[PSUBS-MAILIST] K-600 buoyancy mystery

[Jon Wallace via Personal_Submersibles]

I'm stuck on a buoyancy issue with the K-600.  The operating and service manuals state that the working weight of the vessel (dive ready) is 4500 pounds less operator.  However, when I calculate the buoyancy of the vessel based upon it's physical dimensions I don't even come close to offsetting the projected weight as documented by Kittredge.  I know the stripped weight of the vessel is 3060 lbs, because I had it weighed at a CAT scale used by truckers which is suppose to be guaranteed accurate.
My buoyancy calcs (inches) and results in pounds are:Main hull - 36 x 72 = 2712.96Main tank heads - 36 x .5625 = 66.5 each = 133Conning Tower - 24 x 18 = 301.44Battery Pod - 12 x 45 = 188.4 each = 376.8Battery Pod Tank Heads - 12 x .365 = -1.83 each = -7.32
Total potential buoyancy comes out to 3516.88 lbs.  Deducting the 3060 known weight of the steel leaves 456 lbs of buoyancy however there is easily more than 456 lbs of machinery, electrical, and plumbing components that will be added to the stripped hull.  For example, Kittredge used 8 lead-acid batteries with a combined weight of approximately 320 lbs, 200 lbs from three 1-ATM motor containers, 150 lbs drop weight, and then operator weight would produce a combined total of about 800 lbs additional weight not including electrical, plumbing, and instrument components.
So from a weight perspective, 4000 to 4500 pounds sounds reasonable for a dive ready K-600.  But with only 3516 lbs of physical vessel buoyancy it would be 500 to 1000 pounds negatively buoyant which is obviously an impossible configuration.  Given that we know this submarine dived successfully, what am I doing wrong with my calculations?
Jon
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