[TorpX]

Originally Posted by ETR3(SS)

The underwater performance of all the boats is hosed. The S Class is the worst as it was included at the last minute. Anything below 5 or 6 kts will actually use MORE battery power than running at a higher speed. Try running the S Class out of power and time how long it takes to recharge them to 100% at All Stop. Oh you might wanna try that somewhere safe, like in the middle of your home base or something.

I've been thinking about this a lot because I've never noticed this in my play or testing. Maybe it is different with other mods or stock.


To make sure, I tabulated a few tests with a S-boat and a Gato, using RFB 2.0 (patched):

S-18 class

50% battery @ 5 kt. _________ 20.4 nm.
50% battery @ 4 kt. _________ 27.0 nm.
50% battery @ 3 kt. _________ 33.4 nm.
50% battery @ 2.5 kt. ________ 40.0 nm.
50% battery @ 2 kt. _________ 32.9 nm.

I performed the tests in the order of 5, 4, 3, 2, and then suspecting there was a peak between 2 and 3, tried 2.5 kt.

The recharge took about 19 1/4 hrs., a ridiculous time that, practically speaking, prohibits heavy use of the battery in anything less than life and death circumstances.



Gato class

50% battery @ 5 kt. _________ 19.2 nm.
50% battery @ 4 kt. _________ 26.0 nm.
50% battery @ 3 kt. _________ 31.8 nm.
50% battery @ 2.5 kt.________ 38.9 nm.
50% battery @ 2 kt. _________ 32.6 nm.

Note that there is not really a significant difference here.

The recharge took only 3 3/4 hrs.

Also, the telegraph setting are not what determine fuel consumption; it is the speed. People can use different settings without changing the underlying physics. It's a matter of convenience, really.



The conventional wisdom is to stay on the surface, and avoid using the battery, as much as possible. However, there are a number of things to consider.

All the diesel-electric boats burn fuel at idle. I tested this and found that the fuel consumption to be alarmingly high. Submerging means you use fuel to recharge batteries, but at least you don't burn fuel in pointless idling. So the difference in fuel consumption isn't as great as it might seem.

The S-class is different though, and doesn't idle.

If you are going to conduct submerged patrols, you should not use excessive speed. I would consider anything above 3 kt. excessive. If you have trouble with batteries/recharging, drop it to 2 kt. The speed itself doesn't matter, as you are really just waiting for your next contact to come along. You want to reduce the drain as much as possible.

The fuel used to recharge is roughly proportional to the percentage of battery recharge. If you start with the batteries fully discharged, the rate of recharge is higher, but so is the rate of fuel consumption, so it evens out. I found the rate of fuel consumption in recharging was about 4 times the idle rate.

Another thing about the practice of sitting on the surface; one of the reasons this was done was that they could see farther being higher up. This isn't modeled in the game, though. We can see nothing farther than ~ 10 nm.



I put in a fix for the IDLE FUEL issue in my ISP mod, because I considered it to be important.