REPLY
Most trawlers already have generators with controls, and batteries and
inverter in addition to their main propulsion engine with controls.

Instead of having both a genset and propulsion engine plus a gear box
and controls  the hybrid boat would have one large genset whose primary
job is to charge the battery bank.
A dedicated inverter that produces the voltage needed by the variable
frequency drive powers the electric motor that turns the prop at very
low speed for maximum drive efficiency.

Electronic inverters cost less to manufacturer than precision made gear
boxes.
Even 10 years ago, the cost of industrial speed control devices were
much higher than they are today. Back when you were driving the D/E tugs
the cost for such equipment was indeed prohibitive unless economy of
scale came into play. This has changed.
Hydraulics may also offer possibilities. But once again the cost to
manufacture precision hydraulic parts far exceed the cost of making
electronic parts.

Cheers
Arild

Hello Arlid  I'm not certain but I think your suggesting that a diesel
electric drive can be built for near the same component cost as a conventional
drive. Lets use a single screw trawler with a 220 HP John Deere a 5050 Twin Disc
transmission and a 15 K gen set wholesale cost for these items is about
$29,000. That's just the component cost to turn the prop shaft and produce AC power
for the sake of this discussion lets leave out installation costs. Can you
offer component costs for a similar diesel electric drive. I have given you real
costs for the conventional drive I could buy the components today for that
money so please don't respond with theoretical costs lets look at the reality of
creating this drive system.

Brian Palmetto FL

Can you offer component costs for a similar diesel electric drive. I have
given you real costs for the conventional drive I could buy the components
today for that money so please don't respond with theoretical costs lets
look at the reality of creating this drive system.

This thread caught my interest because I am in the process of designing a
passage making trawler (some details can be found at http://kastenmarine
com/valdemar52.htm ) and I am now looking for and finalizing the selection
of a builder.  The estimating process, as I guess is the norm, had me second
guessing some items and scaling back others (the Niads were dumped in favor
of paravanes, for example).

Electric drive for planning hulls would seem to require much larger systems.
The horsepower to reach hull speed, though, should be quite different.

One system I am now looking at is the get home second engine.  It is
currently conventionally designed . . .  full redundancy.  Of course, with a
wing engine you end up with a third engine on board (main, genset, and wing)
with the wing being (hopefully only rarely used -- but requiring all of the
maintenance and upkeep nonetheless).

At any rate, Michael Kasten ran into a Victron representative over at a show
in Sweeden and now has me looking into using the generator as the power
source for an electrically driven auxiliary drive.  That would still get me
emergency propulsion in the event of a main failure, but would allow me to
avoid the costs and space of a conventional wing engine.

There is some information at the web site on a possible get-home engine
strategy using an electric drive.  Their drive motors are DC, run by
inverters off a standard genset.  You
get the AC gen, inverter, and the get-home system all in one package.

Victron / Fischer Panda are able to achieve hull speed with around 3.5hp /
ton.  By comparison, a diesel will require some 4 to 5 hp/ton to achieve a
hull speed of S/L 1.34.  If we can use a direct ratio, that implies that the
DC drive may be able to achieve the same speed using 70% to 85% of the power
required by a diesel.

We do not need to achieve hull speed, only a Speed/Length of 0.85 (for my
boat to be, square root of 49.7' wl times 0.85) or around 6 knots or less as
get-home).  The DC motor hp requirement would possibly be in the range of
around 0.75hp / ton, or possibly somewhere around 20 hp from a DC motor.

Some details about the drive can be found at:

http://www.fischerpanda.de/w09_product_eng_154_product.html

I have communicated with Victron to get more details and pricing -- not only
on the DC drive, but to see about them specifying the the entire vessel for
Victron electrical components.  When I hear anything, I will be happy to let
the list know what is out there from at least this source.

Any other ideas about what's out there now would, as usual, be most welcome.

Alan Wagner
Tampa, Florida

Currently:
1978 44' Gulfstar MY
"Morning Delight"

Soon to be:
52' Kasten Designed Valdemar
"Passage of Time"