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Explorer Paddle Boat

My first paddle boat. Features an underwater camera.


Completion date: 06/05/2014
Power: electric (PF system)
Dimensions: length 52 studs / width 56 studs / height 30 studs
Weight: 1.043 kg
Displacement: 1.8 kg
Suspension: none
Propulsion: 2 x PF M motor geared 3:1
Motors: 2 x PF M motor

Having made plenty of experiments with various conventional propellers, and one with an airboat, I decided to try yet another method of propulsion: paddle wheels. I also wanted to experiment with putting a camera under water, preferably on some jib that would move it up and down. However, the GoPro camera with the watertight housing on it proved quite large and heavy in relation to the boat (it alone constituted to about one-sixth of its total weight, and a jib would probably make it even worse), creating a risk of losing stability while moving the jib. I also didn’t see much sense in putting the camera deep under water, expecting very limited visibility, so the boat ended up with fixed camera located just below the waterline.

The boat itself was very simple, with PF system used instead of the RC one for easier steering (RC system makes skid steering difficult, as it has single output for propulsion motors).  I had no experience with paddle wheels whatsoever, and it took me a few takes to figure out that they require plenty of torque – boat variant with two PF L motors geared 1:1 was actually slower. The wheels also proved to splash water all over the deck, which could be remedied by building housings over their upper halves or by separating them from the deck with tall sides. Due to wheels’ size both solutions would be massive, heavy and difficult in transport, so I decided simply to move all the electric elements to the middle of the hull, covering the battery and putting the IR receiver on top of a tall structure. Everything but the receiver ended up with water splashed over it, but luckily all the sensitive areas – plugs and power outlets – remained dry.

The paddle wheels proved fast and efficient propulsion method, but also a messy one. They stirred water a lot, to dismay of some fishermen, they required way more torque than conventional propellers do, and they splashed so much water on deck that I had to empty the boat every few minutes. The underwater camera didn’t really work out because visibility was so low that the recordings looked like diving in a soup. I also lacked any interesting underwater structures to swim over. Clearly, a swimming pool would be a much better location for using such a boat.


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  1. Gavin McLelland
    January 1st, 2015 at 23:30 | #1

    Sariel you could try fitting a Weis Fogh mechanism between the hulls. This exploits the lift generating mechanism used by flies and bees to push the hull forward. Here’s a paper that goes into some of the theory. http://www.tcsme.org/Papers/Vol38/Vol38No3Paper10.pdf

  2. ethan24
    October 22nd, 2014 at 13:13 | #2

    hi paul,
    i am sorry i have not had a chance to look at your work for a while but i am glad to see that you still at it.
    i saw in your video that you seem to be having s problem with water flooding the deck and getting into your motors, and i have a solution to solve it that i once used on one of my first boat and it seems to work well,
    anyway the solution is to use vaseline as a cement on the lego bricks, so maybe you could build a box around the motors using this technique,
    i hope this is a help,
    tell me whether you think it works as it worked for me.

  3. Sariel
    June 5th, 2014 at 09:10 | #3

    Not really. Doesn’t seem worth the complication.

  4. June 5th, 2014 at 02:30 | #4

    Have you thought about designing a boat such as this with a subtractor instead of classic “tank steering”?

  5. May 12th, 2014 at 04:35 | #5

    @Sariel Haha! …Yeah, I should have remembered you have already done this. 🙂 You’re work is great!

  6. EV3fan
    May 10th, 2014 at 10:19 | #6

    Hmm, your boats are really good… maybe someday a bigger version and some detailed stuff like that found on real ships? I’d love that!!

  7. EV3fan
    May 10th, 2014 at 10:17 | #7

    I know it has some serious drawbacks, but it looks qite fast to me in the video… .

  8. Sariel
    May 7th, 2014 at 10:47 | #8

    I would have to develop some custom sails, because LEGO sails are apparently no good.

  9. May 7th, 2014 at 07:38 | #9

    Hi Sariel. I like your boats 🙂 I’m working on a sailboat but it’s not going very well… I’m trying to build a sailboat similar to a Laser (sailboat)… Do you have plans of building a sailboat in the future?

  10. jacob
    May 7th, 2014 at 01:48 | #10

    or make 3 winged paddles or 2 winged paddles

  11. jacob
    May 7th, 2014 at 01:47 | #11

    maybe make the paddles smaller to make less splaches

  12. Sariel
    May 7th, 2014 at 00:57 | #12

    They have lower speed and higher torque, but less torque that M motor geared 3:1.

  13. Alexander
    May 6th, 2014 at 20:51 | #13

    Why was the variant with large motors slower? they have the same speed and higher torque( I think).

  14. Sariel
    May 6th, 2014 at 17:01 | #14
  15. May 6th, 2014 at 16:57 | #15

    Could you make a boat with 2 sets of paddles like this? Front/Back … The idea would be that the boat would work well in water and then be able to crawl onto land.

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