ADVICE NEEDED: carving rotor for hand-powered "helicopter"

Hi all,

I'm trying to carve a simple, hand-powered "helicopter" that consists of
a horizonal rotor w/ a hole in the middle, in which a vertical shaft is
attached, round in section and a little smaller in diameter than a
pencil. When you spin the shaft rapidly between your palms, I've seen
these things before, and if correctly

...If done correctly. Trouble is, I didn't have a diagram for the
rotor, and had to wing it (so to speak). I made it with a simple
airfoil, fat in front and tapered at the back, and canted the blade at
about 20 degrees to the vertical. The resulting "helicopter" will hover
pathetically for a split second, and maybe even ascend a foot or so if I
give it a particularly violent spin. But we do not have a liftoff,
Houston.

Anyone have any suggestions on the correct blade proportions, angle of
inclination, etc?

Many thanks,
Tom

I can't really answer your question but I think I saw a design in a cub
scout book years ago. I am pretty sure the blade wants to be warped or
twisted so that it is level at the shaft and more inclined as the tip is
approached.
Dave
wrote in message
.. .
Hi all,

I'm trying to carve a simple, hand-powered "helicopter" that consists of
a horizonal rotor w/ a hole in the middle, in which a vertical shaft is
attached, round in section and a little smaller in diameter than a
pencil. When you spin the shaft rapidly between your palms, I've seen
these things before, and if correctly

..If done correctly. Trouble is, I didn't have a diagram for the
rotor, and had to wing it (so to speak). I made it with a simple
airfoil, fat in front and tapered at the back, and canted the blade at
about 20 degrees to the vertical. The resulting "helicopter" will hover
pathetically for a split second, and maybe even ascend a foot or so if I
give it a particularly violent spin. But we do not have a liftoff,
Houston.

Anyone have any suggestions on the correct blade proportions, angle of
inclination, etc?

Many thanks,
Tom

Hi - I think this is what you need. I used to play with these (70 years
ago). They are of China origin (1500 years ago). George
Included Page: How To Make A Take Tonbo

Yes, Take Tonbo was the magic word -- many thanks, George! Here's a
link, if other folks are interested:
http://www.taketonbo.org/tomake.html

George G wrote:



Hi - I think this is what you need. I used to play with these (70 years
ago). They are of China origin (1500 years ago). George
Included Page: How To Make A Take Tonbo