Realism- and gameplay-related hardcode fixes for SH3.EXE

[Victor Schutze]

@h.sie: I have not observed anything different.
BTW, if I enable "Sergbutos WolfpackMod V3 Reloaded" through JSGME on top of "Supplement to V16A3", JSGME warns that it will overwrite "Shells2.dat", "Shells.sim" and "Shells.zon".

Does it brake anything in "Supplement to V16A3"?

[fitzcarraldo]

Originally Posted by LGN1

...If you are interested in further details, the original handbook of the VIIC contains much information about this.

Cheers, LGN1

LGN1, please: Where can I obtain that original handbook of the VIIC?

Many thanks in advance.

Regards.

Fitzcarraldo

[LGN1]

Originally Posted by fitzcarraldo

LGN1, please: Where can I obtain that original handbook of the VIIC?

Many thanks in advance.

Regards.

Fitzcarraldo

Here you can find an English translation:

http://www.uboatarchive.net/Manual.htm

BTW, it gives the capacity of the pump at 100m depth, but not deeper, i.e., maybe the max. working depth for the pumps is 100m

Cheers, LGN1

[h.sie]

So a possible fix could be as follows:

1) In low depths (0m - maybe 50m or 100m): pumps or compressed air can be used to empty diving tank. That means: Surfacing is only possible if either battery or compressed air is not exhausted.

2) In high depths: only compressed air can be used to empty diving tank. That means: Surfacing is only possible if compressed air is not exhausted.

???

[Hitman]

1) In low depths (0m - maybe 50m or 100m): pumps or compressed air can be used to empty diving tank. That means: Surfacing is only possible if either battery or compressed air is not exhausted.

2) In high depths: only compressed air can be used to empty diving tank. That means: Surfacing is only possible if compressed air is not exhausted.

We know that the deeper the UBoot dives, the more pressure from the surrounding water it suffers, and that same pressure is applied when trying to pump water from the buoyancy tanks to the exterior, in order to increase buoyancy and rise. What we do not know is how much pressure the pumps could withstand (10 At, i.e. 100 metres of depth as LGN1 indicated sounds plausible, but is not confirmed) and also how deep could the compressed air be used. This last one is however easy to determine if we know the maximum pressure at which it was stored. For each At. of pressure, it's 10 metres of depth, IIRC, so we can know how deep could the uboat still use compressed air to empty tanks *if* we have an acurate figure of strong pressure.

I suspect however that the figure will probably be the same as the pumps, because those pumps were actually the ones which stored the compressed air ----> it's logical that a pump that can exert a force of 10 At. to throw water out of the uboat, can also create at most the same one to compress air into a tank.

In that case, you would have:

Depth <100 metres : You can maneuver to change depth with compressed air, pumps and diving planes (speed > 2 knots).

Depth > 100 metres : You can only maneuver to change depth with diving planes (speed > 2 knots).

But we need first of all a trustworthy figure of what the pumps could do

[Gammel]

Depth <100 metres : You can maneuver to change depth with compressed air, pumps and diving planes (speed > 2 knots).

Depth > 100 metres : You can only maneuver to change depth with diving planes (speed > 2 knots).

What about "Das Boot" Gibraltar bottom situation?
Don't now if its a good example, its just a movie but the did surface with air from 280m

[TheDarkWraith]

Originally Posted by Hitman

I suspect however that the figure will probably be the same as the pumps, because those pumps were actually the ones which stored the compressed air ----> it's logical that a pump that can exert a force of 10 At. to throw water out of the uboat, can also create at most the same one to compress air into a tank.

A positive displacement pump can pump to whatever pressure the prime mover can support (horsepower of prime mover) and max pressure design of pump (material properties).

[Sailor Steve]

Originally Posted by Gammel

What about "Das Boot" Gibraltar bottom situation?
Don't now if its a good example, its just a movie but the did surface with air from 280m

They used the stored compressed air to blow the tanks, not pumps. On the other hand they did use the bilge pumps to dump all the gathered water overboard, so who knows? The scene was also in the book, and it's my understanding that it did happen pretty much that way in real life, so maybe they're all good to that pressure.

[Hitman]

A positive displacement pump can pump to whatever pressure the prime mover can support (horsepower of prime mover) and max pressure design of pump (material properties).

Yes, so much I already suspected. The question is what power did those pumps really have and to what pressure they could compress the air.

They used the stored compressed air to blow the tanks, not pumps. On the other hand they did use the bilge pumps to dump all the gathered water overboard, so who knows?

Yes but that air is stored by the pumps. What I mean is that the compressed air will not have more force to displace water than the pumps themselves. So, if the pumps can compress air to say 10 At, then blowing the tanks will only be possible at no more than 100 metres depth. If you are deeper, f.e. at 130 metres, the external pressure of the water will be of 13 At and it won't allow the one stored in the ballast tanks to go out of the sub and be replaced by air -which is what achieves positive buoyancy.

What about "Das Boot" Gibraltar bottom situation?
Don't now if its a good example, its just a movie but the did surface with air from 280m

The scene might have been real, but not at 280 metres. It could have been at, f.e., just 80 metres but it was exaggerated to add dramatism. I don't think that there are many places in the Gibraltar Strait with 280 metres depth, let alone close to the African coast -which the boat was hugging when they got caught.

But anyway, again this all is pure speculation. If the pumps could actually compress air to 28 At., the the scene could have really happened.

We need to know that value, otherwise we are stuck at "best guesses"

[Hitman]

Well it seems I found the answer in the UBoat manual ...

Page 40

2) Blowing installation. a) Compressed air blowing. The main ballast tanks are blown with compressed air controlled from the blowing distributor, which is located on the stb. side of the control room. Blowing takes place until the boat has sufficient buoyancy to safely open the conning tower hatch. All blowing lines are led inside the pressure hull and at places where they pass through hull to tanks they are fitted with cut-off valves. The highest pressure in the installation is 25 atm.

