Re: pteros have lift-off

[jrc <jrccea@bellsouth.net>]

Been away from the computer -- just got back.  Re concern about wingtip on 
downstroke after launch hitting the ground, for talking purposes let's take 
a Qsp glenoid as the reference rather than cg so that we won't have to worry 
about the vertical shifts in cg relative to the glenoid during the launch 
and flapping strokes (animal's cg lowers relative to glenoid during the 
ground based part of the launch).  Note that I'm not implying that the 
velocities and coordinates calculated below are actually known to 3 decimal 
places...... :-)

A 20 Kg Qsp carrying a 15% tail upload in level, steady cruise flight at a 
height above ground (HAG) of 5 feet will flap with a beat period of about 
0.6 seconds (frequency 1.667 Hz) doing about 31.58 miles/hour (46.3144 fps). 
The wingtip flapping amplitude will be about 4.02 feet, with 1.926 feet of 
that being up above the glenoid, and 2.095 feet being down below the 
glenoid.  Now, at a launch to that cruise speed, if the glenoid path at the 
time the manus lifts off is inclined 30 degrees above the horizontal, then 
the glenoid is rising at a vertical speed of 23.157 fps, and the time it 
takes the glenoid to reach its maximum height of 8.33 feet above glenoid 
liftoff height on a ballistic path is 0.720 seconds -- this gives the animal 
enough time to perform a complete upstroke and finish the first downstroke 
as the shoulder reaches its ballistic peak.  As I mentioned above, at that 
point in time the glenoid has risen to a point 8.33 feet higher than it was 
when the manus lifted off, and the WINGTIP at the BOTTOM of the first 
downstroke is 8.33-2.10 = 6.23 feet HIGHER than the GLENOID was at the time 
of manus liftoff.  Which makes it obvious that the wingtip is never in 
danger of whacking the ground during a normal launch.  Most other pterosaurs 
will show similar trends..
JimC

----- Original Message ----- 
From: "David Peters" <davidpeters@att.net
> All I want now is minimum flight speed and apogee as a multiple of  the 
> unit specified by CG height at the beginning of the leap. Been  gone all 
> day. No reply, so far, to those queries.