I agree with the previous comments about superfil - good, pricey, but worth
it considering the time saved.
And here is another method for putting filler on the flying surfaces. It is
based on getting the wing profile right at a small number of thin sections,
and then using these as guides for a long straight edge toapply the bulk of
the filler. It is particularly useful for the 'classic' wings where you need
to get a smooth curve over the ridges of the spars (which were about 2mm
proud on my wings).
Put down a layer of filler as a strip about 25mm wide across the cord of the
wing at intervals of about 900 mm along the spar. You will need 5 if your
straight edge is 1 metre long, more if you use a shorter one. Sand the strips
to form the correct profile. This is quite easy with these narrow strips.
Take time over this - if you get any flat spots then add more filler and
re-profile.
Once you have all your strips profiled run the straight edge across pairs of
strips parallel to the spar. If you hit any high spots then you will need to
add more filler to the strips and re-profile them. Once you are happy that
the strips are right, add filler to the area in between the strips and slowly
draw the straight edge over, using the strips as guides.
It is vital that the straight edge is very stiff or it will bow when you put
pressure on it and won't give you the flat curve that you want. I am using a
steel straight edge - 1 metre long , 60 mm wide, 4mm thick, beveled on one
edge. This was still too flexible so I riveted a length of 1 inch (25mm)
angle iron to the rear face.
You need to do a thin 'scrape coat' to finish off but at least at this stage
the profile is right. You don't put on excess filler which means less waste,
but more important, less sanding.
Roddy Kesterton, #220
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