Whats the deal with Soviet Wing design?

Discussion in 'Aviation' started by Ottobon, Oct 3, 2015.

  1. Ottobon

    Ottobon New Member

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    #1 Ottobon, Oct 3, 2015
    Last edited: Oct 3, 2015
    Just looking at some soviet aircraft of wwii the most distinctive feature is the diamond wings, which basically all of their fighters seemed to feature.

    Any idea why the soviets were so obsessed with this tapered design? and any idea what the big benefits and disadvantages of it were?


    I don't know anything about it but it would seem to be a good design for helping with roll rate, and from the very basic i have read on aerodynamics i would assume that it would be one of the better designs for reducing induced drag (during turns), if not as good as a pure elliptical design, but these are simple guesses and i'd love to know more from somebody who has studied aerodynamics a bit more.


    Just for reference:

    la-5.gif

    MiG-3vu.jpg

    yak3_3v.jpg
     
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  2. fastmongrel

    fastmongrel Well-Known Member

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    What I know about aerodynamics could be written on the back of a stamp with a Sharpie pen. Is it possible the Soviet Air Ministry or even Stalin just liked wings with that plan and coming up with something different could mean a knock on the door at midnight.
     
  3. drgondog

    drgondog Well-Known Member

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    #3 drgondog, Oct 4, 2015
    Last edited: Oct 4, 2015
    That planform has advantages - first the taper ratio is empirically near enough to an elliptical planform that the Induced drag is only slightly higher. Typically fighters had between .3 and .5 Tip to Root Chord Ratio. Second, it is nearly ideal when planning for structural integrity, requiring a thick root chord but easy to design spar combinations to reduce weight. It also has a tendency to 'pull' the lift distribution inboard - another desirable feature for structural design to reduce bending moments due to lift distribution.

    It is also very easy to plan for and execute manufacturing process

    However, the more you taper the more susceptible to tip stall which requires either wash out wing twist or LE devices to decrease safe landing speeds.
     
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  4. fastmongrel

    fastmongrel Well-Known Member

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    IE devices ? drgondog can you tell me what that means thanks
     
  5. drgondog

    drgondog Well-Known Member

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    meant to write LE for leading edge devices (such as slats)
     
  6. Koopernic

    Koopernic Active Member

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    #6 Koopernic, Oct 4, 2015
    Last edited: Oct 4, 2015
    That is quite possible. The totalitarian ideology present at the time interfered directly with scientific ideas (For instance, Darwinism represented a potential threat to Communist ideas in that it might mediate that human nature was somewhat a matter of nature rather than a pure product of socialisation so the Lamarckian ideas of Lysenko were promoted and Darwinists who didn't believe that 1+1=4 knew they would end up in the Gulag). I know of one incidence of communist interference in engineering and manufacturing: in Eastern Germany one reason they kept producing 3 cylinder 2 stroke cars known as Trabants is because any radical improvements (such as 4 cylinder 4 strokes) would suggest that the original planners had made bad choices and such revolutionary improvements might be, well, counter revolutionary. It sounds absurd but these people had kindergarden teachers pass on notes to the Stassi about what TV shows had been watched by the children and thus in the household. It's worth noting we still have this problem with Darwinism in western polities as well.

    More likely the proponents of these tapered plan form had more political clout and those with alternative ideas simply backed away. One can imagine a well connected proponent in the TsAGI as even bombers were effected by this fashion.

    The highly tapered wing planforms used by the Soviet fighters would have had the following characteristics:
    1 Highly tapered planforms stall at the tips first and so need a high degree of twist to avoid premature tip stall near the ailerons and the resultant poor spin stall.

    It's worth noting that the Soviet fighters such as the MiG 1 and MiG 3 had problems in this area. The La and LaGG series seem to have overcome it only with the use of automatic slats.

    For the record the stall characteristic of basic planforms are
    a/ rectangular, excellent: stall develops at the roots and progresses out to the tips. Wing twist may not be needed.
    b/ tapered, stalls first at the tips, wing twist or slats definitely needed
    c/ elliptical, stalls simultaneously at all points of the wing, moderate wing twist needed.

