Inflatable electric kayak

Discussion in 'Projects & Proposals' started by Phil171_Fr, Nov 29, 2021.

  1. Phil171_Fr
    Joined: Jan 2021
    Posts: 2
    Likes: 0, Points: 1
    Location: France

    Phil171_Fr New Member

    Hello Ladies and Gentlemen, ;-)

    I modified a Gumotex Solar 2 seater kayak to be able to be propelled by an electric motor and a battery.
    I adapted a support (homemade) on my kayak, a PWM power variation motor control with forward and reverse gear and battery control, I then adapted a steering control on this motor.
    I am currently in the process of manufacturing a NACA profile to reduce losses caused by the motor support tube and I am considering replacing the original two-blade propeller with a three-blade propeller to chek if I gain in range with a slower propeller.
    The problem is that I am not really an English speaker and apparently cases of electrified inflatable kayaks are quite rare or difficult to find on this forum. I only found rigid kayaks and / or aircraft stepper motors, aircraft propellers and controllers suitable for stepper motors ...
    - How to find these entries easily> kayak + inflatable + electric?
    - Are there on the forum kayaks (inflatable or rigid) propelled by boat propellers that can cut algae or underwater grasses, because the (big) problem with airplane propellers is that they turn slowly and don't really have a cutting power to shear weeds ... I once got stuck with a propeller full of weeds ...
    Thanks in advance,
    Philippe, from France.

    Kayak Gumotex Solar
    Modified Minn Kota Classic 30 Lbs engine
    PWM Drive Forward / Stop / Reverse
    Battery monitor A, Ah,%, V
    40 Ah LiFeYPO4 battery
  2. Skyak
    Joined: Jul 2012
    Posts: 1,359
    Likes: 92, Points: 48, Legacy Rep: 152
    Location: United States

    Skyak Senior Member

    You don't seem to be getting an answer so I will try.
    -A three blade prop of the same diameter will not improve efficiency unless the two blade had a pressure problem -highly unlikely. There may be some improvement in a two blade prop that has a larger diameter or more appropriate pitch.
    -The greatest source of inefficiency in your setup is the eddies and wetted surface of the inflatable hull -speed x drag = waste energy. Trolling motors are typically brushed DC -they have very specific speed, voltage, current, efficiency peaks. Your PWM fixes the wasteful control but the setup still might simply be operating in a range that is not efficient.
    -I presume you looked up efficient electric kayaks and found hard shell kayaks driven by brushless electric motors with model plane props that are dramatically better than your setup. You are looking to take some bit or piece to improve your setup. My advice is that unless you intend to replace the hull you are working with, the improvement will not be worth the investment. Check the prop pitch and the motor efficiency to see where you stand. There might be a different prop and a different voltage you could run to gain significant range. Other than that, the key to your inflatable boat efficiency is go slower...

    For easy, appropriate learning about electric kayak efficiency I recommend William Frasier's youtube channel.
  3. Phil171_Fr
    Joined: Jan 2021
    Posts: 2
    Likes: 0, Points: 1
    Location: France

    Phil171_Fr New Member

    Thank you for your answer, it gives me additional information and highlights the problems of the inflatable kayak, problems that I suspected, alas.
    - I ordered a three-bladed propeller, it's not too expensive and certainly not optimized for my motor, but for the price it will be an economical test, hoping it will be of good manufacture ... I eyed big brand propellers like Torqueedo, but the price got me back.
    - I understood (while sailing) that the big problem with the inflatable kayak is its wet surface, very sensitive to the load (especially if I am alone or with two on board ...). The trim of the boat changes, and so does the performance.
    - I was able to test before and after installing the PWM controller, the energy efficiency is good up to a range of 50% power, after that the efficiency decreases, normal. But as I try to prioritize the performance, the longevity of the battery, that does not bother me too much at the moment.
    - I understood that on an inflatable kayak, the investment must be reasonable and measured (even if the price of the LFP battery is significant). I try little by little to improve my system without going so far as to try to fit a stepper motor in place of the Minn Kota. I also realized that I should have bought a more powerful motor which would have had better performance at the requested speeds and in terms of electricity consumption.
    - Regarding the eddies, I try - at least - to calm those coming from the engine support tube by adapting a NACA profile, the 0025 if I remember correctly, it is being manufactured and the tests will be done when the sun returns, it is cold and humid here now.

    I know William Frasier's youtube channel, I really appreciate this channel, I also told him that in the case of underwater grasses (weeds ?) and algae, adapting an APC propeller was not a good solution.
    Thanks again for pointing this channel to me.
    Last edited: Dec 3, 2021
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