Skimmer built from Model Boat plans back in 2010 (Glynn Guest). I use a 5.5"x4.5" prop. it is hard to control as it tends to skew to the side due to the twist of the drive unit, I think I didn't gave it enough angel of the motor mount. if I was to do another one, I would add small rails on the bottom to give it just a bit more direction stability. (Motor: Speed 400 / 6Volt) (ESC: Robbe air control 819 Lipo) (7/10)