Empathy List Archives

JF

John Ford

Mon, Jun 12, 2006 3:46 PM

Hmm.. Ok, I'm going to be as careful as possible to not be vender bashing or anything.. But I'm looking at some of the fuel burn numbers on some of the recent boats and I'm scratching my head. Let's take Bluewater for instance, he was kind enough to give us all kinds of numbers. He said he got about 1.4 mpg which is probably like 1.3 nmpg at 6.75 knots?? If you go to Nordhavn's website they say the 47 has a range of 3000nm at 8 knots on 1,480 gallons of fuel. Shouldn't that number be higher??

Compare this to my Krogen 44 which when I did the trip north I did nearly 1000nm and burned almost exactly 500 gallons for a 2nm per gallon rate with the Genset running all the time for my pampered crew.

One easy answer I guess is that they were into a head current, or a head sea.. But just to be fair I'll give my conditions.. I was going into a head wind nearly the whole trip.. I kept it at 8 knots 1850 rpm's as much as possible. I did the outside for almost 48 hours exactly in 7 to 10's the first day(7 sec duration), then 4 footers the next day with the occasional 6 footers thrown in. Again all these waves were hitting me on the starboard nose and I had my stabilizers running the whole time. I did get heavy with the throttle once when I was trying to make a marina, and one other time where I was trying to make it to safe harbour. In these two cases I made 9.6 knots at 2200 rpm for a total time of about 15 hours. So I think this makes up for some of the slow no wake cruising you have to do when in the ICW.

I know that cruising out there in the open sea is quite a bit different then doing the ICW or even near shore.. But am I looking at similar decreased numbers when I take my boat further offshore? How are most of you measuring your fuel usage?? Daytanks, Floscan, something else? Unfortunately my boat didn't have a Floscan or a Daytank, so I could just look at the tanks in 50 gallon increments which doesn't help me define how much I was using off shore at any point in time. So I guess I'm looking at info on how much I will probably be changing in mileage, and what and how most of you all are using to determine what your burning.

Many thanks for any info..

John Ford
KK44 Feisty Lady
Annapolis, MD

Hmm.. Ok, I'm going to be as careful as possible to not be vender bashing or anything.. But I'm looking at some of the fuel burn numbers on some of the recent boats and I'm scratching my head. Let's take Bluewater for instance, he was kind enough to give us all kinds of numbers. He said he got about 1.4 mpg which is probably like 1.3 nmpg at 6.75 knots?? If you go to Nordhavn's website they say the 47 has a range of 3000nm at 8 knots on 1,480 gallons of fuel. Shouldn't that number be higher?? Compare this to my Krogen 44 which when I did the trip north I did nearly 1000nm and burned almost exactly 500 gallons for a 2nm per gallon rate with the Genset running all the time for my pampered crew. One easy answer I guess is that they were into a head current, or a head sea.. But just to be fair I'll give my conditions.. I was going into a head wind nearly the whole trip.. I kept it at 8 knots 1850 rpm's as much as possible. I did the outside for almost 48 hours exactly in 7 to 10's the first day(7 sec duration), then 4 footers the next day with the occasional 6 footers thrown in. Again all these waves were hitting me on the starboard nose and I had my stabilizers running the whole time. I did get heavy with the throttle once when I was trying to make a marina, and one other time where I was trying to make it to safe harbour. In these two cases I made 9.6 knots at 2200 rpm for a total time of about 15 hours. So I think this makes up for some of the slow no wake cruising you have to do when in the ICW. I know that cruising out there in the open sea is quite a bit different then doing the ICW or even near shore.. But am I looking at similar decreased numbers when I take my boat further offshore? How are most of you measuring your fuel usage?? Daytanks, Floscan, something else? Unfortunately my boat didn't have a Floscan or a Daytank, so I could just look at the tanks in 50 gallon increments which doesn't help me define how much I was using off shore at any point in time. So I guess I'm looking at info on how much I will probably be changing in mileage, and what and how most of you all are using to determine what your burning. Many thanks for any info.. John Ford KK44 Feisty Lady Annapolis, MD

N

Nunas

Mon, Jun 12, 2006 9:50 PM

John,

Aboard AKAMA (Krogen Whaleback), which has spent most of its running life
Passagemaking, we use a Hart Tank Tender. While running, we keep two logs,
a watch log that is filled in at each watch (usually about every three
hours) and a deck log that is filled in hourly (mostly engine gauge readings
and position). The watch log includes sounding the tanks.

Through most of the range of the gauge, an inch of fuel is about 50 litres
and we have three tanks. So there is plenty of room for error. We don't
use the sounding information to calculate fuel burn, unless we are getting
worried. The readings are just to ensure that we are not suddenly loosing
fuel to a leak. On the other hand, over the long run, it does provide a
relatively good gauge of what the burn rate is, and looking back over the
logs we can draw some conclusions based on real conditions.

