Saturday, August 29, 2009

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

 

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

On Aug 29, 2009, at 10:40 AM, "aweekdaysailor" <aweekdaysailor@yahoo.com> wrote:

The common element in these reports?

Both outfits prone to quite a lot of hyperbole - just like the rest of the EV industry (eestor anyone?)

Vendors need to stick with realistic options, backed by customer testimonials - not sticking 6HP motors and 4 batteries on 47 foot, 11-ton yachts and calling it electric propulsion (plenty of other recent examples in the 3HP range...) Might as well be using trolling motors for all the good those would be in a pinch.

And don't get me started (again) on regen...

The problem is this industry is a lot like selling antiques. The barrier to entry is low, the market is small and the buyers are cheap -- so no one makes any money.

-Keith

[Non-text portions of this message have been removed]

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