Solved the fuel consumption problem

[pocatellodave]

After much thought and soul searching,I have resolved the fuel problem.I removed the checkmark from the limited fuel box.I try to be as realistic as I can,but not having enough fuel to get back to base,is simply not going to be a problem for me anymore.I have tried every speed setting,and no matter what I do,the fuel I have by the time I reach my assigned patrol area,is less than half a tank,and I ain't going to make it back.
The reality is that I have never heard of a ww2 submarine running out of fuel.The officer in charge of such things aways knew about how many miles of fuel they had left,and running out wasn't an option.
In no way am I complaining about the mods,and I guess some of you skippers have found a way to get there and back,more power to you!I can't let one aspect of the game ruin my fun,so I did what I had to do.
Pocatellodave

[John Channing]

The game is meant to be fun, not frustrating.

Play it anyway that you want.

JCC

[sqk7744]

See post 182
http://www.subsim.com/radioroom/showthread.php?t=119064&page=10

Wise words as JC said, "it's all about having fun!"

*Are you using patch v1.3 with the TM and LBO mods?

Storms/headwinds are a good way to burn fuel dramatically

[pocatellodave]

Thanks for replies.I'm using TM 1.4 with the 1.3 patch.I don't know what the other mod u mentioned is.I was doing ok with fuel with the vanilla 1.3 patch.When I installed TM 1.4,that's when my fuel problems began.I like TM 1.4,Ducimus has done a great service to SH4,but I can't figure out how to get to mission area and back to home port.
Pocatellodave

[sqk7744]

Gotcha,

LBO = Living Breathing Ocean adds drag and real sea states.

? Have you modified/tweaked your subs' speeds or horsepower/rpm via mini tweaker?

[chopped50ford]

The reality is that I have never heard of a ww2 submarine running out of fuel.The officer in charge of such things aways knew about how many miles of fuel they had left,and running out wasn't an option.
In no way am I complaining about the mods,and I guess some of you skippers have found a way to get there and back,more power to you!I can't let one aspect of the game ruin my fun,so I did what I had to do.
Pocatellodave

Skippers had to know how far thier limitations were and thier average fuel consumptions for miles driven [or loose thier commands revisiting the XO status due to incompetance.] So that's what has to be applied while at seas. From my experience in the game, using 10knts as an normal running speed, you can go alot further.

If you need more fuel, pull into close ports to refuel and refit to get more distance.

[tater]

The only times I've ever had fuel problems are losing it from damage (seems to be very all or nothing in that regard), or if I do soemthing stupid like put TC on at Full speed.

With a top off at midway, I get to empire waters with 3/4 of a tank, and I RTB when I'm a little below 50%.

[pocatellodave]

I tried again,and I had installed strict range mod,and realistic battery life.Ran at ahead standard as reccomended by mod maker,and had a lot more hours underwater.Result...got to Hokkaido,less than 1/2 a tank :damn:.I've tried ten knots and no go for me.Obviously I'm missing something.
Pocatellodave

[Ducimus]

:hmm: Maybe ill post a guide when i get home from work. I wasn't the self proclaimed "long range patrol affecienado" for nothing.

[pocatellodave]

Thank you very much!
Pocatellodave

[-Pv-]

I've never run out of fuel. Longest patrol distance so far was Hawaii to East China Sea. Topped off at Midway on the way there and ran 2/3 when weather permitted and 1/3 when it was rough but was not forced under. When winds get above 8 m/sec I drop to pariscope depth and run at 2 knots until batt is low (to keep crew from getting hi fatigue rates) then surface run at 1/3 (which provides minimum batt charge time.) Once I got to ECS and dropped off the agent, I shot up some cargo ships and got an extended mission to continue down into the Philippine Sea. I was still able to make it back to Midway with a small amount of fuel to spare, topped off and full speed ahead back to Midway.

