FWD: Argentavis from the Miocene

Hi Gang
This is a tough and pretty rigorous article on the flying
characteristics of todays' and yesterdays' large soaring birds with
comparisons to modern gliders (ASW21). Worth a read. (Originally
posted on the paraglider SFBAPA Group.)
Dave

http://www.pnas.org/cgi/reprint/104/30/12398

On Feb 13, 9:18 am, "
wrote:
Hi Gang
This is a tough and pretty rigorous article on the flying
characteristics of todays' and yesterdays' large soaring birds with
comparisons to modern gliders (ASW21). Worth a read. (Originally
posted on the paraglider SFBAPA Group.)
Dave

http://www.pnas.org/cgi/reprint/104/30/12398

Really interesting article. Thanks for pointing it out.

I wonder how they got around in the winter. If the lift in the pampas
is like it is here in California in the winter time, they must have
done a lot of walking.

Larry

This article claims that this very large extinct condor
(Argentavis magnificens) had a glide ratio of 3% at
67 kph, which is about 33:1. This is better than many
older and some newer (e.g. PW5) gliders. So much for
evolution!

Del Copeland

At 17:24 13 February 2008, wrote:
Hi Gang
This is a tough and pretty rigorous article on the
flying
characteristics of todays' and yesterdays' large soaring
birds with
comparisons to modern gliders (ASW21). Worth a read.
(Originally
posted on the paraglider SFBAPA Group.)
Dave

http://www.pnas.org/cgi/reprint/104/30/12398

Del C wrote:
This article claims that this very large extinct condor
(Argentavis magnificens) had a glide ratio of 3% at
67 kph, which is about 33:1. This is better than many
older and some newer (e.g. PW5) gliders. So much for
evolution!

A 3 degree glide angle is a slightly over 19:1 glide ratio. This is high
school trigonometry - simply look up the cotangent of 3 (the value of
y/x). Not quite as good as a 2-33 :-).

Tony V.

A 3 degree glide angle is a slightly over 19:1 glide ratio. This is high
school trigonometry - simply look up the cotangent of 3 (the value of
y/x). Not quite as good as a 2-33 :-).


Yeah, I know, cot = adjacent/opposite - x/y. I hate typos :-).

Tony

The article claimed a glide angle of 3 PERCENT, which
is 3 in 100 or approximately 33:1.

3 DEGREES is roughly 3 in 60 or about 20:1, as you
say.

I did rather wonder if the article got percent and
degrees mixed up, as I understand that the best modern
soaring birds do not have an L/D of much over 20:1.

Del Copeland

At 15:06 17 February 2008, Tony Verhulst wrote:
Del C wrote:
This article claims that this very large extinct condor
(Argentavis magnificens) had a glide ratio of 3% at
67 kph, which is about 33:1. This is better than many
older and some newer (e.g. PW5) gliders. So much for
evolution!

A 3 degree glide angle is a slightly over 19:1 glide
ratio. This is high
school trigonometry - simply look up the cotangent
of 3 (the value of
y/x). Not quite as good as a 2-33 :-).

Tony V.

Sorry, my mistake this time. I speed read and for some
reason took in the birds glide angle as being 3% rather
than 3 degrees.

Unfortunately this conclusion was compounded by a very
mathematically gifted friend of mine, who is a professional
physicist, writing to me on this subject when he had
also made the same mistake!

Del Copeland


At 15:36 17 February 2008, Del C wrote:
The article claimed a glide angle of 3 PERCENT, which
is 3 in 100 or approximately 33:1.

3 DEGREES is roughly 3 in 60 or about 20:1, as you
say.

I did rather wonder if the article got percent and
degrees mixed up, as I understand that the best modern
soaring birds do not have an L/D of much over 20:1.

Del Copeland

At 15:06 17 February 2008, Tony Verhulst wrote:
Del C wrote:
This article claims that this very large extinct condor
(Argentavis magnificens) had a glide ratio of 3% at
67 kph, which is about 33:1. This is better than many
older and some newer (e.g. PW5) gliders. So much for
evolution!

A 3 degree glide angle is a slightly over 19:1 glide
ratio. This is high
school trigonometry - simply look up the cotangent
of 3 (the value of
y/x). Not quite as good as a 2-33 :-).

Tony V.

Del C wrote:
Sorry, my mistake this time. I speed read and for some
reason took in the birds glide angle as being 3% rather
than 3 degrees.

Well then, we're all miss-reading:-). I read the article several days
ago and remember reading 3 degrees. So when I saw your 3, I never saw
the percent symbol and just assumed degrees. Getting old, I guess. LOL

Tony

Tony Verhulst wrote:

A 3 degree glide angle is a slightly over 19:1 glide ratio. This is
high school trigonometry - simply look up the cotangent of 3 (the
value of y/x). Not quite as good as a 2-33 :-).


Yeah, I know, cot = adjacent/opposite - x/y. I hate typos :-).

Not all calculators have cotan (my computer's desktop calculator
doesn't, nor does my HP-28S), but 1/tan(x) gives the same answer.

If the angle is less than approximately 4.5 degrees it doesn't much
matter whether you use tan or sin - for a 3 degree glide slope the
difference is tiny: 1:19.081 vs. 1:19.107 - an error of just over 0.1%.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Not all calculators have cotan (my computer's desktop calculator
doesn't, nor does my HP-28S), but 1/tan(x) gives the same answer.


Ah, true, but there's this thing called the World Wide Web :-)

http://tinyurl.com/22r8kw

Tony V.