Acceptable rigging?
- Thread starterlen
- Start date
A correctly designed beam is a correctly designed beam no matter what material it is made out of. Wood can be rated just the same as steel... it is harder to do but you can do it. As long as you know the loading criteria you can do whatever you want as long as you are in within that criteria.
cmckeeman
Active Member
If a certified engineer gives me either a breaking strength or a working load limit I would hang from it, in fact i have seen things hung from wooden beams. The only thing I would be concerned about is steel biting into the wood more than it would on a steel beam.
de27192
Active Member
Absolutely, loads of buildings out there made of wood that we still use for entertainment. There are many wooden theatre grids out there with even the counterweight pulleys on the huge wooden joists running through. Also of course are the majority of fly rails and in a hemp system most of the weight is bearing on the fly rail. It's mainly just psychological for a lot of people, I've met people who don't like walking on wooden grids because they don't trust it. But believe me steel can rust and bend/break just like wood can.
As has been said one concern is just that wood is softer and a SWR basket could dig into it given enough weight... but this doesn't have to be a problem using a fibre roundsling, or of course a purpose designed beam clamp designed for use with wooden beams. Burlap folded a few times would probably be ample in most cases.
As has been said one concern is just that wood is softer and a SWR basket could dig into it given enough weight... but this doesn't have to be a problem using a fibre roundsling, or of course a purpose designed beam clamp designed for use with wooden beams. Burlap folded a few times would probably be ample in most cases.
Judge
Active Member
I have flown many sound and lx rigs from wooden beams - here in the UK we have plenty of old theatres where that is the only choice. I used to have to make an informed decision about the integrity of the beam and how it was fixed to the building and where the load went, and if it didnt look good then I would not chance it. Problem is these days that we are being forced into a situation where riggers are not allowed to make informed decisions any more, no matter how much they know about buildings and structural engineering, so usually now we have to fly on pre-designated points that have load ratings on them, and its much harder to get an accurate load rating on a bit of wood than a steel I beam.
de27192
Active Member
The difficulty there is working out who is an experienced rigger able to make those decisions, and who is a bluffer in a harness.
The UK is all about liability now. Meanwhile, there are mickey mouse rigging companies (every AV company can design you a full arena mother grid if you ask them) cropping up by the dozen (same here). So it's no wonder people are tetchy about anyone saying they are a rigger going ahead and making structural decisions about their building.
de27192
Active Member
Sounds like working in Russia where we had to re-do the PA, because the venue engineer told us there was more snow on the roof than they expected and they had to reduce the production load to keep the total roof loading within tolerances.
We offered to go up on the roof with spades and boiling water but they wouldn't let us.
Sounds like working in Russia where we had to re-do the PA, because the venue engineer told us there was more snow on the roof than they expected and they had to reduce the production load to keep the total roof loading within tolerances.
We offered to go up on the roof with spades and boiling water but they wouldn't let us.
The arena in town will send guys up with firehoses connected to extremely hot water to blow off the roof while chipping/shoveling any accumulation. Many places use their snow load to hang shows... and when the snow shows up something has to give. My building actually has a heated roof to keep snow melted because our loading criteria is that close to the wire.
The "old barn" in St. Louis was a totally wooden roof and they were hanging shows in there up until the mid 90's. I was told that they used to hang a rope at center ice that just touched the floor, by the time the show was up a foot or two would be on the ground. Never confirmed that, just what I was told.
de27192
Active Member
Ah well... that happens with A Type anyway.
As for heated roof, don't know why it's not more common in places it's known to be an issue. Airports manage it with their runways and it's clearly the obvious choice.
Everyone is saying its ok. Here's another factor:
The venue isn't a theater, etc., it's an old truck barn which now being used for social events,, etc. it is unlikely that any engineer tested the beams. Granted, we didn't hang more than 200# on a point, but just because it SEEMS ok doesn't mean it is.
The venue isn't a theater, etc., it's an old truck barn which now being used for social events,, etc. it is unlikely that any engineer tested the beams. Granted, we didn't hang more than 200# on a point, but just because it SEEMS ok doesn't mean it is.
I think the key in the discussion above is getting a rating from a certified structural engineer. Doesn't matter what it's built out of or how old it is, as long as someone with the right degree and certification tells you what the load limit is and you follow safe rigging practices from there. On the other hand without that structural engineer's load rating you are completely guessing in the dark. "Seems okay" is always a bad idea.
JD
Well-Known Member
Boy, that brings back memories! Back in 1982, we played an old "forum" style theater/club called "The Playpen." (long gone) The roof had been built out of the hull of an old ship so no one knew how to rate it! After all, it was designed to be upside down and floating in the water. Anyhow, since sound and lights were both flown, the rope trick was used to measure sag. With about 2000 pounds flown, it didn't budge! Years later, after being long closed, it burned down. I remember driving past it, and there sat the roof frame on top of the rubble! Didn't even look that distorted.
It would not be that hard to get the beams analyzed. Old is probably good unless there is rot or rust. Around here the barns built with old growth lumber and iron bolts are WAY over built and you can do whatever you want in them. It always amazes me how over built things use to be before modern structural analysis took hold.
I did lighting on a show a few years back where we were hanging a FOH truss with a few lights. We'd been assured by the client there were big beams available to rig from (note the truss weight with lights was only about 200lbs). We showed up and found massive wooden beams that had been cut through in various places when the loft was added. Myself and the other lighting tech were a little concerned about rigging from these (due to them being cut in places, not being wood). Audio engineer overhears part of the conversations and walks up and tells us its okay to use for a couple thousand pounds. We're kinda like thanks, but I think we need to see an engineering report or something on this at least saying that an engineer signed off on the beams being cut in the first place. Audio guy then introduces himself fully as a licensed structural engineer with a local firm who does audio on the side for fun. Yup we hung the show. He turned out to be a cool guy that we asked about a few other situations as well.
kicknargel
Well-Known Member
Plus the ones that were under-built aren't around anymore.
