No Diesels when decks awash | Forums

[lordish2001]

A common tactic used by US Sub skippers in WW2 was to run at high speed with decks awash. The only part of the boat above water was the fairwater or sail. All US boats had their main induction valve, which was a part of a huge pipe that emptied outside air into the engine room high above the water line in the fairwater.

Running the diesels with decks awash greatly reduced the visibility and radar cross section of the submarine on the surface while allowing speeds close to the boat's maximum surface speed of 21 knots.

I tried this tactic in Silent Hunter and the boat ran on batteries making no more than 9 knots. The graphics couldn't decide if the boat was on the surface or not either. Has anyone suggested this problem be fixed?

lordish

[mush1960]

I've managed to do this in SH