SUBSIM Radio Room Forums - View Single Post - Realism- and gameplay-related hardcode fixes for SH3.EXE

Tom · 01-16-12, 02:54 PM

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.

01-16-12, 02:54 PM	#3056
Tom Gunner Join Date: Oct 2006 Location: Finland Posts: 97 Downloads: 10 Uploads: 0	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.