Take down spray booth ideas.

[Ben Shelton]

My son has gotten into models and I have a couple of guitar finishing projects planned so we are looking to put together a spray booth setup in our basement workroom. We have a window to use as an exhaust port but we need some info about exhaust fans.

To give an idea of scale I don't foresee finishing anything larger than an electric base bolt on neck.

What works for a safe exhaust fan?

[Michael A Shelley]

Hey, it's a topic I can talk about without complete ignorance!

Short answer - I'd go with a 5 or 6 inch centrifugal blower.

Long answer -
I do not have a spray booth myself, simply because I haven't gotten around to it yet, but have done some research on this over the last few years using modeling forums and other related info. (There is some crossover with dust collection systems as well.) The consensus seems to be that the commercial hobby spray booths don't provide enough air movement to draw out all of the volatiles and particulates through a filter, down a duct, and out the window. The typical computer fan or kitchen range exhaust fan just can't move enough air. I suspect they also aren't a good choice for flammable vapors, but I don't know how much of an issue that will be unless you start spraying nitrocellulose lacquer. (Hobby paint is usually water-based acrylic, which is thinned with an alcohol mixture. Some people still use enamel or lacquer but it's less common.)

Looks like the best solution may be to build your own. That way you can be sure that a bass neck will fit, and you can add lights, hinges for folding, use whatever size filter you like, put the power cord in the right place, etc.

Here's a (commercial, but not mine) site that has some info on general construction and blower sizing. I'm sure there are more comprehensive data sources out there, and I suspect other members with practical experience can provide additional info.
https://vent-works.com/blogs/the-ventil ... pray-booth

Not sure what genre of models your son is looking at, but a bass neck is about the size of a 1/350 scale battleship.

Hope this helps, or at least doesn't confuse too much,
MAShelley

[Barry Daniels]

What kind of finish will you be using? I bought an TEFC motor and spark proof fan blade from Graingers many years ago and it is still going strong.

[Ben Shelton]

I have one project in mind that will be nitrocellulose.

[Barry Daniels]

Then you should use a system that will not create any sparks. A totally enclosed fan cooled (TEFC) motor and an aluminum fan blade are the basics. I built my spray booth so that the control switch and lights are remote so I did not have to go explosion proof on those which can be VERY expensive. I have something like this except it was only about $300 when I bought it in the 1970's.

https://www.grainger.com/product/CANARM ... ous-23N613

[Ben Shelton]

Does anybody have a guess about fan CFM vs booth size in cubic feet?

[Barry Daniels]

Are you building a booth or just sticking a fan in your window? I have always done the fan in the window approach.

[Ben Shelton]

I'm envisioning something takedown that I can build on my workbench which sits in front of a window. Building the fan into the back of the breakdown spray booth with a duct going to the window would work. I've also seen several fan units intended to be used with flexible ducting that would work as well.

Unfortunately most of these options are fairly expensive for the limited number of projects I want to do and I'm trying to keep the costs down.

[Barry Daniels]

I have been using the fan in the window approach with nothing resembling a booth for about 40 years with no problems. Since I am applying finish to a small object hanging directly in front of the fan, a booth or side shields or whatever else is really not necessary. In regards to cfm requirements, there is no hard and fast rules for this non-booth approach but you want sufficient air movement to pull the majority of the overspray directly into the vent and prevent overspray from bouncing back into the room. I think you need a minimum of a 1/3 hp fan motor to accomplish this.

Another consideration is how does your make-up air get into the room. You don't want it to stir up dust or create any kind of restrictions. Also, keep in mind that ducting creates friction and will reduce the amount of air your blower moves.