Re: Quetz wing questions

[jrc <jrccea@bellsouth.net>]

Mark, I've taken a quick look at your Qn-giraffe drawing, and assuming the 
human height at 1.75 M, have made a few rough measurements on the drawing. 
I was only able to measure two of the three dimensions due to foreshortening 
into the plane of the drawing, so your dimensions are actually a bit larger 
than I recite here.

Your humerus appears to be about 20% longer than life.  If you use the 
square-cube rule for volume, that would make your volume too great by a 
factor of 1.73

Your r/u appears to be about 15% longer than life.  Same s-c rule, volume 
too great by factor of 1.52

Your MCIV is about 15% short.  Volume factor of 61%.  Not all that much mass 
associated with MCIV though.

PhIV-1 and outer wing are short, but I didn't measure them in the drawing. 
Again, not all that much associated mass.

Your torso seems to be a minimum of about 38% too long, for a torso volume 
too large  by a factor of about 2.63 or more.

For talking purposes only, lets just take a quick average of only the 
humerus and r/u volumes 0.5*(1.73+1.52)=1.625 , ignore the larger torso 
discrepency, and assume the whole thing is large by that 1.625  "average" 
amount, which would imply a mass of 250Kg/1.625=154Kg.  Probably by 
coincidence, this is fairly close to the guestimate of 150Kg that I usually 
use for Qn, based on the wing area and optimal lift coefficient for the 
aspect ratio that I use.  Needless to say, mathematical rigor is sorely 
lacking in the numbers I used above, so what I've just said is strictly for 
talking purposes -- but, in short; I think your 250Kg estimate may be a bit 
heavy.  As an aside, when I do pterosaur mass estimates, I take a series of 
cross sections, actually distribute each of those sections into proportions 
of bone, fat, muscle/ligaments/tendons, air sacs, marrow, voids, lung 
tissue, skin, etc. and apply seperate densities to each.  When I do so, I 
find that the all-up weight of a pterosaur tends to be approximately similar 
to that of an albatross with the same wing span (which isn't really all that 
much of a coincidence, aerodynamics and atmospheric physics being what it 
is....).  I have not used this technique for Qn yet.

Please don't take this the wrong way.  I like what you've done very much and 
encourage you to pursue it.
All the best,
JimC


----- Original Message ----- 
From: "Mark Witton" <Mark.Witton@port.ac.uk>
To: <dinosaur@usc.edu>
Sent: Wednesday, January 16, 2008 3:11 AM
Subject: Re: Quetz wing questions


> Hi all (particularly Jim),
>
> "My projection of 150 Kg is based on
> optimal CL for the aspect ratio that I generate, and his is based on
> Mark's
> estimate (which I haven't seen -- can anyone send me a copy of Mark's
> calculations or summary ? )."
>
> A brief overview of my mass work can be found at:
>
> http://www.flickr.com/photos/markwitton/1386125619/
>
> It's entirely irreverant and informal, but it should give you some gist
> of where I'm coming from. The slightly less informal paper is in review
> at the moment.
>
> So long,
>
> Mark
>
> --
>
> Mark Witton
>
> Palaeobiology Research Group
> School of Earth and Environmental Sciences
> University of Portsmouth
> Burnaby Building
> Burnaby Road
> Portsmouth
> PO1 3QL
>
> Tel: (44)2392 842418
> E-mail: Mark.Witton@port.ac.uk
> > > > jrc <jrccea@bellsouth.net> 15/01/08 10:29 PM >>>
> Comments inserted.
> JimC