On Thursday, May 8, 2014 3:34:48 AM UTC+12, Bill D wrote:
You're exaggerating the stall speed differences. Regardless of what the 2-33 "manual" says, no 2-33 ever got as slow as 30 knots. 35 knots is a practical minimum speed. The flight test stall speed for a DG 1000 is 37 knots.

I knew 40 knots was conservative with the DG1000 stall speed, but that difference is less than I'd have expected. I've never flown a 2-33, but I've had Blaniks under 35 knots :-)


However, no one should consider a turn back at stall speed. Virtually all gliders will be at 50 - 55 knots so the turn radius will be essentially the same.

I've put together a spreadsheet for the calculations and In fact it turns out that for minimum loss of height in a 180º turn -- and also much smaller turn radius -- you should fly a bit faster and bank a bit steeper.

https://docs.google.com/spreadsheets...FXBnfP8tauGK1k

No matter what your stall speed or L/D, it turns out the optimum to minimise loss of height in a turn is to bank at 54.7 degrees.

This is the bank angle at which the total G loading is 1.732 (sqrt(3)) and the G available to turn you is 1.414 (sqrt(2)).

In that glass ship with 120 fpm min sink at 45 knots you're looking at 67m turn radius at 59 knots, with 24 feet loss of height in a 180º turn.

In a Blanik with 160 fpm at 42 knots you'll get a 58m turn radius at 55 knots, with 30 feet loss of height.

In a 2-33 with 168 fpm at 35 knots you'll get a 40.5m turn radius at 46 knots, with 26 feet loss of height.

Feel free to play.