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Re: Aspect ratio and screaming dromies



Jim Cunningham (jrccea@bellsouth.net) wrote:

<I'm sorry, I don't know what your response means.  In flight mechanics,
aspect ratio is defined as wingspan squared divided by the wing area. In
your description below, do you insert body mass into the equation in place
of the wingspan or the wing area?  Once you do so, is the answer still
considered to be a representation of aspect ratio?>

  I detailed the actual aspect ratio was separate from any consideration
of shape of the wing or body mass. My statements regarding the aspect
ratio placed it in a context relative to mass and shape of the wing, but
not that these were any component of the aspect ratio. I do understand
where the confusion was, and walking to work today, I sat and mulled over
this so that I could get a clear idea of why I wasn't making myself clear.
So, I will rewrite the original sentence:

  "In the type of *M. gui*, the longest preserved secondary is almost a
third the length of the longest primary, rejecting this statement. The
aspect ratio is thus 5.77."

  As originally stated, this would assume I derived the aspect ratio from
the shapes of the feathers. Not so. I miswrote. I calculated the wingspan
from the original figure with scale bar added, using the reconstruction as
a guide. This gives me a wingspan of 90cm, nearly 1 meter in width; the
chord of the wing at the wrist and elbow are, using the right wing, 30 and
22.8cm, respectively. As approximated, I gave an aspect ratio that equated
to 5.77. However, I failed to remove the curves from the wing area, and
calculated instead the gross approximate span versus chord at the elbow
(below; gross chord from wrist to farthest trailing secondary is 32.4cm,
resuling in an aspect of 7.7). Instead, with a wing area (both wings
together) of 120cm (my estimates are a few centimeters lower, this doesn't
affect the ratio much), the aspect ratio is instead very high, as
suggested above (span^2/area), and unlike that of forest birds: 13.2. This
ratio is similar to swifts and some falcons, and is indicative of a
high-speed wing, and it even has a strong taper on the wing as suggested
by the longest primaries and their inferred positions.

  I continued to write:

"This is similar to birds with soaring or speed-adapted wings, not what
you would expect in such a primitive flier."

  Where I would stand by my concluding clause, I do not by my opening
clause; rather, as shown above, the "soaring" should now be removed.

  I went on to infer the soaring wing of eagles (around 6 or 7, versus
that of lower-flying raptors like owls and hawks, which are closer to 5 or
6) were similar to swans, as agreed by Jim, but smaller by 20%, at a ratio
of around 8 or 9. I then went on to explain the similarity of a soaring
wing in heavy bodied birds as having a high aspect with rounded tips, and
inferred that a large bodied soaring bird (swans and eagles originally, I
have since added condors in my posts) would have similar aspect ratios and
  distal wing shapes, being rounded. Smaller, but higher, soaring birds,
like albatorosses, as in other and smaller procellariiforms, have tapered
high aspect wings, and seem to be exapted in the albatrosses and terns for
long distanct flight and reduction of the vertical wing vortices, reducing
flapping effort (I assume I'm alright on this score, going off memory).
Higher-speed birds with tapered wings, similar in the effort or reducing
need to flap, contradicting my earlier observation of geese with broad
wings not flapping much (based on observation of local individuals and not
wholly corroborated).

  I hope this helps both Kris and Jim. I do not consider mass as a value
in  the aspect ratio, and my use of mass and the aspect ratio were
admittedly garbled.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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