Double Whip Rigging and forces on Spar

[NWPEZ]

I use double whip to negative rig wood from time to time when the situation calls for it. I understand the positive effects on rope and hardware regarding reduced shock weight. My question is does anyone know if it reduces shock load on the stem itself?

I have a mid sized Fir roughly 30” dbh that’s dead and wood must be negative rigged or cut into cookies due to the location. Stem appears to be sound upon initial inspection. The current plan is to negative rig small. Brain was just ticking and it crossed my mind if double whip would reduce the shock on the stem at all? Being fir and dead always better to play it safe.

 

[Evo]

I use double whip to negative rig wood from time to time when the situation calls for it. I understand the positive effects on rope and hardware regarding reduced shock weight. My question is does anyone know if it reduces shock load on the stem itself?

I have a mid sized Fir roughly 30” dbh that’s dead and wood must be negative rigged or cut into cookies due to the location. Stem appears to be sound upon initial inspection. The current plan is to negative rig small. Brain was just ticking and it crossed my mind if double whip would reduce the shock on the stem at all? Being fir and dead always better to play it safe.

Yes, the more rope in the system the more cushion. The more th geoundie can pay out, the more rope, so reduction of forces, yet locking it up and it’s not much betta

The catch is the groundie needs to allow x2 the amount of rope. If the situation allows
Rigging small and let it run all the way will also reduce force with less roping skills. IMO this is where a half wrap natural style shines.

 

[NWPEZ]

Yes, the more rope in the system the more cushion. The more th geoundie can pay out, the more rope, so reduction of forces, yet locking it up and it’s not much betta

The catch is the groundie needs to allow x2 the amount of rope. If the situation allows
Rigging small and let it run all the way will also reduce force with less roping skills. IMO this is where a half wrap natural style shines.

Copy that. I feel super confident in my man on the ground to run it smoothly whether we are using the double whip and needing less base friction or not. Just deciding whether it’s worth the extra effort , ie multiple blocks etc. And it was kind of interesting to think about how the forces react throughout the system to nerd out a little. Ha Thanks

 

[flushcut]

Is it at all possible to use a vertical speed line?

 

[NWPEZ]

Is it at all possible to use a vertical speed line?

No sir. A favorite tactic but stump is within 6 ft of the home, steep hillside above, and fresh radical cedar deck on the other side. No trees of height or stability within reasonable distance to tip and butt tie to. Classic lame deal.

 

[flushcut]

Bummer.

 

[Bart_]

Evo, I'm going to agree but qualified.

In the case of letting it run, equally, the run profile determines the forces. All good.

In the case of a catch shock load, we're familiar with keep the rigging tight to the cut to keep the free fall drop distance as small as possible. Let's agree that the same success/drop distance is achieved in traditional -ve riig as double whip tackle.

Here's two cases. a) normal -ve rig with a groundie down rope leg locked off at the bottom or b) dwt with a groundie down rope leg locked off at the bottom. in a) there's one short leg of rope to the log and one long leg of rope going down the tree base. That rope goes through one rig tip pulley/xring whose losses lessen the transfer of stretching force to the down leg which does a lot of the shock absorbing. In b) a little less than half the log's shock force comes back up the 2nd short rope segment to the dwt rig tip pulley/xring and that tension gets reduced again before going into the long down leg which again does a lot of the shock absorbing.

Having written it out, it seems to me the on-the-log's dwt pulley/xring/biner does a force dropping just like for SRT base tie tip force (it's the same, upside down!) - the two short legs aren't 50-50 of the log's weight, they add up to less - so it's an advantage that way. It does drop the down leg force a bit extra too. So at the rig tip a) has log weight + bit less than log weight in down leg. b) has 1/2 log + bit less than 1/2 log + bit less than ( a bit less than) 50% log weight in down leg. So roughly 2x log vs 1 1/2x log - a clear win for dwt.

There's a good chance that the long down leg will absorb better at lower loads too.

