Recent content by Llyricist

I see that the term has changed from "Advance Ratio", which also refers to something else related to props, to vehicle speed ratio. Fair enough :)

The advance ratio between the rotor and the wheels sets the hard theoretical limit. For instance, in the downwind case, a propeller pitched and geared to advance half as far through the air as the wheels go over the ground, will be limited by that to twice wind speed. Of course, since a...

I don't know if that is true in the absolute sense, but in the case of their downwind VMG, the multiple definitely does get higher with higher wind speeds. And their limit is also determined by their structural strength.

Just to nitpick, the first half appears to be talking about the upwind turbine cart, but then you talk about putting the motor on the turbine and the generators on the wheels, which would be the reverse of what you would want to do with the upwind cart.

If you go here: https://skydrive.live.com/redir.aspx?cid=27579d7d745f6b79&resid=27579D7D745F6B79!103&authkey=qc!eaR1FyTA%24 You can get AF_6.xml, which is the 6412 at Re 350,000 Change the number after the underscore to match the next higher that you actually have.

Is that still a NACA 64XX airfoil? Nevermind, I see it referenced in there.

One more of the many esoteric things I learn from this discussion. I had never heard of a skid steer before, now I know what one is.

And if anyone is interested, and you have flash player installed, they are animations of all the runs they did on July 3, 2010, showing the wind direction and relative wind direction, cart speed, wind speed, apparent wind speed, and wind speed multiple. And they can be viewed here: Runs 1 and...

Thanks, I have to admit, I had a tough learning curve for the energy accounting in a frame of reference where the ground is stationary. I knew it worked, and could do it in other frames, but that negative work thing gave me a hard time.

Thank you.

The first numbers I posted were indeed messed up, like I said. The prop IS twisted, like all well designed props, and it is twisted to keep the angle of attack more or less constant at design speed. If you go to fasterthanthewind.org, and scroll down on the right to get to the older blogs, for...

Let me try that data again: Radius(ft) Chord(ft) Angle of incidence (deg) 1.325 0.18983 80.1249 1.475 0.31718 76.89058 1.625 0.46091 73.75922 1.775 0.61252 70.74371 1.925 0.76452 67.8535 2.075 0.91077 65.09468 2.225 1.0467 62.47044 2.375 1.16922 59.98132 2.525 1.27652 57.62588...

I have a feeling it was because I used links in the posts that got waylayed. I guess I need to read the rules about that.

Trying again, here is the geometry data I used for the propeller, I had to shift the radius stations from the original that spork posted since it was originally designed for a 16 foot diameter, but they extended the spars to make it 17.5 feet. Edit: something went very wrong, what I originally...

I posted 2 posts last night, one in reply to omcheeto, and both got lost somewhere.