Notes On Ice Pro and Basic Ice Climbing Technique. Jerry Heilman. 2015

Transcription

1 Notes On Ice Pro and Basic Ice Climbing Technique. Jerry Heilman Chris Harmston, MSE. Myths, Cautions and Techniques of Ice Screw Placement Black Diamond Quality Control Labs The ice used for all of these tests was created with tap water poured in steel cells and placed into a large freezer. The ice would probably be considered high quality, dense ice in the real world. The testing was done as static slow pull testing by Black Diamond Quality Control Labs. The Major Results: 1) What is the difference in strength between various lengths of ice screw? Table 1 shows the number of samples, average, standard deviation, high, and low values obtained during routine batch testing that Black Diamond has conducted in ice during the last 2 years. Length 22cm 17cm 13cm combined #samples Average (Ibf/kN) 5006/ / / /21.2 Std. Dev (Ibf/kN) 1299/ / / /6.1 High (lbf/kn) 9074/ / / /40.2 Low (lbf/kn) 2748/ / / /8.8 Table 1: Batch test strength results for Black Diamond Ice screws placed in solid dense ice. All this data is from screws placed within 5 degrees perpendicular to the ice surface. 2) What is the impact of placing ice screws at different angles?

2 3) What is the effect of exposed length of ice screw and tying off the screw? Figure 3. Effect of exposed leverage on the strength of a placement. The data points represent averages of tests conducted over several years with no record of what the angle of placement was (approximately 10 samples per data point). The line represented by "Tie Off" is the average of four tie off tests (7-8 cm of leverage) that ranged from 2354 to 3299 lbf ( kN). This suggests that if the screw sticks out more than 5cm it should be tied off to increase the strength.

3 Craig Luebben. How To Ice Climb Static belay drop test results (aerated ice, 5 meters of 10.5 dynamic rope, 185 lb mass, fall factor 1.0 to 1.7): screws ripped out in 7 of 12 tests and ice hooks failed in 3 of 3 tests. Dynamic belay drop test results (aerated ice, 5 meters of 10.5 dynamic rope, 185 lb mass, fall factor 0.9 to 1.2): screws held in 3 of 3 tests, ice hooks failed in 3 of 3 tests and v-thread held in 1 of 1 test. Static pull tests results (in both aerated and solid ice, come along and dynamometer, 41 tests): 1/4 of the screws held between 2,000 and 3,000 pounds and half of the screws held more than 3,000 pounds force. The other 1/4 of the screws were in highly aerated or slushy ice where the threads could barely get a purchase on any ice. Average force for medium to long screws was 3,300 pounds and for short screws was 2,670 pounds. Summary and Conclusions: 1) The most important skill in setting ice pro is the ability to judge the ice and find the best places to set gear. 2) The only sure bet for bomber pro is a flat or concave section of solid blue, green or yellow ice. 3) Screws should be angled 15 to 20 degrees below perpendicular to the surface of the ice. 4) Important exceptions to #3 are the ice has to be solid, there should be no chance of melt out, the screw should have large, aggressive threads, and the hanger should be solidly attached to the screw. 5) Fully drive screws. 6) Scrutinize the placement as the screw goes in. Feel the turning resistance all the way in. 7) Screws set in bad ice are a waste of effort and gear. 8) Avoid setting pro in or near bulges or on small columns. 9) Always clear brittle or weak surface ice before setting pro. 10) Clear ice below a screw so that the hanger and carabiner can hang flat on the ice. 11) Long and medium length screws are stronger and more consistent than short screws, especially of the ice is not great. 12) Use long screws at belays and at the start of pitches. 13) If you take a fall on a piece of pro, do not trust it to hold a second fall. 14) Do not tie off a screw unless there is absolutely no other option. It is better to clip a hanger on a screw with up to 2 inches of exposure. 15) Ice hooks are sketchy. 16) If you have to tie off a screw, Spectra like material is more resistant to cutting than nylon. 17) Small diameter and high elongation ropes are best for ice climbing. 18) Load limiting quick draws (Screamers) will not help make a bad placement good. 19) Ice tools do not make good ice pro. 20) Lead climbers should climb like they are soloing do not fall. Warren Bennett. Simulating And Testing Ice Screw Performance In The Laboratory Used very controlled conditions as well as ice formation. Typical study as far as a controlled experiment goes. Seems more like an over achieving senior study versus a master s thesis or doctoral dissertation. From the abstract: For the purposes of the project the problem was divided up into two stages. The first stage was the development of a test bed for the ice screw testing, namely ice that has measured characteristics that can be repeated. The second stage of the project is the development of a quantitative, repeatable test methodology for ice screws.

4 It was discovered in stage 2 that it is the loading rate that affects the ice screw failure load most significantly and also that the screw placement angle does not give the trends suggested in the Harmston & Luebben Study. Instead it is zero placement angle that seems to be safest in all cases. The data in Stage 2 shows that the most significant factor affecting ice screw safety is actually the loading rate. The data shows that the higher the loading rate, the lower the failure load. Table 4: Stage 2 pull-out test results. Ice Type Load Rate (inches/s) Screw Angle (degrees) Peak Value (lbs) Test 1 Test 2 Test 3 Test 4 Mean (lbs) Standard Deviation (lbs) ABS ABS ABS ABS ABS ABS ABS ABS ABS ABS ABS ABS ABS1 ice is solid or good quality ice. ABS2 ice is aerated or poor quality ice. Peak Mean Failure Load vs. Screw Placement angle ABS 1 (low rate) ABS 1 (high rate) ABS 2 (low rate) ABS 2 (high rate) Failure Load (lbs) Angle Figure 14: Graph showing Stage 2 data, failure load of the ice screw plotted against screw placement angle.

