I would like to add some more facts to help determine the problem I am the
owner of the tow vehicle spectra line and chute. The chute is a toast
cross- panel and is 1450 mm diameter. It came with the minimum 2 m
connecting cable and 3 m safety cable. The chute kept fully opening the
first day I used it. You can see it in the video that I have on my web
site. http://www.caglesonline.com/video/autotows.wmv Since that day I have
increased the 2 m connecting cable to 4 m. It does a better job as you can
see in the next video taking the same day and place that jims glider ground
looped. http://www.caglesonline.com/video/07fallroachlake.wmv The tow
vehicle has skid control on it witch means if the tires breaks traction the
computer automatically backs of power to get traction back. Since the first
day towing with it we have figured out how to disable it. I don't know for
positive if it was disabled during the tow in question because there was a
new driver at time. Unless the ignition was turned off then it should of
still been disabled. There was two more contributing factors 1 allot of the
dry lake bed was soft. The tow vehicle was breaking the crest and in some
places leaving 3 inch deep tracts. 2 the winds was variable and had a
slight till wind about half of the day. Some times the tow vehicle was
doing 65 to 75 all the way till some gliders was releasing. I think more
then pilot error or vehicle driver error I believe it was a combination of
several factors butt I would be interested in other thoughts.
John



wrote in message
ups.com...
On Oct 31, 3:40 am, Chris Reed wrote:
Andy wrote:
On Oct 30, 12:42 pm, wrote:
On Oct 30, 1:49 am, "Bert Willing" bw_no_spam_ple...@tango- On this
(aborted) launch, I was still rolling, both wheels on the
ground. I noted the chute opening in front of other gliders too,
while on the ground. I'd had no problems launching with our non-
chuted poly rope.

How springy is 3000 feet of spectra? I imagine that would be more of
a factor for auto tow than winch. I'm speculating that the problem
with the spectra launch is not the parachute itself but the dynamics
of the rope tension. The result may be strongly dependant on how the
tow vehicle accelerarates to nominal launch speed.

Andy

That makes senses. My guess would be that the tow vehicle changed gear
and thus briefly reduced power, which would probably be enough to allow
the chute to start to open. Some automatic gearboxes have quite a
deliberate gear change, enough to reduce the tension on the rope. If
there's a lot of spring in the rope a gear change could set up some
brief oscillation, enough to allow the chute to flap around.

Did it close again, or remain open? If the latter, either the tow
vehicle wasn't pulling or there's something very odd about the chute
design.

The chute stayed open. (at least until I was too sideways to see it!)