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Old January 24th 06, 06:03 PM posted to rec.aviation.soaring
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Default Winch Launch Stresses on Vintage Gliders

Yes,
Remember that on the winch there is no "G" relief of the increased lift
from the wings as you pull the G. This is worth between 1 and 1.5 G
which is why speed control in terms of slow is important as the stall
speeds are increased appropriately. It is also one of the reasons why
over speed can become dangerous far more quickly at the top of the wire
than in a dive.

Robin

In message , Chris Rollings
writes
Not really the same as pulling 3 'G'. If you take
an example of a glider where the total weight is say
700 lbs, of which the non-lifting surfaces (ie everything
but the wings) weighs 400 lbs, the 1 'G' load on the
wing roots (wing root bending load) is 400 lb. When
the weak link is close to breaking, at 1400 lb (twice
the weight of the glider), the total load on the wing
roots is 1800 lb, a wing root bending load equivalent
to pulling 4 1/2 'G' in free flight, somewhat narrower
margins.

I have chosen a fairly benign case, if someone takes
the time to go through the actual figures for a few
different types, I'm sure they will find some worse
examples than my (hypothetical) one.

At 01:06 24 January 2006, Brian wrote:
Someone please correct me if I am wrong,

But as I recall the weak link is supposed break before
it carries twice
the gross weight of the glider.
So during the launch the wings must lift at a maximum
the weight of the
glider plus up to 2 times weight of the glider through
the weak link.
So the maximum load you should be able to put on the
glider is 3G's.

I don't think I would want to fly a glider that could
not withstand
3G's.

Brian






--
Robin Birch