3 ms·

Simple material strength is not the only consideration. I'm not saying ULT4 rope would have been better in this case, but it is worth noting that ULT4 comprise

by jzwinck 11y ago

Simple material strength is not the only consideration. I'm not saying ULT4 rope would have been better in this case, but it is worth noting that ULT4 comprises strands which are not round and are arranged in a special pattern which among other things widens the contact patch with drums, sheaves, etc. I'd like to see the design of the block with sheave that the rope came out of. Some designs have the rope quite captive, while in others it's easy for the rope to come out (sometimes intentionally). The point is, there is a lot going on when you see one of these shows--it is truly "high performance."

jacquesm 11y ago
Shear strength for rope is a totally different parameter than load-bearing capability. It looks from the account that the rope encountered something approaching a knife edge while traveling at high speed. It could have all the load bearing capacity in the world, if it isn't designed to deal with impact damage like that it will fail. What surprises me about the whole affair is that a single rope breaking could lead to a death. This may be a function of the degrees of freedom required for the artists, so don't take this as a 'why don't they' entry, more of a what parameter caused them to choose this particular setup?
- jzwinck 11y ago
  My experience is on high-performance sailboats rather than acrobatics, but single-rope seems to be the standard. You could imagine having two ropes for redundancy, but then not only would swiveling become more complex (at the sheaves, not the swivel), you would have something like twice the rope weight damping the movements of the acrobat. Coming from a sailing background, another question would be: could they use synthetic/polymer ropes? Where cost is not much of a concern, things like Dyneema have taken over in a lot of roles.
  - jacquesm 11y ago
    Funny, I was writing that with my stint for a sailmaker in the back of my mind and yes, single rope is the standard. But in sailing gravity is not always luring to catch you if something goes wrong (though you can absolutely die from an accident during sailing if a line (or a stay) breaks). Probably a better comparison would be mountaineering and there there are plenty of people that climb without ropes at all...

by jzwinck 11y ago

jacquesm 11y ago

Shear strength for rope is a totally different parameter than load-bearing capability. It looks from the account that the rope encountered something approaching a knife edge while traveling at high speed. It could have all the load bearing capacity in the world, if it isn't designed to deal with impact damage like that it will fail. What surprises me about the whole affair is that a single rope breaking could lead to a death. This may be a function of the degrees of freedom required for the artists, so don't take this as a 'why don't they' entry, more of a what parameter caused them to choose this particular setup?

jzwinck 11y ago
My experience is on high-performance sailboats rather than acrobatics, but single-rope seems to be the standard. You could imagine having two ropes for redundancy, but then not only would swiveling become more complex (at the sheaves, not the swivel), you would have something like twice the rope weight damping the movements of the acrobat. Coming from a sailing background, another question would be: could they use synthetic/polymer ropes? Where cost is not much of a concern, things like Dyneema have taken over in a lot of roles.
- jacquesm 11y ago
  Funny, I was writing that with my stint for a sailmaker in the back of my mind and yes, single rope is the standard. But in sailing gravity is not always luring to catch you if something goes wrong (though you can absolutely die from an accident during sailing if a line (or a stay) breaks). Probably a better comparison would be mountaineering and there there are plenty of people that climb without ropes at all...