    2 These highly tapered wing planforms might have been easier to produce given the thickness of the spar at the roots and the space for fuel and undercarriage it might provide.

    The Spitfire's elliptical plan form had less need of aerodynamic twist than the tapered plan form of most other fighters yet it in fact had as much if not more (Approx 2.25-2.5 degrees compared to the 2 degrees common in other aircraft)
     
  7. GrauGeist

    GrauGeist Well-Known Member

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    You're pretty close with that.

    The Soviets were caught up short at the start of the war, so there was a rapid succession of changes to the airframes, trying to not only keep the Germans at bay, but almost as important: keeping Uncle Joe happy.

    When Kalinin's designs failed (and crashed, killing several), Stalin was unhappy. Therefore, Kalinin was "removed" - permanently.

    The difficulties with the LaGG-1 and LaGG-3 caused great displeasure with Uncle Joe, nearly costing Lavichkin more than his aircraft facilities (which were handed over the Yakovlev). Lavochkin, now working in a tiny hut on the edge of an airfield, managed to save himself by taking a LaGG-3 and placing the nose of a Su-2 (ASh-82 radial and all) onto the LaGG's frame. The result was a game-changer, the La-5. Not much else was changed, so there's no surprise that the La-5 looks a great deal like a LaGG-3 (wings and all). Of course, now that Lavochkin saved his hide and got Uncle Joe smiling again (it is good when Uncle Joe is happy), he was able to go on to take the La-5 to the next level: the La-7, which did go through several changes to improve on the La-5.

    So if a large number of the early war Soviet aircraft looked similar, it's because in many cases, they were directly related.
     
  8. Koopernic

    Koopernic Active Member

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    One thing to note about Soviet aircraft production is that the organisations that designed the aircraft did not also produce it. There were design burro and there were factories that were quite independent.
     
  9. Timppa

    Timppa Active Member

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    Wooden wings were heavier than all metal -ones. I guess that lower taper ratio was chosen just to save weight.
    De Havilland aircraft (DH. 88 , Mosquito, Hornet) also have low taper ratio.
     
  10. Milosh

    Milosh Well-Known Member

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    I like the play on words. A burro is a small donkey.
     
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  11. gumbyk

    gumbyk Well-Known Member

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    These wings would have been much easier to produce than spitfire wings. Each spitfire wing skin is a compound curve, rather than a simple flat sheet bent around the leading edge.
     
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  12. GregP

    GregP Well-Known Member

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    #12 GregP, Oct 5, 2015
    Last edited: Oct 6, 2015
    Good point.

    A lot of the design aspects of Soviet aircraft were done to adapt for harsh climate conditions and the use of unskilled labor being for maintenance.

    I daresay the wings could easily have been designed for ease of manufacture by unskilled labor, too.

    Actually, when I say "unskilled," I mean rural farmers, not completely inept people. Most rural farmers are pretty good at fabricating and inventing things because there is nobody to help them. They either figure it out or do without. A guy like that can easily get you into trouble by being inventive on an aircraft structure. Most aspects of the aircraft must be as designed or the strength calculations are out the window.

    A number of Soviet prototypes crashed under strange circumstances, sometimes by inflight breakup, and I have often wondered if that might be due to deviation from plans by inventive-but-untrained rural farmer-type labor used for construiction of prototypes.

    I've never seen a Soviet book or article that addressed the many strange crashes with any indications they might have actually looked into the crashes. Of course, information was government property in the former Soviet Union, so maybe the information was simply never dissiminated.
     
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  13. gumbyk

    gumbyk Well-Known Member

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    Yeah, particularly when you think that original spitfire wings would have required an English wheel to manufacture. Having tried an English wheel - I've got a real appreciation of the skills involved with the manufacture of the aircraft. There isn't a straight line on a spitfire wing.
     
