Project Suck – Update 5 The Unavoidable Truth
April 9, 2009
After a quick review of what was available in the local Salvation Army stores I didn’t find anything suitable that could be modified to be a boot.
So, it was off to Home Depot to get some more MDF and build a booth from scrach.
The biggest challenge is cutting the wood without a table saw. Circular saws are horribly inaccurate for cutting wood. They are fine on a deck, or framing as you can be off 1/8″ or more without any major issues. Trying to build a box that lines up perfectly is just not possible with a circular saw.
The only way to improve the quality of a cut using a circular saw is to use some sort of guide for the saw. This is doable with some sawhorses, a straight piece of wood for the guide and some C clamps. I happen to have all of those things available but this technique results in significant delays so it’s not something I’d recommend if you have a lot of cutting to do.
Fortunately Home Depot will cut wood for you as long as the cut is 90 degrees. This will take care of 95% of my cuts so I had them do all of the 90 degree cuts for me. I highly recommend sketching out how you want the board cut, with measurements, before you get them to cut it though. The fellow I asked at first was going to the 5 pieces one piece per board, when I had sketched out all the pieces on two boards! I politely showed him how the cuts should be done and he graciously blushed and used my sheet from then on. Apparently Rona will do angle cuts too; so it might be possible to have all of the cutting done for you.
After assembling the box, I still had the job of mounting the plenum and blower from before. I was worried that the combined plenum and blower would weigh too much and tilt the booth backwards. My fears were confirmed and I ended up mounting the plenum and blower flush with the bottom of the booth so the plenum and blower rested on the table; thus holding its own weight and not tilting the booth.
I should mention at this point that I having the plenum mounted on the back as a separate piece is not the best way to do this. I did it this way as I had already built the plenum and I didn’t want to waste all of that work. The easiest way is to simply include another back panel in the booth that would create a plenum chamber a as part of the booth. This would also simplify the blower mounting as it too would be integrated into the booth. You will also be saving a fair amount of MDF. Probably 30%. You’ll be saving 50% aggro though.
Anyways, I used standard 1/4″ rubber weather stripping to create a seal between the blower and the plenum and the plenum and the booth. This provided a great seal.
I did encounter a major issue with the design. If you recall earlier photo’s I had made provisions for the filter to trap the overspray to be inserted into the side of the plenum.
Due to some aerodynamics I don’t completely understand this feature was a total failure.
What seems to be happening is the plenum is being pressurized by the blower, and you get very good flow out of the vent, but some of the air in the plenum is leaking out the slot I made for the filter. It’s enough that the booth was basically useless as there was plenty of fumes coming out of the slot.
The only solution was to seal the slot and put the filter inside the booth in front of the grill. Easy fix but what a waste of all that work on the plenum.
The other consession I was forced to assume because of having to use the window is the flexible ducting. Man that stuff really impedes airflow. I can hear the blower change speeds if I collapse the flexible ducting or stretch it out. I’m going to see what I can do about making most of the ducting rigid and only have flexible ducting to allow removal from the window.
