I have to say Mike I agree re safety. Whatever you fit needs to be able to match the correct prop to the boat, motor and controller. I note folk though often fit more 'powerful' drives than they need to - to achieve hull speed using their old prop that they had when a diesel was fitted.
Moral - fit the right prop for your electric drive. Often the reason they don't get what they expect is because they have not matched the whole system properly. Also it is a question of cost and to decide if you need more continuous thrust than the electric motor and controller 1 hour ratings. If so there is more battery expense and different motor and controller choices. Personally I choose my cruise speed and work from there. That is all a calm water baseline. Usually this will be 1/2 to 2/3rds hull speed (which is where electric is best) and within the 1 controller rating and within the motor rated (not max) current draw. That should be enough to get any sail boat off a lee shore and there is still a system reserve for burst thrust/speed .
I also like to remind folk it is a sailboat.
This sheet of my own boat below shows what I mean. Sure I can burst the power within the burst limits of the controller and motor to hull speed. That is my reserve if you like. You will also note in the sheet it is direct drive and my motor continuous rating of 110 amps mismatches with my controller 80 amp 1 hr rating. That is when you decide to gear on not, which introduces less efficiency but better matching into the system and to some extent more cost and noise as the motor is running faster. but it is better to have volts than amps but geared means other losses. But if you put 1.27 gearing into the sheet you will now see the system voltage spot on and controller and motor ratings matching.
The question is do I want to spend more on batteries, get more noise for the sake of a continuous 1hr cruise at better than my current max cruise speed of 4.5 knots (3/4 hull speed) and optimum of 4 knots. No, is the answer and therein is a risk as such, for safety, but I'm happy with the compromise and there is enough margin in foul conditions.
If I wanted to punch waves in bad offshore conditions I'd have fitted a heavy duty nigh on continuous run diesel that would go all day above 3/4 hull speed and closer to hull speed. But electric suits me. So for safety the question is in my case - To gear or not to gear? I've already chosen and done 600 miles on non geared electric, so diesel is history for me, but still I feel safe.
You will see I'm using a 2.5Kw motor driving a 26 ft boat displacing over 7,000 lbs.
http://John.Rushworth.com/ELEKTRA-Electric_Propulsion_Performance_Modelling_Spreadsheet.xls
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http://John.Rushworth.co
--- In electricboats@yahoogroups.com, <electricboats@yahoogroups.com> wrote:
I have a SolidNav that has never been installed - took it in trade on an upgraded Electric Yacht system. It would push the 6500 pound Paceship 29 with authority. We are in Southern California. Contact me at my website www.electricyachtssocal.com
Now my simple question is why not just replace the A4 as you can usually find good working unit for around $800-$1000 or just do a used 7hp outboard for even less. I find it difficult to get my thinking around the idea of putting something that may be inadequate because it is cheap. When boating I first look at safety and then reasonable cost. The idea of putting in a "cheap" but less than adequate and therefore less safe system is not what I would want to do on any boat. As a vendor I cannot in good conscience and in a society that is litigious sell products that may not provide adequate service to my client. But as a boater, I am truly at a loss to want to put something in my boat that is less than adequate. I have seen too many boats that cannot reach more than 60% of hull speed. In a poor sea state, the boater would be at peril.
Mike Electric Yacht of Southern California
--- In electricboats@yahoogroups.com, <sweeney.dillon@...> wrote:
Earlier this summer, someone on this list was selling an electric conversion they no longer needed, and this at a very good price, batteries included. I was unable to jump on it at the time.
Today, a friend called me in a bind. His atomic4 has thrown a rod and he is looking to rip it out and convert. But, he's even more of a cheap bastard than I am. I'm pretty sure he can source some batteries locally, but the drive system is what's lacking.
The boat is a Paceship 29 (C&C 29-1 hull).
The sailing conditions are May-October, on a freshwater lake in the st. Lawrence river. Some current, sometimes. He is very capable of making-do and changing his plans according to conditions of weather and boat.
So, a 3-5kW direct-drive would likely suit him fine. I'm going to point him at the smaller Thunderstruck sailboat kit if nothing pops up in eastern Canada or the NE states.
So how about it? Anyone sitting on an uninstalled conversion collecting dust? Now's your chance to pass the dream off to someone else!
Cheers,
/Jason
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