Hanging sandbags up in air or shotbags

[Dagger]

Truss rigged, turned into a diamond shape due to load only one side ( it was a 52" TV on 8ft truss. )

I have heard the PM say hang sandbags to level the truss.

Argument was it is illegal to hang sandbags . ( at the end , truss was choked differently to compensate for one side being heavier)

But my question is .

Not acceptable to hang sandbags?

I have seen 20lbs shotbags being hung on pipes up in air. .

How likely are shotbags to rip and fall down?

 

[bobgaggle]

I'm no rigger, but i've worked in an old school hemp house with literally tons of sand in the air... I don't know how hanging sand is "illegal". Perhaps best practice dictates you would hang these

in stead of these

.

 

[Dagger]

I haven seen sandbags handle seam that are ripped. When hangingnitnin air it has potential to rip and fall. ..

Shotbags (1. Pic) I do see hang alot up in air.

 

[ML.Rice]

My theatre was just converted from a hemp system We had easily 50x 100-200lb bags in the air at all times. We still use sandbags all the time to balance electrics or truss. I've never heard of hanging sandbags being illegal. I would agree with @bobgaggle about the type of bag to hang.

 

[Dagger]

What type of bag are you hanging ? Shotbags are the right bags to hang.

And again my concern is the seam stitching ?

Chances it will ripp? ( i have this concern because i have seen sandbag seam stitching ripp - not in the air though)

 

[bobgaggle]

Shotbags (1. Pic) I do see hang alot up in air.

This is a vocabulary issue. What you're calling "shot" bags (first pic) have been used for 100s of years with sand in them to counterweight battens. Yes they can tear. When I was on the rail for a show we had one rip when it caught on a sharp piece of steel still bolted on the rail from a previous show. someone got lazy on the strike and hadn't removed all the stuff. Bad situation. but remember these are made of heavy canvas, so even the sharp piece of steel only managed to gouge a hole and it started dripping out. We had plenty of time to finish the scene change before any significant weight was lost. A guy scampered up the lines with a roll of gaff tape to repair it for the rest of the show.

As for the seam ripping, that's a matter of inspecting your gear and making sure its shipshape. I doubt it was stressed so much during use that the seam tore.

All that being said, there are many reasons the industry has moved away from sand. I think re-choking your truss was the way to go, especially for something as light as a TV

 

[tjrobb]

Can shotbags rip, tear, fail? Yes
Can a spanset rip, tear, fail? Also yes
ANY TIME anything is overhead it needs inspected. And as long as it remains aloft it requires regular inspection. Random failures can happen, but this reduces your risk.
When in doubt, throw it out applies here too.

 

[RonHebbard]

Can shotbags rip, tear, fail? Yes
Can a spanset rip, tear, fail? Also yes
ANY TIME anything is overhead it needs inspected. And as long as it remains aloft it requires regular inspection. Random failures can happen, but this reduces your risk.
When in doubt, throw it out applies here too.

@tjrobb "Can a spanset rip, tear, fail? Also yes"
While we're beating this thread into submission, PLEASE toss in a few comments regarding GAC-Flex sings as well.
Toodleoo!
Ron Hebbard

 

[egilson1]

All that being said, there are many reasons the industry has moved away from sand. I think re-choking your truss was the way to go, especially for something as light as a TV

The issue with changing the wrap of your slings to level a truss is that you are not solving the initial issue of an imbalanced load on the truss. The image below shows the typical cantilevered fixture on a truss. This causes the truss to "roll" due to the imbalanced force on the truss. This also places all of the load on one side of the truss (the side with the red arrow pointing down). When you offset your slings (EG additional wraps, different lengths,etc) you are leveling the truss but all of the load is still on the one side of the truss. From an engineering standpoint the truss capacity is based on the load being equally distributed on both sides, and when it's not you no longer have the rated capacity as indicated in the loading chart. That's why it's better to have the truss leveled due to a balanced load on both sides. This is often done by extending the cantilever and placing a load at the other end of the cantilever to balance out the lighting fixture. This of course does increase the total load on the truss, so this needs to be considered in your overall load calculations.

Now back to the OPs original questions about using sand bags for this balancing load, i'm personally a fan of not using the hand straps on a saddle bag style of sand bag (second image), but instead placing the sandbag on top of the cantilever arm so its not dependent on the strap for suspension.

 

[bobgaggle]

The issue with changing the wrap of your slings to level a truss is that you are not solving the initial issue of an imbalanced load on the truss. The image below shows the typical cantilevered fixture on a truss. This causes the truss to "roll" due to the imbalanced force on the truss. This also places all of the load on one side of the truss (the side with the red arrow pointing down). When you offset your slings (EG additional wraps, different lengths,etc) you are leveling the truss but all of the load is still on the one side of the truss. From an engineering standpoint the truss capacity is based on the load being equally distributed on both sides, and when it's not you no longer have the rated capacity as indicated in the loading chart.

Would you say that its improper to change the wrap? Or, its ok, but you have to account for essentially de-rating the truss? If a ladder truss was used, all would be well, right?

 

[BillConnerFASTC]

(second image),

??

 

[Dagger]

I think its referred to second image at the top of this thread

 

[Dagger]

If one cannot place another fixture at the other end to cantilever what can be done ? ( other than offset slings)