Fuel Economy Question

[RickB]

FF wrote:The big problem with Rick B 's post is that while the PEAK hp ,fuel flow , hp produced and rpm are always accuratly given , the prop curve and the fuel consumption figures for it are not measured , they are mere math creations.

"Prop demand data bases on .......... a fictional GUESS.

Geez FF, *Have you ever seen the amount of data collected during the certification of a marine (or any other diesel) by a manufacturer or shipbuilder for EPA, class, the owner, and for their own records as well as product development?

They don't just collect a couple of points and fill in the curve to make them meet. With the technology that exists today, anyone - and I literally mean anyone - can rent the test equipment to measure the power being absorbed by his very own personal propeller on his very own boat and measure the fuel consumption down to the milligram and make his very own curve.

We just did that on a boat, we very accurately measured fuel consumption through composition of the hydrocarbon emissions and cross checked it by balancing the combustion of fuel with air equations. This isn't voodoo or backwater magic FF, it is good ole technology in practice. We also knew what the rpm and torque was and one of the guys had a watch so that just about filled in all the boxes. And we are users, not manufacturers or a certification agency.

Since you don't hesitate to*swear by the hull speed formula and*sprinkle it liberally throught almost every power discussion, *it is difficult for me to understand why you find the same theory and practice so difficult to accept when it comes to the propeller curve.

FF,*your're still beating*a dead horse. Those engine fuel maps don't apply and if they did, what would you do with them, make a one off, one speed,*one trick pony boat? If it is that important that you trash every other set of figures available, install the test equipment on your present boat and let us know what you learn from it. Maybe you will turn conventional marine engineering and naval architecture on its head. Maybe there is a new*metric waiting to be discovered - the Fred Factor.


-- Edited by RickB on Monday 25th of July 2011 01:55:22 PM

 

[FF]

Maybe there is a new metric waiting to be discovered?

Not really Pro boat builder ran a series of articles , some on gen sets by Nigel Calder that gave the 300% number for fuel burn at low power from a bunch of small noisemakers.

And one of out members found out what happens with a new noisemaker at minor out put after tossing a 30 year old OHNO or Koler.

In a later series of articles NG went thru the power / fuel flow on a very well funded,instrumented (gov cash) on his 46 ft Malo sail boat.

The sail boat would be pretty close to a similar sized displacement power boat in terms of thrust required.

The article describes the failure of the attempt at using hybrid electric to extend the range.

Use the engine at high (efficient) HP , with some pushing the boat , the rest being stored in batts.

The effort failed as there is no batt system , yet that does work

AS in cars hybrid, is fine for stopped or stop and go city traffic , but useless at cruise , 65 mph for a distance.

You should be able to BS a free subscription to Pro boat builder , try a look.






-- Edited by FF on Tuesday 26th of July 2011 04:43:41 AM

 

[RickB]

FF wrote:


Pro boat builder ran a series of articles , some on gen sets by Nigel Calder that gave the 300% number for fuel burn at low power from a bunch of small noisemakers.

AS in cars hybrid, is fine for stopped or stop and go city traffic , but useless at cruise , 65 mph for a distance.

You should be able to BS a free subscription to Pro boat builder , try a look.

*I bet you can't find that 300 percent figure and provide a link or even a quote.

Was someone talking about hybrids?

No BS required, they give it away to anyone in the industry.*I get it*delivered to the office*and I*use an online sub for research. *