Question Where to find info on why similar sized ships have very different ranges?

[76mmGuns]

Hi,

Websites with info on how to work out why similar sized ships have very different ranges?


TLDR: Title says my question


I've wondered why some ships have longer ranges than others, and why WW2 warships have vastly longer ranges of today. An example of this within the RAN is:

- Arafura Class OPV: 1680tones, 80m long, 4000nm (speed not stated anywhere-RAN/wiki, other sites)
- Leeuwin Class survey vessel: 2170 tons, 71m long, 18,000nm at 9 knots ( Leeuwin-class survey vessel - Wikipedia)

Now confusing this further, the Brunei version of the Arafura wiki says 7500nm < I think, but still far short of 18,000nm.

So I googled my above question, found nothing, so am asking the learned people on this forum for advise for sites which help explain the differences in range, and perhaps why it's so low now compared to WW2 ships.

 

[spoz]

There are many reasons; hull form, installed propulsive power, type of main engine, fuel tank capacity, whether the range is quoted to empty or 30% remaining or some other figure, and a host of others. Plus, whether the range is quoted at full or light displacement or somewhere in between. And the speed at which it is quoted; a difference of a couple of knots in the same ship might make a thousand miles difference in range; while range at full power might only be 10% of the range at economical power.

 

[Redlands18]

There are many reasons; hull form, installed propulsive power, type of main engine, fuel tank capacity, whether the range is quoted to empty or 30% remaining or some other figure, and a host of others. Plus, whether the range is quoted at full or light displacement or somewhere in between. And the speed at which it is quoted; a difference of a couple of knots in the same ship might make a thousand miles difference in range; while range at full power might only be 10% of the range at economical power.

And all that applies to any mode of transport. If you are driving a car around a busy city fully loaded you are not going to get the same mileage as highway cruising in a lightly loaded car. The car manufacturer will publicly quote a fuel consumption but you can bet your bottom dollar it will be based on operating the vehicle in perfect conditions.

 

[alexsa]

And all that applies to any mode of transport. If you are driving a car around a busy city fully loaded you are not going to get the same mileage as highway cruising in a lightly loaded car. The car manufacturer will publicly quote a fuel consumption but you can bet your bottom dollar it will be based on operating the vehicle in perfect conditions.

The other often missed factor is generation capacity. The nature of the equipment onboard and systems required to be supported will determined the generation requirements of the vessel. Modern warships require a lot more power that the WW2 vessels. How this power is provided will impact on fuel consumption.

 

[76mmGuns]

There are many reasons; hull form, installed propulsive power, type of main engine, fuel tank capacity, whether the range is quoted to empty or 30% remaining or some other figure, and a host of others. Plus, whether the range is quoted at full or light displacement or somewhere in between. And the speed at which it is quoted; a difference of a couple of knots in the same ship might make a thousand miles difference in range; while range at full power might only be 10% of the range at economical power.

The other often missed factor is generation capacity. The nature of the equipment onboard and systems required to be supported will determined the generation requirements of the vessel. Modern warships require a lot more power that the WW2 vessels. How this power is provided will impact on fuel consumption.

And all that applies to any mode of transport. If you are driving a car around a busy city fully loaded you are not going to get the same mileage as highway cruising in a lightly loaded car. The car manufacturer will publicly quote a fuel consumption but you can bet your bottom dollar it will be based on operating the vehicle in perfect conditions.

Thanks all for your answers.

Is there any site which shows a ranges when issues are standardised, eg range at 9 knots, at 13 knots, at 18 knots? Or at diff dimensions like beam of 13m,15m, 18m etc?

Or difference between a ships with most electronics turned off vs full alert, everything on?

Yeah, range is a bit of a fixation for me as far as ships are concerned.

 

[alexsa]

Thanks all for your answers.

Is there any site which shows a ranges when issues are standardised, eg range at 9 knots, at 13 knots, at 18 knots? Or at diff dimensions like beam of 13m,15m, 18m etc?

Or difference between a ships with most electronics turned off vs full alert, everything on?

Yeah, range is a bit of a fixation for me as far as ships are concerned.

There is no fixed formula if that is what you are looking for. The anticipated range will be driven by design, equipment and arrangement of the vessel. There is not fixed rule as to what can be achieved at what speed with what installed power. Beam is not necessarily and issue it is the entire hull form and intended operating drafts that determine achievable speeds (the block coefficient and hull dynamics) for a given power.

Vessels are delivered with a contracted speed and range (at different speeds) based on the buyers wishes. A vessel will a very high block coefficient is never going to be quick but bow design can make it more efficient and it will carry a lot more than a vessel with a very low block coefficient.

Finally .... the actual range is impacted by a range of variables:

• The State of loading of the vessel (Bow up stern down or any other odd loading is going to have an impact - this relates to other points made below as well)
• The vessel stability (slack tanks apply dynamic forces to the vessel and these tend be at the bottom of the vessel ... as you use fuel .... your stability margins normally decreases unless the ship can take ballast)
• The weather (poor weather generally results in a higher fuel burn)
• The vessels longtitudinal stability due to trim, vessel speed and other factors (if it is hard to keep the ship straight you are going to burn just a bit more fuel)
• The operating environment (tidal streams, currents and/or the need to manoeuvre in constrained waters ... nature of threat .. do you need to zig zag etc or manoeuvre as an escort around the main body of a group?)

So no ..... I cannot give you that advice.

 

[ngatimozart]

Thread locked because the question has been answered.