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Thread: Spraying beginner - advice

  1. #16
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,599
    Take the leap. After you start spraying you'll wonder why you waited so long to start.

    One thing that we didn't discuss is a spray booth. You need one unless you plan to spray outside, which has it's own set of issues. It doesn't need to be anything elaborate as long as you only spray WB finishes. But you do need one. We can discuss further, as you choose.

    John

  2. #17
    Join Date
    Jan 2018
    Location
    Cleveland, Ohio
    Posts
    83
    Thanks for bringing up the booth.

    I just got the Earlex 5500, and have a former laundry room next to the shop where I thought I'd make a booth with plastic walls (made from vapor barrier, supported with the poles that grip the floor and ceiling joists). I can close the shop door to reduce dust, but that room is never dust-free.

    I might be able to move a Jet air filter that doesn't get much use. But I read of folks who use a filter on a box fan. If I make a frame to hold a filter over a 20x20 box fan, are there specs for the filter to use? (I don't plan to spray much solvent-based finish). Does it make sense to funnel the output to the 4" duct that used to handle the dryer output?

    Do I need another filter to cover an air intake? Same specs?

  3. #18
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,599
    You need exhaust and a 4" dryer vent ain't going to do it. If you want to use a box fan you need an opening as large as the fan, unobstructed. I use the fan from my DC, and I can exhaust over 1000 cfm through a 6" duct out a nearby window.

    FWIW, filters on the exhaust side just blind over. If you put the box fan 6 ft or more behind your spray gun WB finishes will be dry by the time the overspray hits the fan and won't stick (but they will plug up a filter). Even if it does, box fans are cheap and if you need to replace it every few years it's less than $20. If you are spraying in a sealed room you can filter the make up air. My temporary booth isn't sealed so I can't filter the make up air, but it doesn't seem to matter. I don't have problems with airborne dust getting on my freshly sprayed parts.

    John

  4. #19
    Phil,

    I started out with a cheap HF purple HVLP gravity gun. Actually doesn't work bad at all. I also use a pressure pot type gun with a 2.2 tip which really puts out the material. Use it exclusively for primers.

    I wanted to try something different, so I purchased the Earlex Spray Port (6003). I think if you're looking at buying a compressor this is comparable in price.

    +1 on the shellac sealcoat ;-) You can spray that, too. Another thing to consider is grain filling.

    +1 on the spray booth. The last couple projects I sprayed in the shop - not the best way to do it.

    Respirator with gas filters (especially with oil based) and a good exhaust fan are a must. I don't think a box fan is adequate.
    Last edited by Robert Engel; 01-02-2019 at 9:47 AM.

  5. #20
    Join Date
    Jan 2018
    Location
    Cleveland, Ohio
    Posts
    83
    Quote Originally Posted by John TenEyck View Post
    ...a 4" dryer vent (won't) do it. (For) a box fan you need an opening as large as the fan. I...exhaust...1000 cfm through a 6" duct...

    ... filters on the exhaust side just blind over.

    John
    That helps. My old dust collector only pulled 330 cfm, and its output goes to a big flannel bag. The shop now has a 2hp Oneida cyclone, which showed me how much I don't know about volume, pressure and flow.

    I plan on a booth of 4x8x6 (192 cu ft). 1000 cfm means >5 air exchanges per minute (which might be much more than I need?) I can change a 4" hole in my wall to a 6" hole pretty easily, but I'd like to see the math, to know whether I'll be frustrated later.

    Loading up the filter ("blinding over"?) would be ok, if I can get through a project on one or two filters. My bigger questions are how to set up enough flow, and how to funnel from one or more fans to a single round duct.

  6. #21
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    9,599
    Quote Originally Posted by David Kenagy View Post
    That helps. My old dust collector only pulled 330 cfm, and its output goes to a big flannel bag. The shop now has a 2hp Oneida cyclone, which showed me how much I don't know about volume, pressure and flow.

    I plan on a booth of 4x8x6 (192 cu ft). 1000 cfm means >5 air exchanges per minute (which might be much more than I need?) I can change a 4" hole in my wall to a 6" hole pretty easily, but I'd like to see the math, to know whether I'll be frustrated later.

    Loading up the filter ("blinding over"?) would be ok, if I can get through a project on one or two filters. My bigger questions are how to set up enough flow, and how to funnel from one or more fans to a single round duct.
    You won't get much flow if you try to force the output of a box fan down into a 6" hole. With box fans flow drops off very quickly as static pressure increases, and adding more fans won't improve it. You need an unrestricted outlet in order to use a box fan. If you can't provide an opening equal to the size of the fan then you should forget about a box fan. If all you can provide is a 6" hole then you need a blower. A dust collector fan is a blower. Get a cheap HF DC, tear it apart and just use the fan.

    Commercial spray booths were typically based on a face velocity of 100 fpm. The design parameter is different now, nor do you need that much for waterborne products, but the point is you need flow. If your booth has a frontal area of 4 x 8' that's 32 sq. ft, which means a commercial booth that size would have a fan capable of moving 3200 CFM. I get by with about 1000 CFM on a frontal area of about 42 ft, again spraying only WB and shellac, so that's a face velocity of 24 fpm. As long as I spray towards the exhaust inlet no overspray escapes the booth.

    If you want to avoid quickly blinding over a filter you need a lot of filters to spread out the load. Look at commercial spray booths. They might have a single exhaust fan maybe 2 ft square, but they will have a wall of filters in front of the fan. To me it makes no sense to use filters in front of a box fan (or DC blower). There's no benefit, only downside.


    John

  7. #22
    I had the earlex 5500 to start out with and it worked great. I started out spraying GF white poly and then some Target coatings, pigmented and clear. I found a good deal on a FUJI Mini mite 3 on ebay and upgraded. Dont think I can tell the difference in the final finish from the Earlex. The more powerful Fuji just is a little faster at putting out the finish. The Fuji is also a non-bleed gun versus a bleeder for the Earlex. The Fuji is a little more adjustable but I think starting out with the Earlex is a great idea. Think I sold mine for almost what I paid for it too!

  8. #23
    Guys,

    Thanks for the the very helpful suggestions. The cold weather has limited my woodworking abilities over the last month or so, but will definitely be checking around for spraying options in the spring. I suspect most of it is just practice and see what works best for me.

    Thanks again,

    Phil

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