Prop Selection for Electric Motor

[omaolchonaire]

Originally Posted by shyguy68

My best suggestion for this is to browse youtube for Sailing Uma, and look at their videos as Dan took a motor from a forklift and used it on their sailboat and the only glitch they've had since is the batteries quit (can't remember why)

Will check it out I have heard of them.

[waterman46]

1 kilowatt = 1.34 hp. Your 200AH bank at 48V will give you theoretically 9.6KW for 1 hour. 9.6x1.34=12.9hp for that hour. Is this sufficient for your needs? Of course you can't really draw that much current, if you do your battery AH will be drastically less. And effective re charging using only the prop drag is, sorry, just not going to happen. hope I'm wrong here, I just got the conversion from hp to watts from a website.

[MartinMV]

Originally Posted by waterman46

1 kilowatt = 1.34 hp. Your 200AH bank at 48V will give you theoretically 9.6KW for 1 hour. 9.6x1.34=12.9hp for that hour. Is this sufficient for your needs? Of course you can't really draw that much current, if you do your battery AH will be drastically less. And effective re charging using only the prop drag is, sorry, just not going to happen. hope I'm wrong here, I just got the conversion from hp to watts from a website.

You describe the reason, why electric motors haven't yet replaced the other systems. Diesel or other fossil fuels hold so much more energy than even the best batteries can store.

[omaolchonaire]

Originally Posted by waterman46

1 kilowatt = 1.34 hp. Your 200AH bank at 48V will give you theoretically 9.6KW for 1 hour. 9.6x1.34=12.9hp for that hour. Is this sufficient for your needs? Of course you can't really draw that much current, if you do your battery AH will be drastically less. And effective re charging using only the prop drag is, sorry, just not going to happen. hope I'm wrong here, I just got the conversion from hp to watts from a website.

I'm not super concerned about the battery bank, as I am going with a modular system that can be easily doubled continuously. Mostly my concern is to get the right prop/motor/gear reduction set up. But yes, I know people who have run these boats with 10 hp motors, once they get moving along it doesn't take much to push them at 5 knots. I barely ever put the throttle above half with the 23 hp and hydraulic drive. I am not relying on the prop to charge the boat, I have 8x100w and 2x80w solar panels, a 2000w 48v wind generator, and in winter 12x12v pelletier modules water cooled on my diesel stove. I just want to maximise the charging through the drive system while sailing.

[omaolchonaire]

Originally Posted by MartinMV

You describe the reason, why electric motors haven't yet replaced the other systems. Diesel or other fossil fuels hold so much more energy than even the best batteries can store.

Actually they have replaced other systems - diesel motors are now an option with most sailboat manufacturers.

[omaolchonaire]

Originally Posted by omaolchonaire

Actually they have replaced other systems - diesel motors are now an option with most sailboat manufacturers.

Also, you are forgetting about onboard charging capability with an electric system.

[waterman46]

Originally Posted by omaolchonaire

I have 8x100w and 2x80w solar panels, a 2000w 48v wind generator, and in winter 12x12v pelletier modules water cooled on my diesel stove. I just want to maximise the charging through the drive system while sailing.

Just a few more thoughts:
2KW wind generator? Really?
I wish I could figure out a way to mount 800W of *effective* solar on my 46' boat but you have figured out a way to mount that much on a smaller vessel.

The electric setup will require more sailing and less time under power, probably something we all should strive for.

Anyway, "Good on yer", for trying this - just what I love most about owning a boat - you can experiment with as many things as you wish. I'd love to see an update on the results if you are so inclined.

[omaolchonaire]

Originally Posted by waterman46

Just a few more thoughts:
2KW wind generator? Really?
I wish I could figure out a way to mount 800W of *effective* solar on my 46' boat but you have figured out a way to mount that much on a smaller vessel.

The electric setup will require more sailing and less time under power, probably something we all should strive for.

Anyway, "Good on yer", for trying this - just what I love most about owning a boat - you can experiment with as many things as you wish. I'd love to see an update on the results if you are so inclined.

I'm mostly just building a pilothouse/dodger back to the wheel and using Elfeland frameless solar panels, which only weigh about 2 kg per 100 Watt panel. The 80 Watt panels allow me to put a porthole so I can see the mast/sail in the second row. Been thinking about it for a long time !

[omaolchonaire]

As far as a 2 kw wind generator that is 2 kw maximum output.

[omaolchonaire]

O, sorry 80w panels are for a separate 12v house power system.