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Thread: Feedback on my first boat design.

  1. #1
    Join Date
    Dec 2018
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    IL
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    Default Feedback on my first boat design.

    Hello everyone, I'm designing my very first RC boat, and I was hoping for some experienced feedback. I plan to 3D print this boat on my Prusa Mk3, including the rudder assembly and turn fins, so I can fully customize its performance. The prop shaft has a downward angle of 5 degrees, and it's connected to the motor via a U-joint which takes a 20 degree angle. I'm still not sure why many racing boats have just one rudder offset to the right, so I figured I'd plan for two, but check if it works with just one. The propeller will be 35mm in diameter, on a 4mm shaft.

    I've placed the battery in the center so the boat will not be inclined to tip to one side, although I realize this may be an overkill solution to a minor problem. As you can see, the yellow line is 1/3 of the hull length from the transom, which is about where the COM will lie.

    The canopy will be held down with four thumb screws, and it will be sealed either with a sqaure-profile O-ring of the right circumference, or I'll just fill the cavity with silicone and let it cure to create a customized rubber-like seal. The canopy has a lip on the underside which will push into the seal when screwed down.

    Motor: https://hobbyking.com/en_us/turnigy-...___store=en_us
    ESC: https://hobbyking.com/en_us/turnigy-...___store=en_us
    Battery: https://hobbyking.com/en_us/turnigy-...___store=en_us
    Receiver: https://www.amazon.com/Spektrum-AR41.../dp/B07GS2S7W8
    Servo: https://www.amazon.com/Hitec-31055S-.../dp/B0006O3WNW

    I may upgrade the battery to a 4S in the future, but I suspect 3S will be plenty powerful for a boat of this size. The ESC is definitely oversized, but it was a good price (and in stock). The motor seemed like a good average size based on similar-sized RTR boats I found online.
    Attached Images Attached Images
    Last edited by Technoid; 12-20-2018 at 04:13 PM.
    - Technoid (Alex)

  2. #2
    Join Date
    Feb 2018
    Location
    PA
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    330

    Default

    I don't think you will need dual rudders on that small of a hull......but I'm sure others will chime in....seems a bit much to me....looks good though..

  3. #3
    Join Date
    Oct 2008
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    ca
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    no dual rudders! It’s not necessary at all because the single rudder offsets the torque effect of the motor... mono’s 101 ... your power system is good but if you want to run 4s I would definitely drop the kv’s down on the motor! If it were me I would be leaning towards 4s so I could have a better time getting “jiggy with it”.....
    "Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction."
    --Albert Einstein

  4. #4
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    Oct 2008
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    I’ll let these go to you because your doing great things 3D printing boats... let me know in PM if interested 720C85D5-96EB-4112-A412-7C952FA27FFA.jpg
    "Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction."
    --Albert Einstein

  5. #5
    Join Date
    Aug 2008
    Location
    CO
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    Nice! I really like the lines. Unsure of length and performance goals, so take the feedback accordingly.

    If it were me, I’d start raising the chine a bit farther back, like at midship to one third back. This will increase the dead rise toward the front and decrease the air lift, also increasing stability in rougher water.
    As is, it will turn too flat and this will cause excess drag and poor stability in turns.
    The rudders are too long and will create significant drag. Only one rudder will give you sufficient turn, especially if there is a higher chine in the front.

    I love designing, so up for providing as much feedback as you like.
    Jesse
    "Look good doin' it"
    See the fleet

  6. #6
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    Oct 2008
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    ca
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    Quote Originally Posted by Jesse J View Post
    Nice! I really like the lines. Unsure of length and performance goals, so take the feedback accordingly.

    If it were me, I’d start raising the chine a bit farther back, like at midship to one third back. This will increase the dead rise toward the front and decrease the air lift, also increasing stability in rougher water.
    As is, it will turn too flat and this will cause excess drag and poor stability in turns.
    The rudders are too long and will create significant drag. Only one rudder will give you sufficient turn, especially if there is a higher chine in the front.

    I love designing, so up for providing as much feedback as you like.
    Jesse
    You do know there is a fellow in CO that has 30 boats for sail , he lives in some country that passes an ordinance against FE and gassers
    "Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction."
    --Albert Einstein

  7. #7
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    Dec 2018
    Location
    IL
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    3

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    Thanks everyone for the feedback so far! Sounds like ditching the dual rudder is definitely a go. As for the deadrise, that will be very difficult to alter given the way I've modeled it, but if/when the boat does turn too flat, I'll defintely re-model it with a variable chine; I would never have figured that out on my own if that ended up happening. And fortunately, I've modeled the motor holder as a bolt-in piece, so upgrading it to a lower Kv for a 4S battery shouldn't be too hard when the time comes.
    - Technoid (Alex)

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