Monday, August 31, 2009

Re: [Electric Boats] Small displacement boat question

 

Good to have you join the group, Gary.

You are right in thinking a small electric system will give you about as good performance (except range) as the diesel. You will love the silent running where you can hear your own bow wave splash over the stem.

Based on a 1000# boat (including batts) plus 400# of crew:

500 watts, (0.6 hp) will push your boat 4 mph. That's 20 amps at 24 volts - about the power of an electric scooter or bicycle system. (2) 105 ah 12v batteries would give a little more than 3 hrs at 20 amps; (4) 220ah 6v batts would give nearly 8 hours. Slowing down a little bit to 3.3 mph (10a) more than doubles the range.

Your hull speed is 5.7 mph - its highest practical speed which would take 60 amps. (2 hp) A small diesel (5 - 10 hp) would not go much faster than this.

As someone else replied - you want the largest prop that fits. You could have your shaft machined to fit a Torqeedo 12 x 10 prop ($80). You would want to aim for about 800 shaft rpm with this prop.

Running on a 110v gas generator without batteries is a bad idea, IMHO. Speed control is very expensive and what's the point? You have the noise and exhaust of a gas engine all the time. A 2.5 Honda or 3 hp Suzuki OB in a well would be a much better solution.

If you really need more range than batteries alone can provide plug your battery charger into the 1000w generator. Note, though, that (4) 6v batteries will last all day - and that is a long time to be out in a 16' open boat.

Good luck.

Denny Wolfe
www.wolfEboats.com

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[Electric Boats] Re: Small displacement boat question

 

a 13.5' LWL, 16' LOA displacement hull total weight on the order of 1000 lbs., plus an occupant or two. The boat is beamy at 6'

See group files, "Building an Electric Javelin", a 14 ft displacement electric with 3/4 horsepower electric drive. This boat gets along very well with 4 adults on board. 24 volt DC battery power only.
>

> 1. A 1.5 HP electric motor should be capable of pushing me along at a slow but steady speed, even in a good wind, assuming an 8-10" or so prop can be fitted?

ANS: 1.5 HP is more than you need, 1 HP or less will do OK with the proper sized propeller. An 8 to 10 inch prop is way too small, and would be very inefficient, use at least a 14 inch prop. If you use a 10 inch prop, then you may need the 1.5 HP motor, but that would be poor design, using a much larger motor (and battery pack) to get the same performance as a smaller motor could give with the properly sized propeller.
>
> 2. If the motor in question were so small and an AC 110v model, that the power source could simply be a gas-operated generator, say, a Honda putting out about 1000w?

ANS: The 1000 watt Honda generator will not start a 120 VAC motor that is any larger than 1/4 to 1/2 horsepower. In order to start a 1 HP 120 VAC motor, you need to have a generator rated at a few kilowatts at least. The starting electric load on almost any motor is several times the running electric load, and the generator must be capable of handling the starting load.

An alternate option is to install battery powered DC electric drive, and use the 1000 watt generator and automotive type battery charger to charge the battery pack. This would allow silent running with limited range, or continuous charging while underway (or chargine when not underway).
>
> 3. Can I assume that I would not be liable to electrocute myself with such a setup?

ANS: DC system with 12 volts or 24 volts is pretty safe, higher voltages can be much more dangerous in either DC or AC. As an amateur, probably better to stay away fron the 120 volt AC system, although these can be designed and built to have good safety features with proper engineering.
>
> All advice appreciated. And by all means save a life by putting me off the idea if you must!

>

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Sunday, August 30, 2009

Re: [Electric Boats] Re: Torqeedo Owners Club

 

Hi Steve,

I went there but not quite right. but this link works for me

http://groups.yahoo.com/group/TorqeedoOwners/

cheers

chris

On 29/08/2009, at 6:53 PM, sstuller wrote:

> I'll try again on the address. http://groups.yahoo.com/
> torqeedoowners/. Maybe this will work. Thanks. Steve S.
>
> --- In electricboats@yahoogroups.com, "sstuller" <sstuller@...> wrote:
> >
> > I've started a Yahoo group for Torqeedo owners so we will have a
> place where we can discuss the virtues and vices of these motors. I
> believe the address is http://groups.yahoo.com/group/Torqeedo. At
> any rate it should be easy to find in the Yahoo groups listing.
> Thanks. Steve S.
> >
>
>

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[Electric Boats] Re: Problems with Electric Marine Propulsion Inc.

 

A couple of good points brought up here. On the Columbia river where Myles and I live another concideration is current flow. Often the wind direction and current leave sailers doing a lot of tacking making little or no headway so they switch to power. In this situation to have a big enough generator to run off is nearly a requierment as conditions change. For people in other places it is be prepaired for the unexspected and enough power to be safe....

