LEGO propellers in water: performance comparison & ranking

[Sariel]

I'm sure there are other people besides me who never tire of making LEGO RC boats :) So with these folks in mind, I've prepared a simple comparison and ranking of performance of various kinds of LEGO propellers in water.

Of course, the downside of my test is that for simplicity all propellers are run at the same RPM, despite varying wildly in size. This is to see the differences with some common denominator, but in reality, since small propellers generate less drag and hence need less torque than the big ones, you can spin them much faster with the same motor. This is all a matter of playing around with a gear ratio. I could theoretically try and find the optimal gear ratio for each propeller for a given motor, but then the same motor probably wouldn't be best for all propellers, and besides in my experience propellers perform differently in clean tap water than they do in e.g. a lake.

 

[whitepen]

Nice comparison!

[Sariel]

Aaaand here comes part 2, where I test another 6 propellers, but this time much less common ones:

 

[Gray Gear]

I think some of the propeller's performance suffered from not being fully submerged. Still, interesting comparison.

[Brickend]

Can you see the cavitation in slow motion?