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Old Aug 15, 2014, 11:43 PM
B for Bruce
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The 'Wack, BC, Canada
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Fume control for doping.

I've been trying to get outside to do some covering and doping on some new models. But the weather is not cooperating at all.

So I got the bright idea to set up an area for doping right in the new shop area. A bathroom exhaust fan coupled with some portable clear vinyl shields to create a temporary fume hood.

Right after I took the pictures I launched into doping the fuselage you see in picture #3. I didn't wear my usual carbon filter mask as a trial. I'm happy to report that the ONLY thing I smelled were the very odd light wiff of dope when I swung the fuselage around and it came out of the control area... well, that and the smell of the clear vinyl.

Between taking the pictures below and posting this I spent about 3 hours covering and doping. The whole time I had a silly self satisfied grin on my mug at how well this thing is working.

The bathroom fan in the box is a $30 100cfm jobbie. The duct work is 6 inch ducting to provide as little restriction as possible. The collector cutaways were cut into one side of the metal before the remaining stubs were snapped together. A cardboard end cap is secured with duct tape.

Did I mention I was in a hurry so I could finish some models for a contest a little over a week away? I'd thought about this but it only kicked into high gear yesterday. I went shopping and built the window box last night and finished off the rest this morning and partly into the afternoon. Model work seen in the last pic started right away as soon as the camera was put down.

Oh, and yes, it does feel as good to work in that shop as it looks.... It's been a long road to get to this point but I really felt like it was all worth while today with the tunes playing and the model work going so well.
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Old Aug 16, 2014, 08:54 PM
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doping indoors

Try adding a couple of drops of Oil of Wintergreen per ounce of dope. It cuts the smell dramatically. You can find it at the drug store.
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Old Aug 17, 2014, 02:25 AM
B for Bruce
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The 'Wack, BC, Canada
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It's not the smell. The goal is to simply not breath in the fumes which are so harmful.

Also while I don't mind the smell I really don't want it wafting through the whole house.
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Old Aug 24, 2014, 07:19 PM
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I can't tell from the pics: are you forcing air through the chamber, or pulling the air through? This is critical, as, if you are pulling the air through, the fumes travel through the fan motor. Unless you have an explosion-proof motor, you could have a serious issue waiting for the inopportune time to rear its head.
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Old Aug 25, 2014, 12:13 AM
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Quote:
Originally Posted by challenger_i View Post
I can't tell from the pics: are you forcing air through the chamber, or pulling the air through? This is critical, as, if you are pulling the air through, the fumes travel through the fan motor. Unless you have an explosion-proof motor, you could have a serious issue waiting for the inopportune time to rear its head.
Box fans typically use induction motors (shaded pole, I believe), so no brushes to produce sparks. The switch is probably not sealed, so switching that puppy on in a room filled full of fumes might be another story.
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Old Aug 25, 2014, 08:42 PM
B for Bruce
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As Moeregaard writes it's a strictly shaded pole motor with no exposed brushes to spark. Switching is done simply by plugging it into the wall.

If it was being used for SPRAYing then I'd be all over the idea of an explosion proof motor. And it's good that you brought it up. The idea here is STRICTLY for fumes from brushing the dope onto the models. No spray painting allowed.
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Old Aug 26, 2014, 10:25 AM
OCD: Old, Cranky and Disgusted
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Just thought I'd ask.

Back in the late 1930's, the Piper plant burnt down twice, and the Taylorcraft plant burnt once, all caused by the vent fan in the dope shop.
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Old Aug 26, 2014, 12:49 PM
B for Bruce
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The 'Wack, BC, Canada
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It was something that crossed my mind as well. I purposely used a grounded cord so the frame is grounded against static even. Anyway there's no brushes and no switch in the flow path. But just in case I also start the motor ahead of the jars opening up so there's a good flow and the fume concentration will never get that strong.

Again for anyone reading in I'm fully with the idea that for SPRAYING you must use an explosion proof motor or at least use a remote motor and belt system to the blade. This is for fumes from small open bottles and BRUSHED ON dope on the model drying.

We've got few enough FF'ers around. Don't go using a modest setup like this for spraying.
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Old Aug 29, 2014, 10:56 AM
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Painting a model with a brush using dope, with proper ventilation is probably safe fire/explosion-wise. Might be wise to wear a proper mask for breathing concerns. I inhaled a lot of model plane dopes and thinners since the 40's and,where was I??
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Old Aug 31, 2014, 07:46 AM
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Columbus, OH
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I read where Cole Palen used to dope his full-scale WWI Rhinebeck planes in an unventilated hangar with a kerosene heater going.
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Old Sep 01, 2014, 05:25 PM
B for Bruce
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The 'Wack, BC, Canada
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Quote:
Originally Posted by E-Challenged View Post
Painting a model with a brush using dope, with proper ventilation is probably safe fire/explosion-wise. Might be wise to wear a proper mask for breathing concerns. I inhaled a lot of model plane dopes and thinners since the 40's and,where was I??
The setup as shown in the pictures has enough draw along the front of the opening that unless I flip the wing out into the room and draw out a little of the fumes I don't smell anything other than the vinyl sheeting which is right under my nose. And even the odd little bits that do get wafted up into my face are pretty minor and only there for a second or so. By the time I exhale and inhale again it's gone. So all in all there's just no need for a mask as well.

Yeah, I did my share as well. One time I tried to put on a really fast and quick job in my closet size shop as a kid and get the door closed again so my mom wouldn't smell it. I was only in there for literally 40 seconds tops and I was still woozy and could not walk a straight line to save my life for probably 3 or 4 minutes after.
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Old Sep 01, 2014, 09:40 PM
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I made something like this and it was quite helpful for brushing on contact cement and such. A further benefit, unless the power goes out, is that it will keep fumes from pooling on the floor and flowing over to the pilot light in the water heater or furnace!

If I'm not mistaken, "explosion proof" vent fans are commonly sold at boat supply places for ventilating the bilges of motorboats. Of course, then you have to think about the conductivity of the hood and so on, so static doesn't build up. But there sprays and coatings you can use to ameliorate this. Or build it out of wood or cardboard and don't force the humidity too low.

Looks like you did a nicer job with yours than I did with mine.
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Old Sep 03, 2014, 07:45 PM
Balsa Flies Better!
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Hi Bruce

Umm, I hate to rain on your parade- but there's not that much difference in terms of spraying or doping. In both cases the vapors -whether the solvent in the dope or the paint along with its associated solvents are highly flammable.

In the chem lab we used to have solvent cabinets that had shielded fans to prevent sparks. Typically the solvent concentration in the air space in the solvent cabinet would be lower than an open can of dope.

In practice though- I suspect that you're safe enough since as you note, there's a fair amount of air draw that should help keep the vapors away from the motor- and even then the motor is going to thin out the vapors to a non explosive concentration in short order. I think where you really have to worry is if you let the vapors build up- and then turn on the fan! As long as the fan is running while you're doping, my hunch (worth exactly $0.02) is you'll be fine.


Sam
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Old Sep 03, 2014, 08:37 PM
B for Bruce
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The 'Wack, BC, Canada
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I was worried about that too. But since the whole idea is to avoid flooding the area with fumes the fan gets plugged in and starts running before the dope or solvent is opened. So there's no real build up to worry about.
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