5 J. Marc Beverly (BS-EMS, M-PAS) and Stephen W. Attaway (PhD). Dynamic Shock Load Evaluation of Ice Screws: A Real World Look From the abstract: Methods: Over the period of eight days of drop testing, we conducted a randomized placement of short ice screws in real-world vertical waterfall ice. Different fall factors, including the UIAA standard, were evaluated to determine what a climber might expect from dynamic shock loading of an ice screw in real climbing conditions. Sixty-one drops were performed in ice screws in real world ice. The screws used were just referred to as stubby screws, so the assumption is that they were in the 13cm range. The graphs and tables are not very helpful. I have included the only one that seemed to help present the results in an informative way. Summary and Conclusions:

6 Will Gadd. Ice and Mixed Climbing: Modern Technique Notes on Placing Ice Protection: 1) Tied off screws are always weaker, so use a correct length screw if possible. 2) The length of a screw is not nearly as important as the quality of the ice. 3) Place ice pro right after leaving the belay and more often at the start of a pitch. 4) The general pattern for screw failure is the ice breaks at the surface, the outer portion of the tube bends until it is in line with the load and eventually the tube breaks, the threads rip through the ice or the hanger comes off (rare). 5) In good ice with modern screws, most of the holding power is from the high relief threads, not the mechanical picket effect of the tube in the ice. 6) Placing screws with the hanger more than 15 degrees below perpendicular may be too much. Somewhere in the 5 to 10 degree range seems to be the sweet spot. 7) In bad ice, it may make sense to rely on the picket effect with the hanger high, but the strength will be questionable. 8) Good quality ice is usually clearer or blue. Horizontal or low angle ice is usually better quality than high angle ice. Steady, slow accumulation of ice is usually better than ice made rapidly from a cold snap. Ice in shaded areas, like behind a pillar, is usually better than sun warmed ice. 9) When placing a screw, the ice core coming out of the middle should be solid and consistent. 10) Place screws where they are shaded or cover them with snow. 11) Never put screws in any type of free hanging ice. Pillars smaller than a bus should also not be used. 12) Clean a screw out as soon as it is removed. 13) For rappelling off a v-thread, back it up with an ice screw until the last, and lightest, climber descends. 14) There is no definitive proof that reusing an existing screw hole is good or bad. Don t if there is good ice nearby. 15) There are too many variables that make using an ice hook a reliable source of pro.

7 J. Marc Beverly (BS-EMS, M-PAS) and Stephen W. Attaway (PhD). Ice Climbing Anchor Strength: An In-Depth Analysis Again, lots of good data, but it is presented in a way that is about impossible to interpret. For example, here is their example of a chart of what they think is quite insightful and very interesting data: Summary and Conclusions:

8 Major Points From All Studies: 1. A single ice screw, in good ice, can hold in the range of 2,000 lbs (9 kn) to 9,000 lbs (40 kn) with an average force for long/medium screws of about 4,400 lbs and for short screws of about 3,500 lbs. 2. The difference in strength between short and long ice screws is not as much as you might think, with a range of about 350 to 800 lbs. 2. In decent ice, the best angle for placing an ice screw is with the screw sloping down about 5 to 15 degrees. 3. Use the correct length of screw. But, if it is sticking out by more than 2 inches, tie off the screw with a sling, preferably a dyneema type sling. 4. Ice anchors are much more likely to hold with a dynamic belay or a slow failure. A sudden, sharp shock to ice anchors is a good way to blow out screws. 5. Screws placed in bad ice are not worth the effort. Use flat or convex placements; fully engage the screw; stagger screws vertically versus horizontally; clear brittle or bad ice off the top; the ice core should be solid and consistent, the leader should not fall. 6. Ice hooks suck as pro. 7. One study found that an A-Thread is stronger than a V-Thread. 8. One study found that re-bored ice screws are nearly as strong as newly drilled holes. 9. Never use a single anchor for a belay station, rescue loads, etc. Video Resources - Ice Climbing Technique How To Ice Climb Steep Ice. Matt Wade from Peak Mountain Guides Ice Climbing Basics: Ice Screw Placement, Anchors And V-Threads. Petzl Sport ARC'TERYX Will Gadd Ice Climbing in Marble Canyon. Will Gadd

9 LITERATURE Bennett, Warren Simulating And Testing Ice Screw Performance In The Laboratory. Graduate Thesis. Beverly, J. Marc and Attaway, Stephen W Dynamic Shock Load Evaluation of Ice Screws: A Real World Look. International Technical Rescue Symposium. Beverly, J. Marc and Attaway, Stephen W Ice Climbing Anchor Strength: An In-Depth Analysis. International Technical Rescue Symposium. Gadd, Will Ice and Mixed Climbing: Modern Technique. The Mountaineers Books, Seattle, WA. Harmston, Chris Myths, Cautions and Techniques of Ice Screw Placement. Black Diamond Quality Control Labs. Luebben, Craig How To Ice Climb. The Globe Pequot Press, Guilford, CT.