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Scratch building a Cowl

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Old 08-12-2004, 10:31 AM
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*Crash*Johnson*
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Default Scratch building a Cowl

A question for the pro's...

I bought an Extra 300S from Tower Scratch and Dent, and of course it was missing a cowl. I figured I would outsmart them and order a Great Planes Extra 300S cowl, which was the same rough size plane. Sure enough it don't fit right... It's about 4" or 5" too short.

I can use it to make a new plug, but where do I start?

I was thinking, perhaps I can cover the front where the prop sticks out and fill it with plaster to make a mold. Take the mold and try to make it longer with foam or something... Then Fiberglass a new one from the mold.

I want to make one since I cannot find anywhere on the planet who sells Phoenix Models accessories.

Any ideas?
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Old 08-12-2004, 11:59 AM
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Ed Smith
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Default RE: Scratch building a Cowl

I take it this is a one shot item.

What do you want to do with the existing cowl? Make a plug, from which you can make a mold, from which you can produce parts?

For one piece it is not worth it. Is it possible to convert the existing cowlng to fit the airplane. E.G. If the front end is somewhere near close could an extension be fitted to the back end to match the fuselage.

Personaly I would start from scratch and make a new one. Start with a former at the fuselage, one at the prop washer and balsa planking in between.

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Old 08-12-2004, 12:16 PM
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Default RE: Scratch building a Cowl

For one piece it is not worth it. Is it possible to convert the existing cowlng to fit the airplane. E.G. If the front end is somewhere near close could an extension be fitted to the back end to match the fuselage.
Yea. I guess I could extend the rear of it another 4-5" to fit. The question is how would I go about that? One piece manufacturing wouldn't be a big problem. This way if the cowl cracked I could whip up a new one.
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Old 08-13-2004, 07:08 PM
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Default RE: Scratch building a Cowl

[link=http://www.paonline.com/hayman/video.htm]Try This[/link]
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Old 08-13-2004, 10:57 PM
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Default RE: Scratch building a Cowl

I had a similar problem with a Citabria kit. I made a former at the front of the fuselage and then glued foam to that until I had the correct length. Since you only need to extend the cowl you have just add the correct amount of foam to fill the area needed to extend the cowl. Sand the extension to shape between the existing cowl and the former you made. Once you are satisfied with the shape , making sure the length is correct and the proper alignment, right to left,top to bottom you can glass it. I used 4 layers of lightweight glas cloth and epoxy. Don't use finishing resin the foam disappears. I removed the foam with carburetor cleaner and then added 2 layers of heavy cloth and epoxy inside for added strength. The cowl will be slightly thicker than the original but it will not be noticable. Takes a little time but then what doesn't these days.
Good luck

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Old 08-14-2004, 09:46 AM
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Default RE: Scratch building a Cowl

I think that's what I'm gonna do. I have the 1" foam insulation I got from Home Depot and the cowl that is a smidge oversized. I'm gonna use it for the template to cut foam pieces and stack / glue them and shape to the cowl design.

Then follow what you did with the fiberglassing. Only need one, got plenty of time. I can fly her without a cowl for a week or so.
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Old 08-14-2004, 10:26 AM
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Mike James
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Default RE: Scratch building a Cowl

There are lots of (free) tutorials on the web on how to do this stuff, including a nice simple set at the CST site, here:
https://www.cstsales.com/How_to_Articles/index.htm

If you're interested in making some slight modifications to the original cowling, or if you're simply good at shaping foam, here's one on my site, too: http://homepage.mac.com/mikejames/rc...t_cowling.html
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