Aerial Silks WLL

Just had an email conversation with a parent of a dance kiddo that wants to do an aerial silk performance during a dance show rented by a public group. I told her it wasn't possible with our counterweight system (I neglected to mention that ZFX, Foy, Hall, et al could be hired to do such a thing because I think she would've pushed the issue and they don't have the bread to afford them).

She first mentioned to me that she needed a beam capable of hanging 500#. She later tells me her daughter weighs 112# and their coach said it was OK to use a point with a MBS of 500#. Ignoring the fact that (assuming a static load) it's 60# under 5:1 safe WLL, this girl I imagine is bouncing and twirling on these things which would increase her weight on the silks many times, possibly beyond the 500# MBS as dictated neccessary by her instructor. Not to mention that she really should be thinking about using a 10:1 WLL.

I think she's already a bit annoyed with me for saying no dice, but should I say anything more about how 500# isn't really a safe number to go with? I'm concerned that might really piss her off. I was thinking of contacting the dance instructor herself (I don't think this aerial work is through her studio). Any aerialists in here? I'm not sure who her trainer is, but I don't know much about that world.

Aerial silks are a very specialized product, a counterweight system is in no way capable of doing aerial stunts. As far as ratio each industry is different I don't know aerial silks and don't claim to. Tell them to have the coach contact you and ask them as a TD what would it take to make this safe. If the coach can't arguably say exactly what this kind of performance requires then its a no go. This requires a rigid point either from a ground base or tension rigged truss with 3 points minimum with 60-80 psi on each point (not what is holding the truss In the air, just what is keeping that truss static. We did an aerialist at our local theater its doable but requires a lot of planning and special knowledge that I don't believe a student is capable of knowing.

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The instructor may have access to a certified freestanding aerial silk rig that can be brought in and set up for the performance. I've seen a couple of different models used at a few dance competitions.

The 500# part is what really gets me concerned... and basically throws the hole thing out the window. A 112# girl "falling" 1' and stopping over an inch will cause a 1200# shock load. So, there goes your 500# out the window... and I've never seen one of these performances without the sliding and stopping thing. You really should be looking for a point rated for MUCH higher. You won't find that in your fly system. Your pretty much going to have to go straight to your grid... then figure out how to secure and stabilize the point down the line. It can be done, but it won't be quick or easy.

Many of the people who do silks work professionally follow the circus tradition of doing their own rigging... those guys know where to push and where to give to make the rig safe. They are also the same people on the line if it fails. If you are rigging a point for your mother you will do it right. Without them coming in and really doing it I would not do it for them. I would also not do it for a child... way too much at risk if something fails.

I get all of this- that's why I told her no dice. We don't have a walkable grid so there's no easy way to hang a point without significant intervention from a qualified rigging company. What I'm asking is would you feel obligated to tell her that it's not a matter of if her daughter falls from this rig, but when? The picture she sent me had her doing the aerial work from some kind of tripod stand. It was not clear how it was built or how the legs met at the top to support the silks. It was on the beach, so I'm guessing the ends of the legs went into the sand? I will be interested to see if they try and bring in some kind of setup to perform this on stage.

I tried looking into the actual formula for shock loading, but came up short with the elasticity of the material. I was hoping someone on here knew enough about it to shore up numbers. If this stuff is really stretchy I can see it being less of a shock load than if it were rope, but she's still waaaay under 5:1 anyway. Everything I've looked up so far on aerial silks preaches 10:1 like most things in that realm.

Footer said:

A 112# girl "falling" 1' and stopping over an inch will cause a 1200# shock load.

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StradivariusBone said:

I tried looking into the actual formula for shock loading, but came up short with the elasticity of the material.

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The shock load @Footer indicates for the described motion is basically what I'd expect based on Newton's second law of motion (F=MA) and the assumption that the "falling" is close to free-fall. It doesn't really matter much (as far as the support reaction goes) if the performer stops in one inch due to slipping along the silk or the silk streching. The duration of load can have a signifcant influence on the ability of a structure to resist the load; so a point that can support a 500# static load may also be able to support a 1200# shock load, but I wouldn't count on it.

When Hall Associates helped me fly someone a year ago, they set up their fly rig on one line set, then flew it out to the grid. With the arbor stack at the ground, they used an industrial strength ratchet strap (like a trucker would use) to secure the arbor at ground level to our weight rail structure.

This method still depends on you having a decently robust and in-good-condition counterweight system. Also requires some logistical forethought because once the arbor is strapped at ground level, it's not moving. You cannot bring it in and out during a show. You need some other way to get the aerial gak out of the way during the other acts of the show.

If you were to allow it, you'll want to talk to the trainer directly. Ask about how far up she goes (six feet is very different from fifteen feet), her skill level, and how prone she is to falling currently (in what I imagine is a studio with some gymnastics cushions so the falls don't kill).

It's probably not too difficult to get the point installed, but that's probably the least of your issues. You still need to be worried about liability. Liability if your rigging fails. Liability if she simply falls out of her own accord. Liability if your rigging holds up but her materials fail.

For whatever it's worth, our cost of flying someone up, suspending them there for 45 seconds, and then bringing them right back down ended up being about $2300. If you want a fast way to kill this idea, you can expect it'll be a good sum of money to get a professional in there to rig this. Which still does not wash your hands of the liability if she falls of her own accord.

robartsd said:

so a point that can support a 500# static load may also be able to support a 1200# shock load, but I wouldn't count on it.

