Re: pteros have lift-off

[jrc <jrccea@bellsouth.net>]

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

> > Unfortunately, that's really not where I'm looking for clearance.  Let's 
> > move the video back a few frames and see if there is this  thing called 
> > wing clearance much earlier in the launch -- closer to  where the hands 
> > are still only inches to feet above the ground and  rising quickly.

At that point, the hands are rising faster than 23 fps, and the wingtip is 
beginning to lower at somewhat less than that rate, but is still rising 
rapidly.
> You mentioned the animal has .72 seconds to bring the wing to the 
> beginning of the first downstroke. I'm wondering what the wing finger  is 
> doing at .1, .2, .3, and .4 seconds into the launch.

At 0.1 and 0.2 seconds, the manus is still on the ground, and the wingfinger 
is rotating tip forward, though inertial lag is causing the angle at the 
wingfinger pivot to start opening up.  At 0.3 seconds, the manus is about 
1.1 feet above the ground and accelerating upward, while the wingfinger is 
still lagging aftward with the pivot continuing to open.  At 0.4 seconds, 
the manus is more than 2 feet above the ground and continuing to accelerate 
upward while the wingfinger continues to lag and open.; at this point, the 
wingtip is still higher than the manus, though it doesn't have to be.  At 
0.4 seconds into the launch and 0.15 seconds after lifting off, the animal 
still has 0.57 seconds remaining until the "top" of the leap.  Since an 
entire wingbeat only takes 0.60 seconds to do both a complete combined 
upstroke and downstroke, you can see he still has plenty of spare time 
remaining to complete the unfolding of the wing when at 0.4 seconds from the 
initiation of  the launch.

> At 30 video  frames per second, I'm just interested in those first 20 
> frames. If  you want to continue working with Q, as a model, that's fine.

At 30 frames per second, the first 20 frames take 0.67 seconds.  That's 2 
frames more than it takes a Qsp to make an entire wingbeat including both up 
and downstroke.  Is that a coincidence, or did you select 20 frames for that 
reason?  BTW, I appreciate your permission to continue working on Q   :-)

> But  remember there are (relative to torso length) longer winged pteros 
> out there (in fact virtually all of them!)

Yes, but since they are relatively less massive and have relatively longer 
wings, launch is relatively easier for them.  I'll try to remember that I 
spent approximately 80% of my working time for 3 years focused on A 
piscator.  In general, you can usually tell when launch is becoming 
relatively more difficult for a pterosaur by looking at the shape of  his dp 
crest.