Wednesday, July 11, 2007

Slippery Slab Tower near Stevens Pass

July 6 was stunning already, even before we headed in to climb Slippery Slab Tower. Six of us (Mindy, Jim, Cindy, Maggie, Katie, and Steve) left the Tunnel Creek trailhead (FS 6095 off the Hwy 2 hairpin turn just west of Stevens Pass) at 8:45 at a moderate pace. We reached Hope Lake and turned south on the Pacific Crest Trail at 9:45, only to hit snow above the lake that confounded routefinding. We also hit snow at the col about a half mile south, just before descending and making the traverse to Trap Pass, which it easy to lose the trail and posthole. We had a few backtracks looking for the PCT in those spots.


(Traverse on PCT after getting through snow-covered sections)

The snow was just melting out of the east-facing meadows, and the avalanche lilies were in full bloom. From Trap Pass (12:30), we looked for the climbers' trail to the east of the ridge but ended up traversing back over to the west side of the ridge at the high point between Trap Pass and Slippery Slab Tower to avoid steep snow slopes with poor runout. (We had left ice axes at home after seeing little snow below 6200 ft the week before on the Emmons Rte-- mistake!)


(Slippery Slab Tower from the PCT traverse-- mitten-shaped fin on the horizon. Trap Pass is just to the right of the photo, and we followed a climbers' trail behind the high point on the ridge, coming out on the snow just below the tower. We followed the highest snow finger right to "the obvious gulley" that reaches the first belay stance.)

The last 100 ft vertical to the base of the climb we contoured over steepening snow to the south end of the east face of the tower to find a good way up the snow finger leading to the "obvious gulley" without axes. We squeezed behind a moat/cave just south of the gulley and passed packs through-- very fun!


(Katie, Steve, Maggie, and Mindy work through the skinny moat to get to the gulley)

We arrived at the base of the climb 1:30 and began rappelling off the top at 3:00. We set a fixed line up the gulley to the trees and everyone used a prusik backup. The first few moves are a little funky, especially in boots. We were careful about some of the loose stuff, all small, and didn't rain down anything on our party. From the clump of trees, we went straight up toward the open book/slippery slab, past the last (dying?) tree right to the anchor on the ridge in one pitch. Most of us went up the arete side of the slab. Rating of 5.3 was appropriate. We unroped above the top anchor and scrambled to the summit, basking in the sun and light wind.


(East face of Slippery Slab Tower. Moat is behind the highest snow finger, and "the obvious gulley" is just to the right leading up to the belay trees on the right skyline. The route heads directly up from there in one pitch to the summit ridge.)


(Mindy belaying Maggie up to the summit ridge, with Steve's shadow looking on)


(Summit shot, front: Mindy, Steve, Maggie; back: Cindy, Katie, Jim)


(Jim doing "the Monty" on top of Slippery Slab Tower)


(Mindy and Jim setting up the short rap off the summit ridge to the (dying?) tree)

We used three single raps-- a short one from the summit anchor to the (dying?) tree, then a longer rap from the tree back to the trees at the top of the gulley, then down the gully. All three stations had good slings and rap rings, but in the coming years we might want to add bolted anchors since there is no way to back these up effectively. Rock was very solid and great for pro. I left a piece of perma-pro (curved nut) just below the open book/slippery slab if anyone wants to add to their rack.


(Mindy trying to extract perma-pro just below the open book/slipper slab, with Cindy giving a backup from the belay at the top of the gulley)

We were the first to sign the register this year-- probably another few weeks before you can (happily) go without ice axes. On the descent, we were suckered into traversing the steep snow slopes on the east side of the ridge-- not recommended without an axe, but you can avoid by going west of the ridge. Only a bit of bushwhacking required.


(Cindy, looking back on the east face of Slippery Slab Tower. The chimney toward the right/north side has given people fits over the years, so continue toward the south to the high point on the snow finger, on the left side of this photo, to pick up the gulley.)

We returned to Trap Pass for a snack, then traversed back to Hope Lake, where we were greeted by a few black flies (but not bad). Of course, we had to stop and watch the marmots and pika play in the rocks below the traverse. Got to the trailhead around 7:45 and headed to Zeke's for a milkshake.

