Can anyone here explain in plain English what their conclusions were the angle of screw placement? What are they talking about when they say not to place the screw at a negative angle? They say that the optimum angle of placement is between 8 and 16 degrees. Does that mean that you place the screw with the tip higher than the hanger or do you place the screw with the tip lower than the hanger?
When I first started ice climbing, I had read that you always have the hanger angled a little higher than the tip. Since then, however, I've read that you should do the opposite, and place the screw with a slight downslope with the hanger slightly lower than the tip.
I can't figure out what this article is recommending.
Nevermind. With the help of this other article (link below,) I figured it out. Still recommending to place the screw with a downslope with the hanger slightly lower than the tip. (I guess that this is a "positive" angle.) Nice to see that there is some consistency in conclusions.
Really it depends on the snow. Threads and shear are exceptionally strong in firm snow and it reduces the bending/shear on the shaft. Most screws break in bending, from my understanding. So decreased shaft reliance is a good thing. Loose wall....eh probably bad idea. Bad in general, though.
I think the reason they recommend against angled up (away from climber) is if they are loaded and the snow shifts allowing the screw to rotate in the downward direction, the screw will most likely now have the hanger some amount farther from the surface of the wall. Increased bending load. In a dynamic case, not good, because the shaft now has some kinetic energy combined with static loading to overcome. Also means LESS surface area of shaft to load the snow with. More torque may bust out the snow wall.
Good read, it was nice to see some empirical evidence behind several anchor setups. You often hear numerous opinions on strength and configurations out at the crag and online and it is not always easy to discern what is fact based and what is pure opinion and speculation. Although I am not foolish enough to follow one study as if it was law, it is just one more tool to be able to use in my decision making process.