On Sun, 16 Dec 2007 04:35:35 +0100, Heikki wrote:

Richard van den Berg wrote:

Regular outboards do have a fair weight/hp compared to e-motor and
batteries. The only thin you have to worry about is fuel. Or how did you
plan to fill your batteries?

Oh, I was planning to have a diesel engine (and a generator) running most of
the time to provide the electricity. The idea was to be able to place the
generator engine where I wanted it, and the propelller(s) and the driving
engine where they would be most useful. Instead of a solid shaft, I would
have flexible cables in between. I could run it on the batteries for a
minutes, if I needed extra manouvering, but in most cases, the power would
come from the generator. Also, I was hoping that the electric propulsion
would be smaller and lighter, so it would be easier to lift out of the
water when going by sail...

- Heikki


First of all, "there is no magic". If it takes, say, 10 H.P. (at the
propeller) to move your boat then regardless where you get it will
always require 10 H.P (at the propeller).

Second, the more devices you add between the prime mover and the
powered device the more losses you will have.

So, if you install a diesel engine, a generator, a battery bank, an
electric motor, cables and finally a propeller you are building in
losses at every stage between the diesel engine (prime mover) and the
propeller (powered device).

So, your 10 H.P. (at the propeller) plus losses result in the need for
a larger engine - say 12 H.P. Plus added initial cost, added problems
and added maintenance costs.

Unless you are talking about a really large vessel I don't believe
that there will be any advantage and probably several disadvantages in
using a diesel-electric drive.


Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

"Bruce in Bangkok" wrote in message
...
On Sun, 16 Dec 2007 04:35:35 +0100, Heikki wrote:

Richard van den Berg wrote:

Regular outboards do have a fair weight/hp compared to e-motor and
batteries. The only thin you have to worry about is fuel. Or how did you
plan to fill your batteries?

Oh, I was planning to have a diesel engine (and a generator) running most
of
the time to provide the electricity. The idea was to be able to place the
generator engine where I wanted it, and the propelller(s) and the driving
engine where they would be most useful. Instead of a solid shaft, I would
have flexible cables in between. I could run it on the batteries for a
minutes, if I needed extra manouvering, but in most cases, the power would
come from the generator. Also, I was hoping that the electric propulsion
would be smaller and lighter, so it would be easier to lift out of the
water when going by sail...

- Heikki


First of all, "there is no magic". If it takes, say, 10 H.P. (at the
propeller) to move your boat then regardless where you get it will
always require 10 H.P (at the propeller).

Second, the more devices you add between the prime mover and the
powered device the more losses you will have.

So, if you install a diesel engine, a generator, a battery bank, an
electric motor, cables and finally a propeller you are building in
losses at every stage between the diesel engine (prime mover) and the
propeller (powered device).

So, your 10 H.P. (at the propeller) plus losses result in the need for
a larger engine - say 12 H.P. Plus added initial cost, added problems
and added maintenance costs.

Unless you are talking about a really large vessel I don't believe
that there will be any advantage and probably several disadvantages in
using a diesel-electric drive.


Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

But since the torque is greatest at zero rpm. Probably need a lot less than
a 10 hp engine. The cable car system in San Francisco is run on one 1000 hp
electric motor.

On Sun, 16 Dec 2007 04:35:35 +0100 Heikki
) wrote:
Richard van den Berg wrote:

Regular outboards do have a fair weight/hp compared to e-motor and
batteries. The only thin you have to worry about is fuel. Or how did you
plan to fill your batteries?

Oh, I was planning to have a diesel engine (and a generator) running most of
the time to provide the electricity. The idea was to be able to place the
generator engine where I wanted it, and the propelller(s) and the driving
engine where they would be most useful. Instead of a solid shaft, I would
have flexible cables in between. I could run it on the batteries for a
minutes, if I needed extra manouvering, but in most cases, the power would
come from the generator. Also, I was hoping that the electric propulsion
would be smaller and lighter, so it would be easier to lift out of the
water when going by sail...

For 1 kW (1,34 hp) you can count on about 10 kg motor weight for
standard 3 fase 2900 rpm motors. For a lighter motor you might use one
with a permanent magnet, no idea what it will cost.

--
Richard
e-mail: vervang/replace invalid door/with NL.net

Richard van den Berg wrote:
On Sun, 16 Dec 2007 04:35:35 +0100 Heikki
) wrote:
Richard van den Berg wrote:

Regular outboards do have a fair weight/hp compared to e-motor and
batteries. The only thin you have to worry about is fuel. Or how did you
plan to fill your batteries?

Oh, I was planning to have a diesel engine (and a generator) running most of
the time to provide the electricity. The idea was to be able to place the
generator engine where I wanted it, and the propelller(s) and the driving
engine where they would be most useful. Instead of a solid shaft, I would
have flexible cables in between. I could run it on the batteries for a
minutes, if I needed extra manouvering, but in most cases, the power would
come from the generator. Also, I was hoping that the electric propulsion
would be smaller and lighter, so it would be easier to lift out of the
water when going by sail...

For 1 kW (1,34 hp) you can count on about 10 kg motor weight for
standard 3 fase 2900 rpm motors. For a lighter motor you might use one
with a permanent magnet, no idea what it will cost.



Well, it certainly makes no sense to hook up a small diesel engine to a
prop shaft and prop. After all, it's never been tried before.

On Dec 16, 1:07 pm, HK wrote:
Richard van den Berg wrote:



On Sun, 16 Dec 2007 04:35:35 +0100 Heikki
) wrote:
Richard van den Berg wrote:

Regular outboards do have a fair weight/hp compared to e-motor and
batteries. The only thin you have to worry about is fuel. Or how did you
plan to fill your batteries?

Oh, I was planning to have a diesel engine (and a generator) running most of
the time to provide the electricity. The idea was to be able to place the
generator engine where I wanted it, and the propelller(s) and the driving
engine where they would be most useful. Instead of a solid shaft, I would
have flexible cables in between. I could run it on the batteries for a
minutes, if I needed extra manouvering, but in most cases, the power would
come from the generator. Also, I was hoping that the electric propulsion
would be smaller and lighter, so it would be easier to lift out of the
water when going by sail...

For 1 kW (1,34 hp) you can count on about 10 kg motor weight for
standard 3 fase 2900 rpm motors. For a lighter motor you might use one
with a permanent magnet, no idea what it will cost.

Well, it certainly makes no sense to hook up a small diesel engine to a
prop shaft and prop. After all, it's never been tried before.

West (Waste) Marine in their latest catalogue has a 6 hp electric
outboard, kinda expensive though. You could run a generator from a
small diesel like these Listers and have it charge a bank of batteries
that were your sailboat ballast and hav the batteries run your
electric outboard. Why carry around a couple thousand lbs of lead
ballast unless its going to do something like store electricity.

On 2007-12-15 03:50:00 -0500, Heikki said:

I have been speculating about a diesel-electric propulsion for a
smallish sailboat. Does anyone have links to, or experience with, small
electric motors that are suitable for continuous use - most of my
googling finds bow thrusters and other extra machinery.

I am thinking of a fairly small engine, say 5-10 Hp, to be used mostly
in manouvering in and out of marinas, and occasionally coming home from
a calm sea. Would it make sense to mount the whole engine on the
transom-hung rudder? That way it could turn with the rudder, and give
good steering in both directions. When not in use, it could be lifted
out of the water, so I could use a decent size of propeller for it.

For that sort of application, I'd go with a largish solar cell and
battery bank. During the week, let the sun charge things up, then use
it. Our little 10w solar cell would easily give a hour or two usage
with the new electric outboards reviewed in Practical Sailor recently.
Just in case, I'd have a little generator, but probably gas for light
weight.

http://www.practical-sailor.com/ for the outboard review.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

On 15 Dec 2007 21:36:24 GMT, Richard van den Berg
wrote:

Regular outboards do have a fair weight/hp compared to e-motor and
batteries. The only thin you have to worry about is fuel. Or how did you
plan to fill your batteries?

Somebody makes a four horsepower electric outboard. 48 Volt.

Casady

"Richard Casady" wrote in message
...
On 15 Dec 2007 21:36:24 GMT, Richard van den Berg
wrote:

Regular outboards do have a fair weight/hp compared to e-motor and
batteries. The only thin you have to worry about is fuel. Or how did you
plan to fill your batteries?

Somebody makes a four horsepower electric outboard. 48 Volt.

Casady


The Navigator we had had two, 5 hp electric motors. One was the bow
thruster, the other the stern thruster.
12 volts. Battery draw was over 300 amps (fused at 400).

Duty cycle was limited to about 10 percent. Not much good for trolling.

Eisboch