We have completed all our flying surfaces without taking advantage of the
knife trim stage. We have adopted the following technique which is made
easy and not labour intensive by the Permagrit tools used:-
1. Trim layup edges while wet to say 10 to 20 mm of edge. Objective here
is to be close enough that the weight of the cloth plus resin does not lift
the cloth from the foam
2. Scissors with a serrated edge help when cutting cloth which is wet with
resin.
3. Make sure the edge overhange is wetted out
4. Let layup cure to full hardness - don't bother to knife trim
5. When cured do rough trimming of edge with a Permagrit disc (about 40mm
diam) in a Dremel like high speed motorised "drill" if there is a lot to cut
off.
6. Do final trimming with a permagrit hand file. This type of file does
not clog, and goes through the layup very quickly indeed.
When trimming edges do think ahead and work out the role of the edge and
therefore its importance/criticality in the final plane e.g. is it the final
edge, are hinges to be attached close by etc
Donald Kesterton
Builder 216
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