It is better not to use a reserve weak link. This requires a doubled
link which have to be of different designs, The main link has two
round holes and the reserve has one slightly slotted hole. We had a
fatality in the UK where somebody inadvertantly fitted two main links
to the carrier, which effectively doubled the strength of the weak
link, and then a glider had a mainspar failure during the launch on a
rather windy rough day. See:

http://www.aaib.gov.uk/sites/aaib/pu...eon_502118.cfm

There was some evidence that the wood/metal composite mainspar was
slightly corroded in this glider, but it is still unlikely that it
would have failed if launched on the correct weak link.

If you want to avoid weak link breaks using a single link, perhaps you
should change the link after 100 launches, or monitor its condition.
The Tost links have a hole drilled in them, like a tensile test piece,
and this will show signs of distorting or cracking before it fails.

Derek Copeland


On Jun 2, 2:53*pm, "Tim Mara" wrote:
unbelievable! especially since a weak link is such an easy thing to add,
especially for ground launching!
you might be quite amazed at the numbers of pilots who call me asking what
the "proper weak link" should be when it is such a fundamental question and
one that every prospective student pilot needs to know even before taking a
practical test for a private pilot certificate!

using the TOST weak links is easy and the reserve weak link makes a lot of
sense since ALL weak links fatigue in time and become weaker before actually
breaking.the idea of the reserve weak link is so that when this happened and
the main weak link fails from fatigue the reserve link will hold under
normal loads and the launch is still completed without an actual failure but
the broke link is then visible for the next launch (we check these before
each launch .right? ((you are supposed to) and you know then to replace the
broken link before continuing with another launch. simple to use, and even
simpler to change from one weak link strength to another as needed by using
the notch connectors or similar attachment.you can see more on my website
pagehttp://wingsandwheels.com/page30.htm

regards
Tim Mara

Please visit the Wings & Wheels website atwww.wingsandwheels.com

"T8" wrote in message

...
On Jun 2, 4:43 am, Paul wrote:





Currently the club that I am part of don't seem to be too concerned about
the safety aspects of using the correct weak links for winch launching
and I'd like to know how safe it is.

Currently I see two issues with the winch launching:

1. Sometimes a weak link is not used at all. The gliders are attached
directly to the winch cable (via drogue chute and various connectors).

2. When a weak link is included in the cable (only a primary link - no
reserve link) it is used for all glider types (G102 Astir, G103 Twin II,
ASW20, LS4) and I'm not even sure what the breaking strain is. My guess
is it's a Tost #1 black (1000 daN) weak link but that's hard to tell
because its weathered and the protective sleeve obscures the Tost number.