Folks: As most of you know, I've recently been working on a FDM for the Colditz Glider. I was surprised and encouraged by the amount of comment that the original thread generated.
I've not been sitting still, and have now got a second version that you may like to play with: ftp://tallyho.bc.nu/pub/steve/flightgear/colditz_20050525.tgz Changes are as follows: After *much* grovelling the net, I eventually discovered a reputable claim (from Michael Selig at UIUC) that the Colditz Glider used the classic 1930's "Clark YH" wing profile. This ties up with a comment from P.Reid's "The Latter Days at Colditz" to the effect that the bottom surface of the wing was flat (most of it is indeed flat in the Clark YH). So I went looking for lift and drag coefficients for the Clark YH, and found them after a long search in a tutorial document on the web originating from Strathclyde University in Scotland. The new Colditz Glider FDM now uses these stated figures for the Clark YH, and though I don't have proper stall hysteresis figures for that wing, it seems almost impossible to fly the Colditz Glider model so that the airfoil actually does stall anyway. As airspeed decreases, the glider just loses lift to the point of mushing through the air below about 32 knots. With the machine flying normally, its best-case rate of descent is about 4 or 5 ft/sec, agreeing fairly well with the estimates of the original designers in Colditz. Likewise, its glide ratio is about 18:1 as estimated by the pilot who flew the replica in 1999 or 2000. I've adjusted my estimate of the locations of the CG and locations of the pilot and passenger after measuring around the reproduction of the original plans. I've played with (but commented out) an attempt to model the launch catapult with a very short-lived rocket engine. Basically, I need a rocket with a burn-time of 2.2 seconds and a thrust of 1866N (that's about 420 pounds in Flintstones units). However, my attempts have failed so far. Suggestions welcome. For instance, what are the units of fuel capacity for the tanks and fuel usage for the engine? [ Presumably tank capacity is in American Gallons or maybe "Barrels", and fuel usage is in Bushels per Nanofortnight, eh? :-) No chance of litres per second or cubic metres per second around here I suppose? ). The next version might even include a 3D model. Josh Babcock is working on one right now. Thanks, Josh. Whatever - enjoy escaping from Colditz. You should be able to make the intended landing site on the far side of the Mulde from the castle roof with height to spare if the prisoners' estimated distance to that landing site was right. Does anyone here actually live in or near Colditz? Steve. _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
