Ian wrote:

This started from a thread on winch cable breaks, but I thought I should
start a new thread:

On Tue, 28 Jun 2005 20:20:23 +0000, Andreas Maurer wrote:

Flying on the same airfield as the Landau Aero Club, I'd like to add a
few comments:
- There have been lots of cable breaks with Dyneema ropes now (also of
other Dyneema cable users - these plastic cables are used by many
clubs in Germany now). At the moment my club is not sure if the
Dyneema cable is really cheaper to operate than steel cable on the
long run.

I have been wondering when we would start getting real feedback about
Dyneema. I never really believed that it would work out cheaper than
steel on a life cycle cost per launch basis. But I had hoped that it would
suffer less from cable breaks and snarl-ups etc and be easier to handle,
which would make winch launching more user friendly. (After a day of
winching it sometimes feels like we spend more time farming than flying.)

What does concern me is:

- it may be more susceptible to damage due to being mishandled (eg damaged
by rubbing on steel parts) leading to a shortening of its useful life.

- that on high wear surfaces (eg gravel or tar) it will wear out long
before the high capital costs can be recovered.

If anybody has first hand experience, please pass it on.

Thanks

Ian
I don't think anyone really ever said it would be cheaper.

On a winch launch, rope weight and rope diameter are the only two variables
that will have an impact on launch performance (given that there is
sufficient power and length). The longer the run, the more impact.

All Dyneema/Spectra ropes are not equal. There are more expensive products
that have superior strength and abrasion resistence. Superior strength
means even less weight and diameter.

The performance variables are most significant at the glider end of the
rope. Cheaper and larger diameter ropes may enable cost savings at the
winch end without impacting launch performance.

We have some limited experience with exactly this, steel wire rope at the
winch end and a Spectra sample at the glider end. 1000ft or so over a mile
run. We achieved 200-400ft/launch improvement. There are several
opportunities for improving on this concept.

Frank Whiteley