One of the biggest concerns about synthetic standing rigging is creep. There are a lot of misconceptions that any stretch experienced in the rigging is creep, and therefore creep is uncontrollable and inevitable!
Creep is permanent elongation of the fibers due to load, time, and temperature. The higher the load and the higher the temperature, the more creep can occur. When Dyneema is used for standing rigging, the time is infinite and therefore not part of the concerned equation as there is no ability to “give it a break”.
To prevent creep, all you need to do is size the stay accordingly so that the load the stay is subjected to is very low and therefore the “load” is low and the temperature is ambient temperatures, therefore also under control.
Creep tests are “expedited” by setting the temperature to 30*C (86*F) as a minimum. Accelerated tests are performed at 70*C (158*F)! Hot summer days are the only times when the temperature gets out of hand and above the 30*C mark.
While creep is accountable and controllable, Thermal Expansion is a different story. Thermal Expansion is the phenomenon where Dyneema will expand as it cools and contract as it heats. This is not creep, this is merely thermal expansion.
In winter, when synthetic rigging goes slack and is “stretched”, this is not creep, this is simply winter stretch. Creep would remain long and slack, but since it’s not creep, the stay will contract and go back to size come Spring. Thermal Expansion is something that you need to deal with if you have synthetic rigging, but it’s really not that bad.
My rigging is tuned to 80*F. This means that it is a smidge tighter on the hottest of hot days, and well tuned all the way down to 60*F. Below 60*F, we simply keep the sails to only as high as the spreaders to keep the loads lower. If it’s too cold to put up sails, it’s also too cold for us to go sailing and stand outside in the wind! Hence we take that day to relax and avoid the frigid weather by staying inside next to the heater.
