The 22cm Screw?

[Coldfinger]

Just was wondering what you all think about that length and how much you use it.

 

Some manufacturers make 12, 16 and 22cm screws, but BD makes a 19cm as well.

 

I have used the 16 a TON (and the 19 a lot) more than the 22, seems like I have that for the rare times I need a thread, but wouldn't the 19 work well for that?

 

Now that we have some modern test data, seems like the 22 is not that much stronger than the 16 and 19.

 

Anyhow, just curious.....

[ColinB]

They're good for junk ice when you're too lazy to dig for a placement. Other than that, I rarely take anything longer than 16 on routes and its totally fine to rap off v threads from 13s if you bounce test them too.

[Alex]

I have only 1, stowed on the back of my harness as either a final anchor-building screw and/or for building v-threads.

[OlympicMtnBoy]

I'm with Alex, I only have one and it stays on the back of my harness with my Grivel v-threader thingy in it. It goes in a toprope anchor or for v-threading but that'd about it. If the ice is thick enough I'd rather have a 22 for a v-thread although they can be plenty safe when made with shorter screws in the the right conditions too.

[Coldfinger]

Well been doin a little research with help from folks here and elsewhere and the pic below says a lot........

 

 

From here: http://www.jjgeng.com/html/body_ice_screw.html

 

Seems like some folks favor these 22's for bad ice, which the study speculates to be true, but the results show more of a difference between the 17/22 and the 13.

 

However, seems like most folks use and/or carry the 22 for threads, so the Beverly/Attaway study seems to point to not only length, but also orientation (as in horizontal vs. vertical as well as the angle of the bore holes) as the key to stronger threaded anchors.

 

I'm just becoming skeptical of the 22, especially since I'll usually skip "bad ice" or at least skip placing anchors in bad sections. (Or, I hack away the "bad ice" which is one reason I still prefer one adze.)

 

With screws the pic is interesting as the curve flattens at zero degrees, which is the most natural angle to drill, at least for me, with NO diff from 17 to 22, but also has a big diff with the 13 in strength and a different curve (additional strength with increasing positive angle, flatter slope) too.

 

 

 

 

 

[Coldfinger]

PS--I had thought the "new" conventional wisdom with screws was 15 degree down angle was best but the pic makes it look like that really only applies to stubbies.

 

As has been pointed out I can't read graphs--oh well. Still interesting how the stubby's curve is different, looks to be that it's behavior is different as it depends more on the surface layer.

Edited January 1, 2011 by Coldfinger

[Alex]

Neat graph. Please post link to research. I know the articles have run that favored angle is -5 to -15 degrees, but I've always placed my screws perpendicular to the surface of the ice for myself even after that research came out. Which means typically at 0, but also sometimes on cauliflowers etc I'll place them straight down into the top of a small ledge or back of cauliflower.

 

But I also use screamers on every placement, which gives me alot more confidence all up and I don't worry so much about 13 v 16cm.

 

Alot of it depends on the ice itself. In the Cdn Rockies I lead easily with 13s because the ice has generally far fewer voids. Here in the cascades I regularly use all my 16s as the ice tends to be crappier for pro: better for easy sticks with the tools but generally more sparse for good solid screws. But I never place 22s or 19s anymore at all on lead.

[lazyalpinist]

I don't have the ice experience some other posters on this thread have, but my 0.02 is that I prefer a v-thread made with a 22.

 

Since I don't like to carry extra pieces, it usually means I'll use a 22 as an anchor piece. (I often use two 22s as an anchor depending...)

 

I also like them for glacial ice in the warmer months where it takes them longer to melt out and they go deeper to the 'nicer' ice.

 

Like Alex said, I don't place them on lead on pure WI 'cept for an anchor.

 

Looks like with that chart, that the 17 is just as effective as the 22, so doesn't look like I need to use them for anchors.

[Coldfinger]

Neat graph. Please post link to research.

 

It's below the pic, believe the folks were JJ Engineering. They have a link to a BD report that makes good reading too.

 

Very good points folks make about the quality of ice and the temperature of the location (Canmore in Jan. vs. Cascades in July) as well.

 

Personally I used to rely on 22's and some 17's, seems like 16 and 13 are my choices now.

[JBC]

additional strength with increasing positive angle, flatter slope

 

PS--I had thought the "new" conventional wisdom with screws was 15 degree down angle was best but the pic makes it look like that really only applies to stubbies. Suits me fine, never liked the down angle as it is a pain to gauge and more so to place.

 

I don't think your conclusion is correct. It is additional LOAD. The graph lists psi (pounds per square inch) on the y axis. If you read the analysis posted in the link, they are not measuring the strength of the placement, but the LOAD ON THE SCREW & ICE when a 1,800 lb load is placed on the screw! The implication is that the screw is stronger at the NEGATIVE angle because it is being loaded less.

 

The negative angle puts less load on the screw than 0 or positive angle, but most interesting to me is that the 13cm screw at it's highest load (+15) is still as good as a long screw at -10 and superior to one at 0!

 

There is also a very interesting chart of how a 17cm screw loads in hard, medium or soft ice:

 

 

From the same link: www.jjgeng.com/html/body_ice_screw.html

 

Jim

Edited January 1, 2011 by JBC

[Coldfinger]

Good lord, guess my math is rusty. Thanks for the correction.

 

Big point is that the stubby places less stress on the ice (leverage), right Jim?

 

So what's you're take on the flat curve for the longer screws from zero to positive angle?

 

And it appears from the second graph Jim posted that hard ice really reduces the slope to where there ain't much diff.

 

Well I guess I'm sold on two things:

 

1. Stubbies rock, less stress placed on the ice.

2. I'm going to have to re-learn screw placement--figuring in both the ice quality and angle of the screw--especially if I'm using stubbies.

 

Oh well, shouldn't be too hard an adjustment to make.

[Autoxfil]

Ice quality is everything. That's the lesson. I often place screws at a high positive angle because there's awesome ice on top of bulges. But no matter where you find it - put your screw into the smoothest, most consistent ice you can find.

 

 

[ColinB]

Fitting that Will Gadd posts something on his blog about this topic:

Clicky