why did or didn't some aluminum aircraft get paint VS bare finish?

Discussion in 'Boat Design' started by Squidly-Diddly, Aug 4, 2013.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I figure this is as good a place to ask as any.

    American B-17, B-24 and P-51 and P-38 of WW2 all came in both painted and bare aluminum finish(bare towards the end of war).

    Many post war aircraft came both ways.

    Now everything has "low radar" or whatever special paint, but what about WW2 and after?

    Fashion? They run short of paint? Different type of aluminum?
     
  2. michael pierzga
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    michael pierzga Senior Member

    Weight ?

    complicates visual inspection in the field ?
     
  3. Jeremy Harris
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    Jeremy Harris Senior Member

    Weight, more often than not. Paint weighs a heck of a lot on an aircraft, and every kilo/pound of paint is a kilo/pound less fuel or useful payload.
     
  4. wardd
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    wardd Senior Member

    a b-17 unpainted was 5 mph faster
     
  5. PAR
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    PAR Yacht Designer/Builder

    It was actually simpler than this in WWII aircraft from the USA. We were punching them out so fast and needed them so badly, that holding them up for a paint job wasn't deemed all that necessary after a point. In Europe, by the end of '43 air supremacy was nearly assured and surly by the spring of '44 (after big week), so the masses of P-51's showing up, really didn't need paint. The same is true in the Pacific, where air supremacy was achieved by the summer of '43 and high altitude bombers just didn't receive Japanese harassment. Bright finishes where common among the AAC, but not naval, as the carrier borne aircraft needed the corrosion protection, much more so than land based. Range and speed where concerns, but the brightly finished aircraft had both for their roles at the time. The painted versions of the P-51 and P-38 in Europe (and the Pacific) had the range and speed they needed. The P-38 had the range to go to Berlin (painted), but lacked low altitude maneuverability to take on the German single engine fighters and was a costly aircraft to build and keep in operation. With the introduction of the D variant of the P-51, with it's new fuel tank behind the pilot (and other significant changes), the range issue was solved, with paint. The other most notable brightly finished WWII aircraft was the B-29.

    Initially, the B-29 was pretty heavy and laden with technology. Early models where painted, but unpainted versions where coming out, figuring the ground crews would polish them up, which didn't cost the manufacture a thing. In fact, the labor it takes to polish up an aircraft is more then the fuel savings the lack of paint might provide. As this bomber got rolling in production, every effort was made to get them in theater as quickly as possible, so saving a week in the paint shop seemed logical. With a theater command change and fundamental tactics that came with this, the B-29 was stripped of most of it's technology, flown at a lower altitude, so paint had little difference, as air supremacy was overwhelming, with most missions only encountering flack.

    To give you an idea of how much air supremacy we had after the early summer of '43 in the Pacific:
    the 20th bomb group showed 20 B-29 loses to fighters in '44 and just 2 in '45, while the 21st lost 48 in '44 and 4 in '45. The biggest loses where from "other", which could be one of several things, but with early versions of the B-29 likely engine fires that forced them down, but any mechanical or undefined problem could also be a cause.
     
  6. El_Guero

    El_Guero Previous Member

    Weight, cost, time.

    Weight was the primary reason.

    Here is Boeing's current statement on it.
     
  7. El_Guero

    El_Guero Previous Member

    Source?
     
  8. PAR
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    PAR Yacht Designer/Builder

    You've listed what Boeing's current position on the subject is.

    Again, range and speed weren't issues, by the time polished aircraft started appearing in WWII. Every aircraft carries a operational protocol, the most basic, initially at the time, was getting them on the "line". Any and all efforts were used to speed this up. It was a simple business decision, a week in a paint hangar or delivery (a week early) as a brightly finish ship.

