DIY spray booth

[Grendels]

I was inspired by Elm City and his spray booth and I decided to build my own. I have it almost done now, and over the next week, I will get the videos posted. I got side tracked by the video editing software reviews I have been doing this week. (And not working on models.) :'(

Here is part one:

D.I.Y. Spray Booth part 1

This segment talks about design problems, the next couple will talk about lighting, and the actual design.

 

[Biskup]

Hi,
Great you made a video and I'm looking forward to the next parts as I'm thinking on doing my spray booth and now I'm doing research about it.
Cheers

 

[Grendels]

Part two is up:

DIY Spray Booth part 2

I will get more parts up tomorrow.....

 

[Grendels]

And here is the third part. I finish up the design, and start on woodworking.

DIY Spray Booth part 3

 

[Grendels]

And before anyone ask, here is the parts list and the tools used:

Here is my parts list:

two 4x8 sheets of 1/2 plywood
one 4x8 sheet of pegboard
3 6ft 1x2's Poplar wood
1 Bathroom fan, 80cfm
1 dryer duct kit
1 15 ft extension cord
16 gauge household wire (you can use the extension cord for this)
1 3-way switch
1 wall plug
2 plug boxes
aluminum tape
1 light kit
1 Lazy susan
solder
shrink wrap
#6 screws 1 1/4 inch
#8 screws 1 inch
Polyurathane for a finish

Here are the tools I used:

2 tables
2 clams
10 ft level
carpenters square
masking tape
measuring tape
saber saw
circular saw (worm drive)
wire cutters
drill
screw driver

 

[sunsanvil]

I noticed the 25x25 furnace filters.... if that is your aperture, then you would need a fan capable of over 200cfm net (ie after all ductwork is in place) just to get a minimal 50lfp at the capture face. I may have missed something, but with that 80cfm bathroom fan I'm thinking the booth may not function so much as a booth but rather a slow air-exchanger.

 

[Grendels]

Yeah after reading a few articles on this. (After I built the thing of course) The cfm worried me a bit. I haven't tested it out yet. I still don't have it connect to the outside, that is a project for this weekend. It is built, and you can feel the air moving at the surface of the booth. But not very well.

I am looking for a replacement to the motor, so I will keep this in mind.

 

[AKE]

Wish I had all the power tools to do this. My spray booth is more simple.

Parts list:
Cardboard box
window fan
furnace filter
Duct tape

Tools used:
Um, duct tape

 

[Grendels]

You California people are lucky this way. Between June and Mid September, it is anywhere from 95 to 105 Fahrenheit outside with 80 to 100% humidity. I couldn't open a window for more than 5 minutes without heating the whole house up drastically. There is a reason this area wasn't heavily settled until the late 60's you can't live without air conditioning here.

I don't even want to talk about bugs. They love heat, and are everywhere...... I would hate to have tiny bug prints in my fresh paint job.

 

[Grendels]

I noticed the 25x25 furnace filters.... if that is your aperture, then you would need a fan capable of over 200cfm net (ie after all ductwork is in place) just to get a minimal 50lfp at the capture face. I may have missed something, but with that 80cfm bathroom fan I'm thinking the booth may not function so much as a booth but rather a slow air-exchanger.

I gave it a try last night, spraying future for the first time. I didn't really smell anything from the future, but if I went at it too much at a time, I could see vapors backing out of the booth. My solution was to only spray for 30 seconds or less and nothing made it out. A stronger fan would prevent this. Looks like a trip to a suppler this weekend, or I can try it without the furnace filter....

 

[sunsanvil]

Its the ratio of the CFM to the aperture (surface area) which determines your flow. The furnace filter is really not a significant factor in this context (on the other hand curves in the duct work, or worse any flex-duct, definitely is a factor). In fact if anything the filter is helping in that in small part the frame is reducing your aperture a little bit.

Either upping the CFM or decreasing the opening will achieve the same result (or a combination of both). Which you do just depends on whats practical for you at this point. "Bathroom" fans are readily available up to about 130cfm which doesn't sound like much but it would be 60% more than the 80. Decent axial fans upwards of 220cfm are about the same price, but you'd have to mod your design a little.

But I ramble...

 

[Elm City Hobbies]

Mine is 16X20 (or is it 16X24? Can't remember), 100cfm fan. The hose has one 90 degree bend coming out the back, and then up to the whole in the window to extract.

I have to get a pretty good fog on to get it backed up in the booth, and then only when I am using lacquers or primer from a can do you really notice it. A higher CFM fan would be nice, but when I bought it, I balance the cost of the fan, with the # of CFMs and the 100cfm was the best buy

 

[sunsanvil]

Go figure: If its 16x20, the math for a downdraft config calls for 111cfm, and by the time you subtract the frame of the filter your 100cfm is probably right on the money.

 

[Biskup]

How do you calculate the fan cfm from size? Is there same kind of a ratio to use there?
Regards
Lukasz

 

[DreamKnight]

How do you calculate the fan cfm from size? Is there same kind of a ratio to use there?
Regards
Lukasz

No, the fan is rated. Just look at the packaging when you purchase it or on the item specifications/description when shopping online. Big doesn't necessarily mean more CFM.

 

[Biskup]

Sorry my mistake I meant if you calculate what kind of cfm do you need from the size of filter or spray booth.
Regards

 

[DreamKnight]

Sorry my mistake I meant if you calculate what kind of cfm do you need from the size of filter or spray booth.
Regards

OH! From my spray booth thread:
http://www.briansmodelcars.com/tutorials/tutorial.asp?TutorialID=23&CurPage=1

 

[sunsanvil]

How do you calculate the fan cfm from size? Is there same kind of a ratio to use there?

We calculate the required CFM (volume of air) by taking the area of the capture surface in sq.feet and multiply that by the desired airflow in LFM (speed of air), 50LFM for downdraft, 100LFM for cross draft.

So for Elm's booth: [(16x20)/144]*50 = 111 cfm minimum required for proper air velocity
For Grendel's: [(25x25)/144]*50 = 217 cfm minimum required for proper air velocity
(both downdraft designs)

 

[Biskup]

Thank you for the info it helps a lot.
One last thing sunsanvil why do you divide by 144?
Regards

 

[sunsanvil]

There are 144 square inches in a square foot.

When you multiply the dimensions of your aperture (say, "16x20"), you get square inches and need to divide by 144 to get square feet.