What is up with the estimated range based on existing fuel and speed?

[Sgian Dubh]

I will be the first to admit that I have had precious little time to play SHIV and so, with a day off I jumped a the chance today.

So I may be encountering something well known, but it caught me out.

I am on a first patrol (out of Pearl) in mid 1942. It has been an excellent patrol with over 72,000 tons (using manual shooting and lots of deck gun due to misses and dud torpedos - but I have the dud problem in hand now).

I am running 1.4 with TM 1.7.6 (so far).

I had just under a half load of diesel and got a new assigment to partol off Luzon (even though I had just reported no torpedos left and my fuel status). So I decide to head to Midway to re-arm and refuel - but I can't get there. I run out of diesel (running 2/3rds) with over 1300 nm to go.

The range estimator reported (moving at 1/3) with just under a half-load of diesel that my maximum range was under 650nm. So I clicked it again and it came back with a lower number! Each time I clicked it, the number dropped by at least 1nm and then it stabilized about 50 nm less that the original estimate.

So my question is, how much fuel, if you are off the coast of Okinawa, do you need to get back to Midway? It appears to me, based on what I am seeing, that you would need nearly 3/4 of a load of diesel, but it takes nearly half to get from Miday to Okinawa.

I was so irritated that I resorted to something I rarely do with this sim. I rendevous (sp?) with an "oiler" just North and West of Wake Island, so I could make it back to Midway.

I am no novice to sub sims, and I was following all of the usual fuel saving measures. I only had to resort to Full ahead a few times to chase down some contacts during the patrol. I figured I had plenty of fuel left, so I am really puzzled.

Thanks in advance for any advise.

[RickC Sniper]

What type of boat?

With a Tambor or newer, travelling at 9-10 kts I need 1\4 tank to get from the China Sea to Midway.


Heavy seas lowers your mileage, as does battery recharging.

[Donner]

I know that there is a 1.4 issue with estimated range if you are currently charging batteries. The estimates will be waaay off. Also, sometimes your batteries are damaged (with no notification of any kind) and the charging cycle will be continuous. So you will have to manually turn off charging to increase your mileage.

Turn off battery charge and then check your estimated range.

[Sgian Dubh]

Excellent information.

I don't think I have any damage, but I will check back on the saved game to check this possibility.

I did not know to turn recharging off before checking - thanks for that.

[Sgian Dubh]

Originally Posted by RickC Sniper

What type of boat?

With a Tambor or newer, travelling at 9-10 kts I need 1\4 tank to get from the China Sea to Midway.


Heavy seas lowers your mileage, as does battery recharging.

It is a Gato class which I picked off the list at Pearl. I haven't been checking sea-state constantly - so this could have been a factor.

[Munchausen]

Originally Posted by RickC Sniper

With a Tambor or newer, travelling at 9-10 kts I need 1\4 tank to get from the China Sea to Midway. Heavy seas lowers your mileage, as does battery recharging.

In a Porpoise, running at 10 knots, I burn about 2% per day (1% of fuel takes me about 114 nm). That's with batteries charged. Running at 1/3, for every 10% my batteries are depleted, it takes approximately 16 minutes to recharge.

I always check "maximum range at current speed" on the half-minute and never when charging batteries. I find it gives me the greatest accuracy. (My navigator correctly guessed that it would take 26% of our fuel to reach the East China Sea.)

I've read where some players have found the trip back to Midway a lot harder (on fuel). I can only surmise that they were running with damaged engines and/or, as posted above, batteries were never automatically taken off line (they are prone to do that if, for one reason or another, they cannot be charged to a full 100% ... making it necessary to take them off line manually).

[Quillan]

You don't even have to have any current damage. If at any point you suffered battery damage, even if it's been repaired, the boat may not automatically switch recharging off when the battery fills up. This makes you use a LOT more fuel than normal. It happened to me once, I left the East China Sea with 55% diesel remaining to return to Midway, and ran out of fuel about 1500 miles east of Tokyo, even using all the tricks I could to stretch the fuel. It turns out the battery was the problem, because I reloaded an earlier save and confirmed it. I had to manually switch recharging off every time.

