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John Bolding
Joined: 23 May 2006
Posts: 281
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 Posted: Tue Aug 01, 2006 5:44 am Post subject: Paint weight |
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Something you guys have overlooked while discussing0 the additional weight of paint is the transfer effeciency of the0 application method you use. Most of that expensive stuff you bought ends up0 evaporating or on the floor as overspray.
I sold/installed/helped design/repaired/trained0 painters in the spray equipment industry for over 30 yrs. 0 In hundreds of installations across the country where we actually measured0 the part weight and paint weight before spraying, immediatly after spraying and0 again after cure/drying I can tell you for a FACT that the transfer effeciency claimed by some paint spray equipment manufacturers is somewhere0 between wishful thinking and market hype, kinda like cruise speeds in factory0 brochures.
Without going into a long discussion I'll give you0 a few GENERAL guidelines and a couple of examples.
Aluminum airplanes are on the friendly side as0 far as transfer percentages goes, lots of flat surfaces as compared to a tubing0 fuselage or a window frame.
Transfer % of a conventional type spray0 gun (worst) will range from less than 10% (spraying that tube fuselage)to0 a high of 40-50% while coating a sheet of0 alum laying flat on a table. HVLP is somewhat better , lots of times0 we got 50-65% on flat parts. Electrostatic will GENERALLY add 10-20% on flat0 parts and a lot more on complex shapes.
The above numbers are assuming that the painter is0 using proper technique and doesn't increase the air/ fluid pressures after I0 handed the gun to him. They ALWAYS did. Small increase in air pressure over0 optimal will reduce transfer by as much as 25%. But the painter likes more noise0 and recoil and generally they can get away with throwing away thousands of0 $$ in material.
I wanted to know how much the weight penalty for0 powder coating (100% solids) one of the fuselages for the Legal Eagle I sell was0 so took a completed frame to one of my equipment customers and coated0 it. After curing it was less than ONE pound0 difference from uncoated. I know, not much surface area but still less0 than I would have thought and that wasn't my first rodeo doing that0 test.
I still have all my test stuff ( to measure film0 thickness)and when I paint my rudder I'll post some numbers you can take to the0 bank rather than try to go in the back door relying on %of solids0 only. LOW&SLOW John0 Bolding
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larry(at)macsmachine.com
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| Posted: Tue Aug 01, 2006 8:42 am Post subject: Paint weight |
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John,
You've put forward good points, and I'm looking forward to your data. I
purchased my paint on the basis of an aircraft having 650 square feet
over all.
This might include a little extra, but I did measure the thickness of
prime and finish coated inspection plates and found .002 to .0025 paint
thickness.
650 square feet x 144 square inches = 93600 square inches x .0025 inch
thickness as worst case and I have 234 cubic inches. There's 231 cubic
inches in a gallon, so one
might have the weight of a gallon of paint on a 601HDS with pants,
fairings and all not counting trim which adds an extra 5 to 10 percent.
I bought two gallons of
base coat, one gallon of trim and a gallon and a half of primer. I'll
have to let you know how accurate it all was by the time I get it done.
Larry McFarland - 601HDS and painting since April..........at
www.macsmachine.com.
John Bolding wrote:
| Quote: |
I still have all my test stuff ( to measure film thickness)and when I
paint my rudder I'll post some numbers you can take to the bank rather
than try to go in the back door relying on %of solids only.
LOW&SLOW John Bolding
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