Discussion in 'Finishing Techniques' started by DarylP, Apr 25, 2010.
highly polished aluminum won't corrode if you keep it waxed with mag wheel wax
Is that per layer? I find it hard to believe that the entire painting process doesn't weight a lot more.
We spray a very light layer of gel-coat into our part molds, and it weighs about .08 psf.
With all the layers going into a paint job, it seems like it would be heavier than that.
I have spent some time trying to get weight per coat figures from varoius paint manufacturers, who are to say the least reluctant, partly because.. how thick is a coat?
Further Poly Fibre for example, class "a coat" a 2 cross sprayed layers and also point out that someone used to spraying cars, for example, will give thicker coats than others.
Best calculations, which have been shown to be in the right ball park by tests, show that ( for Poly fibre paints) WITH EXTREME CARE.
0.14 oz/square yard for the "primer"
between 0.13 and 0.3 oz per square yard for colour, (No UV inhibitor included) depending upon the actual colour and sprayers ability
As a matter of interest, Poly Fiber claim 4.9 oz/ square yard for the full paint job
Does the 4.9 oz include fabric? (I assume not)
No. Refers to paint only, based upon absorbsion with the 1.7oz/sq yard "Uncertified" fabric.
Maybe of interest, the minimum and lightest finish for an Ultralight is:
1 coat Polybrush Primer
2 coats SILVER Poly. (not colour)
Can’t help you on the fabric planes paint weight, but to the other part of your question on sheet metal planes, there’s a wealth of info about paint and primer weights at VAF, and it can get as deep as you want it to since there are over 11,000 members on that board, with some paint and primer specialists very knowledable about this aspect. Doing the right search engines in the right areas will give you plenty of reading material, post dating to the beginning.
It seems too many are getting car painters to paint their planes, and their main goal seems to be to just make it look great, and not be concerned with weight like we would want them to. Their paint jobs typically run about 30-40 lbs or so.
And just briefly on primers, certain primed epoxies on the insides of Van’s aircraft when done right and with minimum acceptable.5 mil-spec epoxy primer coverage can actually only add about 3-5 lbs of weight, even though epoxies are the heavier primer.
On the outside paint, Van himself estimated a very minimum paint job on the outside can be done which would only add 12 lbs. This was only two coats, and done without primer. Most paints require primer though (ask Detroit about that during the eighties and nineties), and even his paint specified it, but they experimented and opted taking several other steps in place of the primer which gave his plane one of the lightest paint jobs which still looked good. I don’t have any info on how well his paint held up.
Roller or brushed? I've seen both...
Big airplanes have a lot of surfaces to cover. Little airplanes, not so much, so if your W&B tolerances are so tight that you're worried about the weight of your paint, you need a bigger plane. Let's say it takes a gallon to cover your plane. That gallon of paint IN THE CAN doesn't weigh much -- once it's applied, you lose the weight of the can and the solvent, so that coating of paint weighs about as much as last night's dinner, drinks and dessert. I had a nice, shiny silver plane once. NEVER AGAIN!!! It showed every speck of oil and dirt, far more than does paint, because any color draws the eye when it's against shiny silver. A rivet that catches a little polish isn't a big issue -- hundreds of them, that's an issue. If you don't polish evenly, it's like you sandblasted a strip on the side. I rapidly got tired of flying to visit someone, then rushing to wipe the bird down before they saw it. I like paint, and it's worth the weight and effort.
Yeah...I bet polishing would get old after a few years, but then I like fussing with a bike, car or plane. However, like I mentioned earlier, I would polish the ailerons, rudder, horizontal & vertical stabilizer, then paint the rest. That may not save much, but there is still a scheme for painting and as others have noted, that shiny metal looks good. It does have another purpose, and that is visibility. As long as you don't blind someone. :gig:
As far as weight of the paint is concerned, and as someone has already pointed out, there is over-spray that would be hard to account for. I worked in a factory that used static charge to get the paint to be drawn to the metal, thus eliminating waste which was their mission, where mine concern is weight. Same diff I guess. Still, knowing how much did not stick is important too I guess. I don't know if there are any aircraft painters out there that have a booth like that. How does one go about finding a good painter? It is hard enough with cars...but planes??
I did a bit of gelcoating as well. Weight is extremely critical, especially if refinishing aircraft, since the MTOW is fixed and thus every pound of paint subtracts from your payload. Especially important if you have a "maximum 0-fuel/ballast weight" like many gliders and motorgliders do. That 20 lbs can seriously devaluate your aircraft, since you don't fit in (weightwise) anymore and just imagine, an extra 1/24" means an extra 70 lbs of weight. That's quite a lot.
Even more critical are rudders, flaps, elevators and the like. We once repainted an aileron. Applied close to 350g of paint, but the aileron was only 120g heavier as sanded. How come? We sanded it down every time, to get the weight as low as possible. Every excess gram of paint required something like 15 grams to balance out. There's a maximum weight for the ailerons as well.
It got old within a month, when I realized how ratty the plane looked if I didn't rub it down completely after every flight. I like fussing with a plane, but I don't like being FORCED to. I have airplanes because I enjoy flying them. I want them to look good between flights, but I don't want to spend an hour polishing each time.
So just polishing them makes sense, right?
Yepz, for sure. Except then I'm more of a composites guy where the paint is absolutely essential.
In WWII they quit painting b-17s because the "several hundred pound saved allowed both higher altitudes and 20-30 knots in speed ditto fighters!
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