On Tuesday, January 21, 2014 6:14:33 PM UTC-6, son_of_flubber wrote:
On Tuesday, January 21, 2014 2:04:40 PM UTC-5, Lucas Pirolla wrote:

If manufacturers stopped providing polars for their new gliders, how are the computer manufacturers supposed to calculate data for those gliders, like STF ?



Get a high tow into still air. Go on a sled ride. Determine the stall speed, then fly steady just above stall speed. Increase speed by 5 knots and fly steady. Repeat until you reach VNE.



Use the computer to log airspeed, altitude and elapsed time during this flight. Plot the logged results and connect the dots. Voila! A polar for your glider flown by you.



Thanks to Richard (Dick) Johnson for doing this the hard way on so many gliders.

All soaring software packages I know calculate the polar from only 3 speed/sinkspeed data pairs. The commonly used software has extensive databases of common gliders, often back to pre-historic times. If you don't find your glider, pick a similar one and go flying. Over time you can tell if the polar chosen is about right - if not, make corrections. For a glider manufacturer to offer a new glider without providing a polar would be foolish to say the least.