In article ,
(Parallax) wrote:

snip Cruising
sailboats are not terribly concerned about the overall cost of their
fuel because they will always use a small amount.
Most sailboats have a smaller engine for their displacement than a
powerboat because their primary power is supplied by free wind.
However, fuel use (hp/liter or hp/ounce) and overall power sometimes
are important for a sailboat. A long distance cruiser can only carry
a small amount of fuel and if he has a long period of no or contrary
wind, he might want to be able to motor for a long time with little
regard for the cost of the small amount of fuel. He might consider it
rreasonable to pay a premium for a fuel that was formulated to produce
more more power for ounce of fuel burned even if that fuel was twice
as expensive as conventional fuel. So, are fuel additives available
that would effectively increase the hp/ounce of fuel burned even if
they greatly increase the overall fuel cost? Would octane boosters
help (or cetane boosters)?

Not significantly. More significant is a large, slow prop... more later.
Also, I believe diesel has a slightly higher btu/pound rating than gas.

A related issue is that most sailboats have a fairly small engine
intended only to get the boat up to hull speed in calm water. Putting
in a larger engine would be considered wasteful because then the boat
would have to always carry around that heavier engine even when it
wasnt needed. Is it possible to temporarily increase the power
outpuit of a small engine by some means, perhaps a blower, a turbo or
even using NOS?

Yes, but KISS would preclude that, though turbos wouldn't spin hard at
most cruising speeds. I suspect NOS wouldn't work, for the same reason I
was told never to use ether to help start: premature ignition.

This might give the sailboat the ability to better
motor off a lee shore in strong winds, motor against a strong running
tide, etc. I am primarily interested in times when it is a safety
issue, not for convenience so potential engine damage might be
acceptable.
Any ideas?

We have a Yanmar 2GM20F on our 7,000# boat. At full power, in calm
water, we can motor at 7.2 knots, our hull speed is 6.65. When I wanted
to get home a few minutes earlier a couple of weeks ago (I could see the
front bearing down), I firewalled it and did 6.5-7.5 knots for those two
hours, got into the slip, got the first (most important) spring line on,
and got plastered by a monsoon. If I had to, we could pretty much
maintain hull speed through anything -- though I usually slow down.

We used 2+ gallons for that trip. More usually, we would use 0.6 gallons
at 5.5 knots. If I were cruising, it'd be closer to 0.4 at 5 knots.
(yeah, I'm retentive enough to have checked all these numbers: we've
averaged 0.30 gph for 1200 hours.)

In other words, consumption is directly related to speed once a real
load is on the engine (5 knots doesn't improve consumption), and
increases significantly as you approach and exceed hull speed.

The diesel it replaced would have used about twice the fuel for the same
speeds because it swung a little 12x8" prop at about engine speed. The
Yanmar swings a 16x10" prop at about 1/3rd the engine revs. The
difference: drag and bite.

Our 15 gallon tank gives us about 40 hours' range at high cruise, up to
60 hours if I'm not in a rush -- about 300 nm. Add another tank or a
couple of jerry cans and I'd be happy with an honest 6-700 nm range,
particularly since Xan moves on a breath of wind.

Get good sails, particularly light-air ones. That'll work nicely.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

Jere Lull answers this question quite well from a cruising sailor's
viewpoint. My experience in offshore cruising sailboats 37 to 42 feet
in length yields fuel consumption of about 0.4 gallons per hour at
cruise. This comes from consistent engine use when our speed under
sail drops below 3.5 or 4 knots - firing up the engine is always the
call of the man on watch - our goal is to make good about 135 NM or
more each 24 hour period underway. I have a hard and fast rule to not
leave on a voyage unless we have 200 hours of fuel onboard, or, as is
the case with the boats I normally take offshore, about 80 gallons of
fuel. This pencils out to about 900 to 1000 NM under power, with some
leeway for daily battery and frig plate charges while under sail
alone. This fuel quantity has worked quite well while on voyages of
30 days nominal length, yet we've come in on fumes once or twice,
having to wait for wind during the last week out to make it into port
with enough fuel remaining to negotiate the harbor and docks.

T A Will

0.4 gallons of diesel fuel used per hours equals of about 6.4 hp. but who's
counting.

