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Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)




----- Original Message ----- From: "Erik Boehm" <erikboehm07@yahoo.com>
To: "jrc" <jrccea@bellsouth.net>
Cc: <dinosaur@usc.edu>
Sent: Sunday, September 28, 2008 9:31 AM
Subject: Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)



In general, its more efficient, that means a glider could glide more before having to climb a tree again, saving time.

Agreed.

You can produce the same amount of lift, with less drag, giving higher max glide speeds,

Keep in mind that induced drag decreases with the square of the airspeed (for a given aspect ratio, doubling the airspeed reduces the induced drag by a factor of four). For this reason, animals partially retract their wings in order to reduce the aspect ratio when gliding at high speeds -- because the induced drag has become inconsequential while the rapidly increasing profile drag due to the high aspect ratio is becoming overwhelmingly significant. This is why birds that glide very fast will use the double-diamond configuration, actively reducing their aspect ratio down to roughly about 0.5 or less. High aspect ratio is not conducive to maximum glide speeds -- there is a trade-off where it is no longer an advantage (it is an advantage at slow glide speeds where induced drag predominates). As an aside to others (Erik already knows this), aspect ratio is defined as the span squared divided by the wing area.


better headwind penetration, etc.

Better headwind penetration comes with higher wingloading. Sometimes higher aspect ratio is conducive to better headwind penetration, sometimes not. It depends upoin quite a few factors other than aspect ratio.


It would also allow an early ridge soarer to make use of lighter winds,

I agree with that, since it implies flying at higher lift coefficients.

and thus it would be still be capable of getting around by flying when a lower aspect ratio glider could not.

Not necessarily. For avian flight, at aspect ratios less than about 11 or 12, tip slots work better than triangular tips. For aspect ratios greater than about 11 or 12, triangular tips work better. An early flyer is probably going to have an aspect ratio well under 12, increasing the liklihood that tip slots might develop earlier than the progression to high aspect ratio.
JimC