T-Pain Is On A Boat: Re: [Electric Boats] Re: Problems with Electric Marine Propulsion Inc.

Sunday, August 30, 2009

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

Arby:

There is a saying that goes: You can out think the ocean but, you can't out slug the the ocean. Most professional mariners take this to heart. I was on a freighter a few years ago and some nasty stuff was coming down on us in the Gulf of Mexico. The captain did not attempt to plow into the head seas but, set a course that would minimize the pounding on his ship and made adjustments as needed and this was a BIG cargo ship with a BIG ICE. I think a sailor electric or ICE should plan their trips and do the same. When I ran into a nasty thunderstorm with some real nasty gusty winds last year on Long Island Sound I dropped sail and ran under electric power alone for about 45 minutes on a course that was comfortable . What a pleasure to be able to converse with the crew down below while standing watch too. I felt my 8 ton 30 foot sailboat was never under powered with it's Thoosa 9000 system which is supposed to provide about 9 HP. So far I am using the
same prop I had (3 blade 16" 14p) that the diesel used too. Since it was my first season with electric propulsion it was also a first test of what it could do in those conditions. I was happy with the results and felt more comfortable knowing the system was able to handle it. Not that I look forward to being in such conditions if I can avoid them.<g>

Mike
http://biankablog.blogspot.com

c--- On Sun, 8/30/09, Arby Bernt <arbybernt@yahoo.com> wrote:

From: Arby Bernt <arbybernt@yahoo.com>
Subject: Re: [Electric Boats] Re: Problems with Electric Marine Propulsion Inc.
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Date: Sunday, August 30, 2009, 1:07 AM

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

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