Rope Drag Simulation

Based on:

• Experimentally found equation for friction.

• 30% humidity environment.

• Mid-life 9.9mm BD non-dry rope.

• Black Diamond neutrino carabiners.

Typical-ish Route

Drag is calculated immediately before the "Bend Number".

Max Rope Drag (lbs): 7.9956*

*Way too many significant digits so as to remind you that this is obviously not rigorous.

Typical-ish Pitches Linked

Max Rope Drag (lbs): 38.8822

Drag isn't just double the single pitch (8 lbs), it's way more. (30lbs)

Lots of Bends on a Long 68 m Pitch

Max Rope Drag (lbs): 109.4912

Perhaps obvious, but rope drag compounds on itself at every bend*. The larger the bends, the faster the growth. Not exactly exponential growth, but kind of like that.

Also maybe worth pointing out, with a lot of compounding occasions, the total drag is really sensitive to small changes in the friction calculation. So small changes in angles make a big difference over a lot of bends. Same goes for coefficient of friction. A humid day or a fuzzy rope could have big have a big effect for max drag over a lot of bends. So maybe don't try to climb your 70 meter linked mega route with a fuzzy rope and no extensions? Already a bit obvious I suppose. But maybe fuzzy ropes are holding you back.

Perhaps the take away is that if you already have a lot of drag on a climb, it might be worth really prioritizing a straight line for the rope because the drag is increasing very rapidly with more bends at that point.

*Approximation error also compounds, so the max drag value is more likely to be further off in nominal terms.

How Much Drag Does a Z-clip Add?

Does it Matter if You Zig Zag at the Beginning of a Route?

Some may think zig zagging at the beginning of a rock climbing route doesn't really matter because the weight of the rope is so small that not much drag is created.

Zig zagging high has a higher max. But if you zig zag low and end up zig zagging higher up, you might have a lot of bends and a lot of drag. My take on this is that all of this doesn't really matter relative to the common climbing wisdom out there about rope drag.

Sharp Corners vs Smoothed Corners

Smooth corners don't reduce the drag much in this case. Generally, I saw that smoothing out the corners doesn't matter much if the rope doesn't follow a much straighter total path overall.

Traversing

Max Rope Drag (lbs): 2.3641

The droop was pretty accurate when I roughly tested it. Surely this would be off if the friction calculation is off due to fuzzier/different rope, humidity etc.