I've noticed that ahead 2/3 seems to get the best performance for the trade off of speed vs. battery life.

I've been running a Gar for my boat out of Pearl... and 1/3 allows me to stay submerged during daylight hours with about 40% of my battery remaining. I'm guessing that the 48 hour endurance is real world as opposed to game?

I started playing with the S-Boats out of Cavite.... They're rough.

Akotalaya, with the Gudgeon (A Gar class boat) I've found that she cannot go from Pearl to the home islands and back on one tank.... My first trip out, I tried handling her like I had been with my S-32 and, having kept an eye on my fuel state, I headed back at standard on the surface. At about the halfway point, I realized I wasn't going to make it unless I changed things... So, I reduced speed to 1/3 and adopted running submerged during the day and on the surface at night. I managed to limp into Midway, refuel and head back to Pearl at standard, on the surface. Since then, I refuel at Midway after a surface run, and then proceed to my patrol area at 1/3, with daylight hours submerged and night time surfaced. Even still you really have to keep a close eye on your fuel state. Once you hit the 50% mark you really have to think about heading back to the barn (probably sooner if you're farther out than Kyushu). Hope this helps!


Torpx, I'll have to pick up those mods... (currently only running the radio ones...if they can be considered mods!)

Fizwalker dont run submerged unless you have to, because recharging batteries does burn more fuel, and as far as running 1/3, dont do that on the surface or you will only fo a few thousand miles at that speed, ive found that fleet boats normally get the best range at around 9 kts, on a full tank ive gotten up to 23,000 nm..allowing me to stay in enemy waters longer and come back with an empty torpedo load because im not having to head home for refuel, i will have to take the gar class out for a patrol or two and see what she can do! i love trying new things

so far on full realism runnign at around 9 kts i have gotten the gar to reach a maximum range of 21,000 nm..she has been a decent boat to me so far, ill see what the performance under water is when i run into a ship!

Thanks for the info! I'll have to try that out some time! To be honest... I've not really had a problem in hauling back unfired torps... (except once, where the interface, status reports I sent said I had four(4) and it showed 4 greyed out torps in tubes 1,2,3, and 5, but I was unable to use them...Figured they were faulty Mk 14s and carried on...).. In fact, I've been setting a pattern of coming back to port without shells or torps....Which begs the question of can I kill a ship with AA guns.... Something to try. (I don't think Gudgeon can pull it off tho-- It's guns have a nifty wall that prevents it from firing on targets on the water). *EDIT: I've come to realize that I think I left my crew on Silent Running, so they didn't reload them.

Almost forgot, is the extra fuel that the diesels use enough to offset the savings by using batteries for 12 hours? (Gar seems to charge the things in a few hours while on the surface....)

She's treated me well, my Gudgeon. Now... If only her captain could shoot torpedoes worth a darn. :P

fiz, it burns more diesel when you charge the batteries, because all the boats engines are is generators, those diesels just run the electric motors from what i have heard, but no, running on battery power isnt exactly worth it because when you really do need to dive the boat your battery reserve isnt full and that limits you, stay on the surface as much as possible

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.

With 40mm: merchies and DD's yes, capital ships, no
With 20mm: merchies no, DD's no, and capital ships not a chance, the exception being sampans and fishing boats

Good to know! Thanks for the info on that.

Interesting. I guess my patrols won't be over until after I exhaust my AA gun ammo too now. :P

Please confirm or correct! S-18 on the surface can just attain 13 kt and while submerged with 4 50 cal deck gun is barely capable of 9kt. Don't know yet about S-18 with 3 50 cal or the S-42! :down:
I'm currently driving Gar class. Would a stern 4 50 cal improve submerged speed??? Maybe from 8.75kt with bow position to 9:9.25kt. :salute::ping:

I wouldn't presume that even the deck gun is capable of piercing the capital ship's thick armor assuming its crew are helplessly watching. Torpedoes are definitely the ideal weapon for the encounter.

It has all been hashed and rehashed in the forum ifd you look around enough.

It is all semantics anyway because all of this changes depending on what mods you use. Some mod appropriate speeds and some do not. Some mods adjust the jack rabbit starts and stops and some do not.

The key is finding the mods that make it realistic.

If you want to read what the real skippers thought and did during WWII all you have to do is read the reports.

http://www.hnsa.org/doc/subreports.htm

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How many subs do you know of that had submerged speeds better than 9 knots?

All of the nuclear ones (you did not specify time period hehe).

If you want more realistic speeds and turning radius from ships and your boat use Improved Ship Physics created by Torpx. He is working on version 2 at the moment.