[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: WING FEATHER ATTACHMENT
Jim Cunningham wrote:
> But surely the fact that there is a non-continuous lift surface across
> body (as a result of the substantial gap between the distal wing and
> means a *lower* lift-to-drag ratio.
Please explain why? And note that I didn't say it wouldn't be lower, I
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
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.
aside, I have doubts that archaeopteryx had such a gap, but don't consider
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
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
> maximal leverage against the air [snip]
No, I wouldn't particularly expect to see those features selected for in
avian flight. If I'm not misinterpreting you, they seem to make
that flight developed through a gliding stage rather than through active
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
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).
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp