So... you might be right. No reason for me to look into this option any
further. Spend my money on a good main engine and a nice small generator and
saving a lot for extended cruising time ;-)

"Roger Long" wrote in message
...

"Marc" wrote


My main objectives are :
- having a backup engine with which she should at least run 4 kn without
having the need for double propellors (too much drag it's a fast
sailing yacht nog an moto sailor ;-)

You already have the back up. They are called sails. If a diesel used in
auxilliar sailboat service doesn't run, it is as apt to be a fuel problem
as anything else. Your second engine will then be down as well.

- not needing a seperate generator by using one of the main engines as a
generator
- less noise / vibration?

A big generator is going to be noiser than a small one. One large enough
to drive the boat is going to be big. Air supply and exhaust are major
and hard to control noise sources. Bigger generators just make it even
more difficult.
Generator's are not happy running at light loads. Unless your hotel load
approaches 50% of your propulsion load running just the one generator for
ship's service will probably result in it's running too lightly. If you
do put in enough hotel load, AC, Jacuzzi, etc., to load up the generator,
where are you going to carry all the fuel?


Hope to get in contact with someone who has a 60 or 70 foot sailing yacht
running with diesel eletric propulsion. If there is any :-)

I'll be amazed if you find one for the above reasons. If you do, please
let us know.

Grtz Marc
sy Beluga
wrote in message
...
On Wed, 1 Aug 2007 08:36:11 -0400, "Roger Long"
wrote:

I've gone around the diesel electric question on a few research vessels
where it is a good solution.

It is going to be quite expensive.

It makes most sense when the loads while the boat is not moving are a
significant percentage of propulsion loads. This doesn't fit the ususal
cruiser profile (except maybe for Skip and Lydia

You had better have a builder who really understands it. There are
going to
be some complex boxes and equipment in between the generators and the
props.
Keeping them cool and dry will be a challange. The wiring will be
unlike
anything most builders have seen.

It's going to take up a lot more space than a conventional propulsion
plant.
There will be some effeciency losses so you will need to carry more fuel
on
a boat that already is devoting extra space and weight to this
enthusiasm.

When you have problems with it and pull into Pango Nowhere, it's going
to
be amusing watching the locals trying to figure out how to fix it.

I love diesel electric but it would not have crossed my mind to try it
in a
60 foot sailboat. If having a DE sailboat is a goal in itself because
you
like to tinker and want to be a pioneer, cool. If you just want to sail
and
cruise, I would forget it. You can use that space, weight, money, and
research effort much more usefully.


There was an article in "PassageMaker" a while back about the
conversion of a trawler yacht from diesel to diesel-electric. It,
frankly, looked like a corporate promotion article -- perfectly
lighted photos and from the prospectives , obviously professional
camera equipment, but anyway.

The crux of the article was that the owner removed two main engines
and replaced them with a single, larger prime mover driving either an
alternator or generator (I don't remember which way he got his
electricity). Each of the original propellers/shafts, etc, were
replaced by DC motors directly coupled to the shafts. The whole
caboodle was SCR controlled and the genrator/alternator and both DC
drive motors were water cooled. The electric controls looked similar
to the SCR controls in an off shore drilling rig.

From looking at the pictures there appeared to be little of the
installation that was "off the shelf" and my guess was that the whole
installation must have been far in excess of what the original twin
engine installation was.






Bruce in Bangkok
(brucepaigeATgmailDOTcom)