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From: Ed Minch
 On Jan 28, 2015, at 3:46 PM, David Nighswander  wrote:

>> The rope instead of chain or cable is interesting because of the weight
reduction compared to chain, no fish hooks like in the cable, and being able to
have 30 feet of pull.

>Rope is great stuff, but there is a problem.  With modern synthetics, the
braking strength of even small lines is very high, and you are tempted to buy a
line that will just barely handle your load.  Safety in this case is fine, but
that line will stretch quite a bit making things a little hard to handle.
On our tall ship, we use synthetic lines that are the same size as the original
natural fibers  Where the original 1” diameter hemp line would have a breaking
strength of about 4,000 pounds (when new!!), the synthetics that we us in the
same size have about 18,000 pound.
>So the load is easier to handle with less stretch with a larger synthetic rope.



There are so many variables in the design, materials used, and how ropes are
used. I only know what I’ve read.
There is a wealth of information on synthetic Amsteel Blue rope at the Wyeth-
Scott website
https://www.wyeth-
scott.com/documents.asp
At Demmer Corporation we were redesigning the suspension on an 20,000 lb MRAP
Recovery Vehicle. On the winch it was rigged with 1” diameter blue rope instead
of chain or cable. In the vehicle specs it was claimed the rope was lighter,
stronger, and safer than chain or cable because it didn’t stretch. Without the
stretch it didn’t store energy like a cable or chain. If it broke under load it
didn’t whiplash but just dropped.

I’m assuming that they were referring to a straight pull. If it was going around
a block and lifting an object the stored energy in the load would cause it to
whip around the block.

Dave N. 
aka Old Sneelock