Motor sizing

[ken webb]

New to FE. How do you determine what size motor to use in a boat? Any books on the subject?

[tbonemcniel]

New to FE. How do you determine what size motor to use in a boat? Any books on the subject?

A little trial and error. It?s always better to go too big on the motor than too small.

You can ask other ls with similar boats what they have successfully run.

Typically, for boats up to say 30?, a 3660-3674 will do well, up to around 34-36? a 3682 to 4074, up to around 40? a 4082-40100, above that, a 56mm.

[ken webb]

Thank you for the info.

[properchopper]

Ken,

Once you figure out the motor size (based on its diameter & length) for the type and size of hull, your next decision, choosing an appropriate KV, depends on your battery voltage choice. This chart is useful, particularly if you're going for reliability - or completing a heat race - as the figures are made with that in mind. Of course many others are simply interested in momentary bursts of max top speed and will go "outside the green" ( unfortunately encouraged by greedy vendor marketing - or those qualifying for membership in the ZSP/WTS* club).



kv voltage.jpg


*ZoomSplashPop/WhatsThatSmell

[RaceMechaniX]

Hello Ken,

Castle creations used to have a great application guide referencing motor and ESC sizes to the common racing classes. Unfortunately I cannot find it.
The best advice is to post a question with the hull in question and what your aims are for the boat. i.e. play boat with long run time, heat racing or SAW boat, etc.
You will get plenty of opinions on different combo's and you can go from there.

-Tyler

[pescador]

Wow what a struggle to find that chart I thought I had a copy of it. Finally found it through a web archive site. Best I could do is a screenshot.


Sent from my iPhone using Tapatalk

[ken webb]

Much thanks. That helps alot.

[NativePaul]

For what it is worth I race most of my boats for 6 minutes, on about 500W/Kg, my motors are all around about 15% of the boats the all up weight.