Why no hitch for SRT?

[Handy2]

The question is this: Why can't you climb SRT on just a hitch?


My understanding: The way we tie hitches for DRT does not work for SRT, because the hitch will bind up, making descent impossible.

But why? If you are 200lbs climbing DRT with a hitch on some kind of pulley saver, your hitch and the moving end of the rope will experience 100lb of force.
Without adjusting the hitch, you can base tie your fixed end and have a 100lb climber climb SRT on it, and it should experience pretty much the same forces.
This should work, right?
If not, why not?
So should there be a way to tie a hitch that would work for you climbing on it SRT? Maybe it would require a different approach to hitch cord (the rule-of-thumb 2mm thinner than the climb line might not apply)?


note: I know about Brocky's Sticht Hitch. I'm talking about a pure hitch with no hardware in it.

 

[Tom Dunlap]

IN my early days of working on SRT systems I spent a climbing season...March through December...trying out so many combinations of:

Rope
Hitch cord
Hitches
Climbing requirement---single ascent/descent---ascend/work...ascend more/work..descend---Ascend..work a whole tree...up and down...removals

It took such a long time to work through the itterations.

I couldn't find a combination that worked reliably for sliding then locking off/sliding. I could find good ascending combos, good descending, good working...but not so good for ascent/descent

As I went into winter I decided that I'd try and find something to add into the hitch wraps to make a Bachmann-esque solution. That all got shelved when Morgan Thompson and I crossed paths with his intro of the Unicender. Then, Kevin comes up with the Rope Wrench.

In SRT I look at the hitch like a volume knob. A plain cord/rope hitch is like a volume knob with set stops 1-2-3... The combos that incorporate mechanicals divided the volume down to hundreths....1.XX...2.XX...3.XX

In the decades since I started dabbling in SRT I would have expected the cord on rope friction issue to be solved. So far..no solution.

 

[Cereal_Killer]

If you are 200lbs climbing DRT with a hitch on some kind of pulley saver, your hitch and the moving end of the rope will experience 100lb of force.
Without adjusting the hitch, you can base tie your fixed end and have a 100lb climber climb SRT on it, and it should experience pretty much the same forces

In your scenerio you're overlooking friction completely. Even on the best pully there's still some additional friction. Even if you had a theoretically perfect pully that really did add no extra friction just simply bending the rope 180° adds friction.
The tie in point is contributing a good deal of friction allowing the hitch to hold less than 50% of your weight. On SRT the device is having to hold the full load on its own with no friction from the tree.
This is why when the RW came out Kevin used the marketing phrase "the branch that goes with you" (or something to that effect).

 

[Chris Schultz]

I believe I watched a discussion with Kevin Bingham (on treestuff maybe) where he talks about climbing SRT on strictly just a hitch. Closest I’ve come to this was shoveling my roof off on single line, threw a hitch on just for extra flexibility....

 

[Brocky]

The Sticht can be tied using the cord to replace the ring, but doesn’t run as smoothly.

The Cornell hitch when used with tied eyes with the shortest legs possible will not bind up, there may be others that will also.

There‘s the Synergy X hitch that is long but no hardware used in the hitch.

Some hitches can be used to descend by hold the carabiner and legs with one hand and twist the wraps to unwrap them, and twist back to stop, generally takes about 90 degrees of turning. This eliminates the loading and unloading of the hitch that leads to the binding.

 

[Tuebor]

Just guessing here - and not a big user of DdRT - but like Cereal Killer said: friction. I think when you are motionless, hanging on your hitch while DdRT, more of your weight is on the hitch and running side of the rope. Friction at the limb or friction saver and at the hitch is keeping everything in balance. When you break the hitch to descend, you reduce the "friction" of the hitch and transfer weight to the standing end, enough to allow it to overcome friction at the top and to "pull" the running end through the hitch until forces rebalance at whatever descent speed you've obtained. Friction is allowing the transfer of weight from one side to the other side of a moving system. With SRT, you have nowhere to transfer your weight to when you reduce the grip of the hitch.

 

[Abovealltrees]

If your hitch is binding up try less wraps or try a different configuration. Schwabish, distel , michoacan hitches all behave a little differently. Also you should not do a descent to the ground on any hitch whether your using SRT or Ddrt. The friction on descent creates glazing and ecessive wear. It undermines the hitch rope and the climbing line. A figure 8 work fine but you do have to swicth and that can create a safety vulnerability. That is one reason its more convieniant and easier to use a mechanical device is an ascender AND DESCENDER.

 

[southsoundtree]

I don't use a F8, and do long descents, slowly.

Easy to put a munter hitch on a biner on a sling, or a F8, above your hitch.

 

[LordFarkwad]

I don't use a F8, and do long descents, slowly.

Easy to put a munter hitch on a biner on a sling, or a F8, above your hitch.

Recently experimented with that. Hitch above fig8, collapse hitch and control line coming into fig8 to come down. Hitch above munter/biner, collapse hitch and control line entering munter to come down. Both were great, except the munter twisted the line like crazy.

 

[DSMc]

...
Also you should not do a descent to the ground on any hitch whether your using SRT or Ddrt...

Having done exactly that, for decades, I can't say I agree with such a blanket statement.

