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



I've been off-list for a couple of days on two different occasions during this thread. I too am quite confused about who said what (I do generally recognise Mike Habib's comments from writing style and content, but that's an exception -- mostly I don't).

Comments inserted below.
JimC

----- Original Message ----- From: "don ohmes" <d_ohmes@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Sunday, September 28, 2008 7:32 AM
Subject: Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)



It seems to me you are understandably confused as to the chain of claim and counter-claim here.

Me too. :-)

Mike stated that arm oscillation in mid-flight will not improve a gliders performance due to reduced vorticity. I do not argue that point.

There are occasions when a sudden translation of the leading edge perpendicular to the relative wind will establish full circulation in about half a chord length of travel rather than the 2.5 chord lengths that it might otherwise take. Other than that, I mostly agree with Mike's statement. I note in passing that unsteady effects can roughly double the effective lift coefficient relative to that achieveable from constant vorticity -- but production of those effects require a highly derived wing, articulations, and musculature, and mostly wouldn't be available to an incipient flyer, particularly one that was developing from gliding origins.


I will dispute the conclusion(s) that *therefore*, a) passive gliders cannot transition to powered flight, and b) gravity-driven flight origin in birds is falsified -- if and when such claims are made. I frankly do not remember if such claims WERE made. I THINK they were at least implied by someone, but am not sure at this point.

I don't recall anyone implying that, but I'm not sure at this point either.

In any case, I have spent all the time I can on posting for now, although I owe Jim C an explanation re "appealing" ptero's. Maybe later this week.

No hurry, Don. I'm swamped too and at the moment, wouldn't be able to give your response the attention that it deserves.


It was not advanced as a hypothesis in and of itself, being (imo) only a cartoon*, although it is certainly possible that it occurred, assuming a gravity-driven path is possible at all. I think most will agree that 'gravity-drive' is at least possible, and if so, even "jumping" can get the ball rolling, although there is more to it than that...

I do agree with that (dunno who said it).
JimC