Hello Mr. Tore.
I was thinking about adding this info to the Prologue: diving sequence... What do you think???
"Using the trim tanks while diving or surfacing
During a normal dive procedure there are lots of people moving around particularly from the crew quarters to the fwd. torpedo room, the aft control room, the engine room, and the aft torpedo room. This movement has an influence on the U-Boat's trim and you have to compensate for this by using the fwd. and aft trim tanks. So prior to giving the order diving station, you pump water from the aft trim tank to the fwd. trim tank; our experience was you needed approximately 400 liters of water to compensate for the movement of people. Hence, the trim tanks take part in the diving and surfacing procedure. Likewise, when battle station order is given (which are almost the same as diving station) similar actions are taken. When the situation is cancelled you operate the trim tanks in the opposite way.
While on the surface, if the officer of watch orders an emergency dive, then we would have several things happening at once. There would be an order to pump 400 liters of water from the aft trim tank to the fwd. trim tank to balance the U-Boat, and then the crewmen are quickly manning their assigned diving station. In addition, there would be a mad rush of non-assigned crewmen to the fwd torpedo room. This would be the added weight of the human ballast to assist the U-Boat's bow in breaking the ocean's surface and getting the emergency/crash dive started expeditiously. The Q tanks would be of no additional assistance because they were already flooded while on the surface.
While submerged and the U-Boat is in a trim state; if the officer of watch has to make an evasive dive (collision or ramming danger) at periscope depth, there is no time to move people, and you can`t use dynamic (hydroplanes) diving, steep angle, the officer of watch would order fill Q! An extra weight in excess of 4 tons which gives a pretty good sinking effect and as Q is placed about mid-ships; there is no trimming moment and the crew remains where they are. If the officer of watch is free to use dynamic diving, then he orders the hydroplane angle and goes dynamically deeper. Only in extreme conditions using Q. Thus emergency actions would not necessarily be carried out by diving station manning, but handled by the officer of watch. However, I can assure you, the CO and EO as well as the control room engineer would be in the control room in a split second to take over. Such procedures would be laid-out in the CO order book and every CO would require that he be called in immediately to take over. Pumping additional water into the fwd. trim tank from the bow trim tank, even in an emergency, to get the bow down for going deeper would normally not be done because you want to maintain the U-Boat's trim; you can do a lot by hydroplanes and it is a very smooth process."
Regards,
Don_
