxy seem to creep into the foam making it a better glue joint.
Glue test, Divinycell H80 left & H60 on the right. 0.8 mm plywood. Great Planes Pro CA kicker on plywood (no glue on plywood). Zap CA+ green on foam. My favorite technique. It seems that when spreading CA over the foam one has the most time to line up the skin your gluing etc, but when assembled, it sets quite fast. Left overnight to set properly (for testing purpose - when actually building your sponsons you could move on with the build after a minute or two), it sat good after a couple of minutes though. Works equally good with GP medium CA or slow CA's if you need more time = bigger sponsons maybe...
Do note, I have not tested with any other brands of glue or kicker - thats up 2 U...
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