FWD: Argentavis from the Miocene

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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

[[email protected]]

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

[Del C]

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
>

[Tony Verhulst]

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.

[Tony Verhulst]

> 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

[Del C]

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]

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.
>>
>
>
>
>

[Tony Verhulst]

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

[Martin Gregorie[_1_]]

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 |

[Tony Verhulst]

> 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.

[Martin Gregorie[_1_]]

Tony Verhulst wrote:
>
>> 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 :-)
>
I think I may have heard of that somewhere, but its nice to have these
things on the desktop.

I just checked the old standby command line calculators. No joy there
either. However, all is not lost - my spreadsheet has the lot. I'm using
Open Office, but Excel probably has them all too.


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