The scenery was outstanding!

What sunscreens are effective and safe?

Have you ever wondered why your skin turns nearly purple under your SPF 50, or whether what you're applying is mutating you into a lizard? You're probably using a sunscreen that is neither effective nor safe. Since the FDA does not regulate claims on sunscreen, the Environmental Working Group compiled information on both the effectiveness and the potential health hazards of hundreds of products. Unfortunately, the one I (used to?) use, AloeGator, was not tested, so I may switch to another that is both effective and has fewer known health hazards. Check out your own brand or search for effective and safe ones at the Skin Deep Cosmetics Safety Database:

http://www.cosmeticsdatabase.com

Climbing Nerd Level 0

Tuesday, July 10, 2007

Chalk: Are we sandbagging our fingertips???

This just in (well, in 2001): the use of chalk decreases the coefficient of friction between you and those holds. What? No really, it's sort of like adding talc to a baby's bottom. OK, not exactly. But 15 climbers were the guinea pigs in a study by Li et al.:

http://www.sportex.bham.ac.uk/staff/lifx_files/Coeff%20friction%20climbing%20JSS%202001.pdf

On sandstone, slate, and granite, four hand conditions were tested: dry, dry with chalk, wet, wet with chalk. The coefficient of friction (ratio between the tangential force and the normal force) was highest for sandstone (as non-physicist climbers already knew), but the coefficient of friction was higher without chalk than with chalk for either dry or wet hands. And non-physicist climbers already knew that dry hands have a higher coefficient of friction than wet hands.

So what's going on? Looks like the chalk particles fill in those ridges that give you palm and fingerprints and act a bit like ball bearings or actually slippery flat layers.

Outcome? Find another way to dry your hands. If you use chalk to dry your hands, wipe the chalk off to maximize your Spiderman-like tendencies.

Climbing Nerd Level 0.5

Friday, June 22, 2007

Anchor testing of equalized anchors (cordelettes)

More recent information has been published on cordelettes and alternative equalizing systems (and I'll track those down), but here is some work from 2004-2005 by Beverly et al. on the effectiveness of cordelettes at equalizing loads. (Climbing Nerd Level 1)

Meaty tidbits of knowledge:
  • Even with a symmetrical setup, the load is not perfectly distributed among the legs
  • Asymmetrical or off-axis setups aren't always worse than a symmetrical setup
  • Under load, the system can stretch as much as 10 cm (4 inches)
  • The authors didn't discuss it, but it looks like the middle or the shortest leg often had the greatest force
  • The force required to break one of the legs was >15.2 kN (pretty high!)
  • Going with four pieces instead of three didn't necessarily increase the strength of the anchor (why waste pieces?)
  • Even if your anchor spans a total angle of 90 or even 120 degrees, finding the best pro placements is more important to the structural integrity of the anchor
  • Avoid short, stiff legs; better to extend the other pieces so the cordelette has more uniform legs
The article also references some previous research that showed...
  • the shelf is an appropriate clip in point
  • an overhand is sufficient



Link to source file (Multi_pointpre_equalizedanchors.pdf): http://www.sendmefile.com/00547721

Not climbing physics, but what do climbers think? (Beverly, 2005)

Beverly conducted an online survey of climbers in 2005, and found some really interesting responses to 28 questions from 407 climbers. (Climbing Nerd Level 0)

Did you know that...
  • 73% expect their belay device to hold fall factor 2 events (see separate blog entry)
  • 71% have had some formal climbing training
  • Only 25% believed that ice screws should be placed angled 10 to 20 degrees down from perpendicular to the ice (31% said up and 16% said straight) (see separte blog entry)
  • 50% of climbers have taken <10>
  • Only 9% of climbers have taken falls with a fall factor >1.5, but 20% have witnessed other climbers taking FF1.5-2 (so who are they?)
  • Only 24% of respondents had a piece of pro fail during a fall, so 76% have not had pro fail
  • 51% had been hit by rockfall while climbing
  • 18% report climbing weights >190 lbs, which means those standard tests for gear strength don't necessarily apply
  • 41% had witnessed a climbing accident where bones were broken from a fall
  • 17% had needed assistance or rescue from a climbing accident

Here's something interesting. In response to the question, what's the greatest distance you have fallen on a rope outside...

