We have blogged about the issue of static-on-static footlocking lines/strops in the past. New Zealand womens climber, Nicky Ward-Allen pretty much started the debate back in March '09 with a world record footlock climb on Globe 5000 .
Following Nicky's record breaking climb a 'Caution Notice' was issued (and since withdrawn) by the ITCC regarding a potential safety issue with the use of static footlock strops on static footlock lines.
A fall while footlocking with the static-on-static configuration could result in significant stress on the body - see previous Omnitree blog.
One way around the issue was the use of a 'dynamic' rope in the construction of the footlock strop.
Trouble is, what 'dynamic ' line do you use?
Any analysis of dynamic climbing lines throws up a number of specifications not usually associated with tree climbing ropes so it can be a little confusing for the uninitiated.
A summary of the dynamic rope testing criteria can be found on the Mammut website - this is a real help when comparing dynamic line specifications.
One figure to look out for is the Working Elongation Test. In this test a piece of rope is preloaded with 5 kg and then further loaded with 80 kg. To reach the UIAA specification, elongation cannot exceed 10% for single ropes, and 12% for half (doubled) ropes. (Elongation has some relevance in the event of a fall).
Even if you can figure out which dynamic rope is best they are usually sold in 50m lengths. This is not very practical when you only need 2.0 meters to make a tree climbing footlock strop!
Treetools has made it easier for you by making 'dynamic' lines available by the meter, for use in the construction of footlock strops. We have selected dynamic lines from Beal, Tendon and Edelwiess in both 8mm and 10mm cords (these specs are close to what is currently available as friction cords for tree climbers).
See the comparison figures below, Beal Ice Line 8.1mm appears to be a real winner - pricing and availability to be announced soon.
