Hi Garrett,

Thank you for the reply. I was able to find the article online.
http://www.nordhavn.com/constr_con/diesel_electric.php4
(http://www.nordhavn.com/constr_con/diesel_electric.php4)

Of course, Nordhavn is a marketing company first, and a boat  builder second,
as is any successful business, in their particular  field, these days. And,
they do a splendid job of both, don't  they? And marketing, it's obvious, had a
lot to do with  this  "proof-of-concept" project, as they call it. But, I
didn't see  any claims as to efficiency. The specs given prohibit a comparison of
the  geared-drive 72 with the hybrid. It would be interesting to see some
actual  data. But, the figures they do give for the hybrid don't look that good
to  me. Note that the owner, rather than Nordhavn speculates on the fuel
consumption. Hmmm...

As I said before, I think the concept is very cool, but there are  drawbacks.
Note that there was no mention of MTBF on the switchgear and control
systems, only on the motors and generators.  And, I can't see starting  and stopping
engines just to cruise at reduced speed for a short time.

As one who was heavily involved with a proposed General Electric  D-E
propulsion/ship's power project in the early 80's, I will continue  to have an
interest in the subject, and will be pleased to receive any factual  data.

I have no connection or interest with any of the firms herein  mentioned.

Regards,

John
"Seahorse"

If anyone wishes, I'll seek permission from Nordhavn to reproduce the  entire
article written by Jim Kirby, but here's a synopsis:

"Highly  efficient hybrid systems have been the driving force for years in
commercial  craft such as ferries, tugboats, small warships, oil-platform
supply vessels  and research vessels... Now Pacific Asian Enterprises
(Nordhavn) has taken  the lead in adopting an advanced Siemens-developed
version of this proven  propulsion system to large yachts in the form of a
proof-of-concept  diesel-electric Nordhavn 72... Like its larger commercial
cousins, the hybrid  72 uses its diesel engines to drive electric generators;
there is no direct  connection between the engines and propellers. The
electricity that is then  produced is used to power electric motors that drive
the yacht's  propellers... Dave Fulton, the electric 72's owner, says the
system should  give the boat tremendous range. He estimates that when running
seven knots on  the 200 horsepower engine, the yacht's 3,030 gallons of fuel
could take it as  far as 8,200 miles..."

Dan Streech, PAE's President, says, "We envision  20 years from now it [hybrid
power] could be so common that even 40 foot  boats might have it."

control

and stopping

REPLY
I echo Johns scepticism. For smaller trawlers doing mostly coastal cruising,
I think the best solution is the CPP - controllable pitch propeller.

Coastal cruising as opposed to trans-oceanic passagemaking involves a great
deal more slow and partial speed maneouvering, and depending on what area
you cruise even a lot of reversing of thrust.
Two typical situations that come to mind is waiting for a bridge opening or
waiting for a lock opening when you cannot tie up to a dock.  So called
"fast trawlers" or semi-displacement cruisers that have the power to exceed
basic hull speed suffer most in restricted seed zones like Florida;s canals.
Some of these cruisers literally have to creep at dead slow idle to keep
their speed down to the legal  limit. Although the total fuel burn is less,
the miles per gallon consumed is not.

A CPP allows the engine to be run at a more efficient RPM while controlling
the prop to give the desired thru water speed. From my own experience in the
Great Lakes canal systems  you often end up having to position yourself in a
fast moving current whiel not making any headway over the ground while you
wait fro the lock doors to open.  Docking against the current also poses
some interesting problems  that are eased with CPP.

If you are set up with high power alternators to drive your onboard
electrical system under way, you also gain a benefit.  Alternators seldom
put out maximum power at slow engine speed. Nor do their own pulley fans
draw sufficien tcoolign air. Slow speed combined with high electrical power
demand is the worst operating mode for such an alternator system. A CPP
allows you to run the engine/alternator at best RPM while maintaining over
the ground  or through the water speed to deal with the conditions.

regards
Arild