I just had a discussion about this yesterday with Max during a break in the class he did with Mark Yu. The discussion went as follows:

The weakest link in your suspension "chain" is the bottom. If you're using climbing/rescue gear for all your hardware and have a solid fixed point you shouldn't have to worry about those as long as everything has been inspected prior to use,and discarded if necessarry. For suspensions in the range 2-5 feet off the ground he uses no less than 8 (4 doubled) pieces of 8mm finished hemp. If it's an instance of extreme height or a dangerous situation he'll switch to the rated climbing rope.

I'm not trying to argue, nor speak for Max, but 6mm rope just seems small for suspension. At least in that quantity. It might do the job, but it just seems undersized to me. I think that aesthetically using the smaller rope doesn't have as much impact either. I generally use 8-12 pieces of 8mm because I like to the look of more rope and want to overdue the engineering.

To expand on Waldemars point about the vertical lines being different from the harness wraps, when I think about suspension I classify ropes into 3 roles:

(1) Rope attaching the first (and perhaps only) piece of hardware, ('biner, ring, swivel etc), to the suspension point (beam, girder, suspension frame etc).
(2) Vertical lines, attaching rope tied around some part of the bottoms body to a piece of overhead hardware.
(3) Rope actually tied around some part of the bottoms body.

Role (1) may not exist, say if you attach a ring directly to the hook on a chain hoist. One concern here is abrasion of the rope by rough edges on a beam or girder.

Role (3) tends to be non-critical stengthwise since in order to adequately distribute the forces on the bottoms body you end up with a number of wraps, with thinner rope needing more wraps, and consequently the force on each part of the rope is very low compared to the breaking strength of the rope. One concern here is of the rope slipping over the bottoms body.

Role (2) is the interesting case. For a reason I will explain in a moment, vertical lines often appear as a bundle of 4 - a doubled line which goes over the suspension hardware and back along itself. For a simple* suspension I like to subdivide role (2) into 3 subcases:

(2)a The primary suspension lines - this is a bundle that often (but not always) goes to a chest or arm harness. If this fails bad things happen. On the other handle if this bundle holds, it will keep the bottoms head, neck and spine off the deck.

(2)b Secondary suspension lines - these are bundles that goes to other places on the bottoms body, and carry a fair amount of weight. If they fail, the bottom will at very least get a nasty jolt and possibly feet will hit the deck causing injury.

(2)c Tertiary suspension lines - these typically hold an arm or lower leg in a given position, but carry very little weight and will have little consequence if they fail.

Now the technique that I think Bill is alluding to, is what I have heard called the "rope winch". Basically you fold a rope in two, pass the bight over your ring, around the harness on the bottoms body and tie it off, perhaps with a half hitch or two. You then take your tails and bring them down through the original bight. Thus it appears you have a bundle of 4 lines joining the ring to the harness and furthermore when you pull up on your tails you have a factor of two (minus friction) mechanical advantage. A variation is where you tie a cuff around a limb using a folded piece of rope, pass the tails around the hardware and back through the bight.

The problem here (and I think this is what Bill is worrying about) is the bight. This is clearly a weak point and if it fails the whole bundle fails. How weak? Well at one of the Shibaricons (2006 maybe?), Taipan mentioned in his suspension class that he handle conducted some experiments and on hemp rope this bight failed at around 20% of the breaking strength of the rope. I was shocked by this and checked with him after the class to be sure I had understood it right.

Now I don't think the rope winch is necessarily a bad technique - in fact I use it all the time. But only on tertiary lines or on secondary lines with with very strong rope. If I need mechanical advantage on a secondary line I more often use a rated rap ring to reduce the friction loss and the wear and tear on my rope.


*More complex suspensions can't necessarily be analyzed like this. In particular I have seen Midori do a trick where she hacks through what was her primary lines with a knife, transferring the load in a dynamic way to secondary lines, that now become primary.

Speaking as a Rope Performer, it seems that you find Spectacle an inValid reason for suspension. Rope bondage is not just about sex.

I disagree that all treated 6mm hemp (~1/4") has a breaking strength of 250 lbs. My own tests on my rope have shown me that it's at least twice that. However, different manufactures vary, and even individual batches from the same factory will vary from batch to batch.