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

[james cho]

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

[Dave Jackson]

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