Part of John Channing's reference:
Quote:
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A persistent enemy may remain in vicinity 24 hours or longer; therefore, conserve the battery by balancing or bottoming, when practicable.
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Do you know what "balancing" is? It is a twin to bottoming, which is sitting on the bottom lightly by carrying just enough ballast to sit motionless on the bottom without use of engines of other noisemaking equipment. This is dangerous as if you are too heavy, localized stresses could cause hull damage.
Balancing is similar exploitation of a thermal layer. With the boat at neutral buoyancy, a condition never exactly achieved, if you sit motionless in the water you could remain there suspended until someone uses the head and your buoyancy is no longer neutral.
Maintaining neutral buoyancy for fifteen minutes drove many a crew batty while they were being evaluated by the Captain's CO. It was a useless exercise, whose main value was determining whether the crew could continue to work together efficiently under severe stress.:rotfl:
However, with a friendly thermal barrier down there, we have a new water surface. Neutral buoyancy in the top, less dense water, is flotation buoyancy in the colder and denser water below. There is a range of displacements that will sink in the warm layer, yet float on the cold layer. See what I'm driving at? If you hit the middle of that range, now you can sit on top of the dense layer with all power off. Since there is a range of displacements that satisfy your suspended conditions, this is something you could do for days, if necessary, with all systems turned off. This is absolutely the quietest a sub can be, and the only limitation is your air supply so the crew can continue to breathe!
On a trim dive, the object was to mark the negative buoyancy tank at the neutral buoyancy position. Then you decended across the thermal barrier and marked it for neutral down there. Any level between the two marks allowed you to sink to the the bottom of the upper layer and float on top of the lower! I've always wanted to issue the order, "Flood negative to the mark!" Now you know what that means.
Now the bad news. We have no control over the ballast tanks. We can't do this. An important evasion stragegy, which saved several subs, is totally outside our grasp. Merry Christmas!
