# Cruising range question

Discussion in 'Diesel Engines' started by htoykoc, Nov 9, 2009.

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### htoykocNaval Architect

Hi all,

I came across the yacht Arcadia whose cruising range was anounced to be a good 5000 miles at a cruising speed of 10 knots.

I was curious,

what would enable this boat to achieve that kind of a cruising range?

Does anyone have any idea on this?

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You need to know the fuel consumption of the engine!

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### htoykocNaval Architect

Fuel consumption at the lowest RPM (which is 1200 where the RPM at cruising speed was said to be 1800) is given as 78 lt per hour.

As for my calculations, it gives a range much less than 5000.

I am wondering what I am missing.

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well...if you know the consumption in l/h.....you know the capacity. So from this you can find the amount of hours. Knowing the speed, you then get the range, since velocity = distance/time.

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### gonzoSenior Member

43000/78=551 hours of running@10kts=5510 miles
Unless the water is flat,it would be sucking air.

Last edited: Nov 9, 2009
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### htoykocNaval Architect

Hmm, so it is the range on one engine only.

Always thought of two..

And probably very low consuming generators..

Thanks!

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### fcfcSenior Member

Some correction.

You do not have the propeller fuel curve of the cat 3412E. the 78l/h you got is the maximum fuel burn of the lowest rated cat 3412E (the one rated at 425 bhp , 1200 rpm).

The one on the arcadia is the one rated 540 bhp , 1800 rpm. Then the fuel burn at that maximum power is 105 l/h.

Know, you need to know what is the power needed to propel that yacht at 10 knot cruise. Obviously, it is not 2 * 540 hp, which is the maximum power. But if you throttle down, you engine will obviously burn less.

You can reverse compute if you have the fuel burn : 40 000 liters for 5000 nm at 10 kts make around 80 l/h. for BOTH engine. so 40 l/h each. Engine at full power is 105 l/h. So power (each engine) at cruise is around 540 * 40 / 105 = 205 hp.

Now, is 2 * 205 hp enough to push a 122 tons yacht 36m lenght at 10 knot. Probably yes. And power needed is probably lower than that to give allowance to genset and weather conditions.

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