I am hill challenged, if it is good enough to soar from, my health prevents me from getting to it. However, dynamic soaring is totally interesting and I was considering the process.

I read an explanation about dynamic soaring (I believe that Joe Wurts has theorized this and I respect his knowledge) that involved moving the airplane between different velocity layers on the back side of the hill.

Assume a clock with 12 at the top of the hill and 6 at the bottom of the hill. The impression I got was that the velocity increment each pass was at roughly the 3 and 9 oclock positions as the airplane moved between the vertical volocity shears on the back side of the hill.

Could it be achieved by another mechanism? The airplane as it comes across the 1 to 11 oclock position could pick up velocity like the side thrust on a skaters blade.

It would certainly be interesting to put an accelerometer in the airplane and see where the increments in velocity come from.

Hi Ben,

Found this article on the Charles Rivers site: http://www.charlesriverrc.org/articl...rkdrela_ds.htm

I watched a couple of videotapes on this...unbelievable!

Some of the DS fliers have been using radar speed guns to measure how fast they can fly. They have reported seeing speeds of 225 mph - from a slope flying sailplane.

Thanks Mike, Mark's description is along the lines that I was trying to describe except I would suggest that the flight path of the airplane in inertia space is the "keel" of the iceboat analogy. The propelling force is just a vector of the wind relative to the flight path at the top of the hill.

Energy is added at the roughly 12 oclock position each time the airplane comes around. Low drag means it is retained at 3, 6 and 9. The gravity energies cancel each other out (up and down).