At 11:01 PM 3/09/2007, you wrote:
>But on the topic of performance, it pays to know your history. In the
>mid-70s, hang-gliders had a glide angle of maybe 3:1. In 30 years the
>performance in terms of glide-angle has improved 5-fold. Whereas in
>gliding, the glide angle has not quite managed to double. Old Otto
>would be astonished and delighted to see a modern hang-glider!
30 years ago was 1977.
15m gliders such as the ASW20 with glide angle of 42:1 had just come
out. The top Open class gliders were the Nimbus 2 and ASW17 both with
glide angles around 47 - 48:1.
Depends who or what you believe but I think the Eta has about 70:1.
The best 15m glider Diana 2 allegedly gets about 50:1. (I'd like to
see the DLR testing before believing any of this.)
Fairer comparison is 1920 to 1950 for sailplanes. The first gliders
on the Wasserkuppe were better than 3:1 I'm sure (some were rigid
wing hang gliders). Maybe as good as 8:1 . By 1925 the modern
sailplane shape had been invented. By 1950 there was Dick Johnson's
RJ5 at 40:1.
Hang gliding grew out of the Rogallo wing which was designed as a
recovery method for re-entry vehicles. Just about anything has a
better L/D than a non steerable parachute. It was intended to use
them for later Gemini spacecraft for land recovery(didn't happen) .
You can probably read all about it at www.astronautix.com
Mike
Borgelt Instruments - manufacturers of quality soaring instruments
phone Int'l + 61 746 355784
fax Int'l + 61 746 358796
cellphone Int'l + 61 428 355784
Int'l + 61 429 355784
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website: www.borgeltinstruments.com
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