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Wayne.B

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.