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Re: L'origine et l'évolution des oiseaux, with a twist

Comments inserted

----- Original Message ----- From: "David Peters" <davidpeters@att.net>

.........Exactly. Sharoviptyerx legs were like wires. Add uropatagia: like struts, or better. Same transverse width (chord),

Umh, chord is length fore to aft. Transverse width is thickness. You're off by 90 degrees.

...... less drag by extending the anteroposterior length.

A thickness/chord ratio of about 3:1 is close to optimum. Roughly the ratio expected with muscles applied to the femur and tibia, but without uropatagium. The uropatagium chord will increase drag relative to that, not decrease it. Plus, when the uropatagium is slack, allowing the animal to run (if it can), then the uropatagium is free to flag, which adds even more drag. Personally, I would speculate that Sharovipteryx may be more of a leaper than a runner.

As an aside, a strut with a thickness of about 2 inches will usually have a chord of roughly about 4 to 6 inches. For the same drag, struts are a lot bigger than circular dragwires.

David Peters

--- On Thu, 1/29/09, jrc <jrccea@bellsouth.net> wrote:

From: jrc <jrccea@bellsouth.net>
Subject: Re: L'origine et l'évolution des oiseaux, with a twist
To: davidpeters@att.net
Cc: dinosaur@usc.edu
Date: Thursday, January 29, 2009, 9:28 AM
I didn't follow the comment below.  A circular cross
section dragwire with a diameter of 3/16 inch has roughly
about the same drag as a strut with a width of 2 inches, due
to the strut's lower drag coefficient.  In normally used
sizes, struts are far lower drag than wires.

----- Original Message ----- From: "David Peters"

> and thus it reduces drag (think of biplane wires vs.