Replies to This Discussion

Permalink Reply by James Sizemore on December 22, 2012 at 11:07am

With 9 tons of displacement, you need around 9000 watts or 12 continuous hp,  if your motor and controller can put out 9000 watts for 4 hours you will be fine.  You will need at least a 48 volt 750 AH battery bank to reach your 4 hour run time at the full 9000 watts. 

• ▶ Reply

Permalink Reply by Martin Jønland on December 26, 2012 at 11:55pm

I dont think you need 9KW to get 4 kts. I`m pretty shore you can hold 4kts with about 2KW in ideal conditions. 9KW is more than the output you get from a 9,9hp outboard motor.

A previus sailboat i had got 5,5kts with the Honda 2.3hp at max. Thats about 1500W..? Though boat was about 4 tonns.

 

I read other people talking about 30amps @ 48V to get 4kts in their sailboats. Thats less then 1500W.

 

But i will know more about this when i finnish my own conversion in a 8 tonn motorsailor. I`m 80% finnished, just missing the gearbox.

• ▶ Reply

Permalink Reply by Martin Jønland on December 29, 2012 at 6:37am

When it comes to gearbox i found that James Lambden who is a member at this forum have done several innstalls with the Browning 3301 gearbox with thrustbearing. It can do 9,42KW@1750rpm, it should be plenty. I`m trying these days to order one, but its christmas.

 

Your Kewet motor is about 7KW i guess. It should work .

 

I will go with 4/1 ratio and get about 750rpm on the prop at max. The bigger prop and slower prop speed is in theory the most efficent. Browning 3301 comes from 1,2/1  -  5/1.

 

For extended driving I will use a generator and the charger so i dont need to many batteries.

• ▶ Reply