I had the two #78 samples from before, and a piece of 1 PCF EPS glued to wood and one glued to FR4. The samples were made over a week ago.
The orginal foam samples did fine with an electric planer, a Surform-type tool, a 7" electric sander, pad and disk, and the old hot wire.
The wood and FR4 were adhered…until I started playing with them, like a kid taking apart a peanut butter sandwich. Then the joints failed at the glue line.
I pulled the other foam samples apart the same way as well. The EPS + EPS failed at the glue line, the EPS + XPS + EPS did better, failing in the structure of the EPS as well as the glue line. To be fair, the EPS + EPS joint that failed at the glue line was the same one I messed with a whole bunch of times during the tack stage. So maybe it’s better to ‘set it and forget it’ rather than play with the tacky joints.
I would say:
-The #78 product is useful for tacking and positioning foam and that the seam is workable with normal tools.
-I would not use it as the primary adhesive to assemble a foam surfboad blank since there is evidence that the joints could fail under stress.
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