On Monday, December 31, 2018 at 8:38:21 AM UTC-7, Dave Springford wrote:
I bought 4000 ft of 5 mm diameter "dyneema" from the Shanghai Tough Rope and Webbing Company back in 2016 and we have been using it on our winch for 2 years.

http://www.toughrope.com/productshow_261.html

I tested it on the tensile machine at my college and it reached 3800 lbs before breaking. Lower than expected, but I had not mounted it very well in the machine and it was cut, more than it was broken, and 3800 is well above the 2200 lb weak link required for the K-21 so I didn't bother to mount it better and test it again.

Price in 2016 was $0.50 per meter and $200 in shipping. Much cheaper than Amsteel for pretty much the same thing.

The web site seems to indicate the rope is a blend of sk65 and sk75. Amsteel is strictly sk75. There are two grades of Amsteel and Spectra, which are the basic ropes. The performance ropes are Amsteel Blue and Plasma12 respectively, which are rated to about 5400lbs breaking strength. AFAIK, these are not blended ropes. If the surface is benign, as in lush turf, the basic ropes will give plenty of launches. Our surface is what I would describe as harsh, though the harshest was on a runway that had an abrasive slurry coating. Regardless of the rope and surface, I think a cost amortization over 1,000 launches is reasonable and if banked, may well pay for the next rope after the original rope is paid for. So this could be $2-3/launch. A good surface could result in 2000 launches. A benign surface may well result in a rope life above 4000 launches.

Your rope may well reach very economic performance results, which would be good news. Total launches will be of more interest than service years. FWIW, I have a bird feeder on an untreated, flat weave, sample of Spectra that we attached to the end of our steel wire rope many years ago. No only do the squirrels not like climbing on it, they don't chew through it. It's been out there for at least 13-14 years, so very UV resistant.

I think we are very near 1000 launches on our original Amsteel Blue, which is run over high plains prairie, buffalo grass, clay loam soil with small rocks chips slight larger than sand and encounters the occasional rock, weed, or other obstacle. We have the occasional rope break or less common splice failure (old 4/3/2 tuck splices). We use a different method now, more like the recommended method. The cost was amortized over 1000 launches, so any launch above this is gravy.

Frank Whiteley