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Old 26-05-2010, 09:39   #16
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Why do people always have to respond to every multihull thread talking crap and starting drama?
Jeeze, man. Is it worth getting upset over? Just ignore my posts if you like, but don't lose heartbeats over them

I will take Bash and we will go find a side line to sit on.


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Old 26-05-2010, 10:23   #17
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Actualy Scott, anyone can post in any forum. Please point out where someone posted derisive comments in this thread that beget crap and drama?

As an example of anyone posting in any forum: from a mono thread, scroll down to post 73?

Vote On the 'Best Blue Water Cruising Sailboat of All Time'



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Why do people always have to respond to every multihull thread talking crap and starting drama?

The OP clearly states:
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Old 26-05-2010, 10:26   #18
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Mark the question was power plant, fuel, and driveline. The number of hulls is mostly irrelevent and gives the OP a rough idea of speed and fuel consumtion for a given waterline length.

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Jeeze, man. Is it worth getting upset over? Just ignore my posts if you like, but don't lose heartbeats over them

I will take Bash and we will go find a side line to sit on.


Mark
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Old 26-05-2010, 10:48   #19
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Guys Ill admit I was more intersted in multis but seeing #'s for monos is of slight interest aswell I'm almost done thinking I know what I want now to start looking them over and rethinking everything I think I know.
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Old 26-05-2010, 11:01   #20
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Pro, it's gonna be Hp, drive line efficiency, waterline and weight. The multi has is the ability to shut down on one side and run the other. On the flip side there is more surface area to push through the drink and it works the smaller engine harder. Fuel burn is linear to Hp and rpm for a diesel.

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Guys Ill admit I was more intersted in multis but seeing #'s for monos is of slight interest aswell I'm almost done thinking I know what I want now to start looking them over and rethinking everything I think I know.
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Old 26-05-2010, 12:48   #21
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I will take Bash and we will go find a side line to sit on.
Sitting now.
Quietly.
On the sidelines.
Trying not to upset anyone.
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Old 26-05-2010, 14:53   #22
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I dont hold it anyone that wants to be out there with only one canoe and have a toxic metal floor to walk in thats the same thing I have been sailing for years hell its what I'd likley stay in if the wife would let me.
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Old 28-05-2010, 08:11   #23
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Pro, it's gonna be Hp, drive line efficiency, waterline and weight. The multi has is the ability to shut down on one side and run the other. On the flip side there is more surface area to push through the drink and it works the smaller engine harder. Fuel burn is linear to Hp and rpm for a diesel.
Bingo! The Joli gave the real answer... It's going to vary all over the place by boat and HP and conditions.

Quite frankly 90% of the answers giving fuel consumption are B-S because very few people in sailboats actually know their fuel consumption at different speeds. Sailors need to average between refuels, and that involves varying conditions and speeds, along with idle time. Only power boats have the kind of fuel rate of consumption instrumentation needed to know (generally).
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Old 28-05-2010, 09:37   #24
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Bingo! The Joli gave the real answer... It's going to vary all over the place by boat and HP and conditions.

Quite frankly 90% of the answers giving fuel consumption are B-S because very few people in sailboats actually know their fuel consumption at different speeds. Sailors need to average between refuels, and that involves varying conditions and speeds, along with idle time. Only power boats have the kind of fuel rate of consumption instrumentation needed to know (generally).
Wow, I guess I don't know what I'm talking about! The 6+ years and 1000+ engine hours I've spent studying fuel consumption on my boat was for nothing. Plus, I should probably throw away the engine manufacturer's fuel consumption tables.

Or, maybe I'm included in the 10%........
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Old 28-05-2010, 10:01   #25
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Wow, I guess I don't know what I'm talking about! The 6+ years and 1000+ engine hours I've spent studying fuel consumption on my boat was for nothing. Plus, I should probably throw away the engine manufacturer's fuel consumption tables.

Or, maybe I'm included in the 10%........
Correct, you don't know what you're talking about (kidding!) and I am surprised that you're surprised at that fact (still kidding!!)

When we first bought our boat, we also spent a lot of time trying to understand the level of fuel consumption. We have figured that at cruising rpms we are using about .6 - .8 gallons/hour/engine (that's about 2.3 - 3 litres for "sitting on the sidelines" MarkJ).

SailFastTri does bring up a good point though since most sailboats don't have accurate fuel tank gauges.

Fair Winds,
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Old 28-05-2010, 10:23   #26
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Wow, I guess I don't know what I'm talking about! The 6+ years and 1000+ engine hours I've spent studying fuel consumption on my boat was for nothing. Plus, I should probably throw away the engine manufacturer's fuel consumption tables.

Or, maybe I'm included in the 10%........
If you started with a full tank -- topped right up to the overflow vent, motored 12 hours at one speed (relative to water, not SOG), in protected water with little or no wind, you'd use how many gallons? Maybe around 6-15 depending in your engine(s) and speed. The only way you'd know accurately would be to fill again at a metered fuel pump before you idled or varied speed for a significant amount of time. In any event there would be variables and in the REAL world you'd never get closer than 10% accuracy with your guesstimate. That's why Joli has it right.

OTOH -- if you have calibrated fuel consumption instruments you might be able to do better. I have never seen or heard of a sailboat with that equipment.
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Old 28-05-2010, 11:27   #27
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I've only had a few occasions to motor for long periods, but I try to refuel at around 40 hours on both engines or 80 hours engine hours. I tend to cruise at 2900-3000 rpm and always put 56-58 gallons in the boat. It's quite consistant. This is of course with a clean bottom and props and relatively smooth water. If the water is rough there's usually enough wind for sailing. If I'm going any distance I clean the props and bottom. I don't wory about it for day sailing as I'm not using the engines to any great extent. The RPM range I use is the one recommended by Yanmar for these engines. Since I don't do much cruising at any other rpm I can't produce a consumption curve for my boat. It's accurate enough for my purposes.
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Old 28-05-2010, 12:09   #28
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If you started with a full tank -- topped right up to the overflow vent, motored 12 hours at one speed (relative to water, not SOG), in protected water with little or no wind, you'd use how many gallons? Maybe around 6-15 depending in your engine(s) and speed. The only way you'd know accurately would be to fill again at a metered fuel pump before you idled or varied speed for a significant amount of time. In any event there would be variables and in the REAL world you'd never get closer than 10% accuracy with your guesstimate. That's why Joli has it right.

OTOH -- if you have calibrated fuel consumption instruments you might be able to do better. I have never seen or heard of a sailboat with that equipment.
I use the engine manufacturer's numbers for passage planning (2L/engine per hour at my chosen cruise rpm). I factor for wind/waves, flat water at 7.5kts, I plan for 6kts. I've never run out of fuel. Of course, good planning includes using no more than 2/3 of your tank before re-filling.

The manufacturer's numbers are for hp/consumption for a particular rpm. HP equates to boat speed for the conditions. Given the engine is maintained to spec, that's a good number, you won't use more than that, you might use less.

There is no reason one couldn't add fuel consumption instruments, but I certainly don't see the point. On a sailboat, the engines are 'auxiliary' power!
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Old 29-05-2010, 07:43   #29
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Voyage 440 plus, 39 HP yanmars. 9.3 knots at full power which is 3200 rpm and 8.5 knots at cruising power 2600 RPM. One engine 2800 RPM 6.5 knots. Manufacturer fuel burn spec at cruise power is about 1 gallon per hour per engine.
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