| Here's a brief look at my modeling desk, with some practical aspects shown as well. |
Mid 2001, I drew up a requirements list for an ideal modeling workplace, as a design exercise, just for fun. For example, my old workplace had open closets, so you could see most model boxes. I would rather prefer to have everything in drawers and closets, creating a much cleaner appearance. And I would like a much much larger working space, meters wide if possible. I translated these requirements into a design, and through several iterations I ended up with something I really liked. It was so much better than my old work place, that I starting thinking about actually building it. I decided on two drawer blocks, with a very long (2.5 meter) desk on top. Hanging from the wall I wanted two closed closets for kit box storage, and in the center one wide closet with transparent doors to display my finished models (all eight of them). On the left side I planned a small TV on a swing support, and to make it symmetrical, I wanted a spray booth on a swing support on the right side. I could 'park' my spray booth on the side, and pull it towards the center of the desk when I needed it.
It took me a long time before I found the components I needed. At first I looked at office furniture, but I could not find what I wanted. In the end it turned out that Ikea kitchen components were almost ideally suited. By repainting them, and by adding a different desk piece, a kitchen look could be avoided largely. From the Ikea kitchen catalog, I selected the standard Faktum components with white MDF Applad doors and drawer front pieces. With the selected components, I could finalize the design. The drawing shows the design, with my old work place drawn in dashed lines.
I modified the Ikea components slightly. I added an MDF plinth instead of standard Ikea plinth, to bring the desk height down from kitchen sink level to normal desk level. I replaced the frosted windows in the Applad doors with clear glass windows. The main components were repainted in a brownish dark gray, and the front parts in some sort of terra cotta red. The painting was a major drag, because I wanted a matt finish. The alkyd paints I used were only available as satin paints, in practice a glossy satin, and I did not like the results at all. Matt clear finishes were difficult to find, but I found an acrylic matt varnish at last. It is quite vulnerable though.
I wanted a glass-covered desk, because of its appearance, and because I expected it to be easily cleanable. I used a 30 mm MDF plank as the basis, with Meranti strips all around, protruding 6 millimeters. After painting, the sheet glass was laid in the 6 mm cavity. The appearance was as expected (love it!), and indeed it is easily cleanable, but it also gets incredibly dirty. Every speck of dirt is visible on the high-gloss surface! Another drawback is that the lighting cannot be mounted under the top closets, because their reflection in the glass surface would blind you. I am working on a lighting set-up to solve that, and it appears it could be quite pretty too.
I mounted three-socket electric outlets left and right under the desk, which turned out to be very convenient in every day use. Possibly I will add mountings for floodlights under the desk, to allow for model photography. But I don't have concrete plans for this yet.
Overall, I am really happy how it turned out. I can only think of some minor problems. One problem is that the desk is possibly too large: I can't reach the drawers completely from my chair! I guess I have to update to an office roller chair, but I am not very fond of chairs on wheels. The width/depth ratio of the desk seems optically incorrect. An extra 10 or 20 centimeters extra depth would have been nicer, but that would be incompatible with the Ikea kitchen components. These minor points do not spoil my satisfaction! Total cost was around 700 euros. I did not count man-hours spent on (mainly) painting.
The last item I finished was the spray booth. After finishing the basic modeling desk, I made cardboard mock-ups to design a booth that would fit the overall picture. I had a blower from a kitchen furnace (as used in my old spray booth), and I wanted a storage area for the flexible hose. The booth consists of three main parts: a rectangular air box in which the blower is located, a small storage box for the exhaust hose on the right side, and a working desk with curved walls to the front. Because my design had a fairly complex shape, I made a simple CAD drawing. The box for the blower turned out a little smaller than I hoped for, possibly reducing its performance a little, but I really did not want to build a bigger booth.
I built the booth from 10 mm MDF, and one hefty 30 mm piece of MDF where it connects to the swing support. I used epoxy glue throughout, because the design was not very good from a strength point of view. I needed some putty to make all the connections nice and smooth, but it looked really good in the end. In the photos below it is in primer paint, still missing a filter, and with the back panel (on which the blower is mounted) removed. The spray paint reveals that I used it many times while under construction :-)
After 22 years of use, I finally made some photos of the finished product. The booth has gained a good patina of all kinds of paints. A new filter is fitted, which explains why it looks so clean. On the right you can see the flexible air hose exiting; on the left you can see it running upwards towards the exhaust above the window. The booth has four rubber feet, so I can move it around easily.
The detail photo shows the radial fan. I often read that a spark-free motor is required to avoid igniting combustible vapors, but I don't know whether my motor is spark-free. And I want to add that I'm not so sure that these warnings are valid: firstly the fuel:air ratio needs to be within a defined limited range to ignite, and I doubt whether we achieve that; secondly I have never ever read of a modeler's spray booth catching fire.
