Projection material for outdoor use

[Stuart91]

I've had a call from someone looking to do some outdoor cinema style events. They're anticipating being able to put some events on later in the year, but concentrating on being outdoors and potentially still socially distant.

 

Their first question was about hiring fastfolds from us, which I'm not keen on. They're essentially in an open field, so the screen needs to be self-supported and clearly needs to be more substantial. (I've already suggested finding a way to hang a screen on the side of a building but apparently all the suitable spots have lights or drainpipes that would get in the way) What they're now leaning towards is some kind of scaffold frame, which can be suitably ballasted and have screen fabric stretched out to fill it.

 

That leaves me with the problem of sourcing suitable fabric for them. They'd prefer rear projection, but front projection wouldn't be a deal-breaker if it saves enough money in comparison. The main concern is that the fabric is either easily washable, or cheap enough to be considered replaceable after a few events. This is because it'll be getting assembled in what is essentially a muddy field, if it so much as touches the ground that'll be it dirty. There's probably techniques that could help preserve it (e.g. pulling it directly out of a case and into place) but one misstep and it's muddy. I know that the fabric on our fastfolds wouldn't last long in these kinds of conditions.

 

We should be able to throw ample projection power at it, so we don't need anything particularly high-gain. Years ago a friend of mine used some spandex to basically fill the prosc opening in a town hall style venue - it seemed to work very well and I'm thinking something along similar lines might be ideal.

 

Does anyone have any suggestions for suitable fabric that I could investigate?

[dje]

Yes... I supplied screen material for an outdoor drive in cinema (before COVID... it was a massive fail and nobody went... but that's besides the point).

 

It actually came from a company who make stage roof covers. We came to the conclusion that safety and structural integrity would come first so it made sense to use the stage roof company. We'd effectively make it a projection screen by tensioning it, using the right RAL white (I think we got the RAL number from the Rosco catalogue or something similar).

 

We used a scaff structure built by a kind of generic construction scaffold company (although perhaps given the current climate, you could use an events scaffolder at a competitive price?) which was as you allude to held down with ballast, a mix of concrete blocks and water-filled IBC containers (they actually used 60/40 sand water which apparently gives you more like 1600kg in a 1000L IBC).

 

Screen had pockets on all 4 sides which we put scaff tubes into. Holes were cut in the pockets, scaff tube inserted, then tensioned with lever hoists and the scaff tube clamped to the structure and the hoists removed. We needed to add ladder beams to the structure to clamp the screen pockets into, when we used scaff tube, even thick wall steel tube deflected way too much.But the nice thing about doing it that way was we could remove all the rigging equipment and leave it just on scaff.

 

Washing was done every few weeks by a window cleaner with a 'reach and wash' system.

 

What we found is yes there's always an amount of imperfections in the screens, and some dirt that won't budge... the easiest (although more expensive) solution is to basically accept it as inevitable, and overcome it by using big projectors.

[Stuart91]

Thanks, that's all really useful.

 

One thing I haven't mentioned yet is size. What's been discussed is a screen width of 4-6m It's a big enough sail that it needs properly thought about. I had considered some kind of scrim, although obviously that has an effect on the image.

 

The plan is that they'll likely leave the frame permanently in place, but only attach the fabric when they have a showing. (Which would likely be a couple of times a week, so no point in having the fabric out and vulnerable in between)

 

The stage roof fabric makes sense. What sort of size were you using? I'd anticipated eyelets and bungees rather than putting tube through a pocket but that sounds like a good arrangement. Sounds like it might be a bit more time consuming to put up and down repeatedly though.

 

I hadn't thought of using window cleaning techniques on it - that's quite a smart idea. I'm guessing that this wouldn't work for woven fabric but for solid PVC etc. it'll be a nice simple solution. (Plus any dirt added during setup can be cleaned off before the show starts)

[ImagineerTom]

Have you checked fleabay - "outdoor cinema screens" are a popular chinese export product, come in a range of sizes and have eyeletts etc all in place for less than £20.

For £100 you can get a 5x3m inflatable screen that will solve all your structure and screen material dilemmas in one hit https://www.ebay.co.uk/itm/5x3m-Pro-Inflatable-Giant-Movie-Screen-Outdoor-Projector-Cinema-Theatre-Backyard/174349621898?epid=23031133381&hash=item28980c1a8a:g:-ysAAOSw8Ntf0JSD

[Stuart91]

For £100 you can get a 5x3m inflatable screen that will solve all your structure and screen material dilemmas in one hit

 

Yeah, they're certainly tempting.

 

I've always been wary of inflatables, having seen too many bouncy castles etc. making a break for it when the wind gets up. But there's a solid argument that ballasting or staking an inflatable screen isn't going to be any worse than fabric stretched on scaff - it's the sail area of the screen itself that's the main issue.

 

One other thing I wonder about is the blower(s) - do they need a blower running continually like a castle? That'll have an impact on noise, although it isn't crucial.

[ImagineerTom]

Inflatables are less of a risk in this instance in high winds. Stake the base of it down properly and the worst that will happen in high winds is it folds over and gently boops someone on the head. Conversely if you build a truss/scaffold/wood structure and the wind blows it over you've got a few hundred Kg of solids that crush people and smash things whilst also completely destroying itself. If this is a public event then your screen structure is going to need signing off by some sort of experienced builder or engineer to comply with licensing too...

 

Yes the blower has to be kept running but you choose a small blower, you place it as far behind the screen as you can and (because blowers are generally high frequency sound) some basic mass insulation will chop the noise dramatically.

 

If it were me I'd be choosing the inflatable because it's the fastest solution and eliminates a lot of head scratching and complications

[IainB]

One other thing I wonder about is the blower(s) - do they need a blower running continually like a castle? That'll have an impact on noise, although it isn't crucial.

 

Yes, although you can get (at much more expense) sealed units. I started to offer backyward cinema options with the lack of work coming in, had been using a truss solution, but have since purchased some smaller inflateable screens which means my contact time is now very much reduced.

 

 

 

[MarkPAman]

The inflatable screen at an event I worked on needed one blower to keep it up, but the one they used was really pretty quiet anyway, and a long pipe was used so that it was probably 10m - 15m behind the screen. Certainly from where I was, the seagulls were louder!

 

It was secured with a mixture of stakes & ballast, and I was surprised at just how rigid it appeared to be, in a quite noticeable wind.

[Stuart91]

The inflatable screen at an event I worked on needed one blower to keep it up, but the one they used was really pretty quiet anyway, and a long pipe was used so that it was probably 10m - 15m behind the screen. Certainly from where I was, the seagulls were louder!

 

That's quite reassuring.

 

I've only seen one inflatable screen, which was being used in a large warehouse space. I can't remember much about the blower, but it was definitely smaller than the large metal boxes I see on castles and slides. I suppose it helps that there shouldn't be children bouncing up and down on the screen and squeezing the air out.

 

An extension pipe wouldn't be a problem, as there's plenty of space in behind the screen.

Edited February 4, 2021 by Stuart91

[ImagineerTom]

I don't know the screen you're choosing so take this advice with a pinch of salt but generally a little blower like this https://www.ebay.co.uk/itm/0-75HP-Lightweight-Blower-Fan-for-Inflatables-and-Bouncy-Castles/153148032802?hash=item23a8558722:g:x5AAAOSwWo5bfBid would probably be more than enough to keep it up - as you say it's not having to fight against jumping; only to compensate for the seam losses.

[Stuart91]

I don't know the screen you're choosing so take this advice with a pinch of salt but generally a little blower like this https://www.ebay.co.uk/itm/0-75HP-Lightweight-Blower-Fan-for-Inflatables-and-Bouncy-Castles/153148032802?hash=item23a8558722:g:x5AAAOSwWo5bfBid would probably be more than enough to keep it up - as you say it's not having to fight against jumping; only to compensate for the seam losses.

 

That does look familiar. The screen I remember was probably getting on for 6m wide, and had quite chunky support members. I guess it'd be possible to use a big blower to inflate it quickly, and then the small one to maintain it.

[ImagineerTom]

The small one will still get it up - just a bit slower, don't over complicate things.

[Stuart91]

The small one will still get it up - just a bit slower, don't over complicate things.

 

My main worry is the surface flopping around in the mud before there's enough pressure to keep it up. I'm guessing two people could hold it clear whilst a third switches the blower, but they're not going to stay in that position very long.

[ImagineerTom]

My instinct is that you're over thinking this - I think it will be fine and inflate a lot quicker than you think it will....

[DrV]

My instinct is that you're over thinking this - I think it will be fine and inflate a lot quicker than you think it will....

At the risk of overthinking in a slightly different direction, would a variable speed blower which could inflate quickly then just tick over quietly to maintain be an option? Would also allow you to increase the pressure a little if the wind got up.