Terry
The opening force (hit) depends, mainly, on two factors.
1) Chute design
2) Deployment method.
Design
My book, The Parachute Manual by Dan Poynter, specifies the following:
Simple round canopy, like a WW2 chute, 1.8
Cross 1.2
Ribbon 1.0 - 1.3
The table this came from lists 28 different canopy types.
Deployment.
The lowest deployment force occurs when, after the all components of the
system are in position, the canopy is allowed to open over a period of
time (3-20 sec)..
There are several methods used to try and accomplish this. Only two do
an excellent job and they aren't practice for us. They are the sleeve and
a reefing system. The sleeve is a bag made out of chute cloth that is
a little longer than the chute canopy when it's laying on the rigging table.
The pilot chute attaches to the top of the sleeve. The sleeve has a flap
at the bottom and holes for rubber bands that hold the shroud lines.
The pilot chute pulls the sleeve out full length, then the lines are pulled
from the rubber bands . When the lines come out of the last rubber band
the pilot chute begins to remove the sleeve which allows the main canopy
to begin opening.
A bagged chute works the same way except when the bag opens, after
line deployment, the entire canopy is released. It can't open because all
of the suspension lines (shroud lines) are held together by a reefing
device. As the canopy tries to open, the reefing device is pushed down
(forward) allowing the canopy to open..
Both of these methods are 99.999% reliable when the chute is packed
by a trained rigger in a parachute loft.
I went through all of that to emphasize one thing. Make sure all of the
lines (tow & chute) are pulled out straight behind the car before the
canopy is allowed to start opening
END of part I (The facts)
Part II (My opinions) in my next Email.
Bryan
|