[TEC] Tweaking submarine ranges

[LukeFF]

I'm trying to adjust the submerged engine performance for RFB, but I've run into a bit of a wall here. First off, a quote from the Fleet Type Submarine manual:

Navy type engines are generally rated higher for emergency use than would normally be the case with commercial engines. The economical speed for most Navy type diesel engines is found to be about 90 percent of rated speed. For this speed the optimum load conditions have been found to be from 70 percent to 80 percent of the rated load or output. Thus, we speak of running the engines at an 80-90 combination which will give the engine parts a longer life and will keep the engine itself much cleaner and in better operating condition. The 80-90 means that we are running the engine with 80 percent of rated load at 90 percent of rated speed.

Now, the problem is that SH4 seems to have some sort of optimum engine efficiency built in at around 50 percent of rated speed. I've tried tweaking the range on the Balao, for instance, to be 15000 nautical miles at 18 knots (that 90 percent thing). However, that results in a fuel efficiency of around 41000 miles at 10 knots! Does anyone know how to get around this problem? I've tried, for instance, to put the maximum range at 5000 miles at 5 knots, but this just results in a "maximum range not available" message from my navigator.

Any help with this would be much appreciated. Thanks! :yep:

[Peto]

An important point to remember is that 10--12 knots was a pretty typical "long haul" speed for the fleet boats. They could be running 80-90 but only running 2 engines. If the battery wasn't too low and they were ok with a slow charge they wouldn't even fire up #3, they'd just kick in the mule which was a smaller diesel they had for tasks other than propulsion. Kicking in the other mains did increase speed but the gain became smaller with the 4th engine only providong a couple more knots (not sure of exact numbers here).

It seems to me that most accounts I read talk about making Japan from Pearl in about 10 days. I think that's aproximately 12 knots (again not positive--sorry). The longest non-stop run of a Gato was made by the Redfin from Panama to Australia without refueling. If I recall correctly, they finally fueled at Potshot (Darwin) and were nearly dry.

I guess what I'm saying is that in reality, 50% power for a fleet sub doesn't really translate as 21/2. I think running all 4 diesels at best economical means produced a speed of about 18 knots. More meant they were pushing the engines hard.

Hope this helps somehow... :hmm:

[swdw]

I think you're misinterpreting what they mean by economical.

Could be wrong, but here's how I interperet this.

Economical does not mean 80-90 isthe most fuel efficient of all the running combinations possible. What it means is this is the what the navy considered the best load/speed for normal full load/speed (flank operation with full electrical load). It's economical because it gives longer life for parts, better MBT (meantime between failure), requires less maintenance costs, fuel costs at "full load", and for cost vs performance increase it's not worth it to run the diesels at 100-100 as the full load/speed conditions.

So to me, this doesn't mean it burns less fuel at 80-90 than running at a standard bell, but that the normal full load should be 80-90 of the emergency rating for longest life.

[LukeFF]

I think you're misinterpreting what they mean by economical.

Could be wrong, but here's how I interperet this...

You're right. My oopsie on this one. I should have keyed in on the "for emergency use" part of that paragraph. Thanks for the explanation.

[Capt Jack Harkness]

Well in the book Wahoo, Richard O'Kane mentions a "cruising" speed of 17kts running 3 engines at 80/90 from Mare to Pearl.

I think the real problem is the lack of proper engine room controls...

[Joe Armstrong]

If we review USF 25(A) – The US Sub Doctrine Manual 1944 Paragraph 1122 and 1123 it would appear the best speed we could obtain would be around 16 kts, but to obtain the optimum range of 12,000 we would be required to reduce the speed considerably. If there was a refueling base close it would make since to go full out to that location but after leaving that point 2 to 3 kts would make more since to conserve fuel because of the fast runs required to get in front of some targets.

Information on this can be obtained from http://www.history.navy.mil/library/online/ss-doc-1.htm (http://www.history.navy.mil/library/online/ss-doc-1.htm)

[Fincuan]

If there was a refueling base close it would make since to go full out to that location but after leaving that point 2 to 3 kts would make more since to conserve fuel because of the fast runs required to get in front of some targets.

2-3 knots is an extremely inefficient speed. Ingame(using TMaru) the optimum cruising speed is around 9.5 knots in a Gato or a Balao and a little less in the other Fleet boats and the S-class. AFAIK it might have been a few knots higher in real life, but definitely not much less.

[Peto]

If there was a refueling base close it would make since to go full out to that location but after leaving that point 2 to 3 kts would make more since to conserve fuel because of the fast runs required to get in front of some targets.

2-3 knots is an extremely inefficient speed. Ingame(using TMaru) the optimum cruising speed is around 9.5 knots in a Gato or a Balao and a little less in the other Fleet boats and the S-class. AFAIK it might have been a few knots higher in real life, but definitely not much less.

I don't think they are using 2-3 as a cruising speed to and from patrol areas. But once in the patrol area, it was typical to use Very low speeds. It only required 1 engine for propulsion and 1 to charge the batteries which enabled the boat to be on station for over a month. Cruising at 9 knots in the patrol area would have seriously curtailed the amount of time on station.

