The Existential Terror of Steep Friction 
And the Simple Physics Thereof

By Bill Atkinson

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I can assure you that any roped free climber, regardless of experience or ability, on a serious and committing friction lead has known the fear to which my title refers. This subject comes to mind in the wake of Daniel Duane’s recent brilliant piece in the New York Times [1] on Alex Honnold’s free solo ascent of Freerider on El Cap. In it are evocations of the primal fear of having to trust the shoes while the hands are essentially useless, and of the fatal urge to lean-in toward the false comfort of the cliff face.

A climber can easily sense a small increase in steepness which might lead to a slide:
“It still felt really insecure and I still always felt like the feet might slip,” [Honnold] said …

According to the Web the coefficient of friction of a climbing shoe sole in contact with various rock surfaces varies from 0.9 to 1.1 and is often higher if the surface is particularly rough. For my purpose here I will use a coefficient value of one—a force normal to the rock surface producing an equal friction resistance parallel to the surface.

This means, for example, that a shoe vertically loaded on a featureless forty-five degree slope has a friction resistance just balancing its tendency to slide. In this case there is no margin for error and to lean-in from the vertical, however little, without foot slippage is virtually impossible. Slopes steeper than this are theoretically unclimbable by stepping-up, although there are steeper ones (on the Big Stone and elsewhere) with unusual roughness, or that yield to dynamic techniques, or to raw courage.

Desperate dynamic moments entail stepping up faster than the feet slide down, but have no place in controlled free soloing. Nor do I consider spots with tiny ledges or scoops or places where the hands can do anything other than lightly touch or even leave the face. Even roped, the friction leader has scant opportunity to set protection.

More commonly one is on a lesser slope, say of thirty degrees as is typical of our own White Horse Ledge in New Hampshire. Here the geometry is more forgiving although it takes real conviction to be convinced of it. In this case one need lean-in from the vertical only fifteen degrees for the feet to give way.

Alex learned to control the fierce reluctance to stand free and tall, in effect, putting his hands in his pockets and tip-toeing to the next haven a few steps above. 

Two-thousand feet above the Valley floor! 
Without a rope! 
Sheesh!
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Bill Atkinson, June 2017, friction.docx, 400 words

References: 
1. New York Times, Daniel Duane: 
https://www.nytimes.com/2017/06/09/opinion/el-capitan-my-el-capitan.html?rref=collection%2Fcolumn%2Fsporting&action=click&contentCollection=opinion&region=stream&module=stream_unit&version=latest&contentPlacement=1&pgtype=collection