Metal wing skins over wood ribs and spars?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by SVSUSteve, Mar 29, 2015.

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  1. Mar 29, 2015 #1

    SVSUSteve

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    A discussion about WWII aircraft came up over drinks tonight and the topic of conservation of resources was brought up. The question was put to me whether anyone had tried a wooden spar and ribs configuration with metal over it. I couldn't recall any such design but do recall hearing of the reverse (wood over a metal frame) although the specifics escape me. Anyone have anything further to add? I told my friends that I'd ask my homebuilder friends because I figured if anyone knew about oddball designs, it would be you guys.
     
  2. Mar 29, 2015 #2

    BoKu

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    I think that the big issue is the disparity between the elastic modulii between wood and metal. I thought about making the HP-24 wings using carbon fiber spars and metal skins, but I would have had to make the spars twice as stiff as otherwise necessary in order to prevent the skins from reaching their yield strength at or below limit load.
     
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  3. Mar 29, 2015 #3

    TFF

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    For an engineer it does not make sense. To an inventor, its something to try. I would bet in the dawn of aviation, someone has done it, and I bet someone has made wooden spars metal ribs and skins. It really is the answer to a question that does not need to be asked unless desperate.
     
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  4. Mar 29, 2015 #4

    bifft

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    I haven't heard of that for wartime resource conservation. I have heard of people replacing fabric with aluminum for lower maintainence. Japan did build several wooden models of metal aircraft toward the end of the war, but I think they were all wood.
     
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  5. Mar 29, 2015 #5

    ScaleBirdsScott

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    I think if you're going to skin everything with aluminum, the material used to cover that surface area eclipses that of the ribs and bulkheads by a fair margin: the conservation effort is likely better served the other way: metal frame, fabric covering, or back to wood and fabric. Both of which, many examples in WWII were made with success, and where there is no hard issues due to differing materials.
     
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  6. Mar 29, 2015 #6

    Tiger Tim

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    Plenty of bush planes have been metalized. Does a Norseman have wood ribs? I know their spars are wood (probably enough wood in a set of them to build a whole Piet) and if the ribs are too then there's your answer.
     
  7. Mar 31, 2015 #7

    Aesquire

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    Some of the Yaks & Migs had metal spars and plywood covering, some wood with metal covering, as well as all wood & all metal.... depending on the day & model.

    I had a very interesting talk with a Russian WW2 pilot a few years back at the Geneseo air show.

    He said the expected life of a fighter in combat was days or weeks at best. So durable construction was ignored in favor of production.

    He was P-39 & Yak ace. I told him my history books told me the P-39 was used for ground attack because of the limited ceiling. ...

    He laughed at that. . Told me they used the Airacobra for escort, air superiority, and occasionally bombing. He praised the cannon for its one shot kills on bombers & fighters, loved the maneuverability, that they came with radios, and concluded " if we'd flown them like the Americans told us we'd all be dead." Fast slashing attacks on the Me-109's worked much better. All his combat was at low altitude, often under 1000 meters and often at tree top level, where the Airacobra ruled.

    He also loved the Yaks and finished his career in Mig-21's.
     
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  8. Mar 31, 2015 #8

    ScaleBirdsScott

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    Yeah I doubt high altitude work was a significant factor for Soviet fighter pilots in WWII.

    I often wonder what the dynamics of guns and cannon vs aircraft are. What situations are the primary 'death blow' to a fighter? Is it taking out the engines via foreign object at high velocity? Damaging the spar such that it shears? Puncturing a semi-monocoque fuselage with enough superfluous lightening holes that it eventually separates? Are there any good papers or resources discussing the actual mechanics behind aircraft being hit by various machine-guns that is more than anecdotal? I see viddeo footage showing all sorts of things happening but there's also many tales of airplanes being shot all to pieces and still flying home, sometimes after taking out the poor pilot who shot first. I would be curious if there have not been tests done of what various armaments do to aircraft, and what the reports say about the most effective ways guns take out aircraft tend to be: and if certain designs of aircraft were more or less vulnerable due to their designs.
     
  9. Mar 31, 2015 #9

    SVSUSteve

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    One of the guys who attended the church I attended as a child (I didn't convert to Judaism until I was an adult) was one of the aerodynamics guys on the P-39 project as a young man. I remember him telling me about how they used to get letters from Russian pilots who loved the aircraft for the reasons you describe.
     
  10. Mar 31, 2015 #10

    JamesG

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    WWII aircraft airframes were mostly empty space, even the structures. Poking small holes in it didn't do much. They were always hunting around to hit something important like engines or people. This is why aircraft guns rapidly increased from rifle calibers up to large numbers of heavy machine guns and cannons firing explosive shells that could chew thru and break apart the airframe and cause structural failure.
     
    Last edited: Mar 31, 2015
  11. Mar 31, 2015 #11

    SVSUSteve

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    I don't know of anything formally published. Years ago, I talked to one of the RAF pathologists who served during WWII. He said at his station at least, they would perform autopsies on fatally injured German pilots (and on the killed RAF pilots as well) when possible. From what he told me, he said that a significant number of the aircrew (his exact wording was "most") had suffered gunshot wounds from the attacking aircraft or AAA. I would think that if the issue was simply a matter of structural failure or engine failure that, except at very low altitude, most of the time the pilot would bail out.

    I can ask my contact at the RAF Centre of Aerospace Medicine if they have any records from WWII to this effect.
     
  12. Mar 31, 2015 #12

    Highplains

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    I think that the deHavilland Hornet wing was a wood/metal design
     
  13. Mar 31, 2015 #13

    ScaleBirdsScott

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    That seems to make the most sense. The squishy creature holding the stick is ultimately the undoing of many aircraft. Like with tanks, where a hull penetration wouldn't do anything to the core mechanics of the tank but humans would not react well to spalling and/or explosions. Yet plenty of footage I've seen does show of planes bursting into flames, parts coming off, and generally unfortunate things happening of a structural nature.

    I'd suppose cannon with explosive warheads would be a cause of a lot of that.

    Interesting, I kinda thought maybe that could be a case as I remember that had wood in it.

    Did any of the early jets using wood (like the Volksplane) have metal over wood situations?
     
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  14. Mar 31, 2015 #14
    I agree. The question is not "if", but "why". It makes no sense structurally, and it creates a whole bunch of new problems to solve.
     
  15. Mar 31, 2015 #15

    SVSUSteve

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    That was kind of my thought on the matter. However, I told them I would ask so thank you everyone for your input.
     
  16. Mar 31, 2015 #16

    Highplains

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    The limited research I did, said that the bottom skin on the DH Hornet wing was metal with the rest of the wing built from wood. They had some special glue for bonding, plus the lower surface would not be in direct sunlight so that might also some impact on their design decision.
     
  17. Mar 31, 2015 #17

    Turd Ferguson

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  18. Mar 31, 2015 #18

    PTAirco

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    We've all seen this one before - he's not building a wing, he's building a delusion.
     
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  19. Apr 10, 2015 #19

    Dart

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    In the BC aviation museum, on Vancouver Island, there's a restored aluminum skin over oak frames, mini seaplane

    British Columbia Aviation Museum

    The Eastman E2 Searover


    Unique to Canada and British Columbia, and the only example left in the world, it is one of 18 designed and built by Tom Towle and Jim Eastman of Detroit Michigan, and one of five used in British Columbia for many years. The aircraft displayed here has been restored by using the remains of two Sea Rovers, CF-ASY and CF-ASW.
     
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  20. Apr 10, 2015 #20

    bcguide

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    That is a great museum. If I rember right the pulled the searover ot of a garbage dump.
     

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