Jon

--- In electricboats@yahoogroups.com, "aweekdaysailor" <aweekdaysailor@...> wrote:
>
> Mike's point is spot-on - in fact the first question I pose on my site is "where do you sail?" - because local conditions establish one leg of the baseline of "safety" along with vessel and skill. (and my local conditions seem hell bent on testing both of the latter)
>
> But...this industry needs to go mainstream. The sailors who can sail without aux power are few, those who will take all conditions into account (and have the schedule freedom to account for it) not much more numerous. That's why almost all production sailboats today have ICE's that can comfortably hit hullspeed and those are the boats that today's sailors are being educated on.
>
> So I am just arguing for a bit more discretion in claims about performance/range and honest discussions to set realistic expectations. I think Arby's suggestion of a reference database is outstanding. I don't know if current Groups functionality would allow that, but it would be a great help.
>
> -Keith
>

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[Electric Boats] Story ideas

 

Electric boat owners, I want your stories ... please! As a boater - see "Follow the Reader," Sunset magazine, July `09 edition - I find fellow mariners to be a fascinating group of humanity. As a writer, who currently writes a column, "The Second Half," for people over 50, I am considering writing a book on how many of us are either making mid-life career changes or finding completely new careers after retiring. If you fall into either of these two categories, and you would be willing to be interviewed, would you drop me an email? The book will happen if I get your stories, as I believe personal experience is the most inspiring and provides the best possible read! Thanks. I look forward to hearing from you.

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[Electric Boats] Re: Problems with the Marine EV industry

 

Arby,

This is the type of conversation that I was hoping would develop. We can already identify a couple of constraints that need to be acknowledged. Lead acid batteries weigh about 60-65 pounds per kWh. Therefore, a 10kWh batteries pack will be around 650 - 700 pounds with cables, platforms, and tie downs. Lithium batteries are about 35% of the weight of lead acid batteries.

My boat is around 5 tons displacement and I'm targeting a 48v system that can pull up to 125A, resulting in a 6kW drive. I hope that the boat would perform sufficiently running at around 2.5kW with the rest of the power held as reserve. Given a 24' LWL, the estimate of 500W per ton would result in a cruise speed above 4kts at 2.5kW.

I'm interested how you would dyno the shaft power of an installed system. I'm pretty sure that you're on the eastern half of the country, I wonder if there's anyone in SoCal set up to perform a similar measurement. If we could collect this type of metrics, it would go a long way towards objectively measuring the efficiency of some of the various drives available. While total thrust measured with a bollard pull may be more relevant to the end user; the variations from hull shape, shaft angle, and propeller design would skew the results towards the installation and away from the drive's performance.

Given that the weight of the battery pack seems like a limiting factor to me, and that displacement keelboats already carry thousands pounds of ballast, the elegant solution would be to make some of that ballast "active". I will attempt to do that with my second battery bank after the drive is installed and running. I think that the best solution would be a boat built with vertical battery racks running into an internal keel or a battery filled bulb at the bottom of a fin keel. A power bulb my be able to be retrofitted, but I would want to remove some of the original ballast to keep the boat sailing as designed.

Fair winds,
Eric
Marina del Rey, CA

--- In electricboats@yahoogroups.com, Arby Bernt <arbybernt@...> wrote:
>
> Keith has raised an interesting question...How much power should a boat have to consider it safe? I've read that 2.5kW per ton will allow a boat to reach hull speed. For your Hunter, that would be a 10kW system. 70% of hull speed requires but 500W per ton, however, so a "3hp" (2 kW) system would move your boat just fine.
> Please suggest a standard, in shaft power, not controller input. I'll be glad to dyno your system if you would like an actual curve for your Mars/Sevcon system. Knowledge is power.
> I will agree that 3hp on a 10,000lb boat can provide manuevering power, but would be hard pressed to buck heavy seas and headwinds. By the same token, installing a 15kW motor and expecting to support it with a 100kWh battery pack is not reasonable.
> If other members would care to suggest power to displacement ratios, and the batteries to match, we could help to build a database of working, marginal, and disfunctional boat repowers.
> By creating a standard, we help not only folks like ourselves, we help the boating industry in general to accept a greener option.
>
> Be Well,
> Arby
>

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[Electric Boats] Re: Problems with Electric Marine Propulsion Inc.

 

Mike's point is spot-on - in fact the first question I pose on my site is "where do you sail?" - because local conditions establish one leg of the baseline of "safety" along with vessel and skill. (and my local conditions seem hell bent on testing both of the latter)

But...this industry needs to go mainstream. The sailors who can sail without aux power are few, those who will take all conditions into account (and have the schedule freedom to account for it) not much more numerous. That's why almost all production sailboats today have ICE's that can comfortably hit hullspeed and those are the boats that today's sailors are being educated on.

So I am just arguing for a bit more discretion in claims about performance/range and honest discussions to set realistic expectations. I think Arby's suggestion of a reference database is outstanding. I don't know if current Groups functionality would allow that, but it would be a great help.

-Keith

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