On our last trip, from New Zealand to Australia, we logged 196 engine hours
and burnt about 2150 litres according to our Hart. We will only know for
sure what we've really used when we fill up, but that is fairly close. That
works out to nearly 11 litres per hour (2.9 US gallons), which is about what
the Krogen fuel table says we should burn for the engine speed we averaged.
On the other hand, we rarely run the generator, and the Krogen table is
supposed to include full time generator running.

The bigger issue is how far we will go on the fuel we have, not how long we
can run the engine. That certainly varies greatly with sea state. The
Tasman sea trip was two days of rough water, two days of heavy seas and
swell, one day of short high chop (wind agains current, with some water over
the boat) and three days of "reasonable" power boat weather. We never had
"oily seas" on this trip. I have not delved into the distance traveled
during small portions of this trip, but have done so in the past. We know
that on an oily sea we burn about 6.5 to 7 litres an hour, making a planned
speed of 6.5 knows. We also know that this can double when making into a
gale at about the same boat speed.

Well, I hope this quick (and not very scientific) note provides some
information for your quest. For us, it is rather academic, as we never set
out on a passage without filling the boat to the maximum, and we would
rather set the sea chute than slog into a storm for long enough to put the
boat in peril due to excessive diesel use.

Cheers,
Maurice & Louise-Ann

-----Original Message-----
From: John Ford [mailto:johnpford@mac.com]
Sent: Tuesday, 13 June 2006 01:46
To: passagemaking-under-power@lists.samurai.com
Subject: [PUP] Fuel Burn Rate and boats..

<Snip> I know that cruising out there in the open sea is quite a bit different then doing the ICW or even near shore.. But am I looking at similar decreased numbers when I take my boat further offshore? How are most of you measuring your fuel usage?? Daytanks, Floscan, something else? Unfortunately my boat didn't have a Floscan or a Daytank, so I could just look at the tanks in 50 gallon increments which doesn't help me define how much I was using off shore at any point in time. So I guess I'm looking at info on how much I will probably be changing in mileage, and what and how most of you all are using to determine what your burning.

Many thanks for any info..

John Ford
KK44 Feisty Lady
Annapolis, MD

Passagemaking-Under-Power Mailing List

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John, Aboard AKAMA (Krogen Whaleback), which has spent most of its running life Passagemaking, we use a Hart Tank Tender. While running, we keep two logs, a watch log that is filled in at each watch (usually about every three hours) and a deck log that is filled in hourly (mostly engine gauge readings and position). The watch log includes sounding the tanks. Through most of the range of the gauge, an inch of fuel is about 50 litres and we have three tanks. So there is plenty of room for error. We don't use the sounding information to calculate fuel burn, unless we are getting worried. The readings are just to ensure that we are not suddenly loosing fuel to a leak. On the other hand, over the long run, it does provide a relatively good gauge of what the burn rate is, and looking back over the logs we can draw some conclusions based on real conditions. On our last trip, from New Zealand to Australia, we logged 196 engine hours and burnt about 2150 litres according to our Hart. We will only know for sure what we've really used when we fill up, but that is fairly close. That works out to nearly 11 litres per hour (2.9 US gallons), which is about what the Krogen fuel table says we should burn for the engine speed we averaged. On the other hand, we rarely run the generator, and the Krogen table is supposed to include full time generator running. The bigger issue is how far we will go on the fuel we have, not how long we can run the engine. That certainly varies greatly with sea state. The Tasman sea trip was two days of rough water, two days of heavy seas and swell, one day of short high chop (wind agains current, with some water over the boat) and three days of "reasonable" power boat weather. We never had "oily seas" on this trip. I have not delved into the distance traveled during small portions of this trip, but have done so in the past. We know that on an oily sea we burn about 6.5 to 7 litres an hour, making a planned speed of 6.5 knows. We also know that this can double when making into a gale at about the same boat speed. Well, I hope this quick (and not very scientific) note provides some information for your quest. For us, it is rather academic, as we never set out on a passage without filling the boat to the maximum, and we would rather set the sea chute than slog into a storm for long enough to put the boat in peril due to excessive diesel use. Cheers, Maurice & Louise-Ann -----Original Message----- From: John Ford [mailto:johnpford@mac.com] Sent: Tuesday, 13 June 2006 01:46 To: passagemaking-under-power@lists.samurai.com Subject: [PUP] Fuel Burn Rate and boats.. <Snip> I know that cruising out there in the open sea is quite a bit different then doing the ICW or even near shore.. But am I looking at similar decreased numbers when I take my boat further offshore? How are most of you measuring your fuel usage?? Daytanks, Floscan, something else? Unfortunately my boat didn't have a Floscan or a Daytank, so I could just look at the tanks in 50 gallon increments which doesn't help me define how much I was using off shore at any point in time. So I guess I'm looking at info on how much I will probably be changing in mileage, and what and how most of you all are using to determine what your burning. Many thanks for any info.. John Ford KK44 Feisty Lady Annapolis, MD _______________________________________________ Passagemaking-Under-Power Mailing List -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.394 / Virus Database: 268.8.3/361 - Release Date: 11-Jun-2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.394 / Virus Database: 268.8.3/361 - Release Date: 11-Jun-2006

JF

John Ford

Mon, Jun 12, 2006 10:04 PM

Yes that helps quite a bit.. I'm trying to remove the unknown
variables, as I plan in the future to do longer and longer trips.

