coriolan

40 to 50cm would be optimum (16"<20") and it need to be very light, for props I have used 1" Dumas but want to try X427 Octura in my next build. I Europe it might be easier to find the small 29mm Graupner and trim if needed, for shaft I use .098" Octura cable with 1/8" stub shaft but a 2mm solid drive shaft could be used too with the Graupner prop or Zig-zag prop. There isn't much hardwares available for that size commercialy so almost everything has to be home build! I have a Tarno carb to use with Cox engines but I found and exhaust ring to be easier to use because of the sub-induction of most Cox engines which preclude the use of a muffler. Trottle control is actually not really necessary with .049 size boats, they run happily full trottle until the tank runs dry and not using trottle control save you the weight and space of an extra servo! Weight reduction is important with that size of boat and even the rudder doesn't needs much torque because of the low masse and speed,no need for more than a 9 grams servo and since the run is short you can get away with a small Rx battery. I now uses a small 2 cells Lipo in conjunction with an old esc (for its bec) but an UBEC could also be used.