Pre-Tightening Line Tension

Contiued from TreeMachine's long running gold mine thread Friction Devices Aloft Thread

A rig's factor of line tension and angle; especially as pre-set immediately before tearoff is hardly dis-cussed; especially in relation to it's importance of load force control and direction; IMLHO. Petightening can remove some elasticity, but then also eliminate the need for the said elasticity. Laying the load into the line, or turning away from the support on the hinge, can allow pretightening prior to tearoff, by the hinging motion; especially pretightening first before back cutting.

The climber is in a unique position to pre-set this line tension immediately before tearoff; by virtues of having 2 legs of line(load and control; groundie gets control leg only), bodyweight off ground, sometimes a foot cam and direction of mostly backcut/ re-lease etc.

The 2 legs of line that climber generally has affords 2handing, to get 2x a single hand pull (with overhead pulley on anchor) for same amount of effort as pulling line with 1 hand, and other on anchor to steady and increase pull. The bodyweight off ground, allows it to be used in addition to the 2x pull above. Also a foot cam can be added to afford leg lift type forces added to the line tension. The pull up on the load leg can be increased by not grabbing the load leg , but rather further out from hinge on the load itself for a more leveraged position of pull than the hitchpoint.

Also, we can place a 2/1 on the load, to double these potentials. These are all inline tensioning strategies; best if the bent/bights of the line are low - Zer0 Friction. As the bights of the bends take on more friction around on support end (over support limb rather than through pulley on support) and bend on load end (around load to 2/1, rather than through pulley); the tightening strategies are best altered some i think. Now we pretighten inline to stiffen line what you can, then really sweat line tight with perpendicular force to leverage tension and capture purchase behind the now available friction.

Pro-ceeding like this affords either maximizing on the fact that there is friction, or maximizing on the fact that there isn't friction. Either or; covering both ends of the possibilities.

This diagram (any resemblance to any local moderator is purely coincidental); shows the inline strategy possibilities of using leg force, body weight force, 2 handing and multiple pulls on load all orchestrated together to pretension the rigging line.

Rock Around the Clock

Line tension can counter loading forces, steer; but also force a stronger hinge if line is pulling into face at the moment of first folding of the hinge (i use fold as the contraction for a place between fall and hold on the hinge). If, we can orchestrate the line tension to force the hinge stronger, and give good support too as load pivots on hinge; we then have 2 stronger (and spread) points of support on the load; the hinge and the hitch(point).

Most pretension prior to tearoff of the hinge; is done before backcut. But many times in overhead rigging, that support point isn't directly overhead; the line grows more slack, before tearoff as load pivots on the hinge. So, even more pretightening must be done before, or right away. But, if we initially lay the load on the pretightend line down in a direction more away from the support point; than towards it, we can now pretension the line even more so.

The more the line tension pulls up on the load, the weaker the hinge will be, but, the more the line pulls over on the hinge, the more stronger, the hinge can be if moving in that direction; because it will fold earlier.

The most inner face (calculating crossed cuts in face/ dutchman as in Dent's words "...a face within a face...") sets the constraint for the amount of controlled sweep available on the hinge before tearoff (or seizing on close of faces). So to draw a limb/load around from back to front horizontally, the most inner face, or hopefully only face is very wide to accommodate the desired movement.

Rock around the clock strategy; folds slightly left down against an upward Right pull of a pretensioned support line; to tighten the line even more, by easing the load into it. Then folding right by switching backcut some when the rope is fairly 'angry' for setting the load agianst it so. It pulls back hard, forcing stronger hinge. The load now moves around on hinge, to serve the hitchpoint on load to under the support point, on a tight line. At tearoff, low to N0 shock; line tension is set by load itself, to equate the load generally if finessed right.

Ummmmmmmm,





















...WHAT did he say? opcorn:

Is it possible to sweat line hard enough with body weight to lift limbs , as in when tip tying ?

TheTreeSpyder said:

Bending a line perpendicular to it's loading leverages higher line tension. If used to raise tension, then grab more purchase past friction hold to tighten line is called sweating the line. This is how Brion Toss de-scribes how ancient sailors for months aboard a ship without radio, electricity etc. raised sails etc. when the bollard handle was broken or lost, or they all would perish.

Click to expand...

They hoisted sails etc. with the technique on the mighty ships. Given proper conditions can lift spars etc. in short bursts of power. The friction helps keep the purchase maid from the perpendicular leverage; especially when the friction point is remote from user. The highest leverage of return for perpendicular effort; is just a few degrees off of a straight line; giving highest change in distance to leverage force by.

So, you should be able to hoist tips higher etc. in right ranges and conditions.


A line being flexible is generally just visualized as a device that can multiply effort by inline / pulley types of pulls/ Mechanical Advantage. This can trade 2x, 3x, 5x etc. distance for power. After all to exert rotational tourque / Leveraged Advantage, we need a device that is not flexible, that resists bending and a line is flexible. Any bend in a wrench or lever is a loss of force if not springy, but also storage of force if springy. But, under load, a line becomes a stiff device; that can then resist bending, therefore offer Leveraged Advantage.

The short coming of this is that the real high return is only for a few degrees bend when input is truly more perpendicular to loaded line; thus short bursts, over these small ranges. Just like a wrench, the effort must be kept most perpendicular to loaded device.

This is very advanced stuff, I'd not reccommend any climber under 5 years read this. Because they might get squazzhed and rigg a whole tree in one cut.. lol
Right on spydy.:monkey:

I've been working the Black widow I find therees no sweating and super fast riggging with it

I did 8 years turning two for the USN Spydy. On some ship mostly sailing IV've seen bosum chairs used for swings. The chair it seems was tied to the sail I think and when the wind came out the water youd go..