Ship Class Endurance

[GaryChildress]

According to the manual:

endurance = the number of miles the ship can travel at cruise speed before it expends all of its fuel.

But now looking through the AE editor I see a lot of numbers for endurance that don't seem to jive with stats I'm seeing on the web for various ships.

Example is De Ruyter: According to http://www.warshipsww2.eu/lode.php?lang ... dtrida=199 the De Ruyter's range should be 6800nm. In the editor its only 4250. Now for the Renown according to http://www.warshipsww2.eu/lode.php?lang ... trida=2129 it has a range of 3650nm. However, according to the editor it's 10,500 endurance. So on the one hand we have De Ruyter apparently understated and Renown grossly overstated. Are these stats correct? Maybe the web sites are wrong? What sources were used for ship stats? Conway's?

[Nomad]

Notice that De Ruyter is listed for a speed of 12 knots, in game I think it is at 15 knots cruise.
Also, Renown is listed for a speed of 30 knots, which is almost twice the 15 knots of the game cruise speed.

I believe that fuel consumption should be related to the square of the speed, so going at twice the speed should result in about 1/4 of the endurance.

[PaxMondo]

I suspect that the devs had to use several sources and that each source had separate basis for this.  Face it, just getting "cruising" speed for a ship family is going to be tough as there is always a lot of variablity in individual ship performance.  That would have forced them to create a normalization matrix.  Nasty, time consuming, type-setter kind of work.
 
Knowing the caliber of the people who developed the stats, I'm not going to use web based resources to attempt to validate them.  But then I'm not going to attempt to validate them at all.  [;)]
 
That's just me though... 

[Pascal_slith]

The best source for US ship endurance is the post war "War Fuel Consumption" study done by the Navy. I have a PDF of this somewhere. If you want it, I can email it to anyone. Just PM me.

[GaryChildress]

ORIGINAL: PaxMondo

I suspect that the devs had to use several sources and that each source had separate basis for this.  Face it, just getting "cruising" speed for a ship family is going to be tough as there is always a lot of variablity in individual ship performance.  That would have forced them to create a normalization matrix.  Nasty, time consuming, type-setter kind of work.

Knowing the caliber of the people who developed the stats, I'm not going to use web based resources to attempt to validate them.  But then I'm not going to attempt to validate them at all.  [;)]

That's just me though... 

I'm sure they used good judgement and good sources for their stats. I would just like to figure out how they came up with the numbers so I can come up with some stats for some "never-were" ships.

[GaryChildress]

ORIGINAL: Nomad

Notice that De Ruyter is listed for a speed of 12 knots, in game I think it is at 15 knots cruise.
Also, Renown is listed for a speed of 30 knots, which is almost twice the 15 knots of the game cruise speed.

I believe that fuel consumption should be related to the square of the speed, so going at twice the speed should result in about 1/4 of the endurance.

Aha! Good catch!

[Smeulders]

ORIGINAL: Nomad
I believe that fuel consumption should be related to the square of the speed, so going at twice the speed should result in about 1/4 of the endurance.

Not sure actually, you'd need 4 times the energy to get 2 times the speed (Kinetic energy = .5*mass*speed^2), but of course your higher speed will get you further*. There are a lot of other effects playing as well, what about hydrodynamics, the resistance encountered at different speeds ? The boilers probably won't have the same efficiency at all speeds,etc. Not at all sure what a good rule of thumb would be, I am far from an expert on ships, but maybe you could try finding specs for ships at different speeds and try to get a good number out of that data ?



*Let's say you instantaneously accelerate from 0 to x and 2x, you'd need y energy to get to speed x and 4y to get to 2x. With speed x, and no more propulsion used, you can do distance A before being stopped. While de-accelerating from 2x to x, you can do a distance B. So in effect, you can use 4y energy to do distance A+B or y energy to do distance A, so from that simple calculation you'd have more than 1/4th the endurance at twice the speed.

[JWE]

ORIGINAL: Gary Childress
I would just like to figure out how they came up with the numbers so I can come up with some stats for some "never-were" ships.

It takes a lot of math to construct consumption/speed curves like Pascal found. Takes a lot more math to normalize everything to game values. If you really need to know, Lewis, or any other decent Naval Architecture/Marine Engineering text can get you there.

