Re: Pterosaur size

[jrc <jrccea@bellsouth.net>]

----- Original Message ----- 
From: "don ohmes" <d_ohmes@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Saturday, December 16, 2006 9:15 PM
Subject: Re: Pterosaur size


> Let me ask a flight question.  Let us arbitrarily assume that you are a
> bird, or a winged whatever, and that from a height of 1000 feet in no-lift
> conditions, you can glide a distance of 20,000 feet.  Now, let's add 15% 
> to
> your weight.  Without flapping, how far can you glide in the same
> conditions?  Now, let's reduce your weight by 15%.  How far?
>
> --------- Ain't 20:1 high for a whatever? Just asking.

Not particularly.  Diomedea exulans has a glide ratio of about 19-20:1.  I 
rounded off to 20 for convenience in multiplying.


> Going from thin limits.
> However, remember we agreed about that launch/flight/landing thing
> being what counts? How the hell you get way up there at a 1000'? How do 
> your power requirements vary? I
> don't start my marathon from the halfway point, although I have been 
> called a winged whatever.

Let's say that I dropped you out of an airplane.  Or, alternatively, you got 
up there the same way a wandering albatross gets up there.
> When I talk about
> flight or volancy in the context of biosystems, I mean the whole cycle. So 
> I need a more precise term
> that isn't as hard to type as 'ecologically viable volancy' or
> whatever. Flight cycle, maybe?

I repeat my question.  Quantitatively, how does a +/- 15% weight change 
impact gliding range?

> > and the Andes. Blackbirds that nest at 2500’ have lower
> > wingloads than sealevel nesters.
>
> Not for any reason to do with flight -- it's actually to do with launch, 
> and
> the variation between individuals or for one individual over time --  
> varies
> by more than the difference in density due to the 2500' change in 
> altitude.
>
> ----------I don't understand what you mean, but I think I probably 
> disagree.

Let's take Stonker for example.  From memory, when he left Scotland he 
weighed about 26-29 pounds.  Upon arriving in Iceland 2-4 days later, he has 
been weighed at weights on the order of 13 pounds.  That's approximately a 
50% weight change.  On the other hand, the density ratio from sea level to 
2500 feet is 0.929.  That's a change of approximately 7.1%.  Which is 
greater?

> -------------------- Damn. I was really hoping there was an answer to the 
> max observed launch altitude re cygnus. Think there is one,

Maybe, I dunno.

> or do they launch right on up to .59 atm?

I doubt it.  I don't think any of their usual haunts are at that altitude.

Jim