Loads of Paint on the Heavies

[Milt]

Is there a need for the development of light weight paint for aircraft?

What is the average weight of paint that the heavies are carrying around?

Are there currently specific undercoats and final finishes for aircraft use and have I opened a can of worms?

[Fat Clemenza]

that's a good question buddy, I was just about to start a thread about it:ok:

[PaulW]

Paint on a 747 777 weighs approx 2-300kgs.

Which is why JAL and Cathay's latest freighters are being operated without paint to utilise that weight saving. Adds up to a lot of pay load and fuel saved over a year.

Green primer gives the key for the top coat and top coat provides moisture and corrosion protection.

Im sure all the chemical companies that develop paint have been working on decreasing the weight of the paint for years and probably have done so already.

The paint itself is 2-pac - paint mixed with its hardner.

[Mad (Flt) Scientist]

Since, simplistically, the weight of paint should be proportional to the aircraft external surface, and the actual aircraft weight itself proportional to the aircraft's volume, one might expect that with the paint being proportional to the square of a characteristic length, and the aircraft weight proportional to the cube of that length, then the proportion of an aircraft's weight represented by paint and finishes should actually decrease with aircraft size, and it's the little guys who should care most about paint mass and thicknesses....

[matt_hooks]

Since, simplistically, the weight of paint should be proportional to the aircraft external surface, and the actual aircraft weight itself proportional to the aircraft's volume, one might expect that with the paint being proportional to the square of a characteristic length, and the aircraft weight proportional to the cube of that length, then the proportion of an aircraft's weight represented by paint and finishes should actually decrease with aircraft size, and it's the little guys who should care most about paint mass and thicknesses....

I think there's a fault in your logic there.

If the aircraft were solid then I would be inclined to agree, however there's a lot of empty space inside your average aircraft.

As the a/c increases in size, the amount of empty space inside increases, so the "density" of mass is much lower for, say, a 747 than for a C152.

Now the surface area to be covered in paint will increase at a greater rate than the mass of the aircraft for a given volume.

I think anyway! :uhoh:

[Mad (Flt) Scientist]

but there's empty space inside both a C152 AND a B747. The question is, is there proportionately more or less empty space in either. I suspect, to a first approximation, it's about the same.

Let's compare:

B747
length: 230ft (span 210ft)
wing area 6000ft^2
MTOW 900,000lb

C152
length: 22ft (span 33ft)
wing area: 160ft^2
weight: 1600lb

So the lengths are in a 8:1 ratio (roughly), the areas about 40:1 and the weights about 600:1. I agree it's not 10:100:1000, but it's not THAT far off. I'm not a weights conceptual design guy, but it looks like overall average density isn't far off constant.... (if you assumed the nominal dimension of a C152 was 27ft, and the B747 was 220ft [average of length and span] you'd predict a B747 weighed [220/27]^3 = 541 times a C152 - in other words, 865,000lbs. Not a bad guess. :)

[Silverspoonaviator]

I wish I still had my slide rule.

Every one knows that aircraft that are painted white weigh more than those painted orange.

Summit to do with the modulus of elastisity of the colour molicules.


ckuse spelling dew to proximity of Xmas.

[james2210]

Why don't they cover the external surfaces with teflon? It may reduce drag and improve the overall frying characteristics of the aircraft.

OK, I've already got my coat on.

[N1 Vibes]

James2210

why not change your coat of teflon for a ribbed one. We did some experiments with ribbed coatings to reduce drag on our mid-range fleet, just like the transatlantic/circumnavigating yachts have on their hulls. Though I'm not sure what the results were, this was about 4 years ago.

Only thing is the ribs are very good at trapping dirt, so there's the problem with this solution. So I've got me coat and I'm out the door!:8