  • 32% had fallen <10>
  • 31% had fallen 10 to 20 ft
  • 17% had fallen 20 to 30 ft
  • only 20% had fallen over 30 ft

Median number of days climbing per year...

  • 24 in a gym
  • 12 sport climbing
  • 10 multi-pitch trad climbing

So who are these climbers?

  • 34% belong to a local climbing club
  • 29% belong to a mountain search and rescue organization
  • 19% belong to the Access Fund
  • 29% don't belong to any of these

Link to the report summary (WhatClimbersThink.pdf): http://www.sendmefile.com/00547713

Defining Climbing Nerd Levels

How to put an objective measure on a subjective rating? I am a nerd and I climb; therefore, I am a climbing nerd. But there are oh so many shades of climbing nerdiness, and the subject I include in this blog will appeal to climbing nerds of all levels. Here's my shot at a rating system:

  • Climbing Nerd Level 0- Math class is soooo hard! How do you spell fiziks anyway?
  • Climbing Nerd Level 1- I climb, and I want to live. It would probably make sense to learn a little more about the systems that I use to attach myself to the world.
  • Climbing Nerd Level 2- Wow, I guess physics really does have a practical application, and I secretly enjoy the greek letters and equations, even when I don't entirely understand what they mean.
  • Climbing Nerd Level 3- Physics rocks! I'm going to buy my own dynamometer to double-check these findings.

Enjoy!

Ice Screw Testing in Ouray, CO (Beverly and Attaway, 2005b)

It's the ice, stupid!

We've been taught this about falls while ice climbing: DON'T. Not bad advice, but what's it based on? Yes, there are all of those sharp objects involved with our choice of climbing medium, any one of which could do severe damage. But just how much can that screw hold? Beverly and Attaway put real screws to the test in vertical waterfall ice. (Climbing Nerd Level 2)

They tested three hypotheses:
  1. The force determines whether the ice screw fails or not

  2. Short screws in good ice don't resist high forces

  3. Falls on ice protection generate the same forces as falls on rock protection, and placed correctly in good ice may surpass rock gear

Previous drop testing on screws in aerated ice by Luebben found lots of failure, but the study did lead to a change in the orientation of ice screws: counterintuitively, 10 to 20 degrees downward instead of the previous practice of 10 to 20 degrees upward. (Why? Because a hollow tube resists a force better because of skin friction (and threads) than taking a force from the side.)

Details: GriGri with a stopper knot to reduce rope slippage, Rescue Randy (172 lbs.), ice type typical of most water ice characteristics, fall factors 1/2/1.7, both lead climbing and anchored set ups. Screws tested: Grivel 360, Petzl Laser, Petzl Laser Sonic; all (13-cm?) stubbies.



Meaty tidbits of knowledge:

  • Ice screws failed when the force was between 4 and 14.5 kN (message: ice screws can fail under pretty low load when placed in suspect ice as was the 4-kN test event)

  • Ice screws held forces between 5 and 15 kN (message: ice screws can hold even under pretty high load)

  • 11 out of 61 tests showed screw failure, which means 50 out of 60 held the fall

Huh? The screws that failed tended to face a higher load than those that were successful, but clearly there are other factors at play besides how much force is placed on the screw. Turns out it's selecting good ice for placing a screw. Anecdotally, they mention that they found more failures in the morning than in the afternoon, possibly because of morning/afternoon temperature changes. Brittle conditions appear more prone to failure.



Recommendations:

  • The fall factor 2 drops generated a maximum force of 8.6 kN with no failures, but this is not a good reason to place your first screw way above your last anchor

  • Place screws in a zone of compression (read this as a concave depression, as opposed to a convex zone of tension)

  • Small air bubbles doesn't necessarily mean it's poor quality ice

  • Ice hooks did not hold any falls




Source file (sorry for the ads) DynamicShockLoadEvaluationofIceScrews_Final.pdf: http://www.sendmefile.com/00547701