Comments on: Full Load Fuel Burn and Range

By: Perriot

Perriot — Fri, 09 Apr 2010 07:57:36 +0000

Hello ,
The consumption of Avatar seem to be the same than our “passagemaker” “Hoa”.
At 9,75 knts on two engines our consumption is 1,78 lt/nm.
But our waterline length is just 18,26 m (60 feet) and our weight 32,3 tonnes.
Maybe our boat will be more comfortable if she will be loaded to 41 tonnes like “Avatar”
Best Regards
Yannick and Jacqueline from Hoa (France)

By: Steve Dashew

Steve Dashew — Wed, 07 Apr 2010 04:22:28 +0000

Hi Anthony:
There isn’t a lot in diesel engine efficiency to be gained by the slower turning engine, unless you have room to swing a larger diameter prop. If you do, then the slower turning prop – whether from engine or reduction gear – will show a gain in efficiency.
The FPB power requirements are so low that the actual fuel savings beyond where we are at present are not great enough to take the draft hit which comes with the bigger prop.

By: Anthony

Anthony — Wed, 07 Apr 2010 03:20:10 +0000

Steve,
They’re good figures. I guess even conservatively at somewhere between 9-10kn it’ll still do 6000+NM. Enough to get you from pretty much anywhere to anywhere(within reason). I’m sure most people would be more than happy with that!

I used to have a BMW 328, and my mates 325 regularly drank more fuel over a given period/distance, even though it was smaller capacity, because he had to work it harder to achieve the same performance.

It got me thinking, would a larger engine working less hard be any more efficient.
IE: would an engine that could do 10kn at 1200rpm use any less fuel than this one at 1800rpm?

Understandably there would be a weight penalty, and would most likely upset the balance you have striven so hard to achieve, right?

Just interested on your thoughts.

Cheers,
Anthony

By: Matt Marsh

Matt Marsh — Tue, 06 Apr 2010 20:44:24 +0000

Yep, we Net boaters can get a bit impatient for information! Kudos to Steve and Linda for keeping the rest of us up to date, even with all that testing and commissioning going on. And what a wonderful outcome to the project (or so the photos seem to say).

Still…. back when the 64 was just drawings, there was a post ( http://dashewoffshore.com/power_range_64.asp ) about the new ship’s expected fuel consumption. And, now that she’s in the water, the preliminary measurements are looking remarkably close to Steve & Linda’s earlier calculations once the difference in displacement is considered. Not orbital-mechanics close, but certainly far more accurate than anything I’ve seen from any car company or most boat builders.

Of course, this is hardly surprising, given the design philosophy and the level of expertise involved. It will be interesting to see how these figures look once the 64s have a few thousand miles behind them. Her tanks may be too big for most of us Net boaters to fill, but I suspect this is a boat that will rarely offer her happy owners any surprises at the fuel dock.