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Re: WING FEATHER ATTACHMENT


Jim Cunningham wrote:

> But surely the fact that there is a non-continuous lift surface across the
> body (as a result of the substantial gap between the distal wing and torso)
> means a *lower* lift-to-drag ratio.

Please explain why? And note that I didn't say it wouldn't be lower, I said it
wouldn't take a substantial hit.

I guess I was saying that the lift-to-drag ratio would take a substantial hit. A continuous lift surface allows the torso+wings act as a single functional unit. This expanded surface (torso+wings) is able to push against a greater volume of air during the descent.


>  I have modern patagial gliders (flying
> squirrels, colugo, etc) in mind when suggesting this.

My ignorance is showing here -- do any of these have a substantial gap between
the distal wing and torso similar to the one suggested in this thread?

And I think my ignorance of basic aerodynamics is showing... As for patagial gliders (flying squirrels, flying possums, colugo) they have a gliding surface (patagium) strung between the fore- and hindlimbs and contiguous with the body wall on each side of the body. Hence, the patagia meet the torso to form a single effective gliding surface.


As an
aside, I have doubts that archaeopteryx had such a gap, but don't consider it to
be a 'go-no go' in terms of flight capability.

I also have doubts; I suspect tertials might have a lesser chance of being preserved than the secondaries and primaries.


And why would the theropod want to land upright on its prey?
I'd expect it to want to make contact feet first.

Actually, this is sort of what I meant. "Upright" meaning "feet first" rather than "head first" or "fanny first".


When landing, I'd expect the
animal to use active vortex shedding with momentum reversal in a manner similar
to the 'fast-start' mechanism in fish, rather than a steady-state gliding
configuration with its inherent limitations in CL max. Wouldn't you? 

You're going to have to explain "CL max".  ;-)


> In other words, for both lift *and* maneuverability to be selected for,
> wouldn't you expect to see (1) feathers along the inner wing to meet the
> torso [snip] and (2) feathers along the outer wing (the wing-tip) to provide
> maximal leverage against the air [snip]

No, I wouldn't particularly expect to see those features selected for in early
avian flight. If I'm not misinterpreting you, they seem to make presumptions
that flight developed through a gliding stage rather than through active
flapping.

Oh, I see what you're driving at. But are these aims necessarily mutually exclusive - lift and maneuverability. If the proavian is flapping its proto-wings, either for thrust (such as Burgers and Chiappe's running-takeoff model) or steering (a la Garner et al.'s descending "pouncing proavis") would it also be a good idea to enhance your effective lift surface as well?.

Hence, if the feathers are developed *equally* down the length of the forelimb, from wing-tip to armpit, the outer feathers can generate thrust and the inner feathers can generate lift concurrently.


, and they seem to make the presumption that increasing stability is an
advantage, when all flying animals seem to develop toward decreasing stability
as their brains evolve to handle the requirements of flight.

Increasing stability might be an advantage at an early stage of proavian evolution, when the biped just wants to alight feet-first (since the forelimbs can't be used for support, like a cat).


Regards

Tim

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