Although time compression gets you into the action faster, the trade off is you zoof through storms on the surface at high speed thereby reducing both your miliage and your crew efficiency for keeping your engines in top condition. You also risk damaging your sub in a storm causing increased fuel rates and reduced submerged depth.

Even if the 10 or 11 knots 2/3 speed isn't giving you the range you need after taking great care, further reduction in speed to 1/3 will increase your range even further. Run at that speed for a day or two until you are sure you can make it back at 2/3, then go ahead and increase your speed. You can even return home at 1 knot if you have to. It might take 4 months to get home, but you will arrive with plenty of fuel to spare.

In short, there is no "magic" speed. You are always trading off the mission distance, what you are willing to expend chasing targets, ALWAYS keeping an eye on the return distance and breaking off (no matter your personal tonnage target or mission occomplished) to return home. I'm convinced keeping all this in mind, there is nowhere you can't go in the Pacific from any port and be able to make it back home. At worst, your tonnage might be low on the longer missions. You might even fail to accomplish the mission (which has never happened to me) but there is no reason you cannot get to mission and return home if you manage your resources, keep and eye on the fuel level, and above all, remember it's a game of patience not of speed.

-Pv-

[EAF274 Johan]

A book I've been reading about US submarines in WW2 (The Last Patrol by Harry Holmes) often mentions how submarines "topped off" their tanks at Midway on the way to their patrol area. I suppose Asiatic Fleet boats would use Darwin or another allied port.

[chopped50ford]

I think I saw a mod to put a Sub Tender in Darwin...does anyone know if this works?

[PepsiCan]

I tried again,and I had installed strict range mod,and realistic battery life.Ran at ahead standard as reccomended by mod maker,and had a lot more hours underwater.Result...got to Hokkaido,less than 1/2 a tank :damn:.I've tried ten knots and no go for me.Obviously I'm missing something.
Pocatellodave

So, where are you starting from and with what kind of boat?

And why are you running submerged?!? Stay surfaced! Uses up less fuel.

[Von Tonner]

I think I saw a mod to put a Sub Tender in Darwin...does anyone know if this works?
NOW you are talking!! That has always been one of my pet gripes as I am sure iRL subs would have refuelled there. I had to abandon a Baloa with a damn fine crew in Darwin - it still hurts to think about it.:cry:

[sqk7744]

I think I saw a mod to put a Sub Tender in Darwin...does anyone know if this works?
You can always add one to the .mis file via the Editor (make it date specific)

http://www.subsim.com/radioroom/showthread.php?t=119090

[pocatellodave]

PepsiCan,kind sir how do you save fuel running on the surface?When you are submerged,the diesels aren't running?
Pocatellodave

[PepsiCan]

PepsiCan,kind sir how do you save fuel running on the surface?When you are submerged,the diesels aren't running?
Pocatellodave

I stay on the surface. I never dive, except when attacked by aircraft. And then I wait an hour while running at 1/3, surface again and continue. And I'll submerge when I attack a convoy. But even then I will stay on the surface to reach my point of intercept. Then I dive and lie there to ambush the convoy.

As you probably have learned by now from various other posts, as well as from historical records, diving and using your batteries actually greatly increases your fuel usage. The more you use your batteries, the more diesel you'll burn. Why? Simple, in order to charge your batteries, you need to run your diesels. But there is something called loss of energy. So, in order to get say 100 Kilowatts of electricity, you may need to burn 200 kilowatts of diesel fuel. The 100 kilowatts of energy you do not convert into electricity is lost on heat, radiation and friction (you can test this: why is a light bulb hot? Because most of the electricity is not converted into light but into heat and radiation). And the game models this.

Suppose that that 100 kilowatts of energy moves your boat 50 miles. Because you ran submerged it actually costs you 200 kilowatts to cover that 50 miles (during the recharge you lose 50% of your energy). But If you hadn't used your batteries by running submerged, but ran on the surface, that same distance would have cost you only 100 Kilowatts at its worst (and probably less because it takes less effort/energy to propel your boat on the surface).

