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Gear Review: Sentinel Stoppers

The July Moab sun eviscerated the pavement into a mirage as I pressed up the hill on my thirsty bike. Even in a packed town of only 8,000, tucked away corners and remote outskirts often go neglected. I came armed with this understanding as I approached the ramshackle building whose yellow paint was cracked into a spider web of crumbles. The owner of the old pawn shop wanted to unload her merchandise and begin anew in the town’s center. A friend told me that among the televisions, faded checkerboards and tape players were a few gems of climbing equipment. The day off of the boiling Colorado River gave me the chance to see if this rumor was true. While walking among the isles of sandy floors, parched decay and aged electronics I caught glimpse of an assortment of gear hung from the ceiling above the main counter, drifting like chimes in the warm breeze. To my surprise, the three locking carabiners, two quickdraws, two ascenders, full set of hexes and full set of stoppers were brand new. Not a piece in this conglomerate had touched rock. With a stern face and voice filled with resolve, the ghostly graying blonde offered me the whole bunch for $175. I laughed until the raspy coughs of a man with desert lungs ended the fit.

Enjoying a day at Mill Creek outside of Moab.
I said, “Dear woman, see what remains of my shirt. Too fragile to mend, it will no longer take thread. Feel the heat of my sun-worn face – years have been baked from my soul. Run your fingers through my knotted, wire-strewn beard. You will not get far. I pressed her palm to my cheek then moved her hand through a hole in my tatters, pressing it firmly against the rhythmic pulse of my imploring heart. “If I had $175 I would buy a razor, sunscreen and some beans to go with my bread. I’ll give you my last toothpick and my lucky buffalo nickel.”

She thought for a moment, trailing her fingers across my salty chest as she removed her arm from my rag, tearing off a lonely button in the process. Obviously moved by my stone hazel eyes complimented by the wisdom housed in their neighboring cavernous crow’s feet she asked, “How ‘bout $100?”

“Deez,” I replied, handing her a crisp $100 bill.

The stoppers were the long Sentinel variety by Frostworks and they’ve been in my protection arsenal since. The Sentinel nuts come with either short (~8.5”) or long (~13”) wire slings. They have a uniform taper, both lengthwise and sideways. In both cases the taper is more severe than the traditional Black Diamond nuts.


Left: The full set of Frostworks Sentinel nuts #1-9, 0.23″-1.25″; Right: The full set of BD nuts #1-13, 0.17″-1.38″

Having used both the BD and Frostworks long Sentinel variety, I’ve found the latter has the following advantages:

1. The more accentuated symmetric taper design allows for a quicker trial-and-error placement process and requires less precision in fitting a stopper in a seam. Often more than one size will fit the same formation. Thus instead of fiddling around for the perfect fit, more often the Sentinels can be well seeded on the first attempt.
2. The straight edges allow for significantly easier cleaning. Because of the symmetric design, the stoppers lend themselves better to slot placements as opposed to wedging them into inconsistencies with a series of orientations and movements that must then be reversed for removal. Even when seeded strongly, the Sentinel placements are usually straightforward to clean.
3. The longer wire slings provide more flexibility and slack. This helps ensure the placements will not pop out when climbing above the piece. The Frostworks website claims that the long slings can preclude the necessity to extend the placement with a quickdraw. However, even with the added flexibility, I always recommend extending the placements.
4. The longer wire sling permits reaching higher features. This can come in handy for your quest to never leave the comfort of a toprope.
5. The symmetry and greater degree of taper in the transverse dimension make for easy sideways placements. There is not a great difference in placing the Sentinels sideways or straight.
6. The more extreme taper allows the set of 9 Sentinel stoppers to cover nearly the same range as the set of 13 BD nuts. Because of this, the Sentinel set is cheaper ($81 vs. $115) and less bulky.
7. Though the BD stoppers cover a slightly larger range of sizes, the #1 and #2 are only rated for 2 kN and are thus only useful for aid or resting. (See below discussion for an explanation of the kN unit.) The #1 Sentinel (0.23″ x 0.37″) is rated for 4 kN and could hold a fall. It’s dimensions are smaller than the #3 BD stopper (0.24″ x 0.45″), the first of the set rated to hold a fall.


Left: The BD stoppers have a gentle C curve while the Sentinel nuts have a symmetric design. Right: The transverse dimension of the largest nut in each set. The photo also illustrates the different degree of taper of each style for both dimensions.

