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Default Diesel electric

On Wed, 01 Aug 2007 21:00:52 -0400, Wayne.B
wrote:

On Wed, 1 Aug 2007 16:44:41 +0200, "Marc" wrote:

Roger & Bruce; thanks for your reaction. Pioneering is nice.. but not at any
price ;-) Not my main reason for looking into this...

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


Consider putting a folding or feathering prop on the "wing" engine to
minimize drag. Mount two large alternators on each engine (200+amps),
and use them to drive a large battery bank and redundant inverters.
That will be much cheaper to build and service than a diesel electric
system, and will give you full backup for everything. Many long range
cruising trawlers are being built that way.


You are talking about a 60 ft. sail boat. right?

Generally sail boats have auxiliary engines for those times that the
wind doesn't blow. There are also motor-sailers with somewhat bigger
engines but they really don;t go much faster.

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.

Now, that is probably a bit underpowered as you will be going "up
hill" sometimes but say you add another 25 - 30% and you still aren't
talking about a very big engine.

You've already decided on a sail boat so you have one source of power
and a secondary, the auxiliary diesel. Now do a little research. Go
down to the commercial docks and see how many commercial boats, guys
that spend their whole lives on the water, have more then one source
of moving the boat. The world's fishing fleet is probably 99% single
diesel engine powered and if you've ever been on the Grand Banks in
the winter time that alone should convince you that a second engine is
not really vital to life and happiness.

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
really strong wife or you are going to need powered winches. So you
have to figure on a gen-set that runs much of the time, if only to
operate the autopilot.

So there you go. A sixty ft. mast and enough dacron to build a circus
tent, a 75-100 H.P. auxiliary engine and a generator set.

And round the world you go =:-)


Bruce in Bangkok
(brucepaigeATgmailDOTcom)
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On Thu, 02 Aug 2007 10:40:27 -0400, Wayne.B
wrote:

On Thu, 02 Aug 2007 18:16:04 +0700, wrote:

So there you go. A sixty ft. mast and enough dacron to build a circus
tent, a 75-100 H.P. auxiliary engine and a generator set.


My point was that if you put a couple of *big* alternators on each
engine you don't really need a generator, and what would have been the
generator engine can now drive an off center shaft with a folding
prop. That way you can have it all more or less. If you want super
reliability, it is also necessary to have seperate fuel tanks for each
engine with appropriate transfer and filtration plumbing, along with
seperate batteries, etc.


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

Your engine sizing estimates do not take windage into account which
can be considerable on a 60 footer trying to motor into a 30 or 40 kt
headwind. And yes, sometimes it is necessary. I also take some issue
with your comparison to single engined commercial boats. Those boats
almost always have spacious engine rooms with room to work, lots of
essential tools and spares, and someone aboard who knows how to get
the job done. That is not the case with most 60 foot sailboats that
I've seen.



Well, I did admit that it was a quick and dirty calculation. But, if
you have 30 - 40 Kts of wind you've got super sailing weather for a 60
ft. boat.

You are right about engine rooms but I'm not so sure about people who
know how to get the work done. Example: The average Thai fishing boat,
say 50 - 60 ft. that makes voyages to Indonesia or Bangladesh to poach
fish usually had a Thai Captain, maybe a Thai 1st Mate, and the rest
of the crew are Burmese who are hired for probably less then $100 a
month. I'm not so sure about their expertise.

But, you have hit the nail on the head -- there are vast quantities of
people driving around in boats that don't know a thing about the
hardware. The neighbor boat to me had some people working on it, I
asked the Owner what was doing and he told me he was having the engine
oil and filters changed. A nice guy but didn't know where the oil
filter was.


Bruce in Bangkok
(brucepaigeATgmailDOTcom)
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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.

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.
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Default Diesel electric

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)


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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


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