So run on the surface and *never* dive unless the enemy forces you to.

[pocatellodave]

Thanks I understand it now.
Pocatellodave

[Ducimus]

Im simpler, hypothetical terms.


High battery drain: (say if you ran at 3-4 kts and your batt drains to 30-40% in 12 hours)

You probably traveled i dunno, 80 units of distance, but to recharge your now 20-30% batteries will require fuel that otherwise could have made 120 units of travel. So you have a loss here.



Low battery drain. (say if you ran 2 kts and your battery drains to 60-70% in 12 hours)

You probably traveled 70 units of distance, and you'll concievably spend about 30-40 or so units of travel on your diesals. (this might be an exaggeration, fuel expenditure is probably a bit more).



The short of it is, a high battery drain takes more fuel to replace, a low battery drain, may yield a gain in distance, but it wont be by much.

In sum, use your battery sparingly, or in modern terms, "Conserve electricity!" :smug:

[sqk7744]

Im simpler, hypothetical terms.


High battery drain: (say if you ran at 3-4 kts and your batt drains to 30-40% in 12 hours)

You probably traveled i dunno, 80 units of distance, but to recharge your now 20-30% batteries will require fuel that otherwise could have made 120 units of travel. So you have a loss here.



Low battery drain. (say if you ran 2 kts and your battery drains to 60-70% in 12 hours)

You probably traveled 70 units of distance, and you'll concievably spend about 30-40 or so units of travel on your diesals. (this might be an exaggeration, fuel expenditure is probably a bit more).



The short of it is, a high battery drain takes more fuel to replace, a low battery drain, may yield a gain in distance, but it wont be by much.

In sum, use your battery sparingly, or in modern terms, "Conserve electricity!" :smug:
* Same theory applies to brakes in a car ;) thanks again Ducimus!

[louist]

I had the same problem last night and figured two things out:

1. If you do not disengage silent running, you will use up greatly more fuel, even on the surface. Disengage silent running.
2. Also, the engines are much more efficient if, once you have charged the batteries, you turn off the battery charger.

Your mileage may literally vary.

[Frederf]

On the surface, applied physics would seem to indicate that running submerged on batteries would have less overall range than running on diesels alone, but this is not neccesarily the case.

While it's true that the energy in the batteries used for submerged travel is not "free" and has to be gotten from fuel reserves and that the fuel-diesel-battery-motor energy chain is not 100% effecient, it's still possible for battery / electric engine use to increase, not decrease the range of the submarine. I will try to explain using the most extreme case of diesel/electric mixed propulsion.

Version A: A stopped sub with 0% charged batteries will run the diesel engines strictly as a generator to charge the batteries. Once the batteries have a charge, the sub uses its electric motor to move 10nm.

Version B: A sub uses its diesel engines to drive 10nm.

Which version uses more diesel? You may be tempted to say Version A uses more diesel fuel since the recharging, eletric motor process has more steps and thus more chances for energy to be lost due to heat, friction, 2nd law of thermodynamics, etc but it is not neccesarily the case.

It is because the diesel engine does not have the same effeciency at all RPM! It is possible to charge the batteries at the RPM that is the most effecient for the diesel engine while maybe the best RPM for the diesel engine/ boat hull is not so effecient for the diesel engine. The convoluted fuel-engine-battery-motor process, despite having more steps CAN (in theory) be more fuel effecient than the diesel engine alone because of the variable effeciency of the diesel engine under various loads.


Now I am completely uncertain about the following two concepts:

1. Were real life WWII submarines more effecient under mixed diesel-electric propulsion compared to pure diesel? It's theoretically possible but was it actually the case? Unknown. I thought German U-boats benefit from the mixed propulsion.

2. Are WWII submarines as modeled by the game (vanilla, modded?) more or less effecient under either method? Again unknown.

