Racks - how big was the speed penalty?

Discussion in 'Aviation' started by tomo pauk, Mar 30, 2014.

  1. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Most of the ww2 aircraft have had those, mostly from one to three. While being very useful to carry drop tanks or bombs, they imposed some performance penalty. Eg. the P-51C and earlier were slowed down 12 mph by their 2 racks, in the P-51D and later it was only 4 mph through use of modified (and smaller) racks. Any definitive data for other A/C?
     
  2. drgondog

    drgondog Well-Known Member

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    Tomo - I have seen 10mph for P-51D/H racks, what is your source for 4mph?

    Also, the P-51B/C racks were stressed for 500# bomb/75 gallon fuel tank - but D/K/H stressed for 1000# bomb/150 gallon ferry tank. As an 'old structures guy I wonder how a rack that has double the load carrying capability could have a six to 8mph reduction in drag..
     
  3. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Here, Bill, under 'Remarks' column. But then, maybe a person that typed it forget to type '1' in front of '4'?
    Someone of our modelers might check out the rack sizes...
     
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  4. Greyman

    Greyman Active Member

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    #4 Greyman, Mar 30, 2014
    Last edited: Mar 30, 2014
    Typhoon was about 20 mph for bomb racks
    Typhoon was about 12 mph for rocket rails (Mk.III rails)
    Hurricane was about 25 mph for rocket rails (I assume Mk.I rails)
    Kittyhawk was about 12 mph for centre bomb rack
    Junkers 88 was about 5 mph for bomb racks
     
  5. Lucky13

    Lucky13 Forum Mascot

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    Sorry, was thinking about a slightly different set of racks....







    *shuts the door on the way out...*
     
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  6. drgondog

    drgondog Well-Known Member

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    Good find Tomo - first Time I ever noticed the note. Helluva drag difference between 4 and 12 mph
     
  7. davebender

    davebender Well-Known Member

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    I think aircraft size and aerodynamic cleanness matters. A small and aerodynamically slippery aircraft such as Spitfire or Me-109 would probably suffer a significant drag penalty by carrying a drop tank. However external racks would be a drop in the aerodynamic bucket for a B-17 bomber.
     
  8. Milosh

    Milosh Well-Known Member

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    Fw190

    Depending on the wing rack: 9.3mph, 18.6mph, 11.3mph
    ETC 501 7.5mph

    @ climb&combat, 2400rpm, sea level
     
  9. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Just want a confirmation - only 4 mph for four racks?
     
  10. Greyman

    Greyman Active Member

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    #10 Greyman, Mar 30, 2014
    Last edited: Mar 30, 2014
    Yeah the 250kg type it seems.

    EDIT: Good thing you made me look at the test again, my notes were wrong: it's 5 mph
     
  11. tomo pauk

    tomo pauk Creator of Interesting Threads

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    #11 tomo pauk, Mar 30, 2014
    Last edited: Mar 30, 2014
    :)
    Rest assured I'd love to see the tests :)

    Re. P-51s: not sure if this is any proof - but it seems like the braces were permanently attached to the racks of the P-51B (and A, and C?), whle they would be detached by the design used on the P-51D?
    P-51B: http://hsfeatures.com/images/p51bks_8.jpg
    P-51D: http://upload.wikimedia.org/wikipedia/commons/0/03/P-51D.jpg

    Of course, I'd like to ask again our members that are more into modeling to chime in :)

    added: P-51B, seems like in historic trim: http://cdn-www.airliners.net/aviation-photos/photos/7/0/3/1576307.jpg

    added2: P-51D: http://www.worldwarphotos.info/gallery/usa/aircrafts-2-3/p-51-mustang/north-american-aviation-p-51d-mustang-at-dallas/
     
  12. herman1rg

    herman1rg Well-Known Member

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    I think there might be quite an aerodynamic penalty from this large rack

    large rack.jpg
     
  13. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Racks = either penalty, or advantage.
     
  14. CobberKane

    CobberKane Banned

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    I knew a girl like that once. Tragic story - she stood up on the back of a pick-up truck and beat herself to death.
     
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  15. mhuxt

    mhuxt Active Member

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    Ah, the sights and sounds of the good old CNE.
     
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    Glider Well-Known Member

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    Wow, a record 11 posts before the obvious diversion.
     
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    GregP Well-Known Member

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    12 now ... and counting .... er ... 2.
     
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    CobberKane Banned

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    I am disappointed at the infantile tone adopted by some people on this forum who should know better. I suggest that all like-minded contributors switch to my soon-to-be posted thread concerning the RAFs reaction to the first P-47 squadrons to arrive in the UK, tentatively titled: "British pilots amazed by massive American Jugs"...
     
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