Sorry for the delay. I apparently lost all of my detailed notes when I moved. So here goes from memory:
Captain Abele, of the USS Grunion sent a status report to ComSubPac reporting attacks on patrol vessels in the Aleutian Island area. Mentioned in this report was his torpedo status. The boat was down to it's last six torpedoes with all being in the forward room. This message was decoded by Edward Beach and mentioned in his book, Submarine. Messages were often decoded by other than the addressee out of boredom and to see what other boats were doing.
Fast forward to the morning of July 31, 1942. Grunion is on it's first war patrol and the crew is inexperienced. They fire two fish at the cargo vessel Kano Maru at 0547. The torpedoes are sited by the target and the captain orders hard right rudder". The maneuvering by the Kano Maru causes the first torpedo to miss astern. The second torpedo strikes the cargo ship in the engine room on the starboard side. This causes flooding of the engine room and disables the 3" gun mount on the stern. This leaves the forward 3" gun and machine guns in the bridge area the only functioning defense for the Japanese crew. The Grunion fires a second torpedo at the ship's starboard side but this shot runs deep and is a miss. At 0607 the grunion fires a third salvo of three fish at the freighter's port side after circling around the ship's stern. The first and second torpedoes strike the side of the ship but do not explode. The last fish misses astern. During this time the Kano Maru has been firing at the Grunion's periscope with her remaining guns. This has no apparent effect. Grunion, now out of torpedoes executes a 180 degree turn to port and proceeds on the reciprocal course. Shortly after the turn the captain of the Kano Maru observers a "low level explosion" in the general area of the submarine's position following the final by the Kano Maru's forward 3" gun.
The Abele family have decided to go with a circular torpedo theory but the details of the attack and the wreck fail to bear this out. The NAVSOURCE site
http://www.navsource.org/archives/08/08212b.htm shows the layout of the high pressure air system with the six flasks providing air to the forward torpedo room secured to the outside of the pressure hull above the forward torpedo room. My analysis hinges on this information and that of the Captain of the Kano Maru.
The Grunion has fired six torpedoes within a 20 minute period. This amounts to the loss of 18,000 pounds of ordinance from the forward torpedo room within 20 minutes. Half of that being at the end of the time period. The transfer rate of the trim pump, with the boat's depth between 0 and 200 ft, is 1,500 lbs per minute. At this rate it will take approximately 12 minutes to compensate for the torpedo shots. Keep in mind the last three were at the end of the time period. Also of note is the fleet boats propensity to squat by the stern while turning. A 180 degree turn will exacerbate this effect.
After executing the turn Grunion's bow is now dangerously close to the surface. The forward diving planes are at full dive. The "washing wave" described by the Captain of the Kano Maru was most likely the water washing over the diving planes and up to the surface. At a 45 degree angle above and aft of the diving planes are the air flasks above the torpedo room. The last shot from the freighter at the 'washing wave" strikes the high pressure air flasks severing the upper part of the pressure hull and flooding the forward torpedo room. See wreck photos showing downward deflection of the upper hull in this area. Forward buoyancy and diving control are lost. The Grunion begins an uncontrolled dive.
The forward battery room is the first to reach crush depth. The forward battery goes to full ground which causes an explosion in the after battery room. The blast severs the dogs on the after battery room hatch forcing the hatch open. The gasket on the hatch cover is dislodged by the blast and is fouled on the hatch itself. The conning tower and control room reach crush depth next. The forward portion of the conning tower begins to collapse drawing the periscope shears down and forward. The bridge hatch is deformed allowing water to enter halting the collapse of these compartments. The motor room, maneuvering room and after torpedo room collapse in turn.
I fail to see how a circular running torpedo striking the bridge could have caused any of this damage. Also, the damage of a circular run striking the bridge area would have left that area of the boat in a much different condition. I would appreciate any comments on this scenario regarding the loss of the Grunion and her crew.