MORE INFO AND CITE:

http://www.ossapowerlite.com/tech_li...efficiency.htm (http://www.ossapowerlite.com/tech_library/fuel_efficiency/fuel_efficiency.htm)

Not all of the points made in this article apply to WWII submarines as they are designed, but there are plenty of valid points made that do.

[-Pv-]

I don't think the game is quite as energy taxing as theory, but to make things even simpler:
-> The slower you go and the calmer the weather, the more range you will have be it battery or diesel.
-> The more time spent fully surfaced the better as this is where drag is lowest in WWII boats.
-> A bad storm can cut your surfaced range by 1/3 for the life of the storm. Anything over 8 m/sec wind adds significant loss.
-> Recharge at the slowest surface speed possible so you spend the least amount of vulnerable surface time with a depleated battery.
-> Silent running prevents your crew from performing maintenance or repair and reloading torps. This costs you in being prepaired for battle and a weakened ship and crew.
-> Battle Stations improves crew response to damage and better all around command responses/targeting/sighting/sensing. The tade off is it tires out the crew very quickly and increases the noise level of the boat regardless of Silent Running.
-> Return to port once in a while and purchase better crew to improve efficiency in all aspects of operating the boat as well as stamina.

Conserve aggressively while you can so when the tactical situation requires it, you can spend what you have saved with equal aggression.
-Pv-

[Powerthighs]

-> The slower you go and the calmer the weather, the more range you will have be it battery or diesel.

Regarding speed, I don't think this is true. I believe you get the most miles per gallon at around 10 knots. Going slower than that becomes less efficient. In the same way most cars get maximium miles per gallon at 40-50 miles per hour.

I haven't tested this in the game but I'm sure others can chime in.

[PepsiCan]

On the surface, applied physics would seem to indicate that running submerged on batteries would have less overall range than running on diesels alone, but this is not neccesarily the case.

While it's true that the energy in the batteries used for submerged travel is not "free" and has to be gotten from fuel reserves and that the fuel-diesel-battery-motor energy chain is not 100% effecient, it's still possible for battery / electric engine use to increase, not decrease the range of the submarine. I will try to explain using the most extreme case of diesel/electric mixed propulsion.

Version A: A stopped sub with 0% charged batteries will run the diesel engines strictly as a generator to charge the batteries. Once the batteries have a charge, the sub uses its electric motor to move 10nm.

Version B: A sub uses its diesel engines to drive 10nm.

Which version uses more diesel? You may be tempted to say Version A uses more diesel fuel since the recharging, eletric motor process has more steps and thus more chances for energy to be lost due to heat, friction, 2nd law of thermodynamics, etc but it is not neccesarily the case.

It is because the diesel engine does not have the same effeciency at all RPM! It is possible to charge the batteries at the RPM that is the most effecient for the diesel engine while maybe the best RPM for the diesel engine/ boat hull is not so effecient for the diesel engine. The convoluted fuel-engine-battery-motor process, despite having more steps CAN (in theory) be more fuel effecient than the diesel engine alone because of the variable effeciency of the diesel engine under various loads.


Now I am completely uncertain about the following two concepts:

1. Were real life WWII submarines more effecient under mixed diesel-electric propulsion compared to pure diesel? It's theoretically possible but was it actually the case? Unknown. I thought German U-boats benefit from the mixed propulsion.

2. Are WWII submarines as modeled by the game (vanilla, modded?) more or less effecient under either method? Again unknown.

MORE INFO AND CITE:

http://www.ossapowerlite.com/tech_li...efficiency.htm (http://www.ossapowerlite.com/tech_library/fuel_efficiency/fuel_efficiency.htm)

Not all of the points made in this article apply to WWII submarines as they are designed, but there are plenty of valid points made that do.

In reality, your theory can probably hold (not sure since I haven't tried it - sorry, didn't get my fleet boat for my birthday this year - or read about it).

But in the game I doubt it. I'd stick with the simple rule that it takes more energy to get from A to B on batteries then on Diesels.