Where you can milk this is using xrings or biners at the rig tips including the log. Rope tensions get lower. Any extra stretch in the one extra short rope leg at the top is negligible vs the long down leg.

Overall a bit more margin to cover for errors in let it run execution.


If the spar is in question - a normal or dwt -ve rig is going to sledge hammer the side of the spar. You might want to reconsider -ve rigging.

edit- y'all know that I used 1G or weight for the analysis, but a real -ve rig log spikes 5G giving about 10G or 10x at the rig tip, normal -ve rig locked/catch-stop

 

[NWPEZ]

Evo, I'm going to agree but qualified.

In the case of letting it run, equally, the run profile determines the forces. All good.

In the case of a catch shock load, we're familiar with keep the rigging tight to the cut to keep the free fall drop distance as small as possible. Let's agree that the same success/drop distance is achieved in traditional -ve riig as double whip tackle.

Here's two cases. a) normal -ve rig with a groundie down rope leg locked off at the bottom or b) dwt with a groundie down rope leg locked off at the bottom. in a) there's one short leg of rope to the log and one long leg of rope going down the tree base. That rope goes through one rig tip pulley/xring whose losses lessen the transfer of stretching force to the down leg which does a lot of the shock absorbing. In b) a little less than half the log's shock force comes back up the 2nd short rope segment to the dwt rig tip pulley/xring and that tension gets reduced again before going into the long down leg which again does a lot of the shock absorbing.

Having written it out, it seems to me the on-the-log's dwt pulley/xring/biner does a force dropping just like for SRT base tie tip force (it's the same, upside down!) - the two short legs aren't 50-50 of the log's weight, they add up to less - so it's an advantage that way. It does drop the down leg force a bit extra too. So at the rig tip a) has log weight + bit less than log weight in down leg. b) has 1/2 log + bit less than 1/2 log + bit less than ( a bit less than) 50% log weight in down leg. So roughly 2x log vs 1 1/2x log - a clear win for dwt.

There's a good chance that the long down leg will absorb better at lower loads too.

Where you can milk this is using xrings or biners at the rig tips including the log. Rope tensions get lower. Any extra stretch in the one extra short rope leg at the top is negligible vs the long down leg.

Overall a bit more margin to cover for errors in let it run execution.


If the spar is in question - a normal or dwt -ve rig is going to sledge hammer the side of the spar. You might want to reconsider -ve rigging.

edit- y'all know that I used 1G or weight for the analysis, but a real -ve rig log spikes 5G giving about 10G or 10x at the rig tip, normal -ve rig locked/catch-stop

Alright, here’s the technical madness was looking for ! Haa. I’ve never claimed to be the sharpest tool in the drawer Haa. I get the minimizing of forces on the hardware and rope with the double whip but maybe I didn’t grasp if you feel the forces are minimized on the spar as well? Also, obviously traditional and double whip negative rigging will cause significant bashing of the stem. But that is not negatable unless you have a remote/ seperate rigging point or someway of keeping the rigging point away from the stem. Were you implying one technic would cause less impact on the stem than another? Becusse I haven’t noted that in my experience.

Long story short I know what the outcomes are with negative rigging period and if it’s not safe I’ll just cookie and quarter. But still curious if you think the 1-1/2 times vs 2x weight transferred to the equipment is equitable to what is transferred to the stem?

 

[Stumpsprouts]

In production climbing years I used DWT extensively when the terminal rigging anchor and the secondary block were in different parts of the tree, which dissipated load between sections of the tree and often allowed the landing zone to be in a better spot than the trunk.

I almost never used it in spar work. Felt like the juice wasn’t worth the squeeze (the extensive set up).

I would extensively use a remote rigging point on the tip of the log in an adjacent tree to dissipate loads and get logs landed in a better position. When you have that set up, yeesh you can stop it in its tracks mid air without feeling a thing.

 

[Matias]

I seem to remember Taylor Hammel saying that it reduces load at the rigging point by 25%, but I think that the caveat is that he was specifically saying this applied when using rings instead of blocks. I think it was at a talk at a conference, so I can't referrence a video, but he showed it with load cells so we could see that the effect was real.

