V-thread : what ice screw length ??

Hi,

   How safe is it to do a v-thread with a 19cm  ice screw ?

Assuming the ice is in good shape .

Here’s a good test: make a v-thread with a 22cm on flat ground. Put in a backup screw above with a touch of slack so you don’t go flying when the thread pops. Then thread the v-thread, weight it with a person or two, and start chopping ice away from the v-thread. See how much you need to chop away before the v-thread fails. 

Then use that experience to decide for yourself whether a 19cm screw makes a strong enough v-thread for your own risk tolerance.

Edit to add: In good ice a 19cm is generally strong enough for a v-thread. The trade off in weight for a 22cm screw and time required to drill is negligible, so most people just carry a 22cm so there’s a bigger margin. A longer screw also gives a bigger target to shoot for when drilling a thread. So there isn’t a ton of reason to use a 19 vs a 22 unless you already have the 19 and don’t want to buy a new ice screw, even though a 19 is generally strong enough. 

https://youtu.be/hz0v-yEKcMc?t=260

Personally, I would not hesitate in the slightest to make ‘em with 16cms for a rappel.
For reference, a few days ago I made A-threads in soft sun baked ice using 10cm screws and 550 cord and slung bratwurst size candles for rappel tests. I do this yearly at the end of “regular” ice season for “perspective testing”. Have yet to have one fail, and can’t make them fail by bouncing and jumping or dead dropping a foot or two. As you can see in one pic, I did make it crack across but it held another rap.

Edit:  just watched Jdejace’s video posted above...  I did that same chop thing while hanging on the 550 cord thread below.  I had to chop away a surprising amount before I finally popped free (seems like it should’ve taken one axe blow.   Took 7 )

Now I’m not recommending these for deliberate normal use, but many people worry way too much about ice.  After decades of ice climbing and testing the edges of the envelope, that shit is way more bomber than you think.  

Also, just to plug Gunkiemike’s super stubbies, 

This is a “not fully sunk” 7.5 cm screw in strong but delaminated ice, and no amount of shenanigans was going to rip that out short of a high FF whip (if then).   I’ll test some of these further, next ice season.  

If Petzl made 10 cm Aluminums, that’s all I’d use 90% of the time for every screw beyond the first 2.  

Thanks !

Recently I was talking to an IFMGA guide about this and he informed me that in bomber ice a 16-17 cm thread hit at the back is 12-14 kn strong. And a 21-22 hit at the back over twenty. I’m sure a 19 in bomber ice is more than enough, us agreeing on around 18kn. 

Eliot Hack wrote:

Recently I was talking to an IFMGA guide about this and he informed me that in bomber ice a 16-17 cm thread hit at the back is 12-14 kn strong. And a 21-22 hit at the back over twenty. I’m sure a 19 in bomber ice is more than enough, us agreeing on around 18kn. 

Concur. I've had guides explain to me that 19 is good to go for V-threads.

David Maver wrote:

Concur. I've had guides explain to me that 19 is good to go for V-threads.

So should we stop buying 22cm screws and just get 19cm? If they work fine for good ice then save the weight and get the 19cm right? I have no intention of climbing any bad ice that requires a v-thread but if it happened the 19cm would probably be fine too.

The difference is <10g for an aluminum screw, still <1oz for steel. I'd just bring the long one personally.

Next season at local ice fests, I’m going to make a dozen A-threads (ya’ll should get rid of the V and switch to “A” -verticals) using 13 cm screws.  Naked or with cordage.  A $300 reward to anyone who can break one (while on separate belay) using their rope and with up to two people.   You can’t do it.

(I’m talking any rappel scenarios, not UIAA drops with high FF)  

Don’t listen to guides, or me.  Prove it to yourself.  Go make one and try.  You’ll see that debating  22, 19, or even 16 for that matter is like debating whether it’ll hold an F-350, an F-150, or just a Tacoma, respectively.   Even the worst case is a 5x safety factor for its intended purpose.  

Now don’t get me wrong.   I’m saying to continue to use the 19 or even a 22 for your threads, it’s just when you prove it to yourself and understand how much margin you truly have with that 19, you won’t be sketched with doubt and let your imagination run wild when you lean back and commit to it.  You’ll have a nice warm fuzzy and will be moving faster.    That’s what it’s all about. 

Mark Pilate wrote:

ya’ll should get rid of the V and switch to “A” -verticals

Another F350 vs F150 argument IMO :-) 

I build whatever is easier at the time, wherever the ice looks best. With a 21-22cm screw. 

curvenut wrote:

Hi,

   How safe is it to do a v-thread with a 19cm  ice screw ?

Assuming the ice is in good shape .

I've done this and rappelled. I'm not dead...yet. 

jdejace wrote:

Another F350 vs F150 argument IMO :-) 

I build whatever is easier at the time, wherever the ice looks best. With a 21-22cm screw.

It's not only horizontal versus Vertical, don't forget 4 and 10 o'clock or 1 and 7. Just go with there the ice is best. 

Mark Pilate wrote:

Also, just to plug Gunkiemike’s super stubbies, 

This is a “not fully sunk” 7.5 cm screw in strong but delaminated ice, and no amount of shenanigans was going to rip that out short of a high FF whip (if then).   I’ll test some of these further, next ice season.  

If Petzl made 10 cm Aluminums, that’s all I’d use 90% of the time for every screw beyond the first 2.  

Blue ice coming out with 10cm aluminum, a full range in fact,  us.blueice.com/products/aer…

Wow those new Blue Ice screws are light! I'd seen a pic but not the specs. You'd save nearly a pound compared to a rack of Petzls. I'll probably buy at least the stubby to replace my steel. 

They also are the largest diameter screw out there so v-threading is easier and it is safer to rebore a hole from say a steel screw.

Are they fatter than BD ultralights ?   I use those for rebores as they were the fattest till maybe now.  

Curious how they place in soft, wet ice.   See the other screw thread discussion, but as the bore fattens, the core plug is stronger and stays attached longer/easier which can sometimes result in binding in certain ice conditions

Bottom line is I’m gonna get some to play with. 

Yeah agreed I'll wait for a few reviews before selling off the Petzl rack. The BD's are lighter than Petzl too but the reviews weren't glowing. I'll try the stubby though. 

jdejace wrote:

Yeah agreed I'll wait for a few reviews before selling off the Petzl rack. The BD's are lighter than Petzl too but the reviews weren't glowing. I'll try the stubby though. 

Bds are sharp out of box and at good except that 3/5 bind no matter the ice. 

Well the Blue Ice folks are clearly aware of the issue per this thread and believe they've addressed it. Seems like there is always a compromise. I'll be eager to hear some comparisons next season.