And page 47:

The maximum operating pressure is 10 atm. The pump is used to drain small quantities of water from regulating tanks, regulating reserve fuel oil tanks, torpedo compensating tanks, bilges and for trimming. Both the main drain pump and the auxiliary drain pump have the capability of pumping water out to main ballast tank 3.

So it seems that the installation was able to withstand 25 atm and the compressed air receptacles up to 28 (Page 43), from what we can conclude that:

1) You could "blow ballast" and expel water out of the tanks for depth changes up to 250 metres depth.

2) You can't make fine control trimming by moving water from one ballast tank to another with pressures inside the trimming tanks of >10 Atm. However, since those tanks were isolated from the exterior (Unlike the ballast tanks) the air that went into and out of them when moving water was taken and returned to the interior of the sub. That means that, if for some reason the interior pressure of the sub would be higher than 10 Atm, you would be unable to regulate trimming. That said, such a pressure would kill the crew unless built up veeeery gradually over a long period of time, and it is unlikely to be the case in normal operating conditions. I don't think that any Uboat ever reached an air pressure of 10 Atm inside the pressure hull.

[Tom]

The air compressors on board a type VII were rated at 205 kg/cm2, or about 205 atm. The compressed air was stored in bottles rated at 280 atm.

However, the maximum pressure of the actual blowing system was rated at 25 atm, which would allow the tanks to be blown at a depth of 240 meters, not deeper. It is possible that in an emergency the tanks could be blown with a slightly higher pressure though.

The amount of compressed air stored in the tanks was 3900 litres, which at a pressure of 205 atm (the capacity of the compressors) would mean 800 cubic meters of air at 1 atm. At 240 meters (25 atm) the amount of water that can be blown out with this amount of air is 32 cubic meters (giving the boat 32 tons of additional buoyancy). If more weight needs to be lost, it must be pumped out.

The VIIC manual doesn't give a maximum pressure level for the main drain pump. (The auxiliary pump has a maximum pressure level of 10 atm, or 90 meters.)

The main pump consists of two pumps which can work in parallel mode (low pressure, high output) or serial mode (high pressure, low output). At 15 meters (1.5 atm difference between inside and outside) the main pump can pump 1300 liters in parallel mode, i.e. 650 liters per pump. At 105 meters (10.5 atm difference) the pump can still pump 500 liters in serial mode, with the two pumps working against the pressure together (each pump having to overcome 5 atm or so). Thus, if a single pump unit is capable of 650 liters at 1.5 atm and 500 liters at 5 atm or so, my educated guess would be that the pump would still work, albeit at a lower rate, with higher pressures.

It is quite possible that the main pump, in serial mode, could pump water out at depths of 200 meters or deeper. The fact that no maximum pressure level is given for the main pump (when one is given for the auxiliary pump) supports this view too, in my humble opinion.

As far as I know, the Gibraltar sinking and repair scene in das Boot did not really happen. It was one of the few things made up by Lothar-Günther Buchheim to make his book more exciting.

Edit: If the auxiliary pump, which only has a single unit, is capable of 10 atm, the main pump, with 2 stronger units must be capable of more than 10 atm + 10 atm, working in serial mode. Thus, water should be able to be pumped out at any depth.

[LGN1]

Hi Hitman,

the water pumps and the air compressors are different devices.

The pressure in the air flasks was 205 kg/cm^2 (operating) and 280 atm (tested).

Unfortunately, the handbook mentions only the operating pressure of the auxiliary drain and trim pump and not the main pump. However, I guess it was the same

Cheers, LGN1

[LGN1]

BTW, would it have ever happened that a u-boat was submerged without battery power and compressed air? I can't imagine that the commander and LI would allow to get the u-boat into such a situation.

[LGN1]

Originally Posted by h.sie

So a possible fix could be as follows:

1) In low depths (0m - maybe 50m or 100m): pumps or compressed air can be used to empty diving tank. That means: Surfacing is only possible if either battery or compressed air is not exhausted.

2) In high depths: only compressed air can be used to empty diving tank. That means: Surfacing is only possible if compressed air is not exhausted.

???

Hi H.Sie,

don't forget the dive-planes.

Here's an interesting link about the diving procedure:

http://www.uboatarchive.net/KTBNotesDiving.htm

Cheers, LGN1

[Leitender]

What we do not know is how much pressure the pumps could withstand (10 At, i.e. 100 metres of depth as LGN1 indicated sounds plausible, but is not confirmed) and also how deep could the compressed air be used. This last one is however easy to determine if we know the maximum pressure at which it was stored. For each At. of pressure, it's 10 metres of depth, IIRC, so we can know how deep could the uboat still use compressed air to empty tanks *if* we have an acurate figure of strong pressure.

E.g. some information is given at Roessler, Vom Original zum Modell. UBoot-Typ 2:

compressor: 6,1l/Min. at 205 atü (=athmospheres overpressure, should be atm+1, IIRC), stored in pressure bottles at 205 atü.

Main gyro pump: Power 1,2m^3/Min. surfaced, 0,25m^3/Min. at 100m. (both:page 74).

These values are for type IIC/D boats designed in the mid-30s.

For the earlier described prototype CV707 (later: type IIA), 180 atü in bottles were mentioned. That was 1930, so there could also exist an improvement for later type VII or IX boats.

2) In high depths: only compressed air can be used to empty diving tank. That means: Surfacing is only possible if compressed air is not exhausted.

h.sie

If CA is emptied, you can use the battery to move on. The compressor can empty the diving cells. This sounds like the behaviour of SH3 could be correct (unlike i asumed ): Surface with empied CA.

Greetings.