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Old Oct 26, 2012, 06:11 PM
Motorized lawn dart
Mopar92's Avatar
United States, MS, Columbia
Joined Nov 2003
2,152 Posts
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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Old Oct 26, 2012, 06:42 PM
AndyKunz's Avatar
Joined Sep 2001
27,642 Posts
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).
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Old Oct 26, 2012, 07:02 PM
M0unt@in M0del$ minion
turbojoe's Avatar
United States, AZ, Mesa
Joined Jul 2002
7,476 Posts
Hey Andy, that would make a great "how to" thread for the new forum. Hint, hint, nudge, nudge.

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Old Oct 27, 2012, 09:55 PM
Not failing=Not trying enough
Wehrdo's Avatar
United States, IA, Coralville
Joined Jun 2011
360 Posts
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.
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Old Oct 28, 2012, 11:34 AM
Mickey from Orlando. Really.
Joined Nov 2004
3,785 Posts
Epoxyglass over foam has it's merits. You can make fun parts like this.
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