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)