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UBC's Human-Powered Helicopter blades questions (kinda technical,engineers welcome)



 
 
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  #1  
Old October 23rd 05, 01:26 AM
james cho
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Default UBC's Human-Powered Helicopter blades questions (kinda technical,engineers welcome)

Here's a pic of their blades layout:
http://batman.mech.ubc.ca/~hph/thunderbirddesign.gif
(note the blade rotation arrows)

What I'm wondering about the blades:
- Why the odd taper? I'm guessing the taper alleviates tip losses,
but why does it begin at the ~.6 span mark? I'd expect taper across the
entire blade for the best inflow results, but then again I'm a non-expert.
- Why no twist? Does the taper alone sufficiently linearize the
inflow?

I'd be grateful for any thoughts on these questions, and I know that
probably no one in this newsgroup has an exact answer. I'm just a
student studying helicopter aerodynamics and am interested in the UBC
HPH design.

Here are some of their CFD visualizations if it helps anyone analyze:
http://batman.mech.ubc.ca/~hph/projects/cfd.html

And here's some info on another HPH design, with blades that are more
conventional (to my knowledge at least):
http://www.calpoly.edu/~wpatters/davi.jpg



Hope someone here knows more about this than I do,
jc
  #2  
Old October 23rd 05, 06:47 PM
Dave Jackson
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Posts: n/a
Default UBC's Human-Powered Helicopter blades questions (kinda technical, engineers welcome)

James;

Mike Georgallis was the person at UBC who was in charge of the project. His
phone number is/was 604 822-3665. He would be the best person to provide the
answers to your questions.
A few thoughts;

The UBC rotors were very large and very slow turning. My impression was that
the two disks should be smaller and identical. Normally a smaller disk will
require more power. However, the slow speed of the these blades meant that
they were not operating in a vertical flow field.

In addition, these blades would have flex in the flapping direction. The
flex recovery, as the blades pass through the downwash/downdraft of the
blades of the other rotor, should maintain a fairly consistent angle of
attack throughout the rotation.

Constant taper and ideal twist should also help.

Dave



"james cho" wrote in message
...
Here's a pic of their blades layout:
http://batman.mech.ubc.ca/~hph/thunderbirddesign.gif
(note the blade rotation arrows)

What I'm wondering about the blades:
- Why the odd taper? I'm guessing the taper alleviates tip losses,
but why does it begin at the ~.6 span mark? I'd expect taper across the
entire blade for the best inflow results, but then again I'm a non-expert.
- Why no twist? Does the taper alone sufficiently linearize the
inflow?

I'd be grateful for any thoughts on these questions, and I know that
probably no one in this newsgroup has an exact answer. I'm just a student
studying helicopter aerodynamics and am interested in the UBC HPH design.

Here are some of their CFD visualizations if it helps anyone analyze:
http://batman.mech.ubc.ca/~hph/projects/cfd.html

And here's some info on another HPH design, with blades that are more
conventional (to my knowledge at least):
http://www.calpoly.edu/~wpatters/davi.jpg



Hope someone here knows more about this than I do,
jc



 




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