Selecting proper prop

Discussion in 'Inboards' started by mirseyavash, Mar 17, 2008.

  1. mirseyavash
    Joined: Mar 2008
    Posts: 2
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    Location: Iran

    mirseyavash New Member

    i am in the middle of experiencing deigning an rc boat and after searching in Internet for selecting a proper propeller for my boat i can't undrstand how to select one and i even not found any thing about how to do this for this size of boats:
    Legth 1200 mm
    planning hull
    6* LiPo 3.7Volt
    and 2 *1KW brushless DC motors (10,000 rpm) so this boat will have 2 propeller :D

    please give me something like (a formula or standard or sth like this) cause i am going to design this for now and i can't test many prop models

    your help is appreciated

    P.S: by the way does anybody knows that how i can get this book:"Basics of Fast Electric Boats"?
     
    mirseyavash, Mar 17, 2008
    #1
  2. Guest625101138

    Guest625101138 Previous Member

    Weigh the total boat. First approximation of the drag is 1/8th of the total weight.

    Open JavaProp applet:
    http://colaco.freeshell.org/mhepperle/javaprop/jp_applet.htm
    Set the options window to water parameters. Set foils to E193 100,000. and then go to the design window and do the prop design. Finally shop around until you find a prop near to what you have designed.

    You can also use this site to estimate the drag:
    http://illustrations.marin.ntnu.no/hydrodynamics/resistance/planing/index.html

    If you have trouble with this then make a post with more specific question and to data on the boat like weight, beam and deadrise. Will you use gearing or straight of the motors.

    Rick W.
     
    Guest625101138, Mar 17, 2008
    #2
  3. mirseyavash
    Joined: Mar 2008
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    Location: Iran

    mirseyavash New Member

    thanks you very much for your valuable informations
    i would be glad if you have some book or data sheet about the fondumentals rc boat size (little size) propulsion system. :)
     
    mirseyavash, Mar 17, 2008
    #3
  4. Guest625101138

    Guest625101138 Previous Member

    Fondamantals are fondamentals whether it is 2ft long or 200ft long. All that changes is the Reynolds number. But if you are going really fast in a small boat then Reynolds number will be the same as a bigger boat going slower.

    You have everything you need to understand a propeller in JavaProp - just take a bit of time to understand what is in there. It is the best fundamantal approach to propellers you will find.

    Rick W.
     
    Guest625101138, Mar 17, 2008
    #4

  6. pila
    Joined: Mar 2008
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    Location: michigan

    pila Junior Member

    There is also a book titled "propeller handbook" by Dave Gerr, published by International Marine. Lots of information, (and lots of math too).
     
    pila, Apr 18, 2008
    #5
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