From your friendly Tayana "Lurker"
Great idea. Those speedometers were never very accurate, anyhow.
I have a Tayana 37, with a Perkins 4-108, and an 18x10 fixed three blade
prop. 2,000 RPM will give me a "more or less" steady 5.5 knots. Maybe a bit
more if the wind is with me, and there is no current. 6+knots on occasion. I
can crank the engine up to close to 3,000 RPM and even get a tad over 7.1
knots (in still water), but I can't get all excited about the idea of going
an extra knot at the price of burning out my engine. I know that a lot of
the books say that you should run your diesel full out. There is the other
school of thought, that says if you run it a bit slower, it will last
disproportionately longer. If I really want to get someplace in a hurry,
I'll ask George Bush Senior to take me there in his Cigarette Boat (60+
Knots and using gallons per minute).
You do want to optimize performance, but there is typically a big gap
between "Hull Speed" and "motoring speed" on a full keel sailboat. It's
pleasant and quiet to sail at hull speed. On our Tayana 37 with a 31'
waterline, the hull speed is nominally about 7.4 knots. It's noisy and
vibration prone to motor anywhere near that speed on a full keel sailboat.
Then there is the matter of fuel efficiency. If I keep it at 6 knots or
less, I easily can get almost 10 nautical miles per gallon. Increasing the
speed 15% to 6.9 (OK, call it 7 knots) decreases fuel efficiency by an
estimated 30% (i.e., 7 nautical miles per gallon.) At $4/gallon (at our
friendly San Diego Fuel Dock), staying at 6 knots won't make that big a
difference in the time it takes me to get back to the local beer hall. (That
translates to taking 6 hours to go 42 miles at 7 Knots, versus 7 hours to go
42 miles at 6 knots. That is 4.2 gallons vs. 6.0 gallons; or $16.80 vs.
$24.00 - or approximately a six-pack. ) On longer trips, when getting in
before dark to a new harbor, then it might be worth the extra wear and
tear - or start an hour earlier.
Great tidbit about the Panama Canal.
regards,
Harvey Karten

----- Original Message -----
From: "Gary Walls & Bill Healy" <amadonlight@mac.com>
To: <baba-l@ballreich.net>
Sent: Tuesday, July 11, 2006 6:11 PM
Subject: Re: [Baba-L] Baba 30 3GMF 3-Blade Max Prop Settings

> Alan,
> The easiest way to get 6.5 knots from your Maxprop is to set your knot
> meter at 6.5 when you are going 5.1 knots. It saves engine wear, makes
> you feel better, and no longer requires stretching the truth on boat
> speed - a tradition among sailors.
>
> Bill Healy
> Amadon Light
>
> P.S. Both the Suez Canal and Panama Canal put pressure on small boats to
> go fast. Our solution in both was to crank up the knot meter to 7 knots
> while going 5.5 and to put a clamp on the accelerator cable limiting
> engine speed to our usual cruising level.
> So, when the pilots put the peddle to the metal they were quite impressed
> and happy to be racing along so well. We sat back and enjoyed the ride.
>
>
>
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>

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Received on Tue Jul 11 19:52:34 2006