my attempt at a spray booth (knockdown type)

67Dart273 said
I think that's a GREAT idea, except.......... you might need better support for the plastic sheet. You ARE going to pressurize it and not evacuate it with blower pressure? But either way, you'll be amazed at how far in/ out the plastic will balloon, and you SURE don't want it sucking inwards.

I'm guessing you'll need some sort of "more" support members for the air pressure on the plastic.

The "cheap way" might be to buy, (fer sayin') 1x4 bats, put the plastic on, and screw the bats through the plastic into the piping, then add additional horizontal bats to that??

Just thinkin' outloud.

Yup I know about the supports. It'll be a positive pressure unit and plastic is on the inside which made a big difference on the last one(wood) I built. this is just a basic setup right now and it looks that I'll have support every 4 ft (Lights stop/slowdown me getting closer right now) or so on the sides and even closer on the front and rear by the intake and exhaust area. I bought special 4ft plastic clamps that go over 1 1/2 inch pcv and tried it out for the top. I was able to get the top drum tight. it suprised me that I was able to pull it that tight with the clamps. the top will be setup every 4 ft with crosspieces and supported by the angles in the walls (I don't mind if the top bows up a little.)
I should have a slight positive pressure. On the last wood/plastic sheeting unit I almost had it balanced in flow in/out with 6 20/25 filters for intake and 6 matching for exhaust and was braced @ 4 ft all the way around and a slight bow on the long walls. I could clear the room in 90 seconds but you could feel the flow,which I didn't like. but I had a smaller (higher force) blower used to check houses for leaks
This unit will have an additional 2 20x25 painters filters per intake/exhaust (8 and 8 8) and tighter support, so I'm looking at even less plastic bow and a good air exchange rate due to changing the pulley's (bigger fan slower flow) to adjust flow or I could use my new speed controller. I don't really know how good this is going to be but it should be a lot better than just shooting it in the garage and getting the mess on stuff and it will be better
than the last one. plus I can knock it down roll up the plastic and put the fsides outside without worrying about it rotting till I use it again (at least 3 more times)