Prop Choice Help for Custom Electric Motor Pod

Discussion in 'Props' started by antimattercrusader, Dec 29, 2017.

  1. antimattercrusader
    Joined: Dec 2017
    Posts: 1
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    Location: Fort Worth

    antimattercrusader New Member

    I am new to the forum so apologize if this is in the wrong section! Anyway, I have a small business building unmanned boats for survey use. Typically, I use trolling motors or ROV thrusters for propulsion and it works quite well, but for this project I need something with a bit more power. I need to propel a ~60lb 1.5m flat bottom boat to around 8-9 knots. Doesn't sound too hard - but trolling motors lack the RPM range and propeller pitch, no affordable thrusters exist for this speed. So, I've built motor pods using a custom potted brushless motors, mounting tab made from plate aluminum welded to a pipe, and 3D printed hydrodymanic cover/mounting hardware.

    Each pod has around a 2kw (2-3hp) output with a max RPM of around 7000. (Theoretically, of course RPM varies with load)

    Unfortunately, I am not getting much speed at all out of this setup. Only about 3.5 knots @ 50a/1.4kw. While I had an issue with motor timing resulting in not achieving anywhere near top RPM - I feel it wasn't severe enough to justify the lack of performance. I am wondering if the fault is the propeller - The first one I tried is a Young's T-5W (Young's Die-Cast Aluminum Trolling Motor Props for Byrd & Lazytrol Electric Trolling Motors My guess is this propeller has too shallow of a pitch for this type of setup. Does anyone have any thoughts - and any idea of what type of prop I should use?

    I went ahead and ordered one of these to try: but feel the diameter is a bit large.

    Anyway, any input is greatly appreciated, especially with respect to propeller choice.

    P.S. This boat is equipped with voltage/current/power consumption sensors, so I don't risk burning anything up by over propping.
    PPS: This boat has two of these motor pods. It should be way overpowered.

    Attached Files:

  2. jorgepease
    Joined: Feb 2012
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    jorgepease Senior Member

  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Maybe you should try outboard propellers.
  4. johneck
    Joined: Nov 2011
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    Location: New England

    johneck Senior Member

    At what RPM are you looking to run the motor? 7000 RPM is far too high for efficient operation. At 2500 RPM, the optimal diameter is probably about 6".
  5. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    If you can get RPM's down to between 500 and 1000, model airplane props are great.
    Especially the adjustable pitch ones available.

  6. BlueBell
    Joined: May 2017
    Posts: 2,733
    Likes: 990, Points: 113
    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    How'd it go?
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