[CaptainHaplo]

As far as editing the range and speed - it shouldnt be too hard. Just decide what your feel is the MOST efficient cruising speed - then input it along with the range that speed will give you. The engine will then extrapolate from there using those variables and the max speed the sub can do.

For instance - if you set "cruise" speed to be 10 knots, and max range at 6500 miles, with a max speed for the sub to be say 15 knots, 10 knots will get you farther than 12, or 8, or any other speed. The farther your speed is from the cruising speed - the less range you will get because your either way your burning fuel faster than your moving.....

The way the game engine does it, you cannot set the range for different speeds, only for the most efficient one.

While I know alot has been made about the lack of multi-engine control, and I agree it would be nice to have, just think of this as something your chief engineer handles. At all ahead slow he might only be running one engine for propulsion, allowing it to do double duty to charge the battery as well, because why burn fuel running engines that are not being utilized? Anyone ever notice you have 4 engines - but the throttle control's are in 1/3 increments? At ahead 1/3 - one engine goes to propulsion - another is fired up to provide a charge.... the only time all 4 engines would be devoted to propulsion alone would be at flank speed (or ahead for home!).

Doing so makes the way the game engine handles fuel and speed algorithms at least... sane. It also limits the way we can modify them. It would be nice if we could define different ranges at different speeds, but that just isnt something that is possible as I understand it.

Hope this helps.

[Tony1]

As far as editing the range and speed - it shouldnt be too hard. Just decide what your feel is the MOST efficient cruising speed - then input it along with the range that speed will give you. The engine will then extrapolate from there using those variables and the max speed the sub can do.

For instance - if you set "cruise" speed to be 10 knots, and max range at 6500 miles, with a max speed for the sub to be say 15 knots, 10 knots will get you farther than 12, or 8, or any other speed. The farther your speed is from the cruising speed - the less range you will get because your either way your burning fuel faster than your moving.....

The way the game engine does it, you cannot set the range for different speeds, only for the most efficient one.

While I know alot has been made about the lack of multi-engine control, and I agree it would be nice to have, just think of this as something your chief engineer handles. At all ahead slow he might only be running one engine for propulsion, allowing it to do double duty to charge the battery as well, because why burn fuel running engines that are not being utilized? Anyone ever notice you have 4 engines - but the throttle control's are in 1/3 increments? At ahead 1/3 - one engine goes to propulsion - another is fired up to provide a charge.... the only time all 4 engines would be devoted to propulsion alone would be at flank speed (or ahead for home!).

Doing so makes the way the game engine handles fuel and speed algorithms at least... sane. It also limits the way we can modify them. It would be nice if we could define different ranges at different speeds, but that just isnt something that is possible as I understand it.

Hope this helps.

I assume that these modifiations are done in the NSS_submarine.sim for each sub class. What program and where can it be found that will allow me to edit the .sim files.

Tony1

[CaptainHaplo]

Tony, I suggest using S3d - which can be found here:

http://www.subsim.com/radioroom/showthread.php?t=119571

Just open the appropriate .sim file for the boat you want to edit. I haven't looked to see what fields would need to be changed in S3d - been using it for other stuff :up:

The other tool you can use it NvDrifter's great MiniTweaker. It (with tweakfiles) can be found here:

http://www.subsim.com/radioroom/showthread.php?t=122997

If using the Minitweaker - open the relevant .sim file and under either diesel or electric propulsion (depending on which your wanting to change) - just modify the MilesSurfaced/MilesSubmerged to equal what you want the max range to be, then set knotsSurfaced/knotsSubmerged to be the "most" economical speed - this speed will go the max distance - the miles specified above it. Any other speed will give you less distance.

Dont forget to make backup copies of files before ya edit! Enjoy and good luck!

[Tony1]

Tony, I suggest using S3d - which can be found here:

http://www.subsim.com/radioroom/showthread.php?t=119571

Just open the appropriate .sim file for the boat you want to edit. I haven't looked to see what fields would need to be changed in S3d - been using it for other stuff :up:

The other tool you can use it NvDrifter's great MiniTweaker. It (with tweakfiles) can be found here:

http://www.subsim.com/radioroom/showthread.php?t=122997

If using the Minitweaker - open the relevant .sim file and under either diesel or electric propulsion (depending on which your wanting to change) - just modify the MilesSurfaced/MilesSubmerged to equal what you want the max range to be, then set knotsSurfaced/knotsSubmerged to be the "most" economical speed - this speed will go the max distance - the miles specified above it. Any other speed will give you less distance.

Dont forget to make backup copies of files before ya edit! Enjoy and good luck!


Thanks for your help. This should keep me busy for a while.

Thanks again,
Tony1

[vanjast]

I'm busy doing a speed/rev chart for all the ships and I've found that they have used simple fomulas for their speed/rev calculations as charts produced from all my timings show the same shape.
The Hiryu carrier's chart is a complete mess (it might be an oversight of the DEVs) so I played with it in Minitweaker to get it like the other carriers and found that I was limited to 'sliding' the Min/Mid/Max points up and down the chart, and was unable to do individual changes.

They might have the same story for the engine speed/fuel consumption.
:know: