I visited a shop specializing in fiberglass aircraft building and repair
recently. The shop owner was very helpful in answering a number of
questions. One thing that came up was removal of the spots of Bondo used to
hold fixtures to the wing temporarily. In his shop was a 7 year old Long-EZ
which had several small areas where the paint had peeled and been repaired
twice previously. The EZ's owner finally brought it to him and he found that
each of the areas which had repeatedly peeled was where Bondo had been
applied. He ground it off and put in fiberglass patches to prevent
recurrence, then re-painted. He indicated that he has seen similar problems
several times when Bondo was not completely removed. Apparently the Bondo
retains a small amount of moisture and when the surface is heated by the sun
it turns to steam, loosening the paint; the process often takes 2 or more
years. He indicated that the only sure prevention was complete removal prior
to painting.
I asked how he normally removes Bondo. He showed me a relatively soft
Scotchbrite wheel which he uses. I located a similar looking wheel but its
apparently not identical since it tends to abrade the fiberglass as well as
remove the Bondo. So, I would like to inquire how other Europa builders have
handled Bondo removal.
For those who haven't used Bondo to secure their jigs yet, perhaps epoxying
some peel ply in place at the points where the Bondo will be used to secure
the jigs would help. Then, after the jigs are popped off the Bondo can be
chipped away and the final remnants pulled off with the peel ply. I haven't
tried this but it seems plausible. Alternately, if a small piece of
fiberglass is epoxied in place beforehand (without scuff sanding) at the jig
contact points it should be possible to peel it or sand it off afterwards,
taking the Bondo with it.
Thanks in advance for the help.
John, A044
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