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And that's assuming a drop of 12". In the photos she was at least 4-5' off the ground at some points.

MNicolai said:

For whatever it's worth, our cost of flying someone up, suspending them there for 45 seconds, and then bringing them right back down ended up being about $2300. If you want a fast way to kill this idea, you can expect it'll be a good sum of money to get a professional in there to rig this. Which still does not wash your hands of the liability if she falls of her own accord.

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If she were to push the issue, I had planned on sending her to one of the big guys. It gets weird though with insurance. We do require they maintain the standard $1M per incident liability, but if I were to rig it how you described and it failed, I'm sure I would then be part of that liability too. I also don't know if my employer would share that burden- hence why I said no. If they bring in their own rig and someone gets hurt it theoretically is on them for the same reason, but I'm sure there's some grey area there. It's much easier to just say no.

Aerial rigging is often 10:1. The portable rig was probably something like this. Biggest problem is the time it takes to set-up, which is probably why they don't want to use it. My daughter often performs on one like it for single point trapeze. They have non-slip pads for feet and can vary in height. Here's a picture from when she was just learning, so it is still pretty low.

In regards to the stretchiness of silks, most that I have used have had very little stretch. The standard tricot, for an ~15' silk, will stretch no more than a couple of inches. Also, the majority of drops don't end with all of your weight hitting at once; most (at least that I do with a couple of years of experience) leave some of your weight on the silks during the entirety of the drop.

For what it's worth, I'm working on an cirque-esque production currently and am using 5:1-10:1, depending on the act. All three of our silks are rigged in excess of 10:1.

Most aerial silks I've worked with stretch enough that I would feel comfortable not knowing the exact max shock load (as it's very hard to account for every variable in a system) with a 10:1 ratio. If you wanted to get down close to 5:1 I would have to bring in an engineer to come and sign off on the system and that wouldn't be cheap.

That of course assumes that you have liability coverage for such an act. I don't know your space, but I wouldn't be surprised if your space's insurance company got upset over the idea of flying an aerialist without a specialist or engineering sign off.

I have done some load testing on silks and have gone over 500 lbs easily.

A friend of mine runs Aerial Angels; I could get her to chime in in useful...

The saga continues. I'm meeting with the parents in a bit here and we'll see what they think. Dad was pushing the issue a bit more so I put out a lengthy explanation of why we can't just loop over the pipe and fly it out. Thank you for the advice on the stands since I think that's where we're pushing, I'm still not sure if the dance company is sanctioning this act yet. I'll report back with any more developments that are worthwhile to the thread, but thank you all for your responses!

I think I've reasonably convinced them that it is not feasible to fly this aerial rig from the pipe (without the proper hardware, setup, et al). They are now asking about constructing a bamboo tripod to support her weight. Ignoring everything else for a moment, I don't think it will be feasible to get bamboo to not slide on a T&G deck, not to mention every other thing that you all are racing to pound into your keyboard at the moment. I said that to go forward with that plan we'd need to have a discussion with the dance instructor and her aerial instructor and all three of us would have to sign off on the setup. Bamboo is wicked strong, but who knows if it's safe?

That all being said, anyone know a good rental house in east central Florida that supplies tripods for this sort of thing? I'd like to at least steer them in the correct direction.

StradivariusBone said:

Bamboo is wicked strong, but who knows if it's safe?

That all being said, anyone know a good rental house in east central Florida that supplies tripods for this sort of thing? I'd like to at least steer them in the correct direction.

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Bamboo would make me nervous because although it is very strong along it's long axis it doesn't do too well resisting forces from the side.

I know some circus people in the area, I've sent them some messages and I'll PM you with contact info if anyone comes back with someone to help you out.

porkchop said:

Bamboo would make me nervous because although it is very strong along it's long axis it doesn't do too well resisting forces from the side.

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That's kinda what I was thinking. When I was a kid in Boy Scouts we'd make these "gateways" (basically large structures that held up our troop flag at the front of our campsite) out of bamboo and paracord. One of my friends had a forest of bamboo on his property so we never were wanting for materials and we'd build these massive towers by making truss out of the bamboo by tourniquet lashing it together with the parachute cord. Some of them were upwards of 25' tall, but all it had to support was its own weight and the weight of a 2# flag. Also, wind loading wasn't a huge deal since there wasn't much to catch, but I don't think I would've climbed on it. All of the weight was borne on the vertical length of the bamboo with a lot of crossbracing.

I'm just wondering how they are lashing the top of this tripod they make. I know how I'd do it, but I also wouldn't swing around on it.

You might see if there are any local aerial arts schools/studios in your area who can lend or rent a rig for this. At least around where I live, the are are so many aerial arts studios that it wouldn't be hard to find, and I know people have them as I have seen them at many local events.

From the people I know, it doesn't sound like you'll find this at a rental house (I'm not very surprised given the liability involved). I did get some good resources for you and parents. damnhot.com (hopefully that makes it past the profanity filter) is a good general resource page that has a lot of links to circus groups world wide. Hopefully you can track down a school or club in your area that will rent you the gear. Beyond that, if they're really excited about their kiddo's career as an aerialist the parents could buy a freestanding rig that could be used for the performance and it at home for practice afterwards (hint: they're not cheap, $1-3k depending on configuration). damnhot.com has links to buy them as well as trapezerigging.com. If they're REALLY excited cbe-circus.com is where I'm told a lot of pro's get their equipment.

Hopefully something in there helps.