Hi Airbrush Paint Booth Construction - With Lots of Pictures!
No real progress on the layout front. I have been "prepping the space" though.
The last several days I've spent building an airbrushing booth to fit under my layout in my workbench area. The idea occured me that I could build my own and found a host of reference material from other including another member on this site about how they did it. I found this website page of particular usefulness.
The booth I made It measures 21" wide x 13" high x 20" deep.
Here is a list of materials.
1/4 plywood which was formerly a 3'x3' 3'x4' crate that housed some lab equipment. So it was free! 
1 Dayton Axial Fan (shaded pole, impedance protected) Specs on the unit are AMPS 0.23/0.22, WATTS 27/25, 115 Volts. 60/50Hz. Can be had at Acklands Grainger here...https://www.acklandsgrainger.com/AGIPortalWeb/WebSource/ProductDisplay/globalProductDetailDisplay.do?item_code=GGS4WT42
1 Dayton cordset for the Fan found here. https://www.acklandsgrainger.com/AGIPortalWeb/WebSource/ProductDisplay/globalProductDetailDisplay.do?item_code=GGS4YD79
A 5 pack of 3/8 x 3" Machine bolts and screws (for mounting the fan and exhaust) also used misc. washers and small lock washers in mounting the fan and duct work
1 5" -> 4" Aluminum Ductwork Reducer
1 "Husky" 8ft long, 16 gauge "Light Duty Tool Replacement Cord". (It comes as a cord that you can wire up to whatever you want).
1 Levitron Lighted Switch (it didn't cost more and it lights up...how cool is that!!! 
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1 Device Box - for the switch.
Carpenter's Glue. Not the white craft glue.
1 Tube of silicone sealant.
Package of 1/8" Medium Length pop rivets.
Tools,
Jigsaw to cut the plywood.
Drill and various sized bits I mostly used 3/8 or 1/8 bits for the holes except I used a larger bit if I needed to get the jig saw inside a panel piece to cut an interior hole.
Sandpaper and Sanding Block
Various Clamps. 24" clamps are needed for holding the panels together while the glue sets during final assembly. I only had two and can see how a couple more could have come in handy.
Long Metal Ruler, Square & pencil.
So where to begin...
I started by measuring and marking the dimensions on the ply. Once I had everything plotted I cut the individual pieces. I notched the pieces to add some strength. I'm also trying to build and assemble it with carpenter's glue so that I don't have use nails or screws and risk splitting the wood. The marking on the ply you see for the side panels are not correct. I extended them back about 9" in order to have some room to mount a switch for the fan motor and to cover the area behind the booth so tools and stuff don't disappear behind it. As you can see I also tried to preserve the "Scientific Instrument - Handle With Care" stamp on the sides just for fun.
Once properly measured and marked, I then cut the pieces. I also cut some 1/4" tabs and notches in the pieces to add strength and assist with keeping things square during assembly...At least that is the intention of them.
I also ended up test fitting the pieces several times to ensure that everything would fit together nice and snug.
A test fit on the bench and under the layout. Nice and snug with a little bit of wiggle room.
The ply underneath the booth was actually removed as it created noise when the fan was running with the booth sitting on it. So there is about 1/2 clearance above the booth installed on the bench work.
A picture of the Dayton Axial Fan prior to installment. It is roughly 6 3/4" dia with an internal dia of 5 1/2" inches. The specs say it will move 239 CFM of air. I only have five feet of duct to move through so this should be plenty of air movement for my purposes. Also make sure that the fan is oriented properly to allow the fan to force the airflow out the back of the booth. The fan is marked with an arrow to show this.
Test installation of the fan. Mounted using the 3/8 3" nuts and bolts and some washers I had on hand. I wired it up to the Husky Tool Replacement Cord and the Levitron Lighted Switch. I highly recommend the Dayton cord for this fan. It made working on the booth construction so much easier as I installed and removed the fan a couple of times. The plug made this process so easy to do. The cord does not have a ground wire though and the unit still needed to be grounded. There is a screw on the side of the fan frame for a ground wire which I attached an 18 gauge wire to. The ground wire then follows the Dayton cord into the device box and is gounded to the other ground wires for the switch and tool cord and device box as well.
And its a go! This sucker really moves some air! I had it sitting face down and didn't feel any air movement at first. But when I tried to pick up the panel I found that the fan was sucking my cutting mat up off my bench! So suffice to say, its pretty windy back there.
The next day I cut an opening for the switch box and drilled a 3/8" hole for the cord on the other side. I suppose it really didn't matter what side I put it on. For some reason, I thought the switch would be better on the right side, and the cord to plug it in would be better suited going out the left. I say choose whatever suits your needs.
...and the switch installation.
Wiring at the back.
...and the side on the bench.
Next step is final assembly.
I picked up some 2 x 2 straping (which acutally measures 1 1/2") and cut four pieces to place inside the booth. I then glued and screwed one of each piece to the respective sides, top and bottom and began to glue and clamp the whole thing together with Carpenter's Glue. The filter medium will sit on top of the straping pieces and provide a 3" plenum behind it.
piece of the puzzle was to figure out how to attach some exhaust duct work to the back of the unit. I picked up a 5" -> 4" plain reducer from the local Home Depot and proceeded to modify it to fit my needs. I marked 1" in on the 5" opening and then marked 1" lines around the opening. I cut tabs into the opening along the lines to create a flange. I also grabbed a scrap piece of 1/4 ply and drew makeshift collar to attach the reducer to.
As the markings say, cut the inner opening first. Otherwise you'll be left with a 6 3/4" disc to hold on to while you try and manuveur a jig saw around in a cirle. The opening first, so you'll have more material to hold on to, while you cut and becareful. (I'm sure there is a better tool for this, however the jig saw is what I have)
So far so good. I removed the fan and marked the four mounting holes where the bolts go through and drilled them into the reducer and the plywood collar. Not seen is a marking I put on each piece which allowed me to match up the pieces quicker. Then proceeded to line them up, clamp them together in my bench top vice and drilled 1/8" holes in each flange to accomodate the 1/8" medium alu pop rivets.
Test fit with most of the pop rivets in place.
I then drilled and installed the remainder of the pop rivets. I also applied a bead of silicone around the inside of the duct and collar to seal any gaps between the two pieces.
Finally assembly. Mounted and securely bolted to the motor. The pop rivets leave about 1/16" space between the fan and the collar. I sealed this using a bead of silicone as a gasket and also applied a bead of silicone aorund the area where the fan sits on the back wall of the booth.
A parting shot of the booth sitting on the work bench top (taken before I installed the duct).
And that is pretty much is that. Obvious considerations for improvement are a light on top of the booth which I do not have room for presently. I'll get around that for now and use a lamp to shine a light inside the work area. I am also going to install a hanging rack at the top to hang small parts off of for drying. A "Lazy Susan" to hold large pieces on a turntable which can be rotated and a clear plexi glass cover to keep dust off of things while they dry. I haven't decided if I'm going to paint the interior white or apply white bristol board ot the sides which can be discarded when it gets covered in paint. These are details I'll be adding over the coming weeks, I'm just happy I got this stage of it completed. In March I'll be installing the rigid ductwork to vent it outside. Thankfully I don't have far to go.
Feedback and suggestions are welcome.
