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Thread: Total Pitch

  1. #1
    Join Date
    Sep 2013
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    NJ
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    141

    Default Total Pitch

    When walking up sizes of props, do most of the experienced racers out there walk up their props via total pitch? If all variables are equal (boat weight, C rating, esc rating, running gear); how does amp draw increase between 2 and 3 blade? If I had an ABC 1914-10-50(2) and an ABC 1914-15-60(3), which would be worse in case of amp draw? I assume the rake difference is directly related to the number of blades, but both these props have the same total pitch (2.66). Or, is it just a matter of corner handling? Application example would be for a GP400 hydro. Any guidance would be appreciated.

  2. #2
    Join Date
    Apr 2007
    Location
    AZ
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    7,633

    Default

    - Rake has nothing to do with the number of blades, it refers to the angle of attachment to the prop hub.
    - The higher the rake value, the lower the lift of the prop and the more efficient it is.
    - The three-bladed prop listed will have considerably more amp draw due to the greater number of blades and the larger area of each blade.
    - A common use for 3-bladed props is to reduce the prop diameter (minimizing prop walk) without reducing thrust.


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  3. #3
    Join Date
    Sep 2013
    Location
    NJ
    Posts
    141

    Default

    So, to follow up; eliminating 3 blade props, when or rather how do you determine to increase total pitch? Is it via diameter only, pitch of blade or combination? I ran my rig today with a small x445. T180 (its all I had), 6s2p turnigy heavy duty 5000 ma, TP 4060 1350kv. Ran for 2 minutes. 50.6 avg mph on the GPS. 55% remaining in batts. 108 esc temp, 109 motor temp, 115 connector temp, 95 batt temp. Props I have are: ABC 1815, ABC 1914(3), M645, X648, X452, and a CNC 5016.
    I'll try the 1815 next. But is it the right incremental choice?

  4. #4
    Join Date
    Apr 2007
    Location
    AZ
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    Default

    No such thing as “total pitch”. Pitch is pitch, it is a numerical value independent from diameter, rake, etc. Diameter determines the size of the thrust cone of water, combined with pitch determines the volume os water moved. Both overall thrust and pitch speed are important. A tiny diameter prop with lots of pitch will not move enough water to move a boat efficiently. A large diameter prop with a small pitch won’t give high speed.

    Ideally you find an appropriate diameter prop, then incrementally increase pitch until you reach the speed/amp limit. Other than relying on the experience of others (valuable!), you have to find a balance between enough diameter and the pitch required to reach your speed goal.


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  5. #5
    Join Date
    Jul 2016
    Location
    IL
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    2,831

    Default

    Quote Originally Posted by Fluid View Post
    No such thing as “total pitch”. Pitch is pitch, it is a numerical value independent from diameter, rake, etc. Diameter determines the size of the thrust cone of water, combined with pitch determines the volume os water moved. Both overall thrust and pitch speed are important. A tiny diameter prop with lots of pitch will not move enough water to move a boat efficiently. A large diameter prop with a small pitch won’t give high speed.

    Ideally you find an appropriate diameter prop, then incrementally increase pitch until you reach the speed/amp limit. Other than relying on the experience of others (valuable!), you have to find a balance between enough diameter and the pitch required to reach your speed goal.


    .
    gold right there
    Vac-U-Tug Jr (13mph)

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