20" mono setup

[Chenige]

Well I think I am getting the calculations at least. Two different setups:

300 watt motor, 3000kV, 5000 maH battery, 3S

300/11.1V=27 amp draw (therefore 30 amp ESC minimum)
27/5000=5.4 amp/min motor draw rate (therefore 10C battery minimum)
60/5.4=11 minute run time
3000x11.1=33,300 rpm


600 watt motor, 4400kV, 5000 maH battery, 2S

600/7.4V=81 amp draw (therefore 85 amp ESC minimum)
81/5000=16.2 amp/min motor draw rate (therefore 20C battery minimum)
60/16.2=3.7 minute run time
4400x7.4=32,500 rpm

By the numbers setup one has higher RPM, cheaper ESC, longer run time. And I believe with a light 20" mono will be faster due to higher rpms?

Why would I go with setup 2? Setup 2 should have higher acceleration? But for a sport boat setup one will be fine?

[Flying Scotsman]

Very interesting questions, but what motors, batteries, hardware and the biggy what prop?

Douggie

[video200]

by the numbers your setups only have rpm without resistance of the water.
in real life setup number 2 would swing a larger prop at the same rpm as you can get in setup number 1.

[Chenige]

But is setup 1 enough to push the boat well?

Currently running 15T speed gems 2 (4000kv) with 7.2 volt nicads which is a bit slower than I would like. 28,800 rpm and x435 prop

With 8.4 v 7 cell nicads it ran real well. 33,600 rpm x435 prop

Will setup 1 swing the same size prop as the speed gem motor with 7 cell stick?

[video200]

if setup is enough is up to you realy. personally i would go for setup number 2 sinse it is most likely to go fast and if your goal is to get the same speed as setup number 1 it wil run alot cooler and more reliable.

your math is based on max reccomended watt and not what a motor can draw. your rpm is based on how fast the motor spins with no resistance and not in a boat in water.

[Chenige]

Very interesting questions, but what motors, batteries, hardware and the biggy what prop?

Douggie

300 watt motor http://www.hobbyking.com/hobbyking/s...00kv_300w.html
600 watt motor http://www.hobbyking.com/hobbyking/s...dproduct=11177

batteries http://www.hobbyking.com/hobbyking/s...Warehouse.html

maybe x435 or x432???

surface drive,

[Flying Scotsman]

Those motors are dubious, the battery is just OK.

My 2 very worthy Canadian cents.

Douggie

[Chenige]

Why are the motors dubious? One is from the JAE Zippkit that was developed by boaters here on the forum.

[Flying Scotsman]

The Kv ratings would not be in my horizon and the prop is the biggie. Start with an X427

Douggie

[Chenige]

Sorry, but could you comment on the "Kv ratings would not be in my horizon". Just not sure what that meant.

Are these setups really that less powerful than the 15T motor? It swings the X435 pretty well and not that much heat.

I will be getting a range of props so I will start out with the X427. thanks

Remember that I am trying to keep cost down because it is going in 3 kids beginner boats.

[Flying Scotsman]

Not a problem, those motors would not be my first choice and yes I understand cost issues...the ESC, batteries and the motor are the most important issues and then the prop, the devil in the equation. Setup of your boat takes experience.

Douggie