What is your strategy for saving fuel?

[CjStaal]

I tend to stay submerged and run off batteries for as long as I can, then go up to charge and rise and repeat.

[Sailor Steve]

That's something that works in SH3, but not in SH4 nor in real life.

In real life the engine recharging the batteries is running at flank speed, using more fuel that surface cruising does.

My strategy is to run at 1/3 (setting 2 on the gauge) while in transit and Ahead Slow while patrolling.

[Kip336]

That actually does not save fuel, as your diesel engines need to be on a higher speed setting to get the batteries charged.

Test this:

1) Stay submerged for a while untill your batteries are down a bit (Atleast enough to need a while to recharge. Maybe at 90%.

2) Surface your boat and order flank speed.
a) Your batteries will be charging; check your speed and remember (For a VIIB itll be about 13-15 knots at flank while charging
b) Go to your chief engineer, and select normal propulsion. Now see your speed increasing to the full 17 knots.

The best way to save fuel is simply by ordering a slower speed while enroute to your patrol area.

[CjStaal]

Originally Posted by Kip336

That actually does not save fuel, as your diesel engines need to be on a higher speed setting to get the batteries charged.

Test this:

1) Stay submerged for a while untill your batteries are down a bit (Atleast enough to need a while to recharge. Maybe at 90%.

2) Surface your boat and order flank speed.
a) Your batteries will be charging; check your speed and remember (For a VIIB itll be about 13-15 knots at flank while charging
b) Go to your chief engineer, and select normal propulsion. Now see your speed increasing to the full 17 knots.

The best way to save fuel is simply by ordering a slower speed while enroute to your patrol area.

Well it seems to be working. I know that in real life it doesn't work, but it works here.

[Tupolev]

Recharging definitely lowers your fuel economy.

Set any speed you want while recharging and ask Navigator for "Max Range at Current Speed" report. Then select normal propulsion and wait a few moments for the other screw to come online and as for another "Max Range/Speed" report. You'll find the difference surprising (or not surprising).

As for best fuel economy, if you're in a VII or IX, set speed somewhere around 7 to 9 knots. If you've got a super calm ocean, you can check your mileage with the Navigator's report to fine tune it if you'd like.

Personally, I set 7 knots on my outbound legs, 5 knots when I'm on station, and 9 knots on homebound legs. The slower you go, the longer amount of time you can stay out on each patrol.

If I'm hunting coastal waters (US East Coast or Caribbean) I'll bottom the boat during the day to save fuel. The game doesn't drain batteries when you're submerged with your E-motors stopped. Surface at night and you're good to go!

T

[Rambler241]

Kip336 stated:

That actually does not save fuel, as your diesel engines need to be on a higher speed setting to get the batteries charged.

No they don't - Sailor Steve got it right - the starboard engine is disconnected from the screw, clutched to the generator, and run at flank speed. The batteries will charge at the same rate whatever speed the boat is moving at, even stationary. Check out the rev counters in the control room, to the left of the planesmen while charging.

Charging batteries uses a lot of fuel - the charging engine runs at flank speed, and the other has to be run at higher revs to maintain ordered speed. There's also the energy lost in the energy conversion - diesel to generator current loses energy, conversion of that current to chemical changes in the battery loses energy, converting the chemical energy to current loses energy, current conversion to electric motor rotation loses energy.

In general, "ahead slow" gives the best fuel economy for a simple engine speed order, though it isn't necessarily the most efficient speed setting. On my current mission, we were ordered from Brest to a grid square WNW of Capetown. Shortest plotted route was 11,595 km to NW corner of GR51. Leaving harbour, I did some range tests. Boat is a type IXC with MAN engine upgrade. Once speed settled down for each ordered speed, The NO reported a range of

1. 23631 for ahead slow, shown as almost exactly 8 knots on the knot meter
2. 26450 for an ordered 10 knots (clicked on the top on the zero of the 10 on the knot meter), settled down to 9.5 on the meter)
3. 24872 for an ordered 9 knots, settled down to about 8.7 on the meter
4. 17,286 for 1/3 ahead, shown as 12 knots but actually 11.5 knots on the knot meter
5. 9276 for ahead standard, 17 knots shown, 16.5 on the meter

Even if I follow the shortest route, using speed setting #2, it leaves little room for bad weather (slower speed or use more fuel?), excursions to intercept targets, running away from nasty inquisitive warships, recharging batteries, and actually patrolling the target grid and getting back home. The Bahamas are nice this time of year.....