rodman 1250 fuel consumption

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mickyspec

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Hi lads
I wonder if anyone on here could post some real world fuel consumption numbers for a rodman 1250?
Im especially interested learning your fuel numbers at lower speeds
lets say 16 kts or 18 kts
thanks in advance
micky
 
Micky,

We cannot possiblyrespond constructively to this mail with so little information.

Fuel consumption is a question on how many HP you take out at a given speed, which is decided by engine configuration (shafts or pod drives on this boat) and engine selection... where pods will be more fuel efficient at planning speeds, which your question spans (16 probably below and 18 above).

So one you know your estimated running RPM, engine type & rating and max RPM etc., we can make an educated guess on what a continous load at the certain speed would be and thus fuel consumption, based on published engine efficiency at perfect state of tune....

As an example, we (45 ft, 21 T Displacement) seem to draw out about 160 hp from each engine at 15 knots (not very fuel efficient for our hull), which at 200 gramme per engine hour (commonly used average for diesel engnes .... modern engines may be more efficient, but if slightly out of tune, they will not meet the published figures...) means 320 hp x 200 = about 64 kg of diesel.... diesel weight is about 0.86 kg per litre, so you then get 64 / 0.86 to get the fuel consumption per hour which roughly is 75 L per hour...

Then you add in the variables such as sea conditions etc., which easily could vary by 10% ...

So without knowing the specifics, we can only guess..... More information = More accuracy....
 
Divemaster1 said:
Micky,

We cannot possiblyrespond constructively to this mail with so little information.

....
Click to expand...
To be fair I can tell someone pretty accurately what a Khamsin uses on fuel without all your sums, simply because I own one.
Presumably someone else might own a Rodman 1250.
Actually, always a boat I rather admired, so I would be quite interested to hear the answer too !
 
Just to clarify:

Classic turbo diesel engines burn 178 to 209 grams of fuel to produce one kw/hour. .
This equals an efficiency of 40-47% - 200 g/kw/h is an approx

So the factors to use are
hp to kw = divide by 1.3
diesel weight to volume (grams to liter) = grams divided by 0.86 divided by 1000 (the latter to cope with grams ~ kg)


Eg. 130 hp takes ((130/1.3) * 200 / 0.86 / 1000) = 23.25581395 liter/hour

Edit: Hands on experience is valuable if someone can share. Variables like weight, hull cleanliness, weather and instrument accuracy will influence on the power needed hence the accuracy of both methods.
 
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I would have thought that someone would produce a "Fuel Flow Meter" for inserting in the diesel pipe between the filter and the lift pump. With rising fuel prices working out your most economical speed is as essential as knowing your exact position.
 
Flow meters are available from a couple of sources. Not really cheap, especially when for diesel since it has to cope with differential computing between feed and return pipe.

As per the OP, asking about what to expect, theres not yet a boat to fit a metering device to :) so the scientific approach is easier (and free).
 
Unless i'm very much mistaken, the OP is asking for real World figures. I suspect he's not interested in theoretical sums and equations, but would rather hear actual consumption figures from the odd Rodman owner.

I can't help him with Rodman figures. But if someone asked the same question of a MF805 i could give him all sorts of figures without getting the calculator out.
 
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PaulGooch said:
Unless i'm very much mistaken, the OP is asking for real World figures. I suspect he's not interested on theoretical sums and equations, but would rather hear actual consumption figures from the odd Rodman owner.

I can't help him with Rodman figures. But if someone asked the same question of a MF805 i could give him all sorts of figures without getting the calculator out.[/QUOTE

Yes indeed sir, what i was hoping for was a rodman 1250 owner, could post real world bona fide fuel numbers.
The boat in question has twin 430 vovlos on shafts.
Click to expand...
 
Maybe a few actual boat user's figures may help? From differing boats,

We have a 28 ftvsports cruiser with twin 150hp diesels

At, 3000rpm 24 kts we use 20l ph
 
I've provided Micky with extremely accurate figures in mixed (average to very rough) conditions at both 8 knots and 20 knots in a 1250 with the same engines for a run I did out to Madeira, but I was unable to help with "just on the plane" figures.
I suspect that the actual facts will be remarkably similar fuel consumption for distance covered when compared to the 20 knots figure. In addition, I also suspect that the boat will struggle at sub 18 knots and try and slip back off the plane... She likes 20 knots.

For the record, over the course of the delivery I did the boat used almost exactly 20 litres per hour (combined) at 8 knots and almost exactly 100 litres per hour (combined) at 20 knots. I forget the rpms now, but "think" that equated to 1000rpm and 2000rpm respectively.
I do remember that the figures were accurate enough to be used for my fuel calculations during a 530nm open water crossing in addition to a long... long... stretch of coastal stuff.

http://www.madeirasportfishing.com/boat/1250-rodman
 
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Here are some real numbers for our 1250 Rodman which have been consistent over the last few years and through each season. I continuously monitor fuel consumption - it's one of the standard screens that the EVC software can display.

Our Rodman 1250 has IPS 500 and the fuel consumption figures are as follows :-

Conditions - fully fuelled (1400litres), full of water(400 litres) and all the cruising junk we carry, together with about 4 people we record,

1000rpm = 6.25knots = 7.5lph = 3.75mpg
1500rpm = 8.6knots = 18lph = 2.15mpg
2250rpm = 15knots = 53lph =1.25mpg
2500rpm =18knots = 67lph = 1.2mpg
2750rpm = 21.5knots =78lph =1.25mpg
3000rpm =25.5knots =95lph =1.23mpg.

These are our real numbers. Engines D6, 400 hours.

The 'sweet spot' at 2750rpm is our normal cruising speed. I don't know the precise reason for this sweet spot, but it is real.

The engine management system EVC gives a readout of fuel usage and is extremely accurate. I always brim my tank when filling-up and the amount needed to refill the tank is identical to that given on the EVC, certainly to within just a few/couple of litres - if it says 515 litres it does mean it and that's what you can squeeze in!

I have noticed that the addition of a few more bodies to an already well laden boat has little effect on these numbers.

Hope this helps
galps
 
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Sweet spot is about 200 revs less than WAT, Without knowing the boat or the engines, I would have said, about 1.3 MPG and it wont make much difference what your speed is, once plaining.

It seems that I am about right.
 
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