On 5 Jul 2005 17:11:09 GMT, "Ian Johnston"
wrote:

Secondly, the point is not to get the weak link breaking at all. As long as
you stay within the limits of max winch tow speed, the overload is zero.

Except you can stay within that limit with 250dN load more on the
winch hook and the wing attachments than the designers of the aircraft
thought safe.

As Bert already stated: As long as you stay within the safe speed
range, there is no way to exceed the stress limits of the glider -
simply there isn't enough lift available.

Besides: I've never seen an ASW-20 break a weak link on my home
airfield. We were using the blue ones for the 20.

Would you fly with 250kg of unofficial extra ballast in the fuselage?
That's not the point since this "unofficial ballast" never shows up if
the speed is kept in the safe range.

One example of how a designer got it wrong is the SF-34:
Officially the only allowed weak link is the blue one. Unfortunately
with this weak link it is nearly impossible to complete a winch launch
- the weak link fails in the moment the glider starts to accelerate.
Solution: a stronger weak link, and careful speed control.



Bye
Andreas