Fuel Managment

[Graf Paper]

Though this has likely been covered before, the recent influx of many Kaleuns fresh out of training and running short on fuel in their first patrols has prompted me to chip in my own two cents on the matter.

Being a fairly recent graduate of the Academy, the lessons I learned early on about managing fuel are still fresh in my mind. I now have eight patrols under my belt and have never run out of fuel getting back home.

I'd have to say the hardest thing for any new Kaleun to get the hang of, next to crew management, is managing fuel.

Direct experience for my own command is this...

Type IIA stock configuration best speed for maximum range is 5 kts.

Type VIIB stock configuration best speed for maximum range is 7 kts.

Type VIIB upgraded with GWK turbo diesels best speed for maximum range is 8 kts.

If you're stationed at Kiel or Flensburg in a type II boat it is highly recommended you use the Kiel Canal to shave some distance off your trip when travelling to patrol grids south of the Firth Of Forth. Use SH3 Commander to change your time compression max setting when near land from 4 to 512 or else transiting the Kiel Canal is about as much fun as having a root canal at the dentist!

To find out what speed will give you the best range for your particular boat, stock or upgraded, is to simply set a speed in calm seas and then ask your Navigator to report the Maximum Range At Current Speed.

His answers can vary by quite a bit each time you ask, so it is best to ask about three or four times spread out over a few minutes of mission time. This will give you a rough idea of the average range at any given speed.

Bad weather, high seas, running with decks awash, and sprinting to intercept targets will cause you to burn more fuel. The rough seas also reduce your speed by as much as 3-4kts below what you ordered due to the boat nosing into waves and the stern heaving out of the water, exposing the props. Having decks awash will similarly affect your boat and reduce speed by 1-2kts.

Don't take your fuel gauges too seriously. I find them to be horribly inaccurate and impossible to read the markings, especially the one that is part of the slideout gauges when you point your mouse at the lower left side of the screen.

The Chief Executive officer's gauges that pop up when you ask him to report are more accurate, especially for battery and CO2 levels, but the Navigator's report for Maximum Range At Current Speed is much more reliable when you need to know if you have enough fuel to make it home (so long as you can maintain your speed in calm seas).

You also need to be aware that dashing off at Ahead Full or Ahead Flank to catch a convoy or task force that shows up two or three grids away will seriously eat your fuel reserves. It's usually just not worth the trouble to do that. Save your fuel for intercepting targets close to your course or in your patrol zone.

You can catch up to a slow moving vessel fairly well at Ahead 1/3 (near) or Ahead Standard (far) if you plot your intercept course correctly.

Vessels moving at medium speeds means you need Ahead Full (near) or Ahead Flank (far) speed.

For vessels reported as moving Fast or Very Fast, forget it unless you're lucky(?) enough to already be positioned ahead of their course.

Ahead Flank will burn fuel far more than you expect and so use of it should be reserved for evasive maneuvers, attack maneuvers, and quickly getting ahead of a target over short distances for setting up an attack.

Submerging to run on batteries to conserve fuel is a mistake many new kaleuns make. The fuel consumption while recharging the batteries more or less cancels out any fuel-saving benfits of running submerged. While it is true you're not using any fuel when cruising submerged you will use fuel recharging your batteries because one engine powers the recharge generator, leaving one engine to propel the boat at reduced speed (and use more fuel).

Bear in mind that U-Boats are very limited with batteries. My VIIB can only stay under for long periods at 3 kts or less, 2 kts being the ideal for best range. Faster speeds consume battery power rapidly.

Submerge only when doing a hydrophone check, avoiding contact with the enemy, making a torpdeo run against a target, or to go under very stormy or rough seas when remaining surfaced would consume more fuel than recharging the batteries later or you need to rest your crew in the quieter depths.

Remember, U-Boats are slow compared to many other ships, especially warships, and it is just not practical to attempt intercepting targets that are very far away or moving fast. Keep your speed set to whatever gives you the best range and stick to it while cruising unless you're intercepting a contact, attacking a target, or avoiding an enemy.

Following these guidelines means I usually have more than enough fuel to sail from Kiel to near Scapa Flow for a 24-hr patrol and then go around to the Irish coast for some deep-water convoy attacks before heading home in my trusty Type VIIB.

[Sailor Steve]

I've always used Ahead 1/3 for cruising and Ahead Slow for patrolling, no matter what the boat. Never had a problem.

[T.Von Hogan]

U-420 IXB uses 9 knots manually inputed on the surface for cruising speed, this is 2 knots slower than regular 1/3rd but adds about 6000 kilometers to the voyage.

[melnibonian]

For VIIC 8KTS and for IXC 9KTS give the optimum range (without any engine upgrades)

[Rotary Crewman]

IIA (I know this as its the only boat I usually go for) is definitely 6kts for best range.

[Abd_von_Mumit]

Optimal speeds tested very carefully:
VIIB without upgrades: 8.25 knots
VIIB with GW Kapselgeblase engine upgrade: 8.5 knots
VIIC without upgrades: 8.1 knots
VIIC with GW Kapselgeblase engine upgrade: 8.3-8.4 knots
VIIC with MAN engine upgrade: 8.4 knots

And there is usually quite a difference in range between going at 8 or a said above 8.5 knots.

