Sorry, but isn't the 'wing' engine in most cases linked to the main shaft
rather than having a shaft of its own??

And if you leave this undisturbed 'emergency' fuel suppy set for quite a
while, the fuel turns sour, particularly these days??

------ Original Message ------
Received: Sat, 01 Mar 2008 10:40:24 PM EST
From: John Marshall johnamar1101@gmail.com
To: Passagemaking Under Power List
passagemaking-under-power@lists.samurai.com
Subject: Re: [PUP] Emergency Power (The Dashew's trip planning)

Basically, per the linked article, it comes down to good maintenance,
and then raising makeshift sails if all else fails.

I hear the argument, but I still like having a wing engine that will
run (on a separate tank of known good fuel) for at least 6 or 7 hours
before I have to tie it into the main fuel system. That gives me some
time to sort out filters, etc. if I have bad fuel.

If you're far offshore, then getting the main running again is the
real answer. But the wing buys you instant propulsion while you figure
things out, albeit not necessarily uphill at any kind of speed. And
the prop is located forward of the main prop on most boats, so
hopefully anything that tangled up the main is well wrapped and/or
streaming behind the boat. Plus the wing prop is folding, so if it
does tangle, you may be able to fold it and get the line to stream off
it.

John Marshall

On Mar 1, 2008, at 6:24 PM, John Harris wrote:

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The Nordhavn wing concept has a few elements to minimize common points
of failure:

1. Mechanical diesels. The mains have to be electronically controlled
   turbo diesels for efficiency and emissions these days, but the wing
   engines use the older tried and true mechanical injection systems. A
   lightning hit or electrical fault that took out the main engine
   computer or controls might leave the wing in operating condition.

2. Separate batteries and electrical systems from main.

3. Separate fuel supply... as Scott indicates, you make sure its
   scrubbed and clean, but you have to refresh it periodically. The wing
   tank is easily drained and the only way to fill it is to use the
   transfer/polishing system which runs through a 2 micron Racor during
   the filling process.

4. Shaft/prop mounted off center, above and ahead of main. Prop is
   normally folded so it can't easily snag lines, which would likely get
   wound up on the main shaft anyway, and hopefully trail behind when
   underway.

5. Separate control system using cables, manual transmission, etc.
   Unlike the main, which are Mathers fly-by-wire control on the mid-size
   and up Nordhavns.

6. Quick engagement... in an emergency, total time from deciding you
   need the wing to getting it started and pushing the boat is maybe 15
   seconds. Not a big deal at sea, but if your main died coming into a
   marina...

Also, even when the main engine is sound, when going through very
hairy narrows (narrow, swirling, salt water rapids) in the PNW or
Alaska, or when docking in high winds or other hazardous conditions,
some owners have the wing warmed up, running and ready to engage.
Losing power for even a few seconds in those conditions can break your
boat. In addition, being that the wing is mounted off center-line, you
get some of the maneuvering benefit of twin engines at the dock,
especially if thrusters are down or need help.

Drawback is speed (5 knots in flat water, a lot less when going
uphill), minimal generator capacity (you'd have to drop back to using
only essential navigational and communications electronics and minimum
lighting), and lack of stabilization (no hydraulic pump -- except
maybe on the largest of the single-engine boats, N62, N64). Between
the lower power and lack of stabilization, you might not be able to
make decent or comfortable headway on some headings in a big sea.

No redundancy is perfect, and I certainly wouldn't want to travel too
many days on the wing engine, but a lot of thought went into making
sure the wing doesn't share the same failure modes as the main engine/
shaft.

John Marshall
Serendipity - N5520

On Mar 2, 2008, at 5:04 AM, Scott E. Bulger wrote: