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Suspension Bondage

Bondage Physics?

Postings from Shibari Network Group:

Frames and more

Obviously there are stability issues. In Theatrerigging we always are on the side of extreme caution - remember "Murphy was an optimists!" So we go for ratings at least 4x the load weight, but that doesn't really take into account swing physics. well secured points with at least a 4x overkill should handle the weight and stress - I like to use kevlar tape with a load of 1600lbs at minimum for a wrapped pooint or climbing webbing with ratings over 5000lbs preferably and carabiners of similar strength.

As to structural stability... from a freestanding structure I have read that you should have "feet" at least i/s teh length of the structure's height. For example my bondage frame is made of pressure treated 4x4's the height is 7ft. there are 2 upright posts each with one side, one front and one back "foot" (ie: 2x4 flat on the floor 2.5 feet long with a diagonal support strut and a vertical piece 2.5 ft long making a triangle) each "foot" is bolted to through the vertical post to the foot opposite its position. The side feet are bolted through the posts and to a center piece consisting of a 2.5 foot high vertical a diagonal support strut and a flat oak 2x12 which serves as a foundation to stand on and has tie off bolts.

I know this is a complicated and unweildy description, but it's a fairly common design look. I can jump and swing around on the thing and it doesn't rock one bit. I have suspended as many as 3 people from it and still maintained stability. Swinging and spinning of suspended subs have occurred with no movement.

While the frame is lined with tie 3/8ths inch and 1/2 inch eye bolts for tying off; I wrap hollow tube climbing webbing wrapped around the top 4x4 and outfitted with carabiners for single point or double point suspensions.

Don't know what the actual physics involved are, but it works well , is Very stable, strong, and sound. Last year at ShibariCon I found that most of the bondage frames rocked back and forth just pushing on them and seemed very unstable when I hung and swung from them. I chose not to use them. However they got LOTS of use and there were no incidents that I know of. It may be that the stability issues were due to inconsistencies in the carpeted floor surface, I don't know.

Stan Devi (author)

All about Physics

Suspension is all about physics. Everything has something to do with physics. I might be a professional artist now, but i use to be a super geek in high school i was ability to do calculus in my head without using paper or a calculator. And i loved science and math (I was dyslexic, I didn't start learning how to read until my second year of high school, and
that why i have terrible email writing some times). In college Iwas receiving awards from Steven hawking at Princeton on thing I was doing with art for science on radiation and radioactivity. But ended up being a artist, because working in labs and on paper with numbers became boring. And to spew out a couple phrases as we use to all the time in high
"Physics is phun". "And Physics makes the world go 'round". ==B)

Of coarse there is physics to suspension! Dealing with gravity, weight/load, force, balance, frames, kinetic and potential energy. All that is physics.

The physics we use is nothing new, we just use it for something a little different and more interesting. But we add a bunch of stuff onto it, sexuality, mental play, medical concerns...which is what makes it more special.

Now a professional rigger answered and said he does 4x weight load of the body, which is a professional (stage) riggers answer, which i good for non-living non-moving objects. But when dealing with humans, which we are, you go to a mountain climbs rigger answer, which is 10x, because you dealing with something that is alive, and active and you want to keep alive if something does go wrong.

So when I tie, and teach tying, I teach 10x (not that i am a professional rigger, but because 10X seems safer then 4X). So if tying a 200pd body, I try to use 2000pds of weight load with ropes and frame. (200x10=2000lbs), which is you stage rigging (200x4=800). I think the reason moutian riggers use 10x, is because thing can fail, and you always was at least double back ups, (200x4x2=1600), and you always over estimate who you are tying, and
under estimate the strength of your equipment. Which is tested in a factory, on brand equipment in a test lab, not used and in the real world. So thats why i think they use 10x, to account for all those other things.

So here is my lay mans calculation for suspension. Which is probably wrong, but that why i always over and under estimate factors for the better....

So with dealing with suspension, you usually try to use a frame to support a ton (2000lbs) if possible. You got your rope... MFP (350 weight load), hemp/jute (1000ish), fold you rope, and tie the bight off with a knot so it acts like 2 pieces of rope (never use a bight in a suspension tie, because that weekends the load by 50%, but putting 2x the weight on 1 point). So its becomes MFP (700), Hemp/jute (2000-ish pds) for each tie. And if you
doing a rope wench tie, supposedly stronger i guess, because it tied, up and over, back down, and through and up and tied. (i been told it make it so you only lift 33% of the weight at that point, so i am not sure how this effect the real calculation, so i ignore it). But using my jute doing a suspension, ignoring that last part i usually end up with at least 16,000-ish pds of weight load possibly on the ropes, which with my 10x factor on the person, i only need 2000. So 16,000 is higher then 2000, so its good. And i also know having knots in thing lessen the amout of tensil stregnt of the rope, which i am guessing can change how i tie up to 50%, so 8,000 is still higher then 2,000 if so. ==B)

Then you have to deal with balance, where pressure is spread out, because to much pressure can lead to physical medical problems, like nerve damage, circulation cut off, etc.

So basically its all physics except for the mental enjoyment/fear etc. Which is happening because of the physics...

Which leads back to physics is phun! And makes the sub go 'round and
'round ==B)

MorTis (author) | Contact / Imprint