Festoon Query

[ScanMan]

Hi all,

 

Currently planning a job to be installed in a few weeks time and need some advice on the festoon if anyone has any suggestions.

 

There is around about 130m of carpeted trackway as the entrance to the site. The plan is to rig festoon zig-zagging above this supported either side of the track by vertical scaffs. I'm trying to work out the best way of suspending/ supporting.

 

My initial thoughts were:

- scaff tube every 15m (maybe 12m)

- half coupler with rigging eye at the top of each scaf tube

- cateenery wire fixed between the scaff tubes with bottle screws to maintain tension.

- cable tie festoon to cateenery

 

 

Any suggestions/ concerns/ ideas for alternative methods would be most appreciated, Thanks.

[Lightworld530]

Hi I would see the stability of single scaff as an issue here. What height is the intended position?

12 /15 metres of festoon and lamps will have some weight. The poles will need to be inserted some way into the ground to allow you to tension a catenary wire.

Regards david

[ScanMan]

Hey,

 

Thanks for the reply.

 

Yes, that was one of my concerns. We have two options at the moment that we are investigating.

 

1. A 1.5 ish scaff hammered into the ground just over a metre down with another (3-4m ish) attached to it with 2x scaff clamps holding them together.

 

2. Getting a similar type of thing made up out of steel angle section.

[jcgoldcoast]

When our local council puts on big events (occasionally with festooning overhead) they actually have scaff poles in blocks of concrete, meaning they dont have to hammer anything into the ground....Just a suggestion

[J Pearce]

My thoughts on this are that you want it to look smart and posh.

 

Scaff hammered into the floor will flex towards the top, is wobbly scaff the look you want? I'd suggest using a steel guy to counter the tension caused by the festoons.

 

Alternatively light both edges of the path instead of zig-zagging.

The problem with a zig-zag is it pulls on side of the scaff, leaving the support unbalanced. Hence a guy is needed to hold it straight.

A straight line doesn't have this problem (except at the ends), as the tension is equal on both sides of the support and effectively cancels itself.

 

Another thought is that you may want to wrap the scaff in fabric to smarten it up.

[ScanMan]

Thanks for all the advice everyone.

 

Yes I had considered having to guy some of the poles (especially the end ones).

 

I realise I made a slight mistake in the initial query - Its more like 400m of path. Apparently, last year only half a dozen supports were ued so I imagine the angles will be a lot less severe.

 

The main reason for the post was to query my thoughts on attaching the festoon/ cateenery to the poles - any worries about this or alternatives anyone?

 

Thanks again

[Seano]

1. A 1.5 ish scaff hammered into the ground

 

Apologies if I'm teaching grannie to suck eggs here, but if you're doing this you'll find it much easier with 1.5m putlogs than with plain tubes. (ie: The kind where the end of the tube has been pressed flat.)

 

If the two couplers you're using are swivel couplers, you can do one of them up in advance, walk up the tube and do up the second - much easier than trying to hold the pole upright whilst doing up two connectors. (That said, the other coupler you might use - band and plate - would probably look neater.) Rather than guying with rope, you might want to look at using a diagonal scaff tube to make a K brace from a second putlog - it probably doesn't need to go to the top of the upright. (Called a K brace because of its resemblance to the bottom diagonal of the letter 'K'). Again, this can be attached to the upright with a swivel coupler before you stand it up. Check out the signage at just about any music festival to see this technique in action.

 

Bottle screws/turnbuckles to tension the catenary wire are an unnecessary complication and therefore a bad idea imo. The tension in a catenary varies inversely with how much it sags (ie: the vertical distance between the ends of the wire and the bottom of the curve) - if you halve the 'sag', you double the tension and therefore if you attempt to reduce the sag to zero, you're also trying to increase the tension to infinity.

 

How are you planning to terminate and tension the catenary? If you don't already have one, you might find a Klein Tool and a light duty bebe quite handy.

 

Fortunately, slightly droopy festoons are much prettier than ramrod straight ones, imo, so a reasonable amount of sag (as long as the bottom of the sag remains safely above the punters' heads) really is your friend.

 

I started to post formulae and stuff here, then remembered I've done that before. See my enormous (and slightly ranty - ignore that) post here:

http://www.blue-room.org.uk/index.php?show...mp;#entry128891 The bit you're interested in start about half way down that post.

 

As mentioned before, if you're running the festoon in a straight line, the horizontal component of the tension in the wire will be balanced. If you have two wires coming off the top of the pole, the horizontal component of their tension is T, and the angle between them is theta - the resultant horizontal force will be in a line bisecting that angle(ie: will be perpendicular to the path), and will amount to 2TxCos(theta/2).

 

As mentioned above, if the festoon runs in a straight line the tension balances out - plug that into the formula above and you get theta/2 = 90degrees, cos 90 degrees is zero, hence zero resultant horizontal tension. Unless the path is very wide, the angle involved in zig-zagging across it probably isn't going to be all that far from 180degrees. You need to do the sums and make sure you have a good feel for the forces involved, (Or have, or employ someone who has, enough experience to make a *good* estimate from experience and gut feeling.)

 

Remember - in the real world, there will still be some horizontal force, which could be in any direction, resulting from wind loading on both the uprights and the festoons.

 

Its more like 400m of path. Apparently, last year only half a dozen supports were used

The festoon was spanning 80m at a time? Seems like a long way.

 

Sean

x

 

ps: Let me add my standard rigging forum disclaimer:

You have no way of knowing whether or not I know what I'm talking about, and I offer no warranty whatsoever on what I've posted here, It is not intended to be advice, merely trying to hint at some things you may find it helpful to think about.

[ScanMan]

Forgot to say - thanks for all the help, much appreciated and I think we are now sorted.

 

Thanks again