SCAT Electronic News August 15 1999
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SCAT Electronic News August 15 1999
Table of Contents
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SCAT News: Avian aerodynamics - Gregorie
Trap for Young ( & Old) Players. - Malkin
Great Internet SNAFU
Soaring Birds - O'Dwyer
SCAT News: Avian aerodynamics
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
I have to echo Gil's comments about the difficulty of finding anything on
bird aerodynamics, though I blame the biologists for this. Some years ago I
met a German lady in India who was studying the vultures and kites there.
I'd been watching the kite's thermal hunting techniques closely so naturally
I asked her about their aerodynamics. She was not aware of any published
information and was not really interested - apparently avian aerodynamics
were not thought to have a bearing on their life styles.
My own observations gave the following tasters:
* the kite family fly a lot on tail tilt and have a forward CG; of
course you can tell this from the tail tilt direction.
* vultures seem to have a more rearward CG and much smaller tails.
* you can easily tell thermal strength from the amount of dihedral the
bird is using. In strong lift the tip feathers are closed and the bird has
lots of dihedral. As lift decreases so does the dihedral, till at the limit
its almost anhedral with the tip feathers spread and raised.
* vultures may be near their strength limits - where a kite can
half-close its wings and dive steeply onto food the best a vulture can do is
to use its feet for airbrakes and come down in a circle at a shallow angle.
As to references:
'The Simple Science of Flight' by Henk Tennekes (MIT press, 1996)
ISBN 0-262-20105--4
is a good start. The book covers everything from insects and indoor models
to 747s. There is quite a bit on A/R and soaring birds but nothing on
sections. When the book was published the author was a professor at the Free
University of Amsterdam and so is probably on e-mail; I'd guess he knows
rather more than he wrote in the book.
I seem to remember a NFFS Sympo article relating section camber and
thickness to Re number.
A more tenuous lead is that I believe that the Thomann F7 model section is
based on a bird section.
I hope this helps
Martin Gregorie
Trap for Young ( & Old) Players.
================================
Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Roger,
I have just recently finished a new model box, identical to my
other box made of Corflute, and required some foam rubber buffers in
certain places to prevent too much movement of the stabs so used
some Contact Adhesive to glue them in place. The Adhesive is the type
that the glue sniffers enjoy!!! and after waiting the nominal setup time
applied the buffers, which essentially finished the box, so placed all the
bits and pieces of the models in the various places, admired my
handiwork and closed the box.
That was four days ago and just yesterday I opened the box to put
another piece of equipment in and casually looked at the stabs, HORRORS.
I have never seen Aluminised Mylar so slack as was on the stabs
and the fins. I would imagine that the material could never be placed on
the framework as slack as it was, and I had thoughts that I would have to
recover the whole mess.
After a stiff whisky to slow the heart down, I decided to see if
reheating with the covering iron would do the trick and Voila! back to
square one. They all reshrunk back to their original condition. Phew!
One interesting observation was that I have one model with the
stab and fin covered in Clear Mylar and these did not slacken off.
Naturally I have now removed all from the box and left it open to allow
the aromatics etc to dissipate, but I thought a bit more about the
situation and I could see that there was some good came out of the deal,
in so far as if I was flying a model with the wings covered in Silver Mylar
which developed a warp all that would be needed would be to place the
wing or whatever into a box with some of the adhesive and slacken the
mylar and retighten correctly.
John.
Great Internet SNAFU
====================
Some of you may have experienced dificulties in getting to
the Website or delays in getting SEN. This is caused by the major
network outage in MCI-Worldcom. Some of the Internet trunks and local
loops run on MCI circuits. MCI installed new monitoring software
that did not work correclty, they removed it, which made the
situation worse. This has affected many major sites ..
fortunately aeromodel.com is not on MCI circuts but
some of your are or the path you is .. hopefully
they will get their act together 'real soon now'
Soaring Birds
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Author : This email address is being protected from spambots. You need JavaScript enabled to view it.
Gil asked and others may be interested.
Back in the late 1950's, Dr. Raspet was head of the aero department at
Mississippi State U. He was very intrigued with soaring bird, especially
the Buzzards around that area. He wrote many reports about them from
photographing them, chasing birds in airplanes and sail planes. He
disected and measured others such as Hawks. Produced a catalog of the
various aifoils and their comparitive effeciencies. Some of his work was
sponsored by NASA but most work was for Miss. State U.
....................
Roger Morrell
