Re: The origin of flight: from the water up

["James R. Cunningham" <jrccea@bellsouth.net>]

Jaime A. Headden wrote:

> This shape is a maneuvering feature for birds that possess it. Birds
> that use their wings to swim typically, as in auklets and penguins, have
> strongly tapered but low aspect wings.

Aren't penguin wings rather high aspect ratio?  I haven't actually measured any 
(nor auklets), but they sure look high aspect ratio to me.  Perhaps someone on 
the list would volunteer to actually measure the aspect ratio of some penguins
and auklets and report back to us?  I don't have time right now, or I would do 
so myself.

AR=(span^2)/area

where the span is the total span from tip to tip, and the area includes the 
planform area extended to the midline (the area which is blanketed by the 
body).  The area convention acts to reduce the aspect ratio, but it still 
appears to be
quite high, as could be expected for an animal which uses flying motions in 
water.  Strong taper is usually a modification of high aspect ratio wings that 
are either cranked or used for flapping.  In both cases, an extended, more 
triangular
tip can reduce induced drag by as much as 15% below the theoretical minimum for 
elliptical planform in an uncranked gliding wing.
(insert -- Jaime, this last sentence is revised slightly from the copy I sent 
to you earlier)

> This reduces drag while retaining flight performance underwater.

Decreasing the aspect ratio would increase the induced drag underwater, while 
possibly reducing the profile drag.  It is a tradeoff.  Some whales also seem 
to have a rather high aspect ratio for their front flukes, probably also in an
effort to reduce induced drag.

> (which I highly value, btw -- there was never an intent to discredit
> the effort to which David is bulldogging Ebel, as he is developing the
> theory in ways that Ebel did not).

I have no opinion in that regard.  It just seemed to me that some possibilities 
were perhaps being arbitrarily excluded without specific consideration.  
Personally, I doubt that Archie was much of a swimmer, but I haven't put a lot 
of
thought into that opinion either.

> the body wing and the feathered wing can be two different things, as can be 
> seen compared to similar armed birds like
> the falconids and the accipitrids, which has distinctly different wing-shapes 
> from each other, given that the arm-shapes are similar.

I agree.