Bruce
Just added to the Photo Album are 20 photos from the HD video and five from the digital camera, all of the conning tower hatch and surrounding structure labeled Atack Analysis 1.The last 4 are from the port side, others from the starboard. The question is what caused the damage? It could be key to the mystery.
If anybody can identify and annotate the parts it may help others develop a viable hypothesis.
To be organized I think we need to first define the hypotheesis and then list consistencies and inconsistencies in a manner clear enough that they can be checked by others.
This process is far from final. We need your ideas on how to make it effective.
Hello Bruce, have followed with great interest your search and discovery. It is also with great interest that I view the photos you have thus far posted. One suggestion I might have is that you provide some sort of ‘context’. From what I’ve seen so far the damaged seems to be mostly related to ‘implosion’, however, without a more descriptive ‘context’ it’s difficult to say. For example, the After Battery hatch is open…is the After Battery Compartment imploded?, or relatively intact? If intact, it supports the theory that the hatch was open upon diving and the compartment flooded. If imploded, hatch could likely have been blown open by that event. I’ve seen your report regarding the missing bow and the ‘goove’ left in the bottom from Grunion sliding down…at what depth does this ’slide’ begin? Such context might help answer, did the bow break off from contact with the bottom, as a result of an implosion event, or from damage related to the attack itself, or a combination of all three. If you could provide a general overview of the condition it might help provide this context.
I certainly do congratulate you all for a magnificent effort, and for bringing it to the attention of the general public. Let us never forget those still on eternal patrol.
David SS-328 SS-396
Past Nat’l Historian USSVI
The photos show what I believe to be a ‘catastrophic structural failure in collapse’ of the conning tower. That is the only way, in my estimation, that the deformation of the upper hatch AND its hatch coaming can be explained. They were bent together with the hatch shut.
That being said, if true, the conning tower could not have been holed. A hole of any significant size (over 1/2″) would admit enough water under the increasing pressure of the sinking submarine to equalize with outside sea pressure within a couple of hundred psi which would be below the pressures required to collapse of the pressure hull.
It would appear the after torpedo room may have suffered the same type collapse, although the photos are not sufficient in number to make an educated guess.
The After Battery Hatch, being open with dogs retracted tell me that that hatch was undogged by someone inside. That does not mean the hatch was opened, however. Someone could have undogged the hatch with sea pressure on the hatch (little depth pressure, say 50 feet submergence) would have kept it shut. The hatch would have swung open by the opening spring (which generally balances the hatch weight) when internal pressure equalized as may have happened by the collapsing compartments.
Was there a hit by a Japanese naval weapon that holed the hull. Possibly. The evidence would be in the form of an uncollapsed hull section.
V/R
Jim Christley
Hatch is clearly evident in all the pictures. It appears closed. It appears to be extremely warped out of round or shape. Appears they maybe tried to get everyone below to keep watertight integrity and try to fight the casualty incurred and any flooding, hence the closed hatch. That hatch should stay open on the spring unless pulled closed. Unsure why the hatch would be so out of shape, or twisted as it is.
The shattering of the forward part of the conning tower fairwater probably happened during the sinking, not as a direct result of the shell hit from Kano Maru. Grunion may have rolled over once or twice against the sloping undersea terrain before sliding to her final resting place.
In “Conning Tower Hatch #13″, the hatch and conning tower cylinder seem to be sharply bent downward and the periscope bent forward. All of the fairwater plating, relatively thin steel compared to the pressure hull, surrounding that part of the conning tower is missing while the after part of the fairwater is relatively intact. This seems consistant with the broken bow and litter of steel plates along the slide path. The fairwater structure just aft of the hatch on each side of the periscope seems to be bowed outward as iif pressed on from above. The stern deck, just forward of the propeller guards also has impact damage that could only have been cause by a rolling over type action. The conning tower fairwater and aft dek areas are fully open to the sea at all times and would not have been deformed by water pressure.
More likely than not, the boat was fully flooded befoe it reached crush depth. Grunion was executing a “battle surface.” The messroom hatch, closest to the deck gun, was probably opened as soon as it was clear of the water. After the shell hit, an attempt to dive was probably made with the hatch still open. The open messroom hatch may have played as mutch a part in the boat’s loss as the shell hit. The submarine could have survived the flooding of the conning tower, the safety tank was there for such an eventuality. Unless there are confirming photos of the after part of the fairwater on the side exposed to the Kano Maru, it will probably be impossible to separate the sinking damage from the shell damage.
II have been scrutinizing the photos of the open After Battery hatch, most particularly the hatch ‘dogs’. Although the picture is not overly clear, it does appear that 2 of the dogs are visible, and appear in the ‘open’ position. However, I find that these dogs do not appear completely correct. I’ve posted a picture at the link provided that shows clearly the upper Conning Tower hatch on SS-328. Charr was also an EB boat, although of a later vintage. The hatch dog assembly may be slightly different in construction than that on Grunion, but the mechanical operation was the same. The dogs on this photo look different from each other only from the perspective of the camera, but from the one facing us, you’ll notice the 90 degree shape of it where the dog contacted the underside edge of the trunk facing. The dogs showing in the Grunion photo do not appear to have this shape. If the hatch was subjected to a pressure wave, either through explosion or implosion, the dogs could have been deformed, or sheared. A clearer picture of the hatch would perhaps provide a better perspective.
I have reviewed wartime damage reports where hatches became temporarily or permanently un-seated due to depth charge attack, most particularly that of Salmon, but can find no written description of the subsequent condition of the hatch dogs. Whether they became deformed or were sheared, I cannot ascertain.
Perhaps if there are any WWII vets reading, they can provide some guidence on the usage of the After Battery hatch. Was it in fact utilized to man the deck gun, or was the normal procedure to use the access trunk from Control Room.
On another note, the “messenger bouy’ has been mentioned. According to Alden in The Fleet Submarine in the U.S. Navy, on March 30, 1942, a design alteration was authorised to ‘Remove Marker Bouy’. This alteration applied to new construction boats, and also as an alteration to boats already in the fleet, to be accomplished in refit. It would be interesting to ascertain if this alteration had been carried out on Grunion.
To correct my comment regarding usage of the After Battery Hatch. Grunion had not received the later alteration installing a ‘gun acess trunk’ in Control Room. Grunion was still in its’ orginal configuration of having a watertight ‘gun acess door’ in the aft end of the Conning Tower. This door would be the one most likely used to acess the deck gun during battle surface. Following damage to Kingfish SS-234 in early 1943, this door was eliminated in new construction, and was removed in earlier boats at overhaul.