(TAWill s/v Lucky Strike)
Date: 9/7/2004 11:16 PM Eastern Daylight Time
Message-id:

Jere Lull answers this question quite well from a cruising sailor's
viewpoint. My experience in offshore cruising sailboats 37 to 42 feet
in length yields fuel consumption of about 0.4 gallons per hour at
cruise. This comes from consistent engine use when our speed under
sail drops below 3.5 or 4 knots - firing up the engine is always the
call of the man on watch - our goal is to make good about 135 NM or
more each 24 hour period underway. I have a hard and fast rule to not
leave on a voyage unless we have 200 hours of fuel onboard, or, as is
the case with the boats I normally take offshore, about 80 gallons of
fuel. This pencils out to about 900 to 1000 NM under power, with some
leeway for daily battery and frig plate charges while under sail
alone. This fuel quantity has worked quite well while on voyages of
30 days nominal length, yet we've come in on fumes once or twice,
having to wait for wind during the last week out to make it into port
with enough fuel remaining to negotiate the harbor and docks.

T A Will

Using the "rule of thumb" of 0.055 gallons/hp/hour, that works out to 7.2 HP.

To maintain 5 knots, a 40 footer is going at a SL ratio of 0.83, which means
about 2200 pounds per HP. If the boat displaces 18,000 pounds, that's a little
over 8 hp.

However, if the boat is motorsailing, the fuel consumption will go down
considerably.

To double check, a Yanmar 4JH4, nominally rated at 54 HP, will deliver 8 HP at
1750 RPM. using 0.5 gal/hour. The smaller 3YM30 would run at 2300 rpm and be
more efficient, using .45 gal/hour.



"JAXAshby" wrote in message
...
0.4 gallons of diesel fuel used per hours equals of about 6.4 hp. but who's
counting.

(TAWill s/v Lucky Strike)
Date: 9/7/2004 11:16 PM Eastern Daylight Time
Message-id:

Jere Lull answers this question quite well from a cruising sailor's
viewpoint. My experience in offshore cruising sailboats 37 to 42 feet
in length yields fuel consumption of about 0.4 gallons per hour at
cruise. This comes from consistent engine use when our speed under
sail drops below 3.5 or 4 knots - firing up the engine is always the
call of the man on watch - our goal is to make good about 135 NM or
more each 24 hour period underway. I have a hard and fast rule to not
leave on a voyage unless we have 200 hours of fuel onboard, or, as is
the case with the boats I normally take offshore, about 80 gallons of
fuel. This pencils out to about 900 to 1000 NM under power, with some
leeway for daily battery and frig plate charges while under sail
alone. This fuel quantity has worked quite well while on voyages of
30 days nominal length, yet we've come in on fumes once or twice,
having to wait for wind during the last week out to make it into port
with enough fuel remaining to negotiate the harbor and docks.

T A Will

use any "rule of thumb" you can find, BUT theoretical hp per gallon fuel burned
per hour is about:

water cooled 4 cycle diesel, 24 hp
water cooled 4 cycle gas, 20 hp
aircooled 4 cycle, or water cooled 2 cycle gas, 16 hp
aircooled 2 cycle gas, 12 hp

that's the theory, the practise is about 2/3rd that.

close enough for gummit werk. all assuming engines in decent working
condition, worn-out junkers not included.



Using the "rule of thumb" of 0.055 gallons/hp/hour, that works out to 7.2 HP.

To maintain 5 knots, a 40 footer is going at a SL ratio of 0.83, which means
about 2200 pounds per HP. If the boat displaces 18,000 pounds, that's a
little
over 8 hp.

However, if the boat is motorsailing, the fuel consumption will go down
considerably.

To double check, a Yanmar 4JH4, nominally rated at 54 HP, will deliver 8 HP
at
1750 RPM. using 0.5 gal/hour. The smaller 3YM30 would run at 2300 rpm and
be
more efficient, using .45 gal/hour.



"JAXAshby" wrote in message
...
0.4 gallons of diesel fuel used per hours equals of about 6.4 hp. but
who's
counting.

