Fabric Covered Control Surfaces

Discussion in 'Aviation' started by silence, Aug 13, 2013.

  1. silence

    silence Active Member

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    It looks like many planes of WW2 had fabric-covered control surfaces, even when the rest of the plane was all-metal. Why do this and not make the control surfaces metal also?

    I also read that wooed propellers such as that on the Doras were fabric-covered. Again, why?
     
  2. swampyankee

    swampyankee Active Member

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    Fabric is light, and it makes it easier to balance the control surfaces. For the propellers, it's probably because the fabric will protect the surface from damage.
     
  3. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    #3 FLYBOYJ, Aug 13, 2013
    Last edited: Aug 13, 2013
    The lighter the control surface you have, the lighter the control surface counter balance you need to prevent flutter. As faster aircrft were produced, fabic control surfaces would "balloon" under certain conditions.

    The fabric covering of props was introduced to help prevent blade errosion from dust, flying grit and rain etc. It also keeps moisture from delaminating the prop.
     
  4. mike siggins

    mike siggins Member

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    an oldtimer told me that the metal control surface could jam from bullet damage where the bullet would pass threw the fabric and keep going
     
  5. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Far stretched comment, LOL! Where will it jam? Fabric surfaces have similar if not the same moving parts as a metal surface.
     
  6. davebender

    davebender Well-Known Member

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    20mm mine shell will explode and rip fabric to shreds. Tough on aluminum too but I would expect metal to be more resistant to shrapnel and blast damage.
     
  7. Civettone

    Civettone Active Member

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    I am not sure a 20mm shell would explode when it hits fabric ...



    Kris
     
  8. bobbysocks

    bobbysocks Well-Known Member

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    thats one for mythbusters to check out... good question.
     
  9. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    I don't know how much pressure would set off an exploding shell but I can tell you that fabric on WW2 aircraft control surfaces is pretty thick and taunt, I have data in some old text books and manuals indicating how strong fabric should be on higher speed aircraft.
     
  10. bobbysocks

    bobbysocks Well-Known Member

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    i just recovered an elevator with some top of the line stuff. its is tight and thick as a drum head. i imagine i could poke a hole in it with a pencil where as i could never get through a piece of .020 ac grade aluminum. then again ww2 stuff might have been way heavier and stiffer. idk, i guess a lot would depend on how sensitive the detonators were on 20mm rounds. FlyboyJ...they test fabric with a poke test....what is the weight or measure they use to fail the fabric?
     
  11. Jabberwocky

    Jabberwocky Active Member

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    #11 Jabberwocky, Aug 13, 2013
    Last edited: Aug 13, 2013
    Control surfaces of WW2 fighters could be fabric (cotton, linen and occassionally canvas), wood, aluminium alloy, or even other metals like steel. Doped, stiffened fabric had been the traditional material of choice for ailerons and rudders and it was used on the majority of WW2 fighters.

    Problems came at high speed, when the airflow caused the aileron fabric to bloom/distort off the frame. Spitfire, F4U, P-47 and 109 pilots all reported this problem.

    I know the Spitfire transitioned to metal ailerons in 1941, resulting in both an increased peak rate of roll (from about 75 deg sec to about 90 deg sec peak) and a generally higher rate of roll above 220-240 mph. Several other fighters (P-47 for sure) transitioned to metal skinned ailerons through the war.
     
  12. gumbyk

    gumbyk Well-Known Member

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    The shear strength characteristics of modern fabrics is quite different to cotton/linen that would have been used in WW2. This is why the FAA AC 43-13 (the universal repair info) states that 'mechanical devices are not applicable to to glass fiber fabric that will easily shear and indicate a very low reading regardless of the true breaking strength'
     
  13. nuuumannn

    nuuumannn Well-Known Member

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    Irish linen was the predominant fabric used in aircraft construction, or mandapolam. These days, Ceconite is the preferred material and it is still used in modern aircraft to cover litening holes in control surfaces. I remember balancing flight controls of C-130s, P-3s and things and fitting pre-cut patches over the litening holes.
     
  14. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    Two tests are generally done, a punch and pull test.

    Here's some good bathroom reading, I don't feel like typing, just had my third beer tonight...

    http://www.faa.gov/regulations_poli...raft/amt_airframe_handbook/media/ama_Ch03.pdf


    Canvas was not a "normal" covering. It's too heavy
     
  15. bobbysocks

    bobbysocks Well-Known Member

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    nice...thanks.
     
  16. nuuumannn

    nuuumannn Well-Known Member

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    Surprised you're on the computer at all, Joe! That's a dedicated mod, does it whilst settling in with a brew!
     
  17. N4521U

    N4521U Well-Known Member

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    Not sure about WWII.

    I wrangeled myself into the Wood Fabric and Dope section of the A&P school years ago when the A&P school was doing the museum non-airworthy aircraft control surfaces for school projects. I was doing sign painting for the museum and they got me into the class, unofficially, so I know "just enough to be dangerous".

    We used seconite and Irish linnen thread for stitching, and patching cuts and tears. Every rib is stitched with a prescribed spacing, leading edge to trailing edge of wing, or control surface. Where prop wash and air speeds are faster over the fabric surface, the stitching spacing is at least halved. A strip of fabric about 2" wide, with the edges and ends "pinked" are "doped" over the stitching of ribs and patches. The leading edges of wings and control surfaces are "padded" with cotton before covering. The whole of the perimeter of the wing or control surface has a "second covering" of a pinked tape doped over the doped wing cover. The stitching and knotting and spacing requirements are very precise.

    It's a blast to do. Something anyone interested in aircraft should have the chance to try.
     
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