  14. GregP

    GregP Well-Known Member

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    #14 GregP, Oct 5, 2015
    Last edited: Oct 5, 2015
    I own one and would not want to try to make 2 identical parts on it, either. Great for one-off prototypes. Lousy for production work.

    English wheeling might get better if you become expert at it, but it isn't going to go fast no matter what you do. I'm sort of OK at it, but clearly no expert. At least I can remove dents and things with it, and do planishing without work-hardening the Aluminum ... most of the time. Sometimes it DOES work-harden the Aluminum. When that happens, I start again and hope for better results.

    I've never tried wheeling with -O Aluminum because there's much too great a chance of ruining the soft stuff in big pieces before it gets into a big oven. Our heat-treat oven is small, so I mostly only do small parts I can heat-treat myself.

    I watched one of Steve Hinton's guys wheel new landing gear doors for a Tigercat and it was a thing of beauty to watch. They looked factory new! His guys are pretty good at Aluminum work! I'm OK for most normal things, but have a lot to learn about forming strange new shapes in Aluminum without generating some new baby scrap pieces.
     
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  15. tyrodtom

    tyrodtom Well-Known Member

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    One thing wrong with your theory, the Trabant was a TWO CYLINDER 2 stroke, not 3 cylinder, the very late production models, 89 and up, had 4 cylinder VW Polo engines.
    Several car companies made 3 cylinder 2 strokes, Saab, DKW, just to name two, and many motorcycle makers come out with 3 cylinder 2 strokes.
     
  16. Koopernic

    Koopernic Active Member

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    The "Berlin Wall" fell just after August 1989 and production of Polo engine versions started well after this in 1990 making it German rather than East German production.

    Admittedly it was the result of trade agreements developed in 1989; it was late in the piece as Eastern European communism was a rotting carcass clutching at straws. I've ridden in a Trabant, picked up from a train station, when Eastern Germany was still under communist domination. I recall the machine gun toting guards confiscating packets of coffee people were carrying to relatives. No, I don't think the cylinder count is substantive to the story. Ideological and political interference hamstrung any progress on the basic design.

    The factory where they were produced once belonged to the "Auto Union" which became Audi. One of the directors and founding partners of Auto-Union, Horche, stayed on in communist East Germany out of parochial loyalty but the regime just kept restricting him in many ways, for instance in the number of employees he could have etc. till it folded. West Germany ended up with a monster like Audi, East Germany with a sick little Trabant which showed little improvement in 30 years.
     
  17. Koopernic

    Koopernic Active Member

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    I think the Spitfire wing ended up being rather easy to produce once large stamping presses were established, there may have been some issue with modifying them after that since the Mk IX was mainly produced at Castle Brownwich but I doubt it was much of a problem. Somewhat ironically the Me 109E wing was rather hard to mass produce as it had been designed to be manufactured by multiple small scale subcontractors and then placed in to final assembly. Ease of mass production was one reason the Me 109F series was developed.

    Comprmising aerodynamics and handling for the sake of mass production seldom works out.
     
  18. GregP

    GregP Well-Known Member

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    Elliptical wings are NEVER easy to produce.

    They can get easier than one-off prototypes, but are labor intensive under the best of circumstances.

    Good jigs help a lot, but it still isn't easy.
     
  19. drgondog

    drgondog Well-Known Member

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    The elliptical plan form is the guarantor of minimum Spanwise Induced Drag due to the spanwise circulation. However it does not eliminate stall at the tip due to the upwash from spanwise circulation/lift vortices. Ergo - washout as you noted or LE devices.

    As you know, introducing twist results in a Delta Induced drag so they wanted additional low speed roll control more than they wanted to further reduce induced drag.
     
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  20. tyrodtom

    tyrodtom Well-Known Member

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    #20 tyrodtom, Oct 6, 2015
    Last edited: Oct 6, 2015
    I'm sorry I'm just a simple mechanic and bodyman, when someone can't be bothered to even get the correct cylinder count on a engine, I wonder what other details might be too unimportant for him to get right.
     
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