T-Pain Is On A Boat: Re: [Electric Boats] RE: new to the group [1 Attachment]

Monday, December 30, 2013

Re: [Electric Boats] RE: new to the group [1 Attachment]

[Attachment(s) from Julian Webb included below]

Gerry

If your calcs are OK with $10k a year fuel and your recharges are free as you are using hydro for power, simplistically all you need do is figure out if you can use a system that when you amortise the batteries out over their life of the yearly cost is the same or under $10k a year. Even thrashed AGMs with a three year life will give you more than that.
One you factor environmental considerations and the fact that replacement battery costs will drop over the same period I can't see the problem.
Getting a true non theoretical hull speed/power figure is a good start, so use the old spring balance tow method and you'll have that in no time.
In your situation you must get some fact into the equations and I think the best place to start is with your own hull power requirements.
I attach an old but down to earth, simple and above all else practical approach from someone who was in the businesses and had lots of proof of his own hard work. Sorry the file or so big but it's worth it.

Cheers

On 29 Dec 2013 20:34, "The Boys" <theboyfam@gmail.com> wrote:

Thank you Mike
The boat I am working with now is the Red Wing 23 from CMD it is a flat bottom displacement hull lwl 21' beam wl 6'6" 7'10" overall, dr 1'6" the designer says on the web site that she should get about 6-8 kts from a 15hp gas outboard. I plugged the lines roughly into delftship and it gave me a hull resistance of 110 lbs at 8 kts and 65 lbs @ 6 kts with a displacement of around 1.5 tons depending how she would be loaded of course.

I will be fitting her with a box keel and am leaning toward inboard power I hope to be able to swing a prop in the range of 3x14x11 or so at about 1200rpm max @shaft (2:1). as the box keel will get my shaft a little lower in the water for the larger wheel.

I had been considering an ME 5kw motor @ 48v like the ME1117
I am also intrigued by the Agni 95 which seems to be capable of powering this boat at 1:1 @24v around 100 amps
My high hopes are for 5-6 kt cruise, hull speed should be around 6.3 I think. I would hope for 3 hrs at cruise in order for the boat to be useful here.

In summer we will use it for supporting canoes on our outdoor adventure program. I hope to be able to run at 2kts for most of the day using solar on multi day trips.

The semi displacement boat is just an Idea and more of a light displacement concept than semi.It would replace one of our planing supply/commutor/watertaxi boats. The Idea is: if it is possible to get a vessel capable of carrying 12 adults to cruise at 10 kts for 3 hr/day in 1.5 hr runs we could save up to $10 000/ year in fuel.

I was thinking something around 30' x 7' at the waterline built as light as possible to keep the displacement way down like 3000lbs, spartan shelter and benches ect. according to Gerr's d/l ratio this light narrow hull should have a hull speed of 13kts and would need 53 diesel horses to get it to 10kts.

do you know if anyone has tried some thing like this? The propeller calculator at Vic Prop says that a 60 hp diesel will get this hull to 10 kts using 15 hp spinning a 3x16x15 prop.with a max output of 53 hp@shaft and 172ft lbs@ shaft (2:1 reduction) giving a full out speed of over 15 kts.

I would love to weigh these theoretical numbers with some real life experience.
I know that not many boats like this are around though other than 1930's rumrunners and old style lobsterboats or boats like Nigel Irens' Rangeboat or his own boat Greta.

I would be interested in any info or advise on either or these boats Especially the first one as it is real and in the shop right now. I hope to get the students involved next school year. but I will be starting and organizing the project until then.

Thank you
Merry Christmas and Happy New Year

Gerry

On 2013-12-27, at 6:15 AM, <mike@electricyachtssocal.com> <mike@electricyachtssocal.com> wrote:

Gerry,
Vendor alert. Welcome to the user group. The semi displacement hull is not as effecient at slow speeds as the full displacement hulls that most of us on this website talk about. There are several with good working knowledge such as the Arc. We are starting to see a growing interest in electric propulsion by the power boat market but most are unreasonable expectations. You can not push a 20000 pound sportfisher with an electric motor at 10kts but you can do some reasonable smaller runabouts and service boats at speeds in the 5 to 8kts. I am sure the other vendors that visit this site will also give you expert advice. We are all dealing with the same physics and the power to push a boat will be the same for all of the systems within a reasonable amount. System design and engineering will also play a part in the effeciency.

To give you an expectation that is reasonable, think in terms of what you know about the current propulsion system. This is including the motor, the propeller and the hull. If you have a 50hp gas/diesel motor pushing the boat today that meets your needs of displacement speed and reliability in your environment, than it is reasonable to look at electric systems from several vendors. Share the following information and I am sure several vendors will respond:
Length at Waterline
Beam
Displacement (include passenger loads)
Propeller
and finally speeds at current propeller RPM would be helpful to know.

We wish you the best with your mission and works.
Regards, Mike
Electric Yachts of Southern California