[Driscol]

I've given all of the recommended conservation methods a try without much success. Topping off at Midway, 10 knots in passable weather, slower during heavy seas, shutting off the battery after recharge, diving only when threatened by aircraft. It may be due to game setup or the interaction between some of the mods and that setup or it may be that there is more heavy weather encountered than historically, but a Gato sub just won't go the distance that it went according to the books. A nominal 11,000 nm was expected from a Gato. I've kept track on a couple of missions and I get closer to 8000. I have know idea how low this would drop if I was less obsessive fuel conservation.

So I operate the boat as if I was trying to conserve fuel (even to the point of making hard decisions about whether to chase a convoy or follow a ship I've crippled) but when I come close to empty and I'm still 1000 nm from Midway I send for help. Rather than a flying boat, CinCPAC sends me a smart technician who knows how to open the save games files and reset the fuel to "unlimited". I then proceed to return to base so that I can continue my career.

[-Pv-]

See what you get without the mods.
-Pv-

[DAB]

Are you guys all using a Realistic Range Mod? [Due to computer limitations, I'm still on SHIII for the time being so excuse my relative ignorence]

If so, then there is no way that a Balo or any other class of Submarine is going to make it as far as the historical record shows they did. Silent Hunter III and IV use a Flat Earth model which means your quickest route to the Bungo Straits is to have a waypoint at Pearl and a waypoint at Bungo. In reality, the shortest route is to leave pearl, cross the dateline around 30N and then actually come along the coast of Japan.

Just a theory, I don't have a copy of SHIV to test it on. But that maybe the source of your woes.

[nomdeplume]

If you're using Trigger Maru, you get a button in the navigator commands to estimate your range at the current speed. This makes it pretty easy to find the most fuel-efficient speed to travel at. (SH3 stock had this, but they removed it for some reason in SH4 -- but the code to do it is all still there. Go modders!)

I'm pretty sure my testing for whatever sub I have at the moment gave 2/3rds as the most efficient (I didn't test particular speeds, only the standard settings).

Just enable a small amount of time compression (to reduce the time it takes for your boat to stabilise at a new speed), and then set a speed, check your estimated range, set another speed, check range again, etc. I haven't had significant problems with the range of my boat for some time, though early on I did end up stranded on a few occassions.

[horrgakx]

I've never run out of fuel. Longest patrol distance so far was Hawaii to East China Sea. Topped off at Midway on the way

I did that but Midway was full of Japs...?!

[Syxx_Killer]

I know this thread is old, but I just can't see why people keep having problems with fuel usage. I haven't once run out of fuel whether it be with stock SH4 and patch 1.4 or with TMO for version 1.4. I think it is easier to monitor fuel in SH4 than it ever was in SH3. :D When I first started SH4, I was kind of annoyed that the stock game didn't include a "range at current speed" order button (now I think it is useless anyway). I was still able to find the sweet spot for my sub to give me the best fuel economy.

[Takao]

I think its because the basic game model is flawed. Sure, the US submarines averaged only 8-10 knots an hour on their trips, but thats because your spending roughly 10-20 days submerged. 10-20 days submerged knocks down your overall surfaced speed. Taking into account a low submerged speed means that the submarines were traveling faster than 10 knots while on the surface.

Also there is no individual engine controls, all four are running all the time, sucking up precious fuel. You would think there was no meaning behind an order "Two engine speed (80-90)", incidently this equates to about 14 and 1/2 knots. It means ONLY two engines are running, not four, and those two engines are at 80% rated load and 90% rated speed.

Personally, I use unlimited fuel, it's more realistic. However, I do conform to usual submarine movements and don't go racing all over the Pacific at 20 knots either. I'm usually cruising at about 14-15 knots, I'll go slower while in storms. No sense in pounding the boat to pieces.

[Rockin Robbins]

I think its because the basic game model is flawed. Sure, the US submarines averaged only 8-10 knots an hour on their trips, but thats because your spending roughly 10-20 days submerged. 10-20 days submerged knocks down your overall surfaced speed. Taking into account a low submerged speed means that the submarines were traveling faster than 10 knots while on the surface.

