A study was conducted this winter regarding the strength of ice climbing protection. As I’ve mentioned before falling on ice is a bad idea, but the data (both empirical and anecdotal) continually point out that ice anchors are, in fact, strong enough to catch and hold falls. Here are the highlights as I see them from this seriesof testing.
* Reusing ice screw holes is better than not placing a screw at all. Placing longer screws into shallow holes can result in placements that hold 10kn (2240 lbs or so) or greater, meaning you’ll have to be taking huge falls to get these placements to fail. So reusing an old hole in “Swiss cheese” ice is better than not placing a screw at all.
* Using 1 inch tubular webbing is stronger than using the more traditional 7mm nylon. I suppose this is due largely to the greater surface area of webbing and the higher overall tensile strength of webbing compared to 7mm cord. I, for one, will continue to use 7mm cordelettes on my ice anchors and V-threads due to the inconvenience of carrying webbing. Just a reminder–tubular webbing should be tied with the Ring Bend, while cord should be tied with Double Fisherman’s knot in V-Threads (using an flat overhand/EDK with 12″ tails is also ok, but uses more cord than necessary).
* Vertically oriented Abalakov Threads (a.k.a. A-Threads) are now being used. These can be stronger than horizontally oriented/traditional V-threads, but care should be taken in aerated, lacy, or chandelier ice since the likelihood of capturing a full, cohesive triangle of ice is low. I’ll incorporate this into the repetoire of skills, but it will come out only when conditions dictate that the thread be placed vertically–such as when the ice is too narrow or thin to place a thread in the more traditional horizontal orientation.
* Placing screws with the hanger 8-16 degrees below the horizontal is still the strongest orientation in dense waterice. This position allows the threads to hold the force, instead of levering the tube of the screw (as would be done in soft glacier ice). Overall this reduces fracturing of ice when dynamically loaded, meaning that your screws will be more likely to hold a fall.
* Falling on ice is still a bad idea.