On Thu, 02 Aug 2007 23:49:12 -0400, Wayne.B
wrote:

On Fri, 03 Aug 2007 08:45:38 +0700, wrote:

Not to start a war, but I still don;t understand why you want sails
and two motors...

Well, they weren't my specs but I can understand the motivation.

Let's start with the premise that a boat needs aux propulsion for
various good reasons - entering harbors; short handed sailing with one
or two people; lack of wind; wind in wrong direction; schedules to
meet; broken furling gear; etc. These things all occur in real life
as opposed to the "ideal".

Let's additionally assume that a modern 60 foot boat also needs a
generator to provide power for air conditioning, refrigeration,
freezers, emergency battery charging, entertainment equipment,
microwave oven, etc. So that's one way of getting to two engines that
most folks on a well appointed 60 footer would not argue with.

I guess that my point was that since we are talking about a 60 ft.
displacement boat two engines aren't going to push it much faster then
hull speed anyway so why two.

Now that you've got two engines, how do you provide backup
functionality if one breaks down? Hence my suggestion for heavy duty
alternators on each allowing them to do double duty as power
generators and back each other up in that role. In addition, I would
also equip the second engine with an off center shaft and
folding/feathering prop which allows it to serve as back up to the
primary aux engine.

Modern boats with modern conveniences have a lot of complexity, and
the more redundancy the better in my experience. My own cruising boat
these days is a trawler with all the back up systems I can manage -
twin engines, twin generators, multiple battery banks, and multiple
charging sources. The idea being to eliminate as many single points
of failure as possible, be able to cruise in the boondocks with
confidence, and to keep the boat going until we can reach a suitable
repair facility.


So far the strategy has paid off. In three years of ownership and
10,000 miles of cruising we have experienced two unscheduled shutdowns
of main engines and numerous generator issues, none of which were show
stoppers because of the backup systems on the boat.

I can't fault your thinking. We were coming bringing a boat back from
Singapore to Phuket last September, coming out of Langkawi Harbor and
were on the Fly Bridge. My wife commented, rather calmly I thought,
"The boat is full of smoke." I looked down the hatch and IT WAS!

Haven't moved so fast in years and trying to remember where the
closest fire extinguisher is.... Got the engine hatch open and no
flames but a lot of smoke. Shut down both engines and jumped down in
the engine room (compartment). No fire that I can see but the bilges
are pretty full.

It turned out that the S.B. exhaust elbow broke letting exhaust and
raw water into the boat. I got everything closed and pumped out and we
motored sedately back to our original anchorage on one engine.
Redundancy IS good.



Bruce in Bangkok
(brucepaigeATgmailDOTcom)

"Michael Porter" wrote in message
...
The 60' LWL motor yacht of our design launched last summer has a
conventional 200 HP 6-cyl diesel (it's a purely displacement boat and
doesn't need 200 HP except in emergencies ).

THANKS! We still have to calculate but expect to end up with 150 to 170 hp.
The yachts displacement should be around 22 to 24 tons metric.

If I were starting on it today I'd certainly take a hard look at the
Siemens ELFA boxes with
GREAT will do for sure!!

the idea of installing 2 smaller engines and using only one of them
most of the time. That way the engine(s) would operate at higher load
and be happier.
Right! Planning on looking into a solution with 2 diesel engines and 2
propellors too. Curieous about the drag (speed loss) due to a second
propellor. And of course it is a saling boat and it is only an auxilary
engine BUT after spending some time in the Med I have the experience that
if you have any type of schedule (even allowing ample spare time) you just
need to motor from time to time.

Cheers Marc

Looks like a great article. THX!

Marc

wrote in message
oups.com...
On Aug 1, 2:15 am, "Marc" wrote:
...
Anyone with experience in diesel eletric solutions in this size for
sailing
yachts? ...


You might want to read the two part series in PBB (http://www.proboat-
digital.com/proboat/20070607/) on hybrid propulsion. They cover
engine sizing and a good deal more. It sounds like you've already
decided that you want to go with electric and I don't want to dissuade
you However, if you are just after fuel economy and are looking at a
true diesel electric system rather than an electric boat with backup
generation a variable pitch propeller will do a better job than an
electric transmission for a good deal less money.

