074038

Hi, I'm new to the forums and hoping someone with more experience than me can offer me some advise.

I am building a 1:32 scale PT-109 boat out of balsa wood and will be fiberglassing the hull. When I'm done, the boat dimensions will be ~ 30 inches long, 10 inches wide, and weigh about 3 lbs. I will be using a single prop that fits inside of a 1/4 inch stuffing tube. Can anyone provide me any recommendations for which motor, ESC, and drive shaft to use for this build?


For the motor I was thinking of using a Turnigy AquaStar 3720-1500KV. Is this going to be too big or too small? Is there something better that will power this boat? The plans I was using recommended a Mabuchi RS-540 motor, but it is a brushed type and I would prefer the reliability of a brushless.

For the ESC I was thinking of using a HobbyKing 90A ESC 4A SBEC


Any suggestions for a prop shaft that would be suitable?

In the end I'm looking for a boat that will travel at a nice speed, I'm not looking for a race boat.

mfr02

A 540 would cough out about 100 watts of power, and probably power it along reasonably given enough volts and the right prop. I have yet to find an unreliable one.
The suggested motor/ESC combo should result in a flying machine on 3S with a small enough prop, and a high performance boat on 2S with a larger prop. What the low speed control would be like is anybody's guess, this important when retrieving the boat, or sailing in company. I have a rescue launch of similar size and hull form running a 650 of unknown type off a viper marine 25 ESC and a 7 cell NiMH 3700. It goes indecently fast and gives good run times. More speed/power would probably be embarrassing.
For a prop shaft, look for something about the same diameter as the motor shaft - this can be a good guide.

074038

Thanks for the response, it appears that I have a motor that is much to large based on your similar sized boat. It sounds like the 650 sized motor will give me the speed/performance that I'm looking for. Do you have a suggestion for a motor to look for? I guess I'm confused how to tell if a motor is a 650 or not. I tried searching the internet and wasn't very successful in tracking something down that was reasonably priced. Everything I find seems to use the manufacturers labeling scheme and give me the kv rating for the motor. Is there a rule of thumb to equate a given physical size of a motor and the kv rating to a 650 class?

Thanks in advance for the help