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Originally Posted by SteamWake
Here is a laymans question...
Why wold they do this? Sure it would decrease the 'dive time' but by how much? How long did it take to open those valves? How much time was actually gained?
What if a top valve should accidently open or fail?
Seems to me like the risks would out weigh the reward.
The only scenario I can see is if the boat 'knew' it have to dive quickly as in a convoy approach or in an area thick with air patrols.
I simulate this "realistically" by approaching a convoy with decks awash on occassion.
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I was asked by Bosje to make some comments on this subject. All hands involved in this thread have made some very cogent observations and comments. Most of the historical aspects of this discussion are dead on with just minor quibbles.
I personally play at 58% realism and that suits my game play style just fine. I have tried to walk a line between moving things along and realism, and I think this is the devil that any sim developer must face. I see the beauty of SHIV is the ability of individuals to mod it as they see fit. Two major things that have been missed: 1. A random equipment malfunction feature (always the bane of a sub CO). 2. The above mentioned process of refining your solution to a high degree in assisted mode. (as in SHI)
Now to answer Steamwake's questions above:
The flood valves on the bottom of the MBT's were known in the USN as "Kingston" valves. Their only function was to close off the flood port and act as a backup to the vents at the top of the MBT. In operation the Kingstons were always opened first. They opened inward, against the air pressure in the tank and thus were difficult to operate quickly and in the days before hydraulics the complex linkages required a healthy amount of Armstrong Engineering (get it?
) to move. If you opened the vents first, you could unintentionally flood the tank through the vents (especially in heavy seas). The operating mechanisms and linkages for the Kingstons were inside the tank and therefore virtually impossible to maintain short of an drydock overhaul. The linkages for the vents were in the superstructure and thus readily accessible. There were a set of Kingstons for each MBT (port and starboard) and that equated to a lot of valves that had to be opened for the boat to dive.
As a higher level of mechanical confidence was gained in the ability of the vents to hold air in the MBT's, the Kingstons came to be viewed as a unnecessary redundancy, and indeed a liability due to their difficult and time consuming operation. During the 1930's the Kingstons were usually left open all the time and by the late 30's they had been deleted from the boats altogether.
The vents also operated inward against air pressure, so having one open accidentally was a very rare occurance. Even if one did open unintentionally, enough buoyancy would be retained by the other tanks to hold the boat on the surface. On the Darter, we did this once alongside the pier. We opened one vent to do maintenance on the mechanism. The boat listed to one side a little, but it didn't sink.
Running with decks awash provided both advantages and disadvantages. It did reduce the boat's silhouette in calm seas or if the moon was behind the boat. You could still use radar and have the lookouts stationed. But there was a huge disadvantage to this tactic. With the decks awash, the mufflers and overboards for the main engine exhausts were submerged. The engines were not designed to continuously push water out of the exhaust pipes, it produced too much back pressure. It would blow out the exhaust manifolds on the engines or even worse flood them. So if you are going to run decks awash you would secure the mains and run on the battery, and if you are going to do this you might as well run submerged. Your speed would be the same. I haven't tried this in the game yet, so I don't know if the speed issue is modeled correctly.
If anyone has any more questions, please surf over to the Real Submarine Technology and History Q&A thread:
http://www.subsim.com/radioroom/showthread.php?t=147577
There have been some great questions asked there. I try to check it as often as I can.
Dave
www.pigboats.com