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Old Feb 27, 2012, 04:25 PM
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dedStik's Avatar
United States, VA, Virginia Beach
Joined Feb 2012
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Help!
Custom Cowling

I've a PT 40, it's missing the nose cheeks from a crash of long ago. I would like to make a cowling for it, I have thought about buying a ready made that would work, but I think a custom made one will look better on the plane, not to mention I could probably make use of the skill set involved down the road on other projects.

My question is would I be better off going a fiberglass route, making the mold then casting from it, or would vacuum molding be a better solution. I'm looking for ease of casting and overall look after completion. Or some other method I've not thought of. Those are pretty much the only ones I've considered and done some research on.

The cowl will be a 1 off, maybe 2 if a crash occurs, but the process I'd like to use with other models down the road.
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Old Feb 27, 2012, 07:52 PM
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Curare's Avatar
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Joined Jun 2005
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IMO a glass cowl makes more sense.

The only time I've liked vaccum formed cowls was when they were a single peice. Multiple peice cowls always broke, and never looked very good, or if they did, were nearly double the weight of a glass cowling.

Making a glass cowling is a lot more labor intensive, however it does pay dividends, in the fact that you'll have a lighter stronger cowling, and if you mangle it in a crash, you can just pull a new one from your existing mould.

A bit of time spent perusing the 'composites fabrication' forum here on RCU will give you a good idea of what you're up for.


Another way to go may be to build a balsa cowl, that's integral to the fuselage. It's a lot easier and with some effort can be very nice to look at!
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Old Feb 28, 2012, 08:21 AM
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dedStik's Avatar
United States, VA, Virginia Beach
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My efforts are not only for looks. I'd like to take out two birds with one stone so to speak, I'm looking at the heaviest option. I'm anticipating my project to be tail heavy and I figure a cowl can counter some of this weight. Fiberglass is an option, I've worked with it in the past, on wings and also repairing surfboard dings.

I had intended if doing vacuum mold to make it one piece, either solution though I am concerned with fuel hatch access, it has to allow me access to the fuel hatch for battery swap out. I think keeping that in mind I'll lean more heavily to the glass solution. Thank you for the help.
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Old Feb 28, 2012, 09:38 AM
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The easiest way to make one would be to shape one from foam, glass over the foam, finish and paint, then melt or scrape out the foam. This will be a little more sanding to get a nice finish, but much less work than making a mold of a one off cowl.

Greg
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Old Feb 28, 2012, 10:48 AM
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San Diego, California
Joined Dec 2004
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What gkamysz said.

Blue foam handles very nicely; carves, sands, shapes. Rather than scraping out the foam, find a solvent for whatever you use for the form and dislove it out.

Les
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Old Feb 28, 2012, 11:56 AM
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Solvent is fine just make sure you don't dissolve your primer/filler!

Greg
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