> I took a damp cloth and wiped both sides of the capstrip to dampen the > wood, as this glue needs moisture to activate it. I put a bead of glue on > the > surface of one side (not both sides like epoxy) of the strip and used a 1" > brush to spread it evenly across the 3/4" surface.
++++++++++++++++++ I learned something in the early hours of this nice day (about polyurethane adhesives) that really bothers me. It has been on my mind (since the recent discussion) that experienced and knowledgeable netters had also done some testing of their own - and were not impressed - why? I was attaching a doubler to a fuselage longeron. The joint offered plenty glue area (my psi logic) so I used the polyU. I have been following the Forest Products recommended procedure of applying glue both sides, rubbing together and leaving things open for a few minutes. This was a mistake on the day, I guess the RH was just to high. Everything looked good until I started clamping up. By chance I noted a gap (maybe 1/32") and came back increasing the clamping pressure on all of the clamps. I say by chance because as we know, once this glue comes fizzing out of the joint, it hides the gap unless you wipe and look. No amount of clamping closed the gap, I assumed that I had something trapped in there (could not imagine what?) so the messy task of de-clamping and opening. There was nothing other than glue? Presumably a core of the expanding "film" of glue actually was resisting my efforts to close the gap. >From my tests I know, ANY gap just leads to a weak joint, so I checked the other side (glued the day before) - same story. I shut down the shop and came to work - another messy task tonight!! For those that use PolyU, be aware of this tendency /possibility - probably when there is plenty moisture in the air. Steve J South Africa