Also there is no individual engine controls, all four are running all the time, sucking up precious fuel. You would think there was no meaning behind an order "Two engine speed (80-90)", incidently this equates to about 14 and 1/2 knots. It means ONLY two engines are running, not four, and those two engines are at 80% rated load and 90% rated speed.

Personally, I use unlimited fuel, it's more realistic. However, I do conform to usual submarine movements and don't go racing all over the Pacific at 20 knots either. I'm usually cruising at about 14-15 knots, I'll go slower while in storms. No sense in pounding the boat to pieces.
First of all several modders have investigated fuel range in the simulation and came up with small adjustments but found that fuel economy in the game is close to real. Top fuel economy in the game is at about 9 knots in every sub but the Sugar boats. Ranges are darn close to actual ranges expected in the real subs. You're way off base there.

The second place you're off base is in strategy. Spending 10-20 days submerged during a cruise is just plain folly. During the war, Admiral Lockwood would yank your sorry posterior out of that sub so fast nobody would know you were ever there. Submarines are surface ships which can submerge when absolutely necessary and for as short a period of time as possible. Their normal configuration is at 9 knot cruising speed covering the largest number of square miles they can in search of targets. The absolute necessity of every second of submergence must be accounted for.

That is why this thread has been buried so long. The questions and basis for unlimited fuel are long since discredited. With that in mind the "unlimited fuel" option wouldn't be there if it was not ok to use it. Just don't go around pretending it's more realistic.

[jetthelooter]

do not forget in RL the US fleet submarine, unlike the german version, has no direct link from the diesel engines to the screws. US fleet submarines ran on electric power much like diesle locomotives 100% of the time to power the screws. all the engines on a fleet sub did was to turn electric generators to either or both charge the batteries and turn the screws.

also fleet subs if i remember correctly had a small tertiary engine just to charge the batteries over a longer period of time. but i am not sure about that.

[horrgakx]

I got round it by setting the diesel to infinite. Yeh its not realistic... but neither is what is expected!

[Rockin Robbins]

That is why it is called a game. If it were a true simulation we would all stink like hell!:up:

[Sailor Steve]

You don't?:p

[Buffalo9]

Biggest factor on fuel usage is co-efficeint of drag. Not being sure how they modeled fuel usage, ie: distance to time ratio or others it's hard to say how fuel usage is calculated.
When you first start out of port you're heaviest, full fuel, full stores, etc, here your drag is highest, as you lose weight your drag is theoretically lessened, think of it as thrust to weight ratio, my thrust hasen't changed but my weight has.
Granted there are going to be variables, some planned, some not; which will affect your consumption rate.
As to running while charging the best example is using your vehicle air conditioner. In general terms you'll increase your fuel consumption as the compressor draws a load from the engine.
Here again there will be variables involved.

Now!!! for running on the surface majority of the time.
Depending on the sea state you may not save as much as you think.
Running submerged may offset the effects of drag during high swells. Staying as close to the surface would be practical, as depth increases so does density, hence drag increases. Also staying in warmer thermals also would be more benefical than cooler layers, being that warm is less dense than cool.
So on and so forth, your mileage may vary.

[Soundman]

I need to relay some info here....I recently started a new carreer and loaded up the newest TMO 1.5, RSRDC & PE2...I have always been very fuel conscious, but on my first patrol, I went to Guam out of Pearl (and man did I hit the jackpot BTW, lots of ships in port) and after sinking around 30 tons, headed home with 2/3 of a tank. Should be plenty right?....Wrong....I fell short by about 900 miles. I could not believe it. The seas were calm too. So I reloaded the most recent save and tried again at ten knts all the way home. Well..almost home..still about 500 miles away and out of fuel. I was pissed! So I tried to reach Midway and fell short about 150 miles. I ended up going to (can't remember the name) the closest port in Austrailia and then on to Brisbane to fill up again. From there I thought sure I could get to Pearl. Nope....after a little over halfway there, I could tell I was not going to make it so I changed course for Midway and BARELY made it. I have heard about currents being modeled accurately in the game, but currents that strong? There was something funny going on there! I have never seen or heard anything like this before and I've logged many patrols and carreers in this game. I don't know how reliable the "miles at current speed" report is, but according to it, I should have been able to sail about 14,000 miles. Comments?