It was a cpuple of years ago, so memory is a bit hazy. Maybe it was 25% reduction of load in the groundies hand. I probably shouldn't say any of this because I am not sure, but maybe someone will recognoze what I mixed up

 

[Daniel]

I use double whip to negative rig wood from time to time when the situation calls for it. I understand the positive effects on rope and hardware regarding reduced shock weight. My question is does anyone know if it reduces shock load on the stem itself?

I have a mid sized Fir roughly 30” dbh that’s dead and wood must be negative rigged or cut into cookies due to the location. Stem appears to be sound upon initial inspection. The current plan is to negative rig small. Brain was just ticking and it crossed my mind if double whip would reduce the shock on the stem at all? Being fir and dead always better to play it safe.

I didn't read all the other posts in their entirety, and in case it hasn't been mentioned, in negative rigging there are two types of force that act on the stem. The first is the loading from the rope or rigging system. The second is the force when the piece slams back into the trunk. In studying video on the subject, it is clear that the piece slamming back into the trunk has by far the greatest effect on the climber and stem. The only trunk failure I have ever heard of in negative rigging happened when a piece slammed back into a tulip trunk around an area of decay and the trunk failed upon impact.

When it comes to the climber going for a ride or getting shaken off the hooks, the study of videos makes that "trunk-impact" effect abundantly clear. So when it comes to allowing the piece to run, the benefit comes more from reducing the force of trunk-impact, rather than from reducing forces on the ropes. A properly run piece has two benefits when it comes to trunk impact. The first is that the lower on the stem the impact happens, the less shake the climber will experience. The second benefit is that as the piece drops the direction of the momentum of the piece changes. The force points more downward upon impact, rather than straight back into the trunk, which again reduces shake.

Seems like your question was more directed at the forces generated by the rope and rigging system. It's a good thought-provoking question. I haven't used the technique much, but enough to appreciate the benefits. It is certainly going to be easier for the groundman to let it run because the reduced force on the working end of the lowering line means he doesn't have to take as many wraps, and it also precludes the potential of taking more wraps than necessary out of caution.

Most groundies are less familiar with negative rigging on big wood, and so they may either take too many wraps, which could lock the piece up and have it slam right back into the trunk. Or they may take too few wraps and burn their hands or lose control of the lowering line. Halving the force on the working end of the lowering line will certainly be welcomed by the groundie. It will allow you to take bigger pieces. And, as mentioned above, it allows more line in the system, which will absorb energy and reduce shock loads. So you can judge the trade-off between the time and energy needed for extra setup and the added benefits of taking bigger pieces more safely.

I almost never used it in spar work. Felt like the juice wasn’t worth the squeeze (the extensive set up).

I would extensively use a remote rigging point on the tip of the log in an adjacent tree to dissipate loads and get logs landed in a better position. When you have that set up, yeesh

SS's post sounds like the voice of experience. His last statement, that when negative rigging, if you can add a tip tie using an anchor point in an adjacent tree, "you can stop it in its tracks mid-air without feeling a thing.", refers to the fact that this rigging scenario completely prevents the "trunk-impact" effect. I hope this reinforces the understanding that reducing the effect of trunk impact in negative rigging is more important than reducing the effects of forces generated by loading the ropes.

 

[TreeCo]

I don't believe that double whipped rigging has any advantage in the scenario presented and just unnecessarily complicates the lowering system.

If the load could be dissipated at the lowering point without shock loading it would be an advantage.

Natural crotch rigging reduces loading at the lowering point. (blasphemy!}



A skilled rope handler on the ground?

There's your advantage.

 

[NWPEZ]

Sounds like the unanimous decision is positives don’t outweigh the setup. Even if the added cushion and dynamic effects of the of the extra rope and block did reduce forces on the rigging point slightly. It could easily be negated by the force of the log striking the stem. It was just something interesting to ponder. Negative rigging from the spar is just gonna be as dynamic as your rope man is. Ha

 

[southsoundtree]

And your rope.