What you need to do is find an in-game ship (or ships) with "very similar" stats - hull form coefficients (mainly block and waterplane), displacement ("standard", not something else), engine horsepower ("shaft", not something else), lwl (not loa, but lpp is ok if you can't get lwl), and plot their fuel mile values. In the Venn circle, plot your ship. then read the number off the 15 knot axis.

[GaryChildress]

ORIGINAL: Pascal

The best source for US ship endurance is the post war "War Fuel Consumption" study done by the Navy. I have a PDF of this somewhere. If you want it, I can email it to anyone. Just PM me.

Thanks. Would this be what you are referring to? http://www.ibiblio.org/hyperwar/USN/ref/Fuel/index.html

[GaryChildress]

ORIGINAL: JWE

ORIGINAL: Gary Childress
I would just like to figure out how they came up with the numbers so I can come up with some stats for some "never-were" ships.

It takes a lot of math to construct consumption/speed curves like Pascal found. Takes a lot more math to normalize everything to game values. If you really need to know, Lewis, or any other decent Naval Architecture/Marine Engineering text can get you there.

What you need to do is find an in-game ship (or ships) with "very similar" stats - hull form coefficients (mainly block and waterplane), displacement ("standard", not something else), engine horsepower ("shaft", not something else), lwl (not loa, but lpp is ok if you can't get lwl), and plot their fuel mile values. In the Venn circle, plot your ship. then read the number off the 15 knot axis.

I'm not much of a mathematician. How about this for "eye balling" some stats:

According to the stats here for the Dutch BC, it should have had a range of 4500nm at 20kts. According to the chart for CB Alaska on fuel consumption, CB Alaska gets 7750 "engine miles" at 20.4kts and 9840 "engine miles" at 15.4kts. 7750 is to 9840 as 4500 is to 5714. Therefore how about 5714 as endurance for the Dutch BC at 15kts.

Granted it isn't very precise at all but I'm assuming there is an algorithm in WITP for getting from endurance at 15 kts to getting endurance at max speed. If that algorithm is a constant for all ships, then it looks to me that one could conceivably calculate the range at 15kts if one has the range at some other speed and that calculation would be reasonably in line with the methods of calculation used by WitP to get from one speed to another in endurance. No? [&:]

EDIT: Basically the calculation would be this:

[JWE]

Yes, there is a program that calculates these things. But if you don't do math, it won't be much use.

Fuel consumption as a function of speed goes with the square of speed up to a point (approaching hull speed) and then the power law increases quickly up to the cube of speed and beyond. Linear extrapolations from the increasing curvature sections aren't worth squat. Linear extrapolations in the flatter curvature portions are only valid if the ships have the same displacement, the same lwl, the same hull coefficients, and the same same engine hp, otherwise not worth very much.

But this is what-if stuff; if you choose not to use the equations, who cares. Pull a number out by any means you please. Just tell folks how you did it. It's what-if, so it really doesn't matter.

[PaxMondo]

ORIGINAL: JWE
Fuel consumption as a function of speed goes with the square of speed up to a point (approaching hull speed) and then the power law increases quickly up to the cube of speed and beyond...

because you are no longer calculating just the power to move the mass, rather you are having to deal with the frictional losses which at 30 knots become very large and increase as you say from there.

ORIGINAL: JWE

Yes, there is a program that calculates these things. But if you don't do math, it won't be much use.

+ 1

You can't eyeball it to any great accuracy without a lot of experience. Too many variables as JWE states. An experienced naval design engineer could do a fair eyeball, but I couldn't even though I'm engineer (chemical). I'd have to do the math along with most of the rest of us.

So unfortunately, if you want any accuracy there isn't a short cut on this one. However, if it is just for you then your linear interpolation or extrapolation might not matter that much.

[JWE]

Ahh. Much better answer. I was trying to be brief but can see how it may have sounded cavalier; certainly not the intention. Pax's perspective is exactly right. Thank you Pax.

Linear comparisons work best when the ships are very similar, the two speeds are fairly close together (5 knots is ok, but pushing it), and both speeds are well below hull speed, i.e., no speed higher than 85-90% of the SQRT of lwl (no speed higher than 19-20 kts for a 500' vessel).

[PaxMondo]

JWE,
 
NP.  Very rare that I get to add something relevant.  Have to take the opportunities when they come.  [:D]
 
Anyway, you were spot on.  I just added a little meat. 
 
