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[Captain Povey]

Hi Peter, If the 17600 rpm is when supplied with 12 volts then using a 6v battery would give aprox half that and the gearbox will take it down to a sensible speed for a tug. If its 17600rpm off  6v volts you well have the first planning tug on the lake. Graham

[peter61_uk]

Hi Peter, If the 17600 rpm is when supplied with 12 volts then using a 6v battery would give aprox half that and the gearbox will take it down to a sensible speed for a tug. If its 17600rpm off  6v volts you well have the first planning tug on the lake. Graham

Graham. If the motor gives out 17600 rpm at 12v, and I have a 3:1 gearbox ........ Then am I not putting 5866 rpm at the prop ??? .......and with 6v then it's 2933 rpm  ......... With a 45mm prop I have know idea now how many rpm I need to get to the prop to chug this thing along at a sort of "tug like" pace?????

[Captain Povey]

Hi Peter, Yes you are right and I think 2933rpm on a 45mm prop will move your tug very well. Graham.

[peter61_uk]

Hi Peter, Yes you are right and I think 2933rpm on a 45mm prop will move your tug very well. Graham.

Thanks .......... So I'm on 6v Lead Acid or Gel ........Which will power the motor ESC, Receiver and Rudder Servo and give me some ballast .......... The only two questions remaing ???? 1) How many Ah for the battery ............ and 2) How long will the Tug run on the water ????

[Steven.T]

A 3000mah battery pack, so technically at 7.2v you can draw 3.0 Amps from your battery for an hour. Obviously in the real world, you probably won't get this unless all your running gear is very efficient, or say you take it easy and draw less than 3.0Amps.
The higher the Mah of a battery, the longer it will last. If you have a 6000mah battery, and still draw 3 Amps, you can techincally get 2 hours of running. Make sense?

Steven

[Captain Povey]

Hi Peter, Well I use gel cells as they are a form of lead acid battery but unlike the car or motor cycle battery the electrolyte between the lead plates is not liquid but a paste. Therefore the battery can be used on its side without the acidic electrolyte running out. In most of my bigger boats I use a separate battery pack for the radio and do not use the battery eliminator circuit and the weight of the  extra batteries is not a problem. In a couple of smaller boats where space is a problem the use of one battery can be useful. Its probably a bit old fashioned to use a radio battery and a motor battery. Basically the bigger the Ah the more running time you will get so 6v 12ah would be good. The running time will depend on the current taken from the battery when running under load so it would be good if you could measure the current drawn when running the prop in water. Your motor spec mentions 1amp but this could rise to 4 amps or more under load i.e with the prop in water. Even so with a 12AH battery you would bet approx. 3hrs running time. Graham

[peter61_uk]

Hi Peter, Well I use gel cells as they are a form of lead acid battery but unlike the car or motor cycle battery the electrolyte between the lead plates is not liquid but a paste. Therefore the battery can be used on its side without the acidic electrolyte running out. In most of my bigger boats I use a separate battery pack for the radio and do not use the battery eliminator circuit and the weight of the  extra batteries is not a problem. In a couple of smaller boats where space is a problem the use of one battery can be useful. Its probably a bit old fashioned to use a radio battery and a motor battery. Basically the bigger the Ah the more running time you will get so 6v 12ah would be good. The running time will depend on the current taken from the battery when running under load so it would be good if you could measure the current drawn when running the prop in water. Your motor spec mentions 1amp but this could rise to 4 amps or more under load i.e with the prop in water. Even so with a 12AH battery you would bet approx. 3hrs running time. Graham

Good Stuff Graham ........ Component Shop have Sealed Lead Acid 6v 12Ah Batteries for £11.65 ....and with the dimensions, I can probably get away with one standing upright (and it'll give me 2kg of ballast ) .............. I'll do some mooching around on the net for gel batteries. 

[Captain Povey]

Hi Peter, Just a quick point. By having the battery on its side you keep the centre of gravity as low as possible and thereby improve the stability of the boat and  a sealed lead acid will be fine. Graham

[peter61_uk]

Hi Peter, Just a quick point. By having the battery on its side you keep the centre of gravity as low as possible and thereby improve the stability of the boat and  a sealed lead acid will be fine. Graham

............ Result. Then I'm sorted in the battery dept. Thanks to all for your help on this.