T-Pain Is On A Boat: [Electric Boats] Re: Repowering 40' 1975 20,000 lb sailboat

Tuesday, September 29, 2009

[Electric Boats] Re: Repowering 40' 1975 20,000 lb sailboat

Don,

I'm feeling contrary today, so I'll volunteer: cruising sailboats have two great electrifying opportunities.

1. all electric
2. fuel electric

1. The all electric folks are old-school (pre-steam engine) or new-school (solar panels, solar ovens, wind generators, tow-able water makers and generators). Fun stuff if you like independence over convenience or have a ton of money. All electric ranges from the super-cheap 24 minute propulsion systems to the very expensive 24 hour propulsion systems.

2. The fuel electric options range from the most common diesel generator(s) driving electric motor(s) to the rare and expensive space-age fuel cells driving an electric motor. Diesel-electric systems usually go about 30% farther than a diesel motor driving a propeller directly.

This is a very complicated average (30% farther) that arises from the stoichiometric and resonant advantages of running a generator at it's optimized power output level (minimizing fuel consumption) and the continuously variable power consumption of propelling vessels up and down swells. Diesel-transmission-propeller systems consume fuel evenly (without regard to swells) and at non-ideal RPMs, so they lose out on both advantages. There might be an "ideal" RPM for a drive diesel, but the fuel consumption vs power curve is fairly flat, since the engine was designed to operate well over a wide RPM range. Good genset engines are designed for specific RPMs, so their "ideal RPM" is much more ideal, like a two-stroke racing motorcycle "on the pipe" (taking advantage of internal air and mechanical resonance frequencies).

Cruizers with diesel-electric systems can be moored all night with the A/C running and never hear a generator. And when the genset does kick on, it is much quieter and smoother than a drive diesel. Additionally, propulsion is instantly available in a pinch. Boats faster than about 7 knots can even stuff some electrons back into the batteries as they sail.

Right now, I'm going cheap on my H55 Marco Polo. Used electric car motor, batteries, and motor controller for about %1,500. I'll add a genset later, but I should get at least 9 knots for an hour, or 4 knots for 4 hours (more if the batteries are healthy). Still working on it.

Mark Stafford

--- In electricboats@yahoogroups.com, "donsaxton@..." <donsaxton@...> wrote:
>
> Hi all,
>
> i am a crusing sailer and i love the thought of a electric drive system.
>
> But from what i see here it doesent sound like a electric drive system
> is a effective option for my crusing life style.
>
> i would be very intrested in any contrary opinions.
>