John

On Jun 12, 2006, at 5:50 PM, Nunas wrote:

en fuel table says we should burn for the engine speed we averaged.
On the other hand, we rarely run the generator, and the Krogen
table is
supposed to i

Yes that helps quite a bit.. I'm trying to remove the unknown variables, as I plan in the future to do longer and longer trips. John On Jun 12, 2006, at 5:50 PM, Nunas wrote: > en fuel table says we should burn for the engine speed we averaged. > On the other hand, we rarely run the generator, and the Krogen > table is > supposed to i

K

Keith

Mon, Jun 12, 2006 11:55 PM

Here's some recent data for my Krogen 42, 1986, non-stabilized, Lehman 135.

We just went from Houston to Port Aransas, TX offshore. 193 nm, 26:40
underway, used about 90 gallons with no genset running. That works out to
about 2.1 nm/gallon, and 3.4 gph. We had 2-5's off the Port bow, maybe 20
degrees relative to Port, 5-15 knot winds. Pretty constant speed of 7.2
knots.

Now, on an earlier trip to Port Arthur, the first leg was 3 hours through
rough waves until we got to the GICW, then smooth. Total time: 13:12, 91.2
nm, 40 gallons diesel, for 2.3 nm/gal and 3 gph. About 6.9 knots avg. The
return leg of the same trip found us with calmer bay waters... total time:
13:04, 91.2 nm, 30 gallons diesel, for 3.0 nm/gal and 2.3 gph. About 7.4
knots avg.

Now my fuel measurements are done by sight glass, so might be off a bit
using the eyeball method, but fairly repeatable. I was surprised at our fuel
burn to Port Aransas offshore, but the autopilot was working hard to hold
our course. Sure looks like the weather and current have a fair effect on
your burn, range, etc.

Keith

The things that come to those that wait may be the things left by those who
got there first.
----- Original Message -----
From: "John Ford" johnpford@mac.com

Hmm.. Ok, I'm going to be as careful as possible to not be vender bashing
or anything.. But I'm looking at some of the fuel burn numbers on some of
the recent boats and I'm scratching my head. Let's take Bluewater for
instance, he was kind enough to give us all kinds of numbers. He said he
got about 1.4 mpg which is probably like 1.3 nmpg at 6.75 knots?? If you
go to Nordhavn's website they say the 47 has a range of 3000nm at 8 knots
on 1,480 gallons of fuel. Shouldn't that number be higher??

Compare this to my Krogen 44 which when I did the trip north I did nearly
1000nm and burned almost exactly 500 gallons for a 2nm per gallon rate
with the Genset running all the time for my pampered crew.

Here's some recent data for my Krogen 42, 1986, non-stabilized, Lehman 135. We just went from Houston to Port Aransas, TX offshore. 193 nm, 26:40 underway, used about 90 gallons with no genset running. That works out to about 2.1 nm/gallon, and 3.4 gph. We had 2-5's off the Port bow, maybe 20 degrees relative to Port, 5-15 knot winds. Pretty constant speed of 7.2 knots. Now, on an earlier trip to Port Arthur, the first leg was 3 hours through rough waves until we got to the GICW, then smooth. Total time: 13:12, 91.2 nm, 40 gallons diesel, for 2.3 nm/gal and 3 gph. About 6.9 knots avg. The return leg of the same trip found us with calmer bay waters... total time: 13:04, 91.2 nm, 30 gallons diesel, for 3.0 nm/gal and 2.3 gph. About 7.4 knots avg. Now my fuel measurements are done by sight glass, so might be off a bit using the eyeball method, but fairly repeatable. I was surprised at our fuel burn to Port Aransas offshore, but the autopilot was working hard to hold our course. Sure looks like the weather and current have a fair effect on your burn, range, etc. Keith _____ The things that come to those that wait may be the things left by those who got there first. ----- Original Message ----- From: "John Ford" <johnpford@mac.com> > Hmm.. Ok, I'm going to be as careful as possible to not be vender bashing > or anything.. But I'm looking at some of the fuel burn numbers on some of > the recent boats and I'm scratching my head. Let's take Bluewater for > instance, he was kind enough to give us all kinds of numbers. He said he > got about 1.4 mpg which is probably like 1.3 nmpg at 6.75 knots?? If you > go to Nordhavn's website they say the 47 has a range of 3000nm at 8 knots > on 1,480 gallons of fuel. Shouldn't that number be higher?? > > Compare this to my Krogen 44 which when I did the trip north I did nearly > 1000nm and burned almost exactly 500 gallons for a 2nm per gallon rate > with the Genset running all the time for my pampered crew.

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Fuel Burn Rate and boats..