Minimum acceptable self-launch climb rate

On Wednesday, April 29, 2020 at 5:07:37 PM UTC-7, Ron Gleason wrote:
On Wednesday, 29 April 2020 17:29:52 UTC-6, wrote:
I'm curious why motorglider pilots don't practice that at 200ft agl, as all student pilots do on aerotows as part of normal training.

FYI- the L/D of the Arcus M with mast extended and engine not running is approximately 13:1 with a sink rate in level flight of 495 fpm. Do you want to try a turn back to the runway with those numbers?

Come on Mark, 1980 vintage hang glider performance. Not an issue, could probably do a 360!

As one who has flown many vintage 1980 hang gliders, 13:1 was a dream that we could never achieve! 5 or 6:1 was more typical. 8:1 for the very high end.

The math is, a 50:1 glider at 1000 lbs has 20 lbs of drag. The dynamic pressure of 50 knots is about 8.5 lbs/ft^2. To get to 13:1 you need to add 57 lbs of drag or about 6.7 sq ft of flat plate area. A spinning 5 foot prop is 20 sq ft, not flat plate but pretty high drag coefficient. So it is plausible. On an ASH26 with a stopped prop at 20:1, it's just like landing a clean 2-33 or 1-26. Students do it all the time.