Performance difference - with or without paint

[Thorlifter]

Mostly asking about the heavies, but is there any data of performance difference of a B-17/24/29 with and without paint?

Also, if the data shows better speed or better range, why didn't the British adopt this?

 

[Peter Gunn]

Here's one for the B-24:

http://www.wwiiaircraftperformance.org/B-24/B-24_EXP-M-51_B779-1.pdf

There may be others there I just didn't have time to look.

 

[Shortround6]

Mostly asking about the heavies, but is there any data of performance difference of a B-17/24/29 with and without paint?

Also, if the data shows better speed or better range, why didn't the British adopt this?

You have a number of factors involved.

What is the surface of the "bare" plane like?
Is the paint acting like a filler to smooth some cracks/irregularities?
do you need to wax the bare metal?

What is finish of the paint?
gloss, semi-gloss, flat, really flat night fighter finish?

What is the weight of the paint.

The British were operating at night, a bare metal bomber might show up much better to search lights than a dark painted bomber. If you are in the middle of the light beam you are in the middle but near the edge?

 

[stona]

You could easily substitute the words 'best guess' for 'estimate' in that report. It is not based on any actual testing.

Estimates for aircraft performance were often very wide of the mark when compared to real world testing.

Cheers

Steve

 

[drgondog]

You could easily substitute the words 'best guess' for 'estimate' in that report. It is not based on any actual testing.

Estimates for aircraft performance were often very wide of the mark when compared to real world testing.

Cheers

Steve

Real world testing varied between aircraft in real world testing with exactly the same configurations. Manufacturing standards, engine performance, test pilot skills in performing the test to the testing objectives, calibration errors, etc often were more complicit in shortfalls to Performance Estimates based on drag data from Wind Tunnel testing.

 

[stona]

Real world testing varied between aircraft in real world testing with exactly the same configurations. Manufacturing standards, engine performance, test pilot skills in performing the test to the testing objectives, calibration errors, etc often were more complicit in shortfalls to Performance Estimates based on drag data from Wind Tunnel testing.

Of course, but when we look at reports from, say, the A&AEE, they give a much better idea of what could be expected from an aircraft type in whichever configuration was tested than any theoretical estimates ever did.
One of the things such institutions attempted to establish is tolerances and variations in manufacturing. It was something that certainly exercised the minds of officials at the MAP and strenuous efforts were made to keep those variations as small as possible.
Cheers
Steve

 

[Greg Boeser]

Removing the paint from a B-26 reduced its weight 46 lbs and increased speed by 4-5 mph.

 

[pbehn]

Also there were different paints, the matt black paint used on night bombers reduced speed but was considered a price worth paying. The British heavies didn't switch to daylight until close to the end when being seen and speed hardly mattered. For fighters and other tactical planes they carried "D Day stripes and so were painted to some extent anyway.

 

[stona]

Removing the paint from a B-26 reduced its weight 46 lbs and increased speed by 4-5 mph.

And a couple of badly fitted cowlings or panels would negate that gain (and possibly more). It's why such small gains in service aircraft are always variable, a point alluded to by drgondog above.

Taking the rear view mirror of a Spitfire V gave another 6 mph, filling and polishing the leading edge of the wing (with that double row of rivets) gave another 8 mph. Polishing the entire aircraft (1 coat wax - unspecified) gave just 3 mph. So many variables, and such fine margins.

Cheers

Steve

 

[Greg Boeser]

True. The fact that camouflaged and NMF aircraft flew in the same formations would negate any benefits anyway. The biggest gain was in production, since the multiple steps of painting the aircraft on the production line were eliminated, saving time and money. Stripping the paint in the field was probably nothing more than psychological. "My plane is lighter, therefore it is faster."

 

[stona]

It must have saved significant man hours in production. To fill, smooth and polish the leading edge of a Spitfire wing (as far back as 20% of the chord of the wing) added 50 man hours to the production of each aircraft, but was considered worthwhile. In the very same letter in which this was authorised the point was made that a corresponding improvement in post production maintenance would be required.

Cheers

Steve

 

[Fighterguy]

One of the main factors for paint (surface treatment in aviation maintenance parlance), is corrosion prevention. It's six to one, half dozen to the other. Do you paint an aircraft, possibly reducing it's performance (slightly), or leave it unpainted, increasing maintenance down time and costs over the long run. It doesn't take much moisture intrusion to cause major structural integrity issues. Still, unpainted aircraft require the same level (sometimes more) of skin treatment to keep them properly maintained. Then there's the effect of shiny airplanes giving away their position to enemy eyes. Localized chipped or eroded paint can be easily touched-up versus polishing an entire airframe.

 

[stona]

Corrosion was not so much of an issue when the life expectancy of an aircraft was relatively short. One of the arguments advanced for not fitting air filters to Australian Spitfires was that

"The life of a fighter in operations rarely reaches 50 hours."

It may have been more in Europe, but not significantly and certainly not the thousands of hours expected today. I believe the average age of a current USAAF aircraft is about 27 years.

Cheers

Steve

 

[Fighterguy]

 

[Old Wizard]