[SteveHump]

...with no damage outgoing Midway to Honshu in a 42 Gato mission, 35% fuel usage. Returning with 55% fuel indicated but 10% hull damage left me stranded 600 nm from Midway.

[M. Sarsfield]

There's a mod that fixes the fuel estimation and usage. It's the same mod that adjusts how high the boat rides in the water. I really like it a lot.

[Sgian Dubh]

Hi all,

Thanks for all of the comments, but I have been checking and I still seem to have an odd problem here.

I have a Gato in mid 1942.

I refuled/rearmed at Midway and set a course for the southern tip of Formosa, as this is the designated point. I used a straight-line plot from Midway to the destination, checking for any shallow spots over the route.

I run 2/3 on surface at night and 1/3 submerged.

I watched each "day" to see if the battery charge light went off, and it did. I also have checked and re-checked the damage control station - I have no indicated damage. I never took any damage earlier in the mission that I can recall. I checked the save game and damage is set to 0.000000 (I forget how many zeros).

The problem is that by the time I reach 128 E Longitude (south of the western side of the Ryukyu islands) I am at 50% of deisel fuel. I will be at about 45% (at best) by the time I make it to station.

So without running any patterns, I am already unable to return to Midway due to insufficient fuel.

Again, I watched the battery charge light extinguish at the end of each charging cycle and I can find no indication of any damage whatsoever.

After a great start to a career, it looks like I am goingto have to scrap it and restart.

This is a fresh 1.4 install with TM 1.7.6 installed via JSGME. I have made no other modification to the installation.

Any further ideas? I don't have much incentive to start a new campaign until I understand why this is happening.

Thanks,

[Quillan]

Trigger Maru changes the default speeds, right? I was using ROW before I installed TM so I'm not certain. Assuming it does, that puts you going roughly 8.5 knots on the surface assuming calm conditions and 1.8 or so knots submerged, right? You should be able to get there on considerably less than that. Admittedly it's a different boat, but in a Balao leaving Midway, sailing west until beyond a 500 nm circle centered on Wake Island, then heading SW to the Luzon Straits, I can get there with roughly 75% diesel remaining. Now, I am running surfaced at Ahead 2/3 almost all the time. I submerge for an hour or so anytime I pick up aircraft, so many days I am on the surface the entire time.

[Sgian Dubh]

Originally Posted by Quillan

Trigger Maru changes the default speeds, right? I was using ROW before I installed TM so I'm not certain. Assuming it does, that puts you going roughly 8.5 knots on the surface assuming calm conditions and 1.8 or so knots submerged, right? You should be able to get there on considerably less than that. Admittedly it's a different boat, but in a Balao leaving Midway, sailing west until beyond a 500 nm circle centered on Wake Island, then heading SW to the Luzon Straits, I can get there with roughly 75% diesel remaining. Now, I am running surfaced at Ahead 2/3 almost all the time. I submerge for an hour or so anytime I pick up aircraft, so many days I am on the surface the entire time.

Thanks.

It appears that something has become SNAFU.

Although I hate to do it, I am going to re start a new career.

On the bright side, I am going to add RSRDC for TM to my installation and I am also going to add in the mod mentioned above that tweaks the endurance (amoungst other things) of the subs. Really the most frustrating thing is the amount of time invested - but that is part of the reality of high-end simulations. Lord knows how much time I've spent in Falcon4 and IL2 sorting things out.....

[raymond6751]

Make sure that you have turned off the battery charge before doing the range check. It will/should turn off automatically when it is charged up, but if a diesel is being used to recharge - your range calculation will be off.

It takes fuel to recharge. The calculation won't take into account if you are going to charge all the way home or not. Turn it off.

[ElAurens]

The most economical speed in the Fleetboats is 10 knots, which you have to set by switching from the standard telegraph to the knot meter, then use the cursor to select the speed. The telegraph will still indicate 2/3 ahead when you switch back.