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Thread: prop and rudder help

  1. #1
    Join Date
    Jun 2011
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    Ta
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    Default prop and rudder help

    Hi guys, im a bit of a newbie to rc boats. i need a bit of help. i am building myself a scale replica of a aluminium trailer boat its going about 53" inches long and roughly 19" wide and 21" high at the cab. i am planning on pulling my mamba monster 2200kv brushless motor and esc out of my rc truck and putting in it. i will probably be running 6s and 4s set up in it, my question is what size rudder should i be putting on it , prop, etc i am not wanting any crazy speeds just a bit of fun , and reliable, cheers Rob



    this is a couple of pics of what im building and progress so far!
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  2. #2
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    Jun 2011
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    Ta
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    Default

    any help plz guys

  3. #3
    Join Date
    Sep 2012
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    Tg
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    Default

    To be fair the motor you have would be a tad small in a boat that size and heavy. What sort of drive system were you thinking of, submerged or surface?
    NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
    2016 SUHA Q Sport Hydro Hi Points Champion.
    BOPMPBC Open Mono, Open Electric Champion.

  4. #4
    Join Date
    Jun 2011
    Location
    Ta
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    Default

    Not sure yet maybe submerged. its either that brushless motor set up or I go with a 50cc 2 stroke motor I have. im not out to break any speed records just something fun to play with?
    any help would be much appreciated
    Cheers Rob

  5. #5
    Join Date
    Jun 2020
    Location
    NT
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    Default

    Hi Rob I am also building a boat similar size, was planning on using a 50cc 3HP engine, what prop did you end up using? a 74mm 4"P?

  6. #6
    Join Date
    Sep 2007
    Location
    CA
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    1,707

    Default

    If a 3 hp motor will work in that application, let's try reverse-engineering an electric system. 1hp is roughly 750 Watts, so 3 hp = 2250 Watts. Watts are Volts times Amps. A 6S battery will be about 22 Volts, so you need a motor that is happy at a tad more than 100 amps continuous to have similar power. Perhaps two geared motors running 50 amps each would work.
    A nation of sheep breeds a government of wolves

  7. #7
    Join Date
    Sep 2012
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    Tg
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    Or if you go to 10s then you can reduce your current draw further. I have a 45" boat with a TP 4070 440 kv motor. On a Prather 245 it will pull around 50-60 A at around 65kph. I can run on 12s also and prop up for more speed (ABC 2314/4) to bring me up around 80kph. The motor is paired with a Seaking 130 HV esc. I would expect if were to run this setup submerged you would be running props in the 47-50 mm size but low pitch.
    So as a suggestion, the seaking 130 hv esc with a leopard 5692 540 kv in either surface or submerged drive, prop to suit. Bear in mind that you have a large and heavy boat, but if you peed expectations are in the scale speed range then current draws should be reasonably low and run times good. 10s 2p could give you 10 mins or so.
    NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
    2016 SUHA Q Sport Hydro Hi Points Champion.
    BOPMPBC Open Mono, Open Electric Champion.

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