fuel problem

[hcs53]

I am on my way from Midway to my patrol area and my fuel supply is already 67%, it's very bad weather.
even if I use the electric power is my fuel consumption goes down.
Is there something wrong?

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Henny

[Dread Knot]

What speed are you cruisng at? I usually keep to nine to ten knots to arrive with a decent fuel reserve. That often means it takes a week and half to reach the patrol area, but that's about on par with the real event.

Running on electric motors doesn't help. It's relatively slow and you're losing speed from the diesels recharging the batteries afterwards.

[TorpX]

I might be able to give you advice, but you need to provide more information.

Where is your patrol area?

How fast are you going?

What class of boat do you have?

Did you follow instructions in ISP regarding the special ability crew?


The Porpoise-class will have about 6,000 nm range, and later classes about 11,000 nm range (@ 10 kn.). The S-class will have less. You should be able to obtain these figures, and if you don't do much battery charging, or see a lot of bad weather, something better than that.

Really, at the start of your patrol, you should 'test' your engines, and have your navigator give you the maximum ranges at the different speeds, so you know. After that, it is a simple matter to calculate what you will use as you transit from one area to another.

For instance, I got the following info for my S-18 class:

at A 1/3 (5.75 kn.) _______9850 nm
at A 2/3 (8.5 kn.) ________4884 nm
at A Standard (10.25 kn.)___3472 nm

These figures were for wind conditions of 5 m/s, so the speeds are slightly lower, but that is ok.

This was at the start, so I know at 1/3, I get 98 nm per point of fuel, and at 2/3, only 48 nm per point, etc., etc.

Knowing how far you have to go to get where you are going (and to get back), you know how much you need. You should always have some extra for contingencies. As a general rule, you don't want to be running submerged, or using high speeds, unless you have a good reason. BTW, running submerged because you are in enemy waters, and you don't want to be bombed and strafed, is a good reason, doing so near Hawaii, just because you feel like it, is not.

When you get to your patrol area, you should operate within a reasonable fuel budget; i.e. not waste fuel. It you are operating within tight limits, there are ways to stretch your fuel.

[fireftr18]

In general, 9 to 10 knots will give you the most efficient diesel fuel consumption. I don't know the physics of it, but slower speeds tend to use more fuel. With electric, the slower, the longer the batteries last. When you use electric, you need to charge the batteries. The diesels will run full to until the batteries are charged. That uses an incredible amount of fuel. Best to run on surface as much as you can at a moderate speed. Only submerge to avoid aircraft and destroyers, then run at slow speed.

[hcs53]

Thanks for your reply

I must go to the Japan-luzon Straits with my Porpoise.
I always use the speed of 9kn.
I did not know about"The diesels will run full to until the batteries are charged. That uses an incredible amount of fuel".

I am going to read the instructions in ISP.

Henny

[TorpX]

I must go to the Japan-luzon Straits with my Porpoise.

Ah, that explains it.

Cruising at ~ 9.0 kn. is the most fuel efficient. fireftr18 is right that battery charging will use up more fuel, but I wouldn't freak out about it.

With ISP, you will be able to get better battery performance than you would otherwise. I was able to patrol all day at 3 kn. submerged, surface, charge batteries, and move 30 nm overnight using about 1% fuel per day. That in a S-boat. I don't remember exactly how much fuel is used by charging, but it is approximately proportional to the amount of depletion. So, it you run submerged at a low speed, say 3 kn., you should not use more than about 30 % of your battery. This can be recharged without an enormous quantity of fuel.

[hcs53]

I started again the journey from Midway to HaHa Lima, 4786km my fuel level is 72/100.
Very good weather,no diving,only surfaced at 9kn
What do you think?

henny

[TorpX]

That looks about right.

Later on, when you have forward bases, you'll appreciate the advantage.