On Wednesday 25 August 2004 12:26 am in rec.boats.cruising Parallax wrote:

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? 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.

If the hull is not designed for planing under power you
will not be able exceed the hull speed, so more power is
a waste.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

thanks, gune, for looking that up. it will save me retyping. unfortunately,
airplane mechanics usually don't have the native candle power to understand the
basics, so it is lost on them.

From: Gene Kearns
Date: 8/24/2004 8:43 PM Eastern Daylight Time
Message-id:

On 24 Aug 2004 16:26:07 -0700, (Parallax)
wrote:

SNIPS

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.
Any ideas?

Certainly.... Jaxashby... on par with Steven Hawking and Albert
Einstein, says you are all wet.... he says,

"Most recreational sailboats made in the last 40 years will exceed
"hull speed" without any heavy lifting, and Hobie cats will go 3x
"hull speed" or more.

Some would argue that those hulls are planing, though plainly that is
not the case.

btw, mathematically the extra effort needed "to climb the bow wave" is
zero at "hull speed" and still doesn't amount to all that much at 2x
"hull speed".

the THEORY is not theory at all, but oft repeated hearsay."

Full text available at: http://tinyurl.com/4ymdg


--



Grady-White Gulfstream, out of Southport, NC.

http://myworkshop.idleplay.net/cavern/ Homepage
http://www.southharbourvillageinn.com/directions.asp Where Southport,NC
is located.
http://www.thebayguide.com/rec.boats Rec.boats
at Lee Yeaton's Bayguide

(JAXAshby) wrote in message ...
thanks, gune, for looking that up. it will save me retyping. unfortunately,
airplane mechanics usually don't have the native candle power to understand the
basics, so it is lost on them.

From: Gene Kearns
Date: 8/24/2004 8:43 PM Eastern Daylight Time
Message-id:

On 24 Aug 2004 16:26:07 -0700, (Parallax)
wrote:

SNIPS

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.
Any ideas?

Certainly.... Jaxashby... on par with Steven Hawking and Albert
Einstein, says you are all wet.... he says,

"Most recreational sailboats made in the last 40 years will exceed
"hull speed" without any heavy lifting, and Hobie cats will go 3x
"hull speed" or more.

Some would argue that those hulls are planing, though plainly that is
not the case.

btw, mathematically the extra effort needed "to climb the bow wave" is
zero at "hull speed" and still doesn't amount to all that much at 2x
"hull speed".

the THEORY is not theory at all, but oft repeated hearsay."

Full text available at: http://tinyurl.com/4ymdg


--



Grady-White Gulfstream, out of Southport, NC.

http://myworkshop.idleplay.net/cavern/ Homepage
http://www.southharbourvillageinn.com/directions.asp Where Southport,NC
is located.
http://www.thebayguide.com/rec.boats Rec.boats
at Lee Yeaton's Bayguide








I am very aware of the limitations on hull speed. What I mean is that
sometimes an engine that will enable you to achieve hull speed in calm
water will only allow you to do half in wind or current. The idea is
to get more power to achieve nearly hull speed for short time when
conditions are such that you would otherwise be going slow. I rarely
buy my diesel at a marina as I dont ever seem to be near a marina.
Normally, I buy fuel and carry it to my boat. In this case, getting a
NOS canister would be reasonable. I agree, NOS simply adds extra
oxygen allowing more fuel to be burned thus producing more power.
Although I have used starting ether when I lived in WY in winter, I do
not think it adds any power, it is simply an easily ignited gas to get
the motor turning.

I am also aware of what octane does and I simply used it as an example
of an additive. My question is, are there additives available, sucha
s long chain hydrocarbons that would give more power than just gas
even though the additive might be very expensive

So, are fuel additives available
that would effectively increase the hp/ounce of fuel burned

no.

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.

the easiest way to make your fuel last longer is to go slower. It takes 2-1/4
times the fuel per hour to go 7.5 knots as it does to go 5 knots. 225% of the
fuel to go 150% the distance.

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