Painted vs unpainted B-17s

[WLJ]

Came across this short video on the results of performance tests on painted vs unpainted B-17s. The results may surprise some.

B-17 Bomber Paint Vs No Paint, Unexpected Results
https://www.youtube.com/watch?v=420fO_-u0nE

Spoiler alert
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Painted B-17s were actually sightly faster and had a small range advantage over unpainted ones.

[Perd Hapley]

There was flubber mixed into the paint.

[230RN]

Surprising.  I would've thought the weight would slow it down.  I guess paint is slicker than I thought.  Like when they started to use flush riveting on planes. The corrugated skin on Ford trimotors lowered performance both for the added weight and the added surface area.  I think re-aligning (not constricting) the exhaustt ports on one fighter gave a couple of MPH advantage for the rocket effect.

I sometimes wonder how much the paint weighs on this or that aircraft. 

[WLJ]

I wonder sometimes how much the paint weighs on an aircraft.

In the case of the B-17 the video says 75lbs

[French G.]

I would guess the paint smoothed up junctions between rivet and skin, possibly kept as much dirt from sticking. Or, how did they maintain the bare aluminum? If it was wax all day the skin might have been too smooth. I know boat racers don't care for dead calm water the boat won't unstick from the water as easy as it will with some chop.

[Big Hairy Bee]

That is a surprise!

I wonder why the B-29 wasn't painted--different construction methods?  Along with the later B-36 and B-47...

[Devonai]

The Luftwaffe had no problem finding them either way. 

[RocketMan]

That is a surprise!

I wonder why the B-29 wasn't painted--different construction methods?  Along with the later B-36 and B-47...

They had flush rivets.  Moar betterer than paint.

[tokugawa]

Two aircraft? Wonder if they swapped engines to confirm results. It's not that I don't believe them, it just that there are so many possible variables.

[230RN]

Video at 4:47: "at the same engine power."

One can legitimately presume that all other variables such as prop pitch, trim, control sufaces, were likewise controlled for in such a critical study, as evidenced by the details of some of the other variables presented at 4:15ff. 

In addition, I doubt they based their conclusions on only one flight. I may have missed comments on that, though.

[tokugawa]

I wish I could ask my father about this- he worked engine test at P+W for some time.
17's had Wrights IIRC, but similar. 

Wonder how small a defect has to be before the parasitic drag is concealed by the boundary layer- they did say no improvement was made by polishing the paint.

[Bogie]

Why do golf balls have dimples?

[RocketMan]

I wish I could ask my father about this- he worked engine test at P+W for some time.
17's had Wrights IIRC, but similar.

Wright Cyclone R1820-97 single row radials for the 'F' and 'G' models. Don't remember what the 'E' and earlier models had.  I'll have to look it up in my library.

[K Frame]

Why do golf balls have dimples?

It makes them cute when they smile.