How are the roots?
Cause of mortality? Root disease?

 

[Bart_]

I'd like to make a small correction. The two short dwt rope legs aren't the same as SRT base tied tip (upside down), they're the same as DRT. The two tensions don't add up to less than the log weight, they add up to the log weight. As the dwt short leg from the log's pullley/xring to the dwt tree tip pulley/xring tension goes down, the short rope leg from the log's pullley/xring to the fixed dwt tree tip tension goes equally up.

The sentences:
So at the rig tip a) has log weight + bit less than log weight in down leg. b) has 1/2 log + bit less than 1/2 log + bit less than ( a bit less than) 50% log weight in down leg. So roughly 2x log vs 1 1/2x log - a clear win for dwt.

should be:
So at the rig tip a) has log weight + bit less than log weight in down leg. b) has 1/2 log +(change in short leg tension) + 1/2 log -(change in short leg tension) + bit less than ( a bit less than) 50% log weight in down leg. So roughly 2x log vs 1 1/2x log - a clear win for dwt.


Sorry. I'll drink more coffee.

I'd like to emphasize that the down leg rope tension can be dramatically reduced by using rings or biners, but on a conifer the rig tips are right on the stem so there's very little stem bending torque created vs a deciduous lateral branch rig tip. I'd say the sledge hammering of a crispy spar would be a concern right up there with let it run.

Hope it goes well.

 

[NWPEZ]

I'd like to make a small correction. The two short dwt rope legs aren't the same as SRT base tied tip 9upside down), they're the same as DRT. The two tensions don't add up to less than the log weight, they add up to the log weight. As the dwt short leg from the log's pullley/xring to the dwt tree tip pulley/xring tension goes down, the short rope leg from the log's pullley/xring to the fixed dwt tree tip tension goes equally up.

The sentences:
So at the rig tip a) has log weight + bit less than log weight in down leg. b) has 1/2 log + bit less than 1/2 log + bit less than ( a bit less than) 50% log weight in down leg. So roughly 2x log vs 1 1/2x log - a clear win for dwt.

should be:
So at the rig tip a) has log weight + bit less than log weight in down leg. b) has 1/2 log +(change in short leg tension) + 1/2 log -(change in short leg tension) + bit less than ( a bit less than) 50% log weight in down leg. So roughly 2x log vs 1 1/2x log - a clear win for dwt.


Sorry. I'll drink more coffee.

essentially what I was thinking. Minus all the equations. Ha. If you’re reducing the load at the rigging point theoretically you should be reducing the shock on the stem. If run properly.

Unfortunately ended up having to do some cookieing for obvious reasons. . Finally got low enough to use this little spruce behind to get some positive rigging going. After I broke out my Bi Mart crabbing ropes things went smooth as silk!

 

[Njdelaney]

We use double-whip when the primary rigging point is way sideways from the piece being lowered to prevent a big swing, or when we need it to land in a very specific spot(sideways travel needed) or the piece is really big and it makes sense to share the load, but not for negative rigging for the most part.

 

[Stumpsprouts]

My introduction to DWT in person was for spar work, and it boggled me quite a bit because I couldn’t really get a good explanation as to why to do it in that circumstance. Around the same time I saw a climber who I followed (Johanna O Boyle), and she had a rigging setup I didn’t understand. I brought it to several colleagues who didn’t get it, and after playing around with it at home I understood span rigging at last (DWT with two separate anchor points, like @Njdelaney is describing). So incredibly useful! It changed my climbing for a handful of years.

P.s. I use she/her Daniel.

 

[Serf Life]

Small chunks and rock climbing line....boiiiinggg

 

[NWPEZ]

Small chunks and rock climbing line....boiiiinggg

Ohh, I’d be careful there. That rock climbing line could increase the “ boiiing “ factor by 0.1437. Resulting in bilateral load on the flux capacitor. Work within your limits!