We made an RC boat for participating in a National Level tech fest conducted by College of Engineering, Trivandrum. It took us a few days of work scrambling, through the junk in the Mechanical Workshop of our college, to get the boat ready.
Using the same idea used in the acceleration sensor of cars, we connected our BLDC motor shaft to the propeller turned CPU cooler fan. And a servo motor did the trick of navigating the boat around the turns.
Everyday Mischief 