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Blanik Weak Link for Winch Launch???



 
 
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Old February 24th 04, 08:08 PM
Craig Freeman
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Our club has hundreds of launches with a L13 on a blue link. Never broken a weak
link, in general the cable fails first. Our winch is a 302cu inch Ford Windsor
motor, so possibly our results may not be representative of newer more powerful
winches. In still wind conditions we get around 1500' launches, dual with a
1800m cable run. Record is 2300', solo into a 25km/h headwind.

One point, if you use a winch and do not transition progressively into the steep
climb angle something is going to break. The Blanik has powerful elevators and
with flaps out can put a huge load on the cable. If the load is applied smoothly
all you get is a descending note from the winch, if you are rough you get a
cable break as often as not.

Similarly the bridle allows the L13 to maintain a large angle of attack at the
top of the launch. This is unwise because of the load on the glider , and will
also break cables. I have seen an over enthusiastic pilot and a strong gust
combine to lift one side (jack and wheel) of our winch right off the ground...
If you do break the cable at this point (and AOA) the probability of a
stall/spin accident is high. Pilots used to the porpoising effect of a CG hook
may inadvertently pull too hard at the top of the launch because the bridle does
not seem to do this?

Our experience is that breaks are usually caused by pilots and winch drivers
trying too hard - result is snatching or "rough" launches, and cable breaks.
Once everyone got used to the idea that a couple of feet was not worth the
regular cable repairs we have had a remarkable decrease in cable breaks.


Our winch at the PSA is big block powered and has no trouble breaking a
blue link when towing the L-13. We have Plasma rope which does not fail.
Sounds like a good reason for the Winch Telemetry System. YO BILL, any
updates??

Craig-
 




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