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Paddle Wheel Boat Mk2

September 6th, 2015 Leave a comment Go to comments

A paddle boat fitted with paddle wheels and SBrick. Features a two independently controlled motors.


Completion date: 01/09/2015
Power: electric (Power Functions)
Dimensions: length 51 studs / width 64 studs / height 22 studs
Weight: 1.305 kg
Suspension: none
Propulsion: 2 x PF XL motor
Motors: 2 x PF XL motor

This boat was built for two purposes: to test paddle wheels that were more complex than these from my first, very crude paddle wheel boat, and to test the new app for SBrick: SBrick Simple Control.

The boat stayed afloat thanks to two #54100 LEGO hulls joined side-to-side, with two PF XL motors driving one paddle wheel per side, mounted on extended booms, with the idea being that extra space between the wheels and the hulls would keep the deck dry. The wheels were connected to the motors directly, without any gearing, and I have used PF XL motors after PF L motors proved to struggle rotating the wheels this large in water. There was a single PF 8878 battery and a single SBrick sitting on top of the motors.

The key feature of the boat  were the wheels, much more advanced than the ones I’ve used before. Each wheel had 8 paddles made of 6 x 10 plates, and a total diameter of 24 studs. The center of the wheel was heavily reinforced, to the point where it could hit a wall and stay in one piece, because I was afraid that if any of the wheels came apart when on a lake, the boat would be lost. Having done some research on effective use of the paddle wheels, I have made sure that the wheels’ angle of immersion was close to the recommended 60°.

When tested on the lake, the boat proved slower than it seemed to be in the bathtub, which may have to do with water, which was visibly full of algae and thus perhaps denser. Its speed seemed slightly higher than that of my first paddle wheel boat, if not equal. It was very manoeuvrable, thanks to being wider than longer and thanks to SBrick’s speed control. A major flaw, which nearly caused the boat to sink on the first run, was that wheels’ momentum pushed stern deeper into water. This wasn’t very problematic when going straight, but when making a turn at full speed the outer side of the stern would actually go under water. This forced me to do all maneuvring slowly and carefully, and go at full speed only perfectly straight. This was clearly caused by placing the wheels near the center of the hulls’ length, and would be certainly negligible if the wheels were closer to the stern. Additionally, there was some minor water splash all over the deck, even over the motors and the battery. It seemed to be caused by paddles exiting water and the amount of water they were lifting, being fixed at straight angle to the wheel. A feathering paddle wheel, in which paddles exit water at angle and very little water is lifter, would have most likely limited the splash severely.

The boat was generally a disappointment. For all the complexity of its wheels it performed only a little better that its much cruder predecessor, and the massive wheels proved dangerous to everything that was on the deck, and to the boat as a whole. I suppose this proves that traditional propellers are a better method of propulsion after all – and certainly a safer one.


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  1. Ev3fan
    September 6th, 2015 at 21:11 | #1

    Very good job with the Paddle Wheels :). Wonderful pages like this help a lot I guess
    Thanks a lot for linking that here without you I’d never found it 🙂

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