The long Sentinels also have the following disadvantages:

1. The symmetric design reduces the orientation options when protecting a variable crack. However, in the vast majority of those occasions, I’ve found that a smaller Sentinel, often placed sideways, can take advantage of the inconsistencies themselves for quality placements.
2. The pure slot placements demanded by the Sentinels can result in less surface area contact in highly irregular seams.
3. Placements that are not seeded well are more susceptible to pulling. Extra care must be taken to extend such pieces sufficiently to avoid torquing the stopper when climbing past.
4. The longer wire slings result in longer falls. Obviously, this is only on the order of a foot, but if you’ve heard anyone screaming with a bolt at his waist, you know how important every inch can feel.

The larger pieces in each set of stoppers showing the length difference.
In most instances, the simplicity of the symmetric design results in easy, quick slot placements that seed well and are simple to clean.

A note on Micro-Stoppers:

For micro-stoppers, the stopper heads are usually made of brass. Brass is softer than aluminum, a characteristic important to ensuring that the integrity of the rock comprising very small placements is not compromised. The force of a fall on a micro-stopper must be distributed to an extremely small contact surface area, making the rock more susceptible to breakage and the nut more likely to pull. The malleable brass reduces the impulse a fall will exert on the rock by lengthening the time of high stress against the rock during deceleration. The brass will also tend to seed better than aluminum by better forming to the rock on a microscopic level. This can make them more difficult to remove, especially after a fall.

The 0, 1 and 2 DMM HB Brass Offsets
As a matter of preference and different from my preference for normal stoppers, I like an offset design for micro-stoppers. Very small placements tend to be in pin scars or other flaring seams. The offset design provides access to the depths of the formation while maintaining surface contact toward the front.

A clear view of the offset design. Included is the #1 Sentinel for reference.
Though I haven’t used many different varieties of micro-stoppers, I will mention the DMM HB Brass Offsets. These tiny stoppers have two distinct advantages over some other micro-stopper designs. First, they employ silver soldering to attach the stopper head to the wire sling. This results in a stronger unit because it eliminates a point of weakness in the wire sling. (The 0 is rated for 2 kN, the 1 is rated for 4 kN, the 2 is rated for 5 kN and up. A kN is equivalent to 225 lbs of static force. Essentially, the 0 is not meant to take a fall, while the 1 and above would hold a fall.) Secondly, the DMM offsets employ a sleeve in which one side of the wire sling can pass freely while the other is held rigid. This can aid in finding the perfect angle for a placement without torquing the stopper head. As one might expect, these accessories result in a higher price ($16.50 each at Neptune Mountaineering). But I don’t mind paying a little extra when attempting to trust something that has the width of two stacked quarters.

The shadowed wind flowing through my hair at the bottom of the hill as I passed Milt’s Diner gave me a serene feeling and a craving for a Gin and Tonic. To celebrate my climbing purchase, I went to the state-owned liquor store and bought a bottle of Tanqueray Ten. I rode over to the boat yard, donned my suit and joined the crew for a Sunday Funday we won’t soon forget.

Why am I wearing this suit?
Thanks to Charlie Sievers for stopper photos. Thanks to Chris Thompson for advice on micro-stoppers.

Justin - More importantly, why isnt everyone else in that last picture wearing equally sweet suits?January 27, 2010 – 11:46 pm

Eli - I believe the Frost nut is essentially the original stopper design that Chouinard and Frost designed. The BD nut is a variant on that design. The longer wires are really nice.

I think you meant to compare brass to aluminum (not S.S.) in the micro stopper section.January 27, 2010 – 11:56 pm

ERICA F. ROGERS - The Suit. It's like an exclamation point for life. Keep it.January 28, 2010 – 9:39 am

weasel_one - your nuts hang lower than anyone else I know.January 28, 2010 – 12:22 pm

Adam - Thanks for the Stainless Steel/Aluminum catch, Eli. I had stainless in my head from the wire slings. I got that suit for $6 at a thrift shop in Moab. It's hand-sewn and in perfect condition.

Weasel_one, thanks. Sometimes having very long nuts can be a burden. While the rest of my rack is tucked away nicely, I'll accidentally step on a nut on my way to the bathroom at night and it hurts.January 28, 2010 – 1:01 pm

Chelsea - You are wearing the suit because Oswald threatened us with the knife he carried in his mouth all night.January 28, 2010 – 4:21 pm

Amy - Adam,

I love your opening anecdote. It painted quite a picture. Quite a contrast from that suave suited fellow in the end.
You’re a man of many faces and talents. But remember, dirty fingernails never lie.
SayonaraFebruary 6, 2010 – 3:42 pm

assirealile - I love your blog. So much useful information. Thank you very very much.May 12, 2010 – 2:05 am

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