Wag B-series to AU (MAU)

Discussion in 'Props' started by bblagonic, Nov 14, 2009.

  1. bblagonic
    Joined: Sep 2005
    Posts: 18
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    Location: Croatia

    bblagonic Junior Member

    Guys, I would like to listen your opinion about Kt/Kq multipliers that MacPherson gave on the site.

    It says that the Kt/Kq values read from the diagrams of B-series should be multiplied with 1,07 factor when dealing with AU propeller type, in order to have accurate Kt/Kq.

    Do you use these correlating factors when calculating the performance of AU type props?

    Maybe I`m reading the article in a wrong way and that those multipliers should be used only when dealing with a five blade prop with BAR of 0,8 as mentioned in the article?

    (In attachement you can find the paper. I hope I`m not violating any law posting this paper as far as everyone can download it form hydrocomp site :confused: )
     

    Attached Files:

  2. baeckmo
    Joined: Jun 2009
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    Location: Sweden

    baeckmo Hydrodynamics

    Hi, I am interpreting this report as follows: You use the correction factor for all AU propellers; i.e. when you use a Wageningen diagram (or computer algorithm) you increase the Wageningen values by this factor. It reflects a slightly higher lift coefficient with the AU blade section, which shows in the increase of thrust at a given Ja.

    If the correction had been expressed as a function of Ja, the slight shift in slope could have been better compensated, but why bother about 4 % in the extreme corners of the operating range anyway....?

    BTW, have you located any info on cavitation performance of the AU props? That is critical for your application!
     
  3. DMacPherson
    Joined: Mar 2005
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    Location: Durham, NH USA

    DMacPherson Senior Member

    Posting papers

    No worries posting the paper. However, for the future, it is considered better etiquette to post the link, not the content of the paper.

    BBlagonic's comments are spot on. For reference, the increase in thrust and torque for the AU/MAU propellers are principally due to a larger "nose-tail" pitch as compared to the BS for the same "nominal" pitch (especially large into the root). The KT/KQ multipliers are a quick way to allow you to use the BS (or other) series predictions to correlate a non-series propeller.

    Regards,

    Don MacPherson
    HydroComp, Inc.
     
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