I wish about engines...

[PhantomLord]

Not to forget the combined diesel-electric propulsion for saving fuel on long journeys... that would be nice.

[pythos]

German boats up to the electro boot, had two direct drive diesels that had only forward ability. The electric motors acted as generators when the diesels were running but were clutched out when the batteries were full up.
The diesel engines had to be clutched in and out for operations. While in harbor the U-boat operated on only electric motors due to the limitations on backing.

Only Us boats, and the type IXD2 had more than two diesels and only the fleet boats from the very start had diesel electric-propulsion.

The S boats were very much like the German propulsion system of earlier boats.

[ETR3(SS)]

The downside to a direct drive propulsion system IMO. Diesel propulsion too to a degree. But I remember Enigma had the option for individual propulsion controls, i.e. ahead flank on the stbd and back emergency on port.

[Sledgehammer427]

god yes, order pivot port and your ship will heel and do its pretty tricks...ordered that a lot when avoiding torpedoes

[Letum]

Originally Posted by PhantomLord

Not to forget the combined diesel-electric propulsion for saving fuel on long journeys... that would be nice.

You do not save fuel by running on electric power.

More fuel is required to charge the batteries and run on electric for 10 miles
than is required to run for 10 miles on diesel alone.
This is because some of the energy the diesel engines produce is lost when
they charge the batteries.

The only source of energy on the u-boat is the diesel fuel. You can convert
it to battery power, but that results in an overall energy loss. You can't get
'free' energy.

Electric cars save energy because they charge the batteries when there is
excess engine power and discharge when the engine would otherwise be at
it's least efficient. U-boats can't do this because their combustion engines
always run at speeds that are less efficacy when switched to electric and
there is never any spare engine power.

[PhantomLord]

@Letum
Maybe my formulation was a bit unclear...

There´s a procedure described in many books... run diesel AND electric engines together. This takes some load off the diesels = saves fuel.

The engine technology is quite plain to me. It´s my job every day

[Letum]

I know that could be done to add half a knot to the top speed, but how did it save fuel?

[totodog]

I think I know what he's talking about.

One diesel engine would turn the electric motor and the propeller. The electricity from that motor would go to power the other electric, which was connected to the propeller, but the diesel on that side was off.

[PhantomLord]

Originally Posted by totodog

I think I know what he's talking about.

One diesel engine would turn the electric motor and the propeller. The electricity from that motor would go to power the other electric, which was connected to the propeller, but the diesel on that side was off.

Exactly! Couldn´t have say that better.
Earlier i was too lazy to find that book... it was 1 o´clock in the morning here

[Letum]

Originally Posted by totodog

I think I know what he's talking about.

One diesel engine would turn the electric motor and the propeller. The electricity from that motor would go to power the other electric, which was connected to the propeller, but the diesel on that side was off.

Yes, but how does that save fuel?

The running diesel has to burn more fuel to run the alternator and charge
the battery. The electric motor can not possibly be more energy efficient
than the motor used to charge it.

If the diesels run most efficiently at 7.5 knots and hooking up the alternator
reduces speed by 2 knots, but running the other electric increases speed
by 1 knot you have lost 1knot of speed for the same volume of fuel burnt.

Why does the diesel lost 2 knots charging the battery, but the e-motor
only give out 1 knot? Because the alternator, rectifier and e-motor all
introduce additional inefficiencies in the energy transfer from fuel to
propeller.

The most efficacy way to use the diesel motor is direct to the prop shaft.
That way you only have the energy loss caused by the inefficiencies in the
diesel motor. If you instead transfer some, or all, of the diesel engine's
out-put through an alternator, rectifier, batteries and motor you introduce
many new inefficiencies that will result in less power per gallon of fuel.

[ETR3(SS)]

Energy Transfer Loss. Isn't that the proper name for it?

[Deamon]

Originally Posted by PhantomLord

The engine technology is quite plain to me. It´s my job every day

And what exactly is your job ?

[pythos]

Deamon

You are correct about only one of the Kaiser's boats having controllable pitch props. However it was not the only German boat to have this. The small boat the Forelle had one, and the Karp, Karas, and Kambala, had these propellers. These were German made boats, but served in Russian navies. In my post I said the really early boats, nothing about the nation under which they served.

Prien's escape from Scapa was done on the surface? I was not aware of this. Nice to have an armored sub eh? My understanding is he escaped submerged due to the number of naval ships in that small harbor. I have really just concentrated on the tech of the boats, and the strategy of the Grand Admiral. Can you recommend any books about Prien's attack?

I know it is a game, but when I try this attack, that is how I do it, the whole approach is done awash, and then submerged, and remain submerged. I have unfortunately not read much about Prien's attack.

(I just looked at your site, Very nice. I like. Are you still trying to make a sim?)

[rocker_lx]

If I remember right, Prien was forced to exit surfaced as there was such a strong current into the harbor, that only the diesel engines had enough power to get out.

[pythos]

Upon some research, I stand corrected about his escape. However, looking at the tech descriptions of the charging system, there does not appear to be a method of engaging the motors for propulsion when operating at flank power. I will continue my research.