Details on the tests here:
http://www.subsim.com/radioroom/showthread.php?t=129286

[Jimbuna]

Originally Posted by Sailor Steve

I've always used Ahead 1/3 for cruising and Ahead Slow for patrolling, no matter what the boat. Never had a problem.

Ditto .....and still allows enough time to count the number of rivets used for construction

[Captain Nemo]

Originally Posted by Graf Paper

Type VIIB stock configuration best speed for maximum range is 7 kts.

Type VIIB upgraded with GWK turbo diesels best speed for maximum range is 8 kts.

You also need to be aware that dashing off at Ahead Full or Ahead Flank to catch a convoy or task force that shows up two or three grids away will seriously eat your fuel reserves. It's usually just not worth the trouble to do that. Save your fuel for intercepting targets close to your course or in your patrol zone.

Thanks for posting your observations. Whilst I would agree that cruising at around 8 knots is very fuel efficient in a VIIB and I do this myself, I'm not sure I totally agree with your tactic of letting convoys get away if their two or three grids away. If you think about it you could in theory use up most, if not all, of your torpedoes on a convoy over two or three separate engagements therefore you would not need as much fuel to cruise around as you would be heading for home afterwards (as long as you don't fall foul of Allied destroyers that is!). Of course, a sensible decision needs to be made at the time you are alerted of a convoy. If you are low on fuel and you will need to go ahead flank for a long distance then it would be wise to think about whether or not it would be wise to chase a convoy, but if you have plenty of fuel sloshing around then I think you should try to engage the enemy in the hope of sinking plenty of tonnage. The downside of course is that you could use up a big chunk of fuel and miss the convoy, but you have to take the rough with the smooth in this deadly game of cat and mouse.

Nemo

[Brag]

Unless it is very close, I never chase a target that is moving away.
The exception being a convoy I have just attacked and plan to attack again . . . and again. But I do watch my fuel and will disengage if it becomes too fuel-costly.

[Abd_von_Mumit]

I'll try to spoil your self-satisfaction a bit with some excerpts from "U-Boot's Commander Handbook".

B. Preparing for the Underwater Attack.

105.) General rules for the attack.

[...]

c) Never delude yourself by assuming that it is right not to attack on the instant, or not to hold on the enemy with the utmost determination, because there may be reason to hope and believe that a better target will subsequently be found elsewhere. What you have got, you have got. Do not let such considerations give you the idea of trying to save fuel.

[...]

C. How to deal with Convoys.

[...]

311.) In keeping contact with convoys, and carrying out the attacks, no attention should be paid to consumption of fuel, provided that enough fuel is saved to enable the submarine to return to its base.

Following the above rules (as well as other listed in the handbook) makes things much tougher, but in the same time much more interesting (for me).
Source: http://www.hnsa.org/doc/uboat/index.htm

[papa_smurf]

I alway stick to these speed regardless of weather conditions (unless im intercepting)

Type IIA - 6knts (this can get a bit hairy in rough seas!)
Type VII - 7-8knts
Type IX - 8-9knts

This is on all basic variations, without any engine upgrades.

[Graf Paper]

In mentioning convoys, I suppose my own style is somewhat more conservative in attempting to intercept a distant convoy when it is moving away. It must work for me since my career tonnage so far is over 200,000 and leaves me with enough fuel to engage the enemy, avoid pursuit, and make it home.

As for the orders laid out by the U-Boat Commander's Handbook, I really feel that does not apply very well as it is a real world document and I'm speaking in the context of the game itself. Using it as a genral rule of thumb for the sake of "realism" seems to be how it is best suited.

If SH3 truly enforced the ROE and operational orders of the real-life Ubootwaffe, then every Kaleun here would have a dossier stuffed full with reprimands, if not outright court-marshalled. Conducting your command as per those rules is not necessarily compatible with the methodology incorporated by the SH3 Dev Team.

Abd_von_Mumit, you're more precise measures of speed and fuel efficiency are indeed welcome information.

As I said, the information I provided is only from my own experiences in the game. I could never presume to be an "expert" on u-boat warfare ( can any of us truly claim that unless they were there? ). I'm merely passing on what I have learned from my own point of view in the hopes that it would help out a lot of the new Kaleuns that seem to be pouring in through the doors lately with complaints about fuel management.

I would hope that anyone has enough brains rattling around to know that it is, ultimately, up to their own judgement on how best to conduct their command to suit their own style and process any information we here at the Radio Room might offer with a critical eye. I would not disrespect them by assuming they do not.

If my observations about technical matters are erroneous, well, that's why we have this community, to collectively share what we know or think so accuracy emerges from the aggregate of discussion, debate, and the occasional dispute.

I appreciate the critique, opinions, and observations all of you contribute. Collectively, we're a smart bunch!

No matter how you prefer to engage the enemy, charging in with all tubes flooded or sneaking in for a surgical strike, so long as you're having fun is all that matters.