Join Date: Nov 2008
Location: Deale, MD
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Re: Forces on a dockline while docking....
I based my original post on drop testing and other dynamic tests of rope energy absorption. It will vary from one line to the other. However, This is a case where energy absorption is what matters, not strength, and the test methods are different. Unfortunately, energy absorption capacity drops off with use faster than strength (ropes stiffen), making the calculation more complex and in the end, empirical.
The other important factor that some understand but a few have missed (those reasoning everything will break) is the length of the line. For example, I'm betting I can stop a 175-pound swimmer with a head start with 15-pound fishing tackle; did it once at the local pool just for laughs. It's all about the math.
Bottom line: a boat-length of standard dockline (3/4-inch for this size boat) will do nicely.
(when asked how he reached the starting holds on a difficult rock climbing problem that clearly favored taller climbers - he was perhaps 5'5")
"Well, I just climb up to them."
by Joe Brown, English rock climber
Writing full-time since 2014
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