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Spitfire Aboukir filter vs Vokes?

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  • Graham Boak
    Rank 5 Registered User
    • Nov 2008
    • 957

    Spitfire Aboukir filter vs Vokes?

    Does anyone know why the Aboukir filter should be any better than the Vokes one? Both rely on passing the air through a convoluted filter, which removes any of the pressure recovery that could have been expected from a well-designed intake. The Vokes has greater surface area, hence more skin friction drag, but the Aboukir is shorter and squatter which makes for more profile drag. Swings and roundabouts, it would seem. Was the Aboukir filter actually proven better, or was it one of those "invented here therefore must be better" sort of things?
  • QldSpitty
    Rank 5 Registered User
    • Apr 2006
    • 2628

    #2
    From what I gather the Aboukir created a lot less drag in combat conditions.
    "If the C.O. ask's you to be Tail End Charlie...just shoot him!!!....A Piece of Cake.
    http://spitfirea58-27.blogspot.com.au/

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    • Graham Boak
      Rank 5 Registered User
      • Nov 2008
      • 957

      #3
      That's the story - but was this ever tested/proven? Is there any evidence? Even any specific anecdotes other than a general "Well they did it so it must be better"?

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      • batsi
        Rank 5 Registered User
        • Jan 2009
        • 51

        #4
        copied from another forum

        Quoted from Morgan and Shacklady's Spitfire book. This all they have written up about the Aboukir filter

        "The large Vokes tropical intake was not well liked by the services and it was not long before unofficial modifications began to appear, the most successful and designed and installed by that most resourceful team at No. 103 MU Aboukir. They trimmed the filter back to a much smaller unit, one that was more efficient and drag reducing. It was named the Aboukir filter and the Vokes Aero-Vee, fitted to the Mark IX Spitfire, was based upon this local modification. Supermarine was quick to appreciate the lower drag of the modified intake and they tested a number of hand-built units on two VC's and a Seafire Mk. II. The test comprised speed runs with the normal temperate intake, the normal tropical and Aboukir. The VC's were EF541 and JK940 and Seafire NM977, the former with Merlin 45's and de Havilland hydromatic propellors, the latter with Merlin 46's and Rotol Jablo. The new type of cowling was infinitely better of the three tested and there was a weight reduction of 20 pounds. Another bonus was that with the filter element removed the Aboukir could be used as a normal temperature intake."

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        • Graham Boak
          Rank 5 Registered User
          • Nov 2008
          • 957

          #5
          That's a good step forward, although the term "infinitely better" is garbage and not something any engineer would say. Perhaps they just meant "definitely". It still says nothing about the how and why.

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