Originally Posted by Ed Smith
No doubt true. However I was not prepared to experiment further.
I can speak only of my own experience. I once joined several balsa skinned foam wings with epoxy. I then glassed the wing using polyester. The polyester did not cure right along the joint line. That was the last time I used polyester for anything.[ATTACH=CONFIG]1934108[/ATTACH]
I have had that happen over CA joints too. Turned out to be the hardener had expired. For some reason the balsa absorbed enough rein for the hardener to kick in, but wherever there was a CA joint, it stayed tacky. I bought a new tube of hardener and ran a swab soaked in it across each joint and a few days later the resin hardened enough to be sanded smooth.
I also had a quart of resin and tube of hardener that was stored for years in the basement, and tested it out. The resin got thick, the hardener didnt work at all, but a fresh tube let me use the resin for projects, and being that it was thicker it stayed in place on a vertical surface without adding anything, so a plus for that.
Been using poly for car repairs for a long time, just started getting into making RC parts with it, and this is my first use of WS Epoxy and really like it.
BTW Hair spray does work as a mold release, but is not as easy to use unless you get a pump bottle and pour it into an airbrush, as it goes on in larger splotches, but if ever in a pinch and run out of PVA, a quick trip to the nearest store can get you back in business. My PVA finally arrived so I can start my second Chippy cowl and see if I can get a smoother finish than the first one. I rushed the gel coat by not letting it set up first, and put it on too thick in places so I have runs. Also want to try the heat curing too. Should that be in or out of the mold?