If you are using a rope and hitch that have been created for tree work and friction hitch use, there is zero need for a changeover when making a descent.

 

[ChippingHipsters]

I used to like that glaze! Almost old-school Arbor Plex being the THE rope back then, I found burning some 'memory' into it made one-hand taughtline tying easier. Pine sap (unavoidable in Massachusetts) adding the grip lost to the glaze, y'had y'rself a nice preformed tail-bridge hitch that not only worked, but kept your senses and reaction times razor sharp!
Ah, the good o'l days.

 

[moss]

The question is this: Why can't you climb SRT on just a hitch?


My understanding: The way we tie hitches for DRT does not work for SRT, because the hitch will bind up, making descent impossible.

But why? If you are 200lbs climbing DRT with a hitch on some kind of pulley saver, your hitch and the moving end of the rope will experience 100lb of force.
Without adjusting the hitch, you can base tie your fixed end and have a 100lb climber climb SRT on it, and it should experience pretty much the same forces.
This should work, right?
If not, why not?
So should there be a way to tie a hitch that would work for you climbing on it SRT? Maybe it would require a different approach to hitch cord (the rule-of-thumb 2mm thinner than the climb line might not apply)?


note: I know about Brocky's Sticht Hitch. I'm talking about a pure hitch with no hardware in it.

To answer your question, in order to have smooth functionality a “standard” hitch can only hold 50% of the climber’s weight. DdRT meets that requirement. With just a hitch on “single rope” 100% of the climber’s weight is on the hitch and it will not release smoothly for descent. Doesn’t matter how heavy or light the climber’s weight is, the principle remains constant.

The Singing Tree Rope Wrench solved that by diverging 50% of the climber’s weight through the wrench tether in effect bypassing the hitch and leaving the hitch to hold only 50% of the climber’s weight. Super elegant solution, problem solved.
-AJ

 

[Tom Dunlap]

When I shifted from trying to find a hitch to the Unicender my next idea was to start with a Bachmann and see what could be done with a biner or ring/oval in the mix.

I still think that there is a solution here but that's for a full time climber to sess out.

Semi-mechanical Ascenders

 

[TheTreeSpyder]

In my mind (a dangerous place to be sure) the basic reason DdRT can get Blake's etc. to slide loaded is cuz they don't slide loaded, in either case must free up load to slide.
.
Load will always carry against firmest applied rigidity to maximize support autonomously. So with 2 support legs 1 can hold as other shears, stretches, slides etc. in other than matching or exceeding firm rigidity of other leg(s) of support.
.
Thus, same hitch dead locks at half load SRT, yet slides under full load DdRT.

 

[LordFarkwad]

Thinking out loud here for a second...

So, when a 200lb climber is hanging motionless on DdRT, there is 100lb per leg. When the climber applies pressure to the hitch to descend, there is downward motion, so there is then less than 100lbs on the hitch side, indicated by rope sliding through the hitch, correct?

When a 100lb climber hangs motionless on solely a hitch in SRT, there is obviously 100lbs on the single leg. But when the hitch is collapsed slightly so as to initiate decent, there is less than 100lbs applied to the hitch (motion in the direction of gravity means that there is less applied force from the moving climber, hence less than 100lbs being applied). Of course, since we accelerate much slower than freefall speeds this differential in applied force prior to and after movement is initiated will be minimal.

This is not intuitive as to why these two scenarios are profoundly different in practice.

In a DdRT situation (with a frictionless pulley at the PSP), is there *that* much less than half the climber's weight applied to the hitch upon descent (that is, after descent is initiated)?

@TheTreeSpyder, I'm still trying to decode your explanation there...

 

[Brocky]

In the decades since I started dabbling in SRT I would have expected the cord on rope friction issue to be solved. So far..no solution.

When I shifted from trying to find a hitch to the Unicender my next idea was to start with a Bachmann and see what could be done with a biner or ring/oval in the mix.

I still think that there is a solution here but that's for a full time climber to sess out.

See post #5 above, or do you not consider them to be true SRT hitches?

 

[Tom Dunlap]

See post #5 above, or do you not consider them to be true SRT hitches?

those weren’t around when I was searching. I’ve never tried them but I’m sure that they work like you described.

 

[misfit]

I will attempt to answer the original question. It seems you are forgetting that only half as much rope passes through the SRT hitch in the same amount of time for the same length of descent. In order to produce the same rate of descent in DdRT, an SRT hitch would have to provide twice the friction (for double the weight) over half as much rope in the same time. An SRT hitch must apply even more friction to the rope to slow the flow rate in half, so a 100lb SRT climber would still be applying more friction on the hitch than a 200lb DdRT climber at the same rate of descent, because he is halving the flow rate of the rope through the hitch. If he kept the same flow rate as the DdRT climber, he would descend twice as fast. The slower flow rate requires more precision of control than a standard hitch can provide because minute changes in the hitch can cause either a stop or a free-fall.

 

[Tom Dunlap]

@misfit got it!

As I got into SRT I found that there is a theme that runs through the whole system in so many ways.


I call it The Doubling Halfing

At so many points there is a double or halfing...awareness is one. Gotta pay twice as much attention because things are so new.

Brilliant share, @misfit