<<...did somebody just oil the air grinder prior to grinding?  Another thing
that can happen with dense layups like the glass prepregs we use.  A dull
grinder disk can burnish the edge of the area being abraded making it less
likely to adhere....Dan>>

Some related observations I have made:  I found the air sander difficult to
use, although that's what I was instructed to use at the factory when
closing my ES wings (Feb. 01 - does that make me the first?).  My conclusion
was that the high speed of the sander heated the laminate and, as Dan said,
tended to burnish instead of cut.  Manually sanding at a low speed but high
force seemed to be much better.  I also found out that the air sander would
occasionally spit water eventhough I had a filter and trap in the line.  Now
I do everything by hand.  Also, a dull paper doesn't do nearly as good a job
at opening up the surface prior to bonding.  Another observation - If Jeffco
layups are applied one after the other the first layup can be partially
cured and the second will adhere just fine.  But if the layup is starting to
kick and it is placed over dry laminate it won't.  All this make sense?

Gary Casey