ah well, that was exactly the type of feeback i was looking for
thanks.

My revised plan is to experiment with building a carbon fiber
propeller. I like the general design theory behind the wind turbine
that i specified, so I am thinking of inverting the pitch for thrust
and making the blade shorter and broader (45-50" diameter, 2-4" wide
tapering to tip). My plan is to make foam airfoil cores with a
hotwire cutter, extensively reinforce the lengthwise direction with
unidirectional carbon fiber roving, and wrap the whole blade with
carbon fiber farbric and vacuum bag. I would use a similar twisting
geometry that narrows and goes from ~20 degrees to nearly a flat pitch
at the tip and transforms from an elipitcal cross section at the hub
to an airfoil at the tip. or would it be better and simpler to have a
constant pitch, width, and airfoil and make the overall pitch ground
adjustable. Rememeber i need it to be as light and efficent as
possible this is for a paraglider fan (backpack type) not some big
beefy airplane. Any suggestions?


"Jan Carlsson" wrote in message ...
Well spoken Dan Thomas,

I wanted Sebastian to see and come to an understanding of the difference him
self.

Even if it was a airplane propeller that was used as wind mill, (just as
wrong) it is the wrong way to start with the propeller, then put an engine
and aircraft to the propeller.

It have to be a careful process picking out a propeller to suit the engine
AND airplane, when correct you can fine tune the purpose of the propeller a
few inch in diameter and pitch, depending on if you want a good climb or
cruise or something in between.

Jan Carlsson

"Dan Thomas" skrev i meddelandet
om...
"Jan Carlsson" wrote in message
...
If the wind-mill fan is correctly engineered to be wind-driven it is
unlikly
good as propeller.
A propeller have the convex side in the direction of flight, and the
round
leading edge in direction of rotation, and the pitch ....

Jan Carlsson
www.jcpropellerdesign.com

Definitely won't work, as Jan says. The blade camber is backward
to a propeller's, since it it designed to convert thrust to rotation
rather than rotation to thrust.
I'd be worried about that turbine failing when driven by an
engine. It is designed for more or less constant rotational speed, but
a piston engine has powerful torque pulses that will cause failure of
such light structures as a wind turbine fan. Airplane propellers are
designed to withstand those forces. If your fan threw a blade, the
vibration would rip the engine off your paraglider, and/or the
remaining blades might do serious damage to you or the machine.

Dan

"sebastian" skrev i meddelandet
om...
Hi I'm working on an aviation project...a motorized paraglider fan
specifically...and i had a question about using a wind turbine as the
propeller

The one on this page is the one im thinking of using:
http://www.hydrogenappliances.com/bladekits.html

Its some kind of plastic reinforced carbon fiber with ~60" diameter.
Six blades. Its supposed to be good up to several thousand rpm and
has a 70 year
outdoor weather rating...so im guessing its reasonably tough...not
bad for $89.

My main question is will it work as a propeller to generate enough
thrust...say 50-100lbs...im going to be able to supply it with
~15hp...(@2000-3000rpm) it seems to have a quite interesting blade
geometry...near the hub it has an eliptical cross section with a wide
base and a severe pitch... as the blade proceeds out to the tip it
goes COMPLETELY flat (no pitch) but in cross section it has a lovely
airfoil with a flat side (bottom of wing) and a curved airfoil on the
other side (top of wing)...for the wind turbine application use they
indicate to put the flat side of the airfoil facing the wind...which
way should I orient the flat side if I want to use it for thrust...how
would I make thrust calculations or even better measure thrust
directly?

Will the flexabilty of the prop be stabilized by centripital force
even when under load (pushing my 180lb body under a paraglider wing)
i.e. will the prop remain reasonably flat if spinning fast enough and
not bend and hack my legs/head off....it seems like it is really well
engineered from a aeronautics standpoint...i would probalbly make a
custom heavy duty hub so please focus replies on the
blades...thanks...more generally have any of you used 5/6 blade props
on an ultralight? id be interesting in hearing your impressions of
how well it worked for you compared to a 2/3/4 blade prop...