Easiest way to make a cowl? - RC Groups
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Oct 26, 2012, 07:11 PM
Motorized lawn dart
Mopar92's Avatar

Easiest way to make a cowl?

What's the easiest way to make a cowl for my 50" Kitfox project? Balsa and hollow it out? Or make a plug and vacuum?
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Oct 26, 2012, 07:42 PM
AndyKunz's Avatar
They're all easy ways. I like making big ones from a foam block (usually several layers of sheet) then carving/sanding to shape and covering with glass. Then I remove the excess foam (sometimes all, depends on the plane).
Oct 26, 2012, 08:02 PM
M0unt@in M0del$ minion
turbojoe's Avatar
Hey Andy, that would make a great "how to" thread for the new forum. Hint, hint, nudge, nudge.

Oct 27, 2012, 10:55 PM
Not failing=Not trying enough
Wehrdo's Avatar
If weight is of the essence, you can make one from plastic.

Make a foam plug like Andy said by carving/sanding a chunk or sheets of foam. I like to glue it to the firewall with hot glue and just sand with ~60 grit sandpaper OUTSIDE(foam dust is terrible).

Then cover the nose of the plane with masking tape where you want your cowl to cover. This part is similar to fiberglassing. Some also apply car wax to make it come off easier. Now, instead of putting glass cloth and resin, use paper mache. i.e. paper dipped in a glue/water mix. Try to use as little glue as possible so it dries quicker. Once all dry, pull off the plane. You might have to dig out the foam. It will be kind of flexible. Then fill with plaster of paris, and once cured, you can tear off the paper mache. Voila, a solid plug for shrinking.

For the shrinking, there's lots of info about that around. To shrink with a bottle, you need to find a PET plastic bottle that fits around your plug. Then you can heat with a heat gun to shrink. Or I've heated it over an electric stove.

Actually, if you have a vacuum former you can get away with just using the foam plug. If you're shrinking a bottle, the foam will get crushed by the force of the shrinking bottle and will deform.
Oct 28, 2012, 12:34 PM
I'm not as bad as they say.
Epoxyglass over foam has it's merits. You can make fun parts like this.
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