(TAWill s/v Lucky Strike)
Date: 9/7/2004 11:16 PM Eastern Daylight Time
Message-id:

Jere Lull answers this question quite well from a cruising sailor's
viewpoint. My experience in offshore cruising sailboats 37 to 42 feet
in length yields fuel consumption of about 0.4 gallons per hour at
cruise. This comes from consistent engine use when our speed under
sail drops below 3.5 or 4 knots - firing up the engine is always the
call of the man on watch - our goal is to make good about 135 NM or
more each 24 hour period underway. I have a hard and fast rule to not
leave on a voyage unless we have 200 hours of fuel onboard, or, as is
the case with the boats I normally take offshore, about 80 gallons of
fuel. This pencils out to about 900 to 1000 NM under power, with some
leeway for daily battery and frig plate charges while under sail
alone. This fuel quantity has worked quite well while on voyages of
30 days nominal length, yet we've come in on fumes once or twice,
having to wait for wind during the last week out to make it into port
with enough fuel remaining to negotiate the harbor and docks.

T A Will

(TAWill s/v Lucky Strike)
Date: 9/7/2004 11:16 PM Eastern Daylight Time
Message-id:

Jere Lull answers this question quite well from a cruising sailor's
viewpoint. My experience in offshore cruising sailboats 37 to 42 feet
in length yields fuel consumption of about 0.4 gallons per hour at
cruise.
T A Will

In article ,
(JAXAshby) wrote:

0.4 gallons of diesel fuel used per hours equals of about 6.4 hp. but who's
counting.


Your point being what?

We cruise comfortably at 5-7 hp. We can go a full knot and a half (about
20%) faster when we want to, but at 4 times the burn. Not worth it to us
most of the time.

Cruising is very different than storming around at full power for an
afternoon.

Hell, we don't fire up until our VMG is under about 2 knots unless we
feel like it.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

a 42 boat motoring using just 6 hp is rare indeed. **planning** on using no
more than 6 hp so one has enough fuel is not prudent seamanship. essentially,
one is engineless in a 42 foot boat with a 6 hp engine. Hell, a 32 foot boat
with 6 hp is damned near engineless.

Now, engineless isn't bad, as long as *you* understand you are engineless.

Jere Lull answers this question quite well from a cruising sailor's
viewpoint. My experience in offshore cruising sailboats 37 to 42 feet
in length yields fuel consumption of about 0.4 gallons per hour at
cruise.
T A Will

In article ,
(JAXAshby) wrote:

0.4 gallons of diesel fuel used per hours equals of about 6.4 hp. but
who's
counting.


Your point being what?

We cruise comfortably at 5-7 hp. We can go a full knot and a half (about
20%) faster when we want to, but at 4 times the burn. Not worth it to us
most of the time.

Cruising is very different than storming around at full power for an
afternoon.

Hell, we don't fire up until our VMG is under about 2 knots unless we
feel like it.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

It's been a couple of years since I've bothered with you. Even though
you persist in posting foolish drivel, it's laughable to think of you
advising anyone about 'prudent seamanship'. What a NYC churl art
thou. Real life experiences are difficult for you to appreciate since
you obviously have no life with which to make comparison. Rick
wouldn't have you as a wiper, nor would I have you so much as secure
one of my dock lines without checking your work. Now, why don't you
go play in the street?

T A Will

(JAXAshby) wrote in message ...
a 42 boat motoring using just 6 hp is rare indeed. **planning** on using no
more than 6 hp so one has enough fuel is not prudent seamanship. essentially,
one is engineless in a 42 foot boat with a 6 hp engine. Hell, a 32 foot boat
with 6 hp is damned near engineless.

Now, engineless isn't bad, as long as *you* understand you are engineless.

dood, you are drunken idiot exposing yourself to little boys. go away.

(TAWill s/v Lucky Strike)
Date: 9/9/2004 11:10 PM Eastern Daylight Time
Message-id:

It's been a couple of years since I've bothered with you. Even though
you persist in posting foolish drivel, it's laughable to think of you
advising anyone about 'prudent seamanship'. What a NYC churl art
thou. Real life experiences are difficult for you to appreciate since
you obviously have no life with which to make comparison. Rick
wouldn't have you as a wiper, nor would I have you so much as secure
one of my dock lines without checking your work. Now, why don't you
go play in the street?

T A Will

(JAXAshby) wrote in message
...
a 42 boat motoring using just 6 hp is rare indeed. **planning** on using no
more than 6 hp so one has enough fuel is not prudent seamanship.
essentially,
one is engineless in a 42 foot boat with a 6 hp engine. Hell, a 32 foot
boat
with 6 hp is damned near engineless.

Now, engineless isn't bad, as long as *you* understand you are engineless.