This is one of the secrets of soaring, especially in thermal lift. Staying where the lift is strong often requires fairly tight turning, which increases your sink rate, so there is a compromise process for efficient climbing that requires well-developed pilot judgment. And getting back to the landing zone often requires flying faster than best glide speed through sinking air to minimize your time in the sink, adding speed to penetrate headwinds, etc., so it also is much more complex than just picking a speed.Would it be reasonable to infer that maintaining 30 MPG indicated airspeed, provided you could stay in the updraft, would offer the best "climb?"
And that once clear of the updraft, maintaining 55 MPH would be the ticket back to the landing zone?
Thank you that puts real numbers to the problem!If you did the numbers you could conceive a single place glider with AUW 350 lbs and 23 ft diameter (cleaned up powerless Bensen). It would have a best sink speed of around 30 mph and sink rate of ~600ft/min and a best glide ratio of 4 to 1 around 55 mph.
You can certainly soar in thermals with the above performance but the best chance for this to work in practice is on a ridge where sustained lift can be found reliably so the 4 to 1 ratio would not to be a penalty.
You can improve this a little by increasing rotor diameter but to keep RRPM in safe limits you would have to significantly reduce chords which in turn brings in other problems. Similarly drag reductions buys you a little but the bottom line is it is hard to do significantly better than a sink rate of 600 ft/min and 4 to 1 glide ratio.
So its a pice of cake ina gyro.
lowest sink rate at 0 AS, so you can just stop in the area of highest thermal strength.