Break Test: Rope Left Outside
My big poplar tree split at the base years ago and developed a certain amount of rot in the split. This worried the neighbor so much that I installed a rope tie between the two leaders about 30 feet up using Samson 1/2-inch TreeMaster. This is a hard-lay 3-strand polyester rope that is treated against UV and is supposed to withstand long-term exposure to the elements providing one examines the rope from time to time.
The first picture shows the rope still in place and the new rope hanging down behind.
The second picture shows the old rope still connected to the other spar.
I replaced the rope with some new rope of the same kind about two weeks ago and decided to do a break test on the old. The rope had been in the tree for 4 1/2 years; when the wind blew, the two leaders would sometimes move in opposite directions causing the rope to go taut and take some unknown amount of load. The neighbor claimed that, prior to the rope, the tree had moved a frightening amount in strong winds and that the rope had almost entirely stopped that.
I did two break tests, one pulling between two bollards and the other pulling between two spliced eyes (splicing old work-hardened hard-lay 3-strand is REALLY hard). The bollard pull was very messy, involving untwisting rope, lots of stretch, multiple pulls, etc. The rope broke at 3590 lbs. The spliced-eye pull was clean, giving a break strength of 3734 lbs.
Nominal rope strength for 1/2-inch TreeMaster is 6100 lbs. Taking the average of the two break results, we have precisely 60% of nominal strength remaining after 4 1/2 years.