[Rockin Robbins]

Regardless of the sea state the greatest drag on the batteries is the drag of the electrics if you have to recharge your batteries. Part and parcel of the yo-yo strategy is having fully charged batteries almost all the time. This will always extend your range assuming you are optimized at 9 knots cruise speed.

Every time you submerge you lose. You lose ground traveled at a couple knots instead of 9. You lose square miles searched by radar and visually while you are on the surface. This means fewer square miles searched and targets not found. Then when you surface, you get lousy fuel economy at any speed while you bring your batteries up to full charge. Submerging is a lose, lose, lose proposition.

Submerging should only be done to save your life or cost the enemy his. Then its duration should be as short as you can make it. Every second your first thought should be "How quickly can I return to the surface? What can I do to be able to surface sooner?"

[AVGWarhawk]

Submerging should only be done to save your life or cost the enemy his. Then its duration should be as short as you can make it.

Exactly. A submarine has the ability to submerge for short periods of time and needs to be run like that. It is not a submersible that has the ability to surface for short periods of time. Best to keep surfaced and rolling, submerge only as necessary.

[Khourieat]

You don't?:p

I do :oops:
(Sink like hell, that is)

[-Pv-]

There are no currents int he game. Rough weather decreases your range (it takes a higher propulsion setting to maintain the same speed in rough weather then it does in calm weather.

I have noticed mods which change the floatation model do not get as much range as the stock game. By lowering the boat in the water so less keel/prop is exposed in high waves, code sensitive to how much hull is submerged is activated reducing your speed and efficiency. For this reason alone (although there are many others) I do not use mods which effect the boyancy model. I'm willing to live with the look in order to get the historical speeds, dive, surface, and ranges the game was coded with (which is well proven.) Been playing the game for a year now and never had had to set infinate fuel or install any propulstion or battery mods. I've also never failed to get to and from a mission based on fuel. The stock game gives missions based on the performance the coders built into the stock model.
-Pv-

[Buffalo9]

I agree 100%, being surfaced is much more practical than being under, but you can't effectively generalize it, there are just too many variables involved.
An example would be in rough seas, you loose about a 1/4 to a 1/2 your screw efficiency, spinning your wheels if you will.
If your only driving the boat half the time you're not making the progress you calculated for at the speed/rpm. You've wasted more fuel that it would have taken to move on batteries then recharge on a time/distance scale.

The charging system is actually quite efficient, you don't loose alot of torgue using a motor/genertor charging setup, the drag is negligible on the shaft rpm.

This being only a game I stay afloat alot of the time, even in rough water, and i dive to PD at flank speed with my attack scope fully extended, the boy's love it:p:p:p:p

[piersyf]

I refer you all to this:http://www.maritime.org/fleetsub/index.htm
It's an online reproduction of a 1946 US Navy fleet sub operations manual. I just had a wade through the pages and pages of info on the diesel electric system on a fleet boat at the end of WW2. Here's a few tidbits...

The subs ran on electric motors, even on the surface. They used the diesels to supply electricity through the generators. This means that the diesels need never be loaded or overloaded at high speeds, they just run at their ideal settings. The manual states 80/90, 80 percent of maximum load (resistance) at 90 percent power.
The reason a sub recharges faster at slow speeds is that the engineers de-couple a diesel and run that generator direct to the batteries, leaving the other diesel to supply power to all 4 elecric motors for propulsion. It can do that if the skipper doesn't want to move fast. Anyway, the manual is VERY extensive... enjoy

Piers