I have plans to build a new, more powerful spray booth. When I'm blasting away with (for example) the Paasche H cranked open, the spray booth cannot keep up. Also, the flow pattern at the filter face is awkward, in some areas the flow appears to be reversed. This is most likely due to vortices, that are caused by the bad aerodynamic layout of the radial fan sucking through a hole in a flate plate. My ex-kitchen hood blower is around 55 Watts power, but I have a 150 Watt blower waiting to be converted into a paint booth. It will also have a better aerodynamic shape.
The required air flow of a spray booth can be calculated quite easily. The American OSHA Criteria for design and construction of spray booths states in section 66(b)(5)(i) that "average air velocity over the open face of the booth shall be not less than 100 linear feet per minute". My current booth is roughly 30 x 40 cm, or 0.12 m2. I convert 100 ft/min to 30 m/min. 30 x 0.12 gives 3.6 m3/min, or 60 liters/second. I think a large garbage bag is 70 liters, so it suck that empty in one second - there's a method do to do very rough flow testing..
Another very useful webpage is Spray booth design and fan selection. It allows the calculation of the drag of the exhaust system, that the fan has to fight against, and what reduces the air flow considerably. The drag is called 'static pressure', the overpressure required to overcome the drag. I calculated the static pressure for my own set-up. It has 100 mm diameter flexible ducting, equaling the 4" ducting on the webpage. In its current, non-optimised layout, it has a 4.3' and a 1' straight section, plus six 90 degree turns. This gives a fictitious total length of 4.3' + 1' + 6 x 6' = 41.3', to be multiplied by 3 for the flexible ducting, making 124' effective length. The required flow of 3.6 m3/min, as calculated above, equals 127 CFM. The static pressure table shows for 4" ducting and 125 CFM a static pressure of 0.84 inches H2O, per 100' of smooth duct. 0.84 H2O times 124'/100' makes 1.04 inches H2O. In other units this is 26 mm H2O = 260 Pascal = 2.6 mbar. Conclusion is that I need a blower that has a flow of 3.6 m3/min at a static pressure of 260 Pascal. However, that requires finding your fan's graph showing flow against static pressure, and in most cases that information is not available. I definitely don't have that information for my old ex kitchen stove blower.
If I would optimise the ducting, by removing four of the 90 degree turns, and switch to smooth ducting, I would have a fictitious total length of 4.3' + 2 x 6' = 16.3'. Static pressure would drop to 16.3'/100' times 0.84 H2O, which makes 0.14 inches H2O (3.6 mm H2O, 36 Pascal), just 13% of the current value.
Note that one thing is missing in the static pressure analysis: the drag of the filter material. I have no idea (yet) where to find that information.
To demonstrate how strong the effect of drag in the ducting is, I took the first fan flow graph that I found, of a Oriental Motor MRS25-T 250 mm axial fan, with a 374$ price tag. I calculated its power to be 140 Watt. I added the red and green bits to the graph below. At a static pressure of 260 Pa (red lines) it has a flow rate of 1.0 m3/min, less than 1/3rd of what I am looking for, and just 5% of the maximum flow of this fan. But with better ducting and a static pressure of 36 Pascal, it has 19.1 m3/min, more than 5 times what I need. Also, at 300 Pa static pressure the flow would be zero!
Some DIY and even commercial spray booths use computer fans. This just might work if no ducting is attached, and the filter is the only part that creates drag. I studied the product catalog of a random brand of computer fans: Wakefield-Vette, and used it to make the picture below. Their smallest fan, 25 x 25 mm, 13000 rpm version (page 11), can take 6 mm H2O only before the flow stops. To get some flow at my 26 mm H2O exhaust system's drag, a 60 x 60 mm fan, 9800 rpm version (page 26) is the minimum, but it achieves 0.13 m3/min only (note crooked scale). Their most powerful fan, a 92 x 92 mm, 8000 rpm version (page 36), achieves around 1.3 m3/min at 26 mm H2O, and consumes 35 Watts. So 2 to 3 of these fans would do the job in my spray booth.
For future discussion: Matching the fan to the ventilation system. The first picture in this online paper shows how flow drops with increasing drag in the exhaust system.
Often mentioned, hardly ever shown: the famous spares box. Well, here are mine! Hundreds of wheels, dozens and dozens of rockets, bombs and tanks, pilot figures, engines, canopies, landing gears. The majority of these items come from a the disposed model collection of a fellow modeler (hi Berry!), with my own surplus stuff added.
My collection of Evergreen, Slaters and Plastruct bags with strip and rod drove me nuts. I could never find the size I was looking for. I recently solved that problem. I used plastic sleeves to put documents in a folder. I used a temperature-controled soldering iron set at 225C to make (say) ten vertical pockets in each sleeve. I made around ten sleeves, and put them together in a paper folder. And then I filled nearly all 100 pockets with all my strip and rod and profiles and metal wire and Albion tubing. I even made small stickers with the dimensions of the content of each pocket. All in all it was a couple of hours work. But it works really well. Every time that I used it ever since made me very happy.
