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



Ian --

We call it Spectra but it's the same material. There is hardly any
comparison between our use of 5000 ft (1500 m) stranded steel vs.
Spectra working off of a hard-surfaced runway. We have had zero breaks
in four or five hundred starts as compared to one break every three or
four starts using steel. The Spectra is still not even getting fuzzy
after two years of use.

The pavement wears out the bottom of the waves in the steel whereas the
Spectra is so light it practically floats over the surface on pull-back.
On grass steel may work fine, but I don't have any first-hand experience.

As far as getting higher tows goes, we don't see a lot of improvement,
about 1700 ft (500 m) either way. This is with about 1600 to 2000 lb
(700 to 900 kg) of line tension (as best as I can estimate) and 15 kt
headwind using a Blanik L-13 and its wishbone cg harness.

Bob