-- Tom.

wrote in message
...


I'm assuming that you will have a modern fin keel, broad beam, shallow
hull depth, type of boat with minimum skin friction. I did a really
quick calculation, assuming 20,000 lbs. displacement and came up with
45 shaft H.P., Shaft RPM of 1100 and a speed of about hull speed.
Sorry... I'm not into these calculations. Displacement is 22 to 24 ton
metric

Lastly, if you are like most owners of 60 ft. bespoken yachts you are
not in the first blush of youthfulness so either you have a crew or a
Sorry I still am at 39 ;-) No crew for me... expect for my wife and / or a
friend (or two)

So there you go. A sixty ft. mast and enough dacron to build a circus
Expect to be using a 24 to 26 meter mast.. so a little more. BUT still
conviced I will be motoring from time to time anf not only for harbouw
manoevres.

Cheers

Marc

On Aug 3, 5:48 am, "Marc" wrote:
Looks like a great article. THX!


You are welcome. I notice the the link I posted is broken in my
browser so if anyone else is interested they might want to go to
http://www.proboat-digital.com and look for the june/july issue.
Professional Boat Builder is an usually good rag. There were a couple
of points that I thought were interesting about the article:

1) despite the fact that Calder is somewhat famous and well connected
he obviously had trouble shaking real numbers out of the d/e folks and
in the end resorted to a good deal of hand waving and extrapolation.
We mortals may have trouble getting enough disinterested information
on small d/e setups to do any valid engineering.

2) thermodynamics version 3.0 for the new digital age (tm) as brought
to you by Solomon Technologies is still pretty much the same old stuff
we learned back in the steam age. You still have to balance the
equations and there ain't no such thing as a free lunch.

3) the inefficiencies in small boat propulsion systems are primarily
the result of propeller inefficiency at slow rpms which result in
lightly loaded engines which are inefficient producing a vicious
circle. The logical place to break the circle is at the propeller.
Attempts to break the circle at the transmission are very likely
become exercises in moving the problem around rather than fixing it.

-- Tom.

Printing the article seems impossible. Understandable.. any idea how I can
get a digital or print copy of the article?

wrote in message
oups.com...
On Aug 3, 5:48 am, "Marc" wrote:
Looks like a great article. THX!


You are welcome. I notice the the link I posted is broken in my
browser so if anyone else is interested they might want to go to
http://www.proboat-digital.com and look for the june/july issue.
Professional Boat Builder is an usually good rag. There were a couple
of points that I thought were interesting about the article:

1) despite the fact that Calder is somewhat famous and well connected
he obviously had trouble shaking real numbers out of the d/e folks and
in the end resorted to a good deal of hand waving and extrapolation.
We mortals may have trouble getting enough disinterested information
on small d/e setups to do any valid engineering.

2) thermodynamics version 3.0 for the new digital age (tm) as brought
to you by Solomon Technologies is still pretty much the same old stuff
we learned back in the steam age. You still have to balance the
equations and there ain't no such thing as a free lunch.

3) the inefficiencies in small boat propulsion systems are primarily
the result of propeller inefficiency at slow rpms which result in
lightly loaded engines which are inefficient producing a vicious
circle. The logical place to break the circle is at the propeller.
Attempts to break the circle at the transmission are very likely
become exercises in moving the problem around rather than fixing it.

-- Tom.

On Aug 3, 12:02 pm, "Marc" wrote:
Printing the article seems impossible. Understandable.. any idea how I can
get a digital or print copy of the article? ...

I'll bet PBB would sell you one ?
subject=Professional BoatBuilder). You could save each page image
(right click save image as) to someplace (eg. your desktop) and then
print them individually. You might also be able to save the web page
for off line viewing with a grabber (eg. spiderZilla)...

Good luck,

-- Tom.

wrote:
On Aug 3, 5:48 am, "Marc" wrote:
Looks like a great article. THX!


