On Sep 1, 10:29*am, John Smith wrote:
For me, the most interesting part was the notion that applying more than
20 to 30 percent of the advertised breaking load will significantly
accelerat the rope aging. I suspect that this may have contributed ot
our early problems with frequent rope breaks, even more so when I
remember how many hardened parts the ropes showed after the first season.

Steel wire or UHMWPE rope on a glider winch are operated well outside
of rated load limits and normal speeds. 1/6 to 1/5 of breaking
strength is the normal rating.

The expense of using of UHMWPE means that the cost of consumption
must be based on anticipated minimum life. My baseline is 1000
launches. Once that price point is built into the unit cost of a
launch, then additional launches are gravy, which can help fund the
next winch, rope replacement, gliders, etc. Yes, it means an increase
in launch rates, but it's also somewhat safer to use than steel.

Frank Whiteley