Scratch Building a U-Control Classic

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larry cottrill
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Scratch Building a U-Control Classic

Post by larry cottrill » Thu Jul 22, 2010 6:46 pm

Last year, my wife was talked into getting me the plan set for the classic 1937 original U-control kit model, the famed A-J Fireball, designed by Jim Walker (the patent holder for the U-control flight system). This year, I decided to try to build it. I am not building it to be "authentic", mainly because I want a stunt version.

The original model has a tail moment arm far too long for stunt flying, so I chopped a mere FIVE INCHES (over 125 mm) out of the fuselage between the wing and the tail surfaces. The original wing plan and horizontal tail surfaces seem to have just the right area for a stunt ship once the moment arm was reduced. Naturally, I have to change the airfoil to a thick, symmetrical airfoil for stunt flying. You can see that in the cutout for the wing, clearly visible in the second photo.

The engine will be a 1940 vintage Forster 29 (0.29 cu.in. displacement) 2-cycle mill. This is a glo plug engine, though the original Fireballs always carried a coil and condenser (batteries, too). So, mine will be that much lighter, again much better for a stunt ship.

The saw-cut slots visible in the bottom hull carving are for the landing gear and tail skid. I started out by band sawing the block outlines, and did the rest by hand carving, using X-acto gouges and a very small Surform(TM), which really worked well. Finished up with a couple different grades of sandpaper. I'll probably set the gouge aside and grab my Dremel tool for the hollowing of the blocks, since I still labor under the delusion that my time is worth something. This old 1930s streamliner style design is known as a "razorback fuselage".

I have no idea when I'll finish her up, but the way things go, she probably won't be flying till next year.

L Cottrill
Attachments
2010-07-13_Fireball_fuselage_02_small.jpg
The carved fuselage blocks (not yet hollowed out) - bottom in front of top.
Photo Copyright 2010 Larry Cottrill
2010-07-13_Fireball_fuselage_03_small.jpg
How it looks fitted together. Of course, there will be a big clunky engine
notched into the nose end. Photo Copyright 2010 Larry Cottrill

metiz
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Re: Scratch Building a U-Control Classic

Post by metiz » Thu Jul 22, 2010 7:03 pm

Ditch your Forster 29 plans and use your Lady Anne instead. Don't forget to post some injector/ pump details :wink:
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