You are welcome. I notice the the link I posted is broken in my
browser so if anyone else is interested they might want to go to
http://www.proboat-digital.com and look for the june/july issue.
Professional Boat Builder is an usually good rag. There were a couple
of points that I thought were interesting about the article:

1) despite the fact that Calder is somewhat famous and well connected
he obviously had trouble shaking real numbers out of the d/e folks and
in the end resorted to a good deal of hand waving and extrapolation.
We mortals may have trouble getting enough disinterested information
on small d/e setups to do any valid engineering.

2) thermodynamics version 3.0 for the new digital age (tm) as brought
to you by Solomon Technologies is still pretty much the same old stuff
we learned back in the steam age. You still have to balance the
equations and there ain't no such thing as a free lunch.

3) the inefficiencies in small boat propulsion systems are primarily
the result of propeller inefficiency at slow rpms which result in
lightly loaded engines which are inefficient producing a vicious
circle. The logical place to break the circle is at the propeller.
Attempts to break the circle at the transmission are very likely
become exercises in moving the problem around rather than fixing it.



A nice summary. I read the 2nd article as basically saying "there
ain't no free lunch and the D/E folks are having a hard time
justifying their systems".

On a cat a SIMPLE D/E system would almost seem to work rationally
(like Glacier Bay "do away with the batteries philosophy"), but I LIKE
the redundancy of twin engines instead of a more complex
genset/motor/controller system

Evan Gatehouse

On Aug 3, 9:43 pm, Evan Gatehouse
wrote:
....
On a cat a SIMPLE D/E system would almost seem to work rationally
(like Glacier Bay "do away with the batteries philosophy"), but I LIKE
the redundancy of twin engines instead of a more complex
genset/motor/controller system
....

One of the joys of yachting for me is that it is supremely and
unapologetically irrational . I certainly don't want to discourage
folks from finding beauty in systems and practices even when they are
hard to rationalize.

Like you, I like the redundancy of twins. I can attest that it has
been comforting to know that when one engine eats the bearings on its
salt water pump and spits them all over the engine room or drops its
propeller into the depths that my boat still has propulsion.

The Ossa (Glacier Bay) system looks interesting and could drive twin
props with multiple gensets so it might be pretty durable. I have
read their tech paper (http://www.ossapowerlite.com/tech_library/
fuel_efficiency/fuel_efficiency.htm). If you take them at their word
the system might well use less fuel in typical service than an old
mechanically governed over sized diesel system with a fixed prop that
was significantly undersized for its average service would... I can
imagine a scenario where it would be an easy system to rationalize (a
large yacht with big hotel needs and big fuel bills). On the other
hand, I was a little taken aback by the argument that claimed a long
commercial history of d/e propulsion because of its inherent
efficiency and also claimed that efficiencies of their system were the
result of very recent advances in technology and their proprietary
systems. I suppose you just have to take them at their word for the
second bit as their tech paper has no sources or verifiable numbers on
efficiencies. My understanding of the history of marine diesel
electric is different from theirs. I know that for the past hundred
years or so d/e systems have been used by navies and commercially for
a number of very good reasons. Those reasons include the ability to
run under water (submarines), to operate quietly (ASW) , to provide
quick changes in power over a wide range (tugs), to provide for
multiple, remote or vectorable thrusters (platforms), to provide for
big hotel needs (cruise ships) and so on. However, I don't think it
is historically correct to put fuel efficiency, per se, in that
list. This is certainly one of those cases where I would love to be
proven wrong. The siren call of a relatively cheap technological fix
for the woes of small boat propulsion and power generation is
strong. But, caveat emptor.

-- Tom.

Some interesting reading on Diesel Electric:

Fischer Panda:
http://www.solarnavigator.net/fische...l_electric.htm

Nordhavn:
http://www.nordhavn.com/constr_con/diesel_electric.php4

FAST:
http://www.feys.org/System/our_system.htm

Cruising World:
http://www.cruisingworld.com/article...ID=396&catID=0


"Marc" wrote in message ...
I am building a 60 foot aluminum sailyacht and considering using diesel electric propulsion with 2 identical diesel enigins of 70 -
100 hp. The builder is not very experienced in ths field so I am doing some fieldwork myself .

Anyone with experience in diesel eletric solutions in this size for sailing yachts?

Cheers.

Marc