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# Re: pteros have lift-off

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.