Troy,
We just completed our first attempt at wing filling. Actually we did an
aileron but the concept is the same. We got help from a friend who has just
completed the wing for his Velocity, so he's done a long of filling!
After curing the aileron, washing it with soap and water and scuff sanding
it, we first applied resin to the surface using an old cotton sock. This
coat is light, just enough to have resin on the part.
Epoxy and expancel were mixed to give a consistancy like a stiff milkshake.
Peaks must stand up without drooping. You can tell the mix is close to
correct when there is no sheen to it.
Glop the filler onto a smooth piece of plywood (18" x 18") and use a 4" to 6"
wide trowel to work a portion of the filler until its smooth and has no
bubbles in it. Scoop this filler up and put it on the surface to be filled.
Continue doing this until you have the entire surface filled to a depth of at
least 1/8", probably closer to 1/4". You can smooth it a little, but just
leave it to cure. You're going to sand off most of the filler anyway.
After the filler thoroughly cures (we waited a week), you're ready to sand it
off. Here's the trick. Andy purchased a 55" long PermaGrit sanding block.
By holding it parallel to the spar and moving it across the surface at a 45
deg angle, you can easily achieve a smooth uniform finish. Start at the
trailing edge and move to the leading edge. You'll develop a "shuffle" that
keeps you and the bar moving and the length keeps from making high and low
spots. Keep moving and going over the surface until you see some glass
starting to show. This is the high spot of your layup and is where you must
stop. If you put enough filler on initially, you won't need to fill again
except for pin holes. It took us about 3 hours to achieve a beautiful
surface on the bottom of one aileron.
This is how we're doing all our surfaces. Granted, its a lot quicker on aan
XS. Andy spent almost 6 months on his Velocity wing, but its huge, has a
large windlet and he's picky about his work.
Another tip, if you don't like how your filling is going, use your Dremmel
with a brass brush. You can easily remove cured filler without harming the
glass.
Good Luck
Jim & Heather A185
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