    5 MPH on a B-17 made absolutely no difference in it's operation effectiveness. Economically, a brightly finished aircraft cost more to keep in service, in terms of materials and labor, than a painted one, but was cheaper for the manufacture to deliver, an AAC ground crew was getting paid anyway, so . . . Again a simple business decision. The speed thing is a pure myth, as they were attacked by aircraft that were 100+ MPH faster, so a 5 MPH gain was meaningless. In the Pacific theater, the B-29 was basically unopposed, so the point is equally as moot. The slowest German attack aircraft could easily chase down a lumbering B-17.
     
  9. tom kane
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    tom kane Senior Member

    Bees wax is great to protect aircraft, nothing better.
     
  10. Petros
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    Petros Senior Member

    I have worked in the industry, five mph is a big issue for a long range bomber, consider that it means it could travel that much further on the same amount of fuel. it means the difference on a long range mission between delivering your pay load, and getting the crew and aircraft back in one piece without running out of fuel. Or it means being able to carry more payload and less fuel for the same mission. The only reason to put paint on a military aircraft is for camouflage or to absorb radar signals. In all other applications all military aircraft have no paint. Paint also makes hull inspections for cracks and corrosion more troublesome and time consuming, and adds another task to be done for any repairs.

    On a commercial aircraft it could mean the difference in turning a profit, or losing money.

    when I worked at Boeing 25 years ago in the commercial division, the standard measure of saving weight was that a one pound savings means $ 1 million in extra revenue for the operator over the useful life of the aircraft. on the Boeing website, it show a 747 uses over 500 lbs of paint, and they have $132,000 a year in fuel costs (in 1998 dollars!). That is enough reason to not paint aircraft, just polish and add a company logo is the way to go.
     
  11. jonr
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    jonr Senior Member

    As Boeing says:

    > the net operating cost of polished airplanes is slightly more than that of painted airplanes
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Tell me that is a typo, please. Could not possibly be correct. Did you mean a thousand ?
     
  13. PAR
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    PAR Yacht Designer/Builder

    Agreed Petros, but the premise of this discussion was the polished aircraft of WWII. The B-17 had ample range for her role, so again not a consideration. In fact, the vast majority (over 90%) of B-17's where painted. We had the opportunity to use the B-29 and it's massive (comparatively) payload and range, but it was decided we had more than enough to get the job done with the aircraft in theater (B-24's, 25's and 17's). As a rule, in the European theater, polished bombers where not seen much. Daylight operations pretty much dictated a paint scheme. The P-51 was a different story, but it was produced in much higher numbers and a much faster rate, which was the primary reason for the polished finish.

    In the Pacific Navy blue was common on carrier borne aircraft. This had little camouflage value, but did have corrosion protection. In the Pacific, the Japanese lost it's air arms very quickly and sorties where flown relatively unmolested, for most of the war.

    A technical debate can be delved into, but reality in WWII was numbers on the line, the fastest way possible and this was the only real goal of the unpainted ships, because by the time they showed up, air superiority was attained in both theaters.
     
  14. Petros
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    Petros Senior Member

    Nope, that was the number we worked with. ONe million dollars lost revenue for each extra pound of weight in the airframe, over the life of the air craft. Consider at the time a new 747 cost 50 million dollars, and cost over 80,000 a day in interest payments alone, add it a crew, fuel maintenace, etc. typical operating breakdown was one third of the total life cycle cost was up front purchase, one third crew and maintenace cost, and one third fuel, for total life cycle cost.

    that "useful life" was a debatable number, but some of the 747s are still flying after 50 years. There is no design life of the airframe, but intended to be rebuilt for an indefinite life. In practical terms the maintenance costs get to be very large and it is cheaper to retire an old airframe and buy a new one.

    excess weight means less revenue generating cargo or passengers, plus higher fuel burn for weight that does not benefit the airline. Thus the push for lighter materials, and lower maintenance, lower fuel consumption, most of which eventually benefits boat owners.
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    I can't see it being even remotely accurate. Given the "obesity epidemic" of recent years, if it cost that much to fly another pound, you'd have a billion added over the life of a plane to its running costs, fares would have exploded.
     
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