UKC

http://www.theascendingpath.com/documents/Ice%20Climbing%20Anchor%20Strengt...

Interesting stuff - he's a big Minitab/6Sigma fan clearly.

Is the Vertical Abalakov thing well known or is this a recent discovery?

In reply to Rampikino:
I dunno, interestingly he says the V threads are not as strong as long screws and are similar to short screws, however from the tests they did you can see the vertical V threads appear to fail at a much higher miniumum values than screws making them more secure for belays IMO as they are more predictable.

Not sure enough tests were done to draw conclusions like this or not though.

In reply to Rampikino:
Do you know why long screws done have a thread all the way to the top of the screw? Wouldn't this add strength in positive angled placements?

Yep, I thought I spotted that too. Wouldn't like to pick over this with a fine tooth comb, but next week in Rjukan I am more likely to try the vertical Abalakov.

Not sure actually - I did see it mentioned on a post here recently but can't remember the answer.

In reply to Rampikino:
I think the idea is that the threads act as a starting point for cracks, so having threads close to the surface increase the chances of the outer layers of ice failing.

All the articles I'd seen in the past suggested that a thread was stronger than a long screw in most types of ice.

In reply to Reach>Talent:
I think it depends on your definition of stronger, is it:
mean fail Kn
max fail Kn
highist min fail kn

Some type of statistical analysis that would indicate which anchor is least likely to commonly fail at a very low value would be what I'm interested in.

Yeah, I hear you, and of course which anchors fail at the lowest values are the ones we want to avoid wherever possible!

In reply to mkean:
out of interest do people on here normally make an abakalov with angles 60,60,60 or more like 40 degrees between the screw intersections.

Did you work out what the depth in figure 8 was? Is it the length of the ice scre or what? Perhaps thats why the figure came out a bit low for abakalovs as they may have tested holes bored with shorter screws.

In reply to CurlyStevo: What I got from all this is:

They are all pretty strong ...

and dont wear t'shirts, jeans and work boots when climbing ice ...or you are likely to loose your axes.

In reply to mux:
haha

although the minumum stength of a horiz v thread was only 5kn, and a rebored scew 3.9 kn two of these is not enough to hold a factor two fall on a belay.

Anyone on here use the already bored screw holes to put there ice screws in for scotland, sounds a wrongun but the data seems to suggest its a reasonable thing to do if you are on steep ground.

In reply to CurlyStevo:

Yeah, there has been some discussion around this already. I have used them myself before and been pretty happy with them. The evidence does seem to suggest that there will not be an awful lot of difference.

In reply to Rampikino:
fair doos not noticed the threads before

In reply to CurlyStevo: interesting article. I was struggling to work out their definition of positive angles. I assume it's when a screw ends up in a position where the hanger is higher than the tip. Now that is contrary to some advice given by BD on Needlesports' webpage http://www.needlesports.com/advice/placingscrews.htm .

It all highly depends on the ice, anyway... Do you vary angle with ice quality?

Cheers,
Michael

In reply to CurlyStevo: They didn't say much about the condition of their holes when they re-inserted screws. If the threads had been filled with ice again, I'd image strengths being much greater than with the old channels from the thread still existing. Again, that could depend on angle a lot. For a negative angle, the results could have been desastrous while for their positive angles the threads don't make much of a difference as strength is achieved via leverage.

Any thoughts welcome,
Michael

In reply to miho:
I'm pretty sure they meant positive as the hanger below screw tip.

I just tend to put my screws in at 90 degrees but I don't climb all that much water ice usually.

In reply to miho:
Actually needle sports also says a positive angle is down.

In reply to CurlyStevo:

This would certainly benefit from a greater number of tests. However, it shows what I would expect.

Most of it is about how the load is imposed upon a fragile material. For instance, that's why the one inch webbing win over the cord: the webbing applies the force over a greater area, so the ice is able to take it.

In reply to CurlyStevo: yep. I understand that about needlesports. Just was under the impression that your article had it the other way round. Given that the absolute figures are quite similar, chances are good that I misread that...

Michael

In reply to Rampikino:
Have not read the document as it doesn't open in my computer, but i thought about vertical Abalakovs before, and my conclusion was that in waterfall ice it'd be weaker, as ice tends to form in vertical columns that end up fusing together to give the impression of a continuous sheet of ice. By doing vertical abalakovs you'd be weakening said columns, and depend on the strength of the bonding between them.
No idea what the result would be on Alpine or Glacial ice. I'll keep trying to download the document to find out about the results.