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Old Nov 11, 2012, 05:16 PM
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United States, MD, Elkton
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odds and ends

I'm trying to enlarge a 32" Sparky rubber powered model to 114"....I have some of the framework completed but I want to turn a LARGE prop.
If every thing scaled properly,I'd need a 43" one. to be properly sized.

I got a .60 size helicopter drive system which is geared 8.5 to 1...
With the engine turning around 8,500 r's and the prop at 1,000,it seems possible..

I need to build up the prop like miniature wings,with strong spars and maybe foam cores,sheeted and glassed.

I don't know if it'll work,but I ain't skeered to try.
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Old Nov 11, 2012, 10:01 PM
I think I'm inverted. Maybe.
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United States, CA, Pacifica
Joined Apr 2012
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A 43" prop... awesome. . Order some thin NACA foam cores from FlyingFoam and give them a good spar and a sturdy glassing and you should be OK for 1,000 RPM. Emphasis on should. That's the only way I can see it working though.

Or order some ~1000mm Heli blades and add them to a 10" yoke.
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Old Nov 12, 2012, 04:41 AM
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United States, MD, Elkton
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My most recent experience is with a 62 cc gas engine with a belt reduction.It normally turns a 22 x 10 prop around 7,000 rpms.With the belt reduction, it turns a 32 x 12 prop at 4,000,with noticeably more 'pulling' power-over 35lbs.!

Since the Sparky is a slow flyer anyhow,with loads of lift,I don't think a prop with lots of pitch will be overtaxed to move it.

I'll never forget the sound of the original balsa prop huffing around on a still evening...Prolly won't hear this one over the engine,but........
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