Winch Launch Stresses on Vintage Gliders

We use a very similar system except the fitting is
L shaped, enough to protect the link but allowing easy
inspection. It is important to remember that the weak
link only works at it's rated value when new and the
force required to break it reduces over the number
of launches. Having the L shape protector allows easy
inspection of the link for necking or elongation of
the holes, both indicate a 'worn' link.
In practice links are used until they break, which
they inevitably will do if not changed.




At 16:30 29 January 2006, Robin Birch wrote:
We use a system where the weak link is held in an H
channel with one end
hole drilled and the other slotted so that the end
bolt is supported but
can pull out when the link breaks.

This gives a good protection to the link. We found
that the metal
shrouds bent and also you couldn't see the link colour.
With the H
channel you can see the whole link.

Robin

In message , Bill Daniels
writes
Andy, that's a good question. Actually, as far as
I know, there isn't a way
to visually inspect then once they are assembled into
the protective case.
One wonders why.

It would be easy to dip one end of the slotted links
in, say, tan paint.
Seeing a link assembly with two white dogbones but
with one showing a tan
end would indicate that the link had been assembled
correctly.

Bill Daniels


'Andy' wrote in message
groups.com...
Is it possible to see that one is slotted and one
round holed when the
cable is ready to be hooked up to the glider? Surely
the pilot must
be given the opportunity to inspect the links before
accepting the
cable. It's a while since I winched and we used rope
weak links then.

Andy




--
Robin Birch

I don't disagree that they'll eventually break, but we've made many
hundreds of launches before a fatigue. When we have broken two at a
time due to a gust load, we replaced them with two new ones. Next
launch we broke both again. We were launching into strong winds with a
shear about 500ft. Over time we have broken the wire much more often
than a weak link failure. Since we train for the proper response to a
launch failure, it no longer makes much sense to use up two at a time.
It does eliminate the potential for mis-assembly.

Frank