Caver John wrote:Scott McCrea wrote:No matter what you do, frog systems and climbing harnesses will not be efficient. They maybe good enough, but not efficient.
But that is my point, I can get a minimum of 18-20" with my setup. So what's your Idea of efficient? How much rope do climb per cycle with your frog setup?
Now I'm by no means advocating for people to intentionally use climbing harnesses for srt, but if if need be, it can work just fine.
Efficiency is not a measure of how much the chest jammer moves up the rope with each sit-stand cycle in Frogging. It's a measure of how much the
chest jammer is moved with respect to how much
you move.
Having the lower attachement point on an SRT harness with respect to a climbing harness just means you have a longer length of rope to move the chest jammer up before it meets the bottom of the top or footloop jammer in a Frog setup so you can climb a given length of rope with less sit/stand cycles.
With a caving SRT harness (there are other brands and designs besides Petzl's) you can have the chest jammer set up with the chest harness so that there is very little movement wasted: you raise yourself by X inches, the Croll is moved up the rope by nearly X inches.
With a climbing harness, some effort is wasted with each cycle (not much in actual length for each individual cycle but it all adds up) as there will inevitably be some movement upwards of the harness and yourself without the chest jammer moving at the start of each sit/stand cycle.
If you only gain 10 inches of height gain measured as movement of the chest jammer up the rope each time you raise yourself by 11 inches, that is much more efficient than if you move the jammer by 18 inches but have raised yourself by 22 inches with each sit/stand cycle, for example. You may have climbed a given length of rope is less cycles in teh second case buit you will have raised and lowered your body weight over a greater distance than as with the first case.
For example, using very rough figures, if you take 100 feet of Frogging or (1200 inches)
Jammer moved 10 inches each cycle = 1200/10 = 120 cycles. Body raised each cycle = 11 inches so total height body raised = 120 x 11 = 1,320 inches or 110 feet.
Jammer moved 18 inches each cycle = 1200/18 = 66.67 cycles. Body raised each cycle = 22 inches so total height body raised = 66.67 x 22 = 1,466 inches or 122.17 feet.