BTW, I looked at some of those equations.  Nasty.  Boundary layer based.  I still have nightmares about fluids and boundary layer conditions!  Then having to add in all of the hull shape and displacement and rigidity and moments and ....  yikes. 
 
I prefer car design.  Air is so much more forgiving. 

[GaryChildress]

Am I correct to assume that the game engine doesn't take into account the hydrodynamic characteristics of individual ship classes? If the game engine itself doesn't take into account the dimensions of individual ships when it converts endurance from cruise to full speed then what difference does it make if one eyeballs the endurance at the relative speeds (so long as the stats are reasonable)? You all make it sound like it's a complicated science, but how does the game engine take any of these stats into account? They're not even listed in the editor. [&:]

[JWE]

They are taken into account in data.

You asked the question. It was answered.

Don't care if you like it, care even less if you understand it.

This has become annoying. Good day.

[GaryChildress]

ORIGINAL: JWE

They are taken into account in data.

You asked the question. It was answered.

Don't care if you like it, care even less if you understand it.

This has become annoying. Good day.

So the game engine, when it converts the endurance from 15kts to 28kts for a King George V class BB, takes into account the lwl and curvature of the hull etc as distinct from, say, an Indianapolis class CA and comes up with the correct endurance even though the hull characteristics appear nowhere in the editor data? I find that hard to believe. There must be some generalization somewhere that is not based upon individual ship hull characteristics. I'm sorry if I'm being annoying, I can't help being a layman.

EDIT: Is the "Manuever" value used in these calculations? If there is some connection between hull characteristics and "Manuever" then I could see some sense to the assertion that the characteristics of individual ship hulls are taken into account. Otherwise I'm perplexed. [&:]

[Nomad]

delete

[PaxMondo]

I think what JWE means is that a look up table was created of the values for max and cruise speed for each and every ship class.  The dev team spent a lot of time to create this table.  The two values contain all of the specific data within them.  How they were calculated is given above.  The game engine only uses the values, but you need to plug in the correct values.

This is about as low level as I can break it down.

And this is a gross simplification.  I wasn't on the team, but I know at the very least they had to normalize the data as it would have come from a dozen or more sources.  And there would have been conflicts between sources, so they would had to have created a decision tree to apply to these.  I could guess at a few more things they had to do, but it would serve no point.

Going back to my original suggestion to you: for a personal mod, go ahead and use a linear extrapolation.  But with this group here, if you want to propose new "real" specs you'd better have done your homework and your math.  [;)]

EDIT: sorry not a lookup table, but a Venn diagram, so multi-axis diagram to account for the multiple variables that are here. They are SO cool.

[Anonymous]

ORIGINAL: Gary Childress

ORIGINAL: JWE

They are taken into account in data.

You asked the question. It was answered.

Don't care if you like it, care even less if you understand it.

This has become annoying. Good day.

So the game engine, when it converts the endurance from 15kts to 28kts for a King George V class BB, takes into account the lwl and curvature of the hull etc as distinct from, say, an Indianapolis class CA and comes up with the correct endurance even though the hull characteristics appear nowhere in the editor data? I find that hard to believe. There must be some generalization somewhere that is not based upon individual ship hull characteristics. I'm sorry if I'm being annoying, I can't help being a layman.

EDIT: Is the "Manuever" value used in these calculations? If there is some connection between hull characteristics and "Manuever" then I could see some sense to the assertion that the characteristics of individual ship hulls are taken into account. Otherwise I'm perplexed. [&:]

Do you play this game? it does not sound like it. If you play this game you will know the answer to this latest complaining. But this was not your original question. And I think you got a good answer and you just did not like it.

There is two speeds, full speed and cruise speed. A TF will move at the slowest cruise speed and the slowest full speed of a ships in the TF. It is stupid to make a fast ship go at 12 kt cruise speed just because a internet site says so. so ships datas are normaled to a cruise speed of 15 kt so they can operate together. Full speed uses 6 times the fuel per hex as cruise speed. and endurance numbers are calculated by mathematics to be normaled to this two features no matter what the ship.

but your question was how to go endurance from 12 or 20 to 15 and you got a good answer. Set endurance number by mathematics so it is accurate at game cruise speed and the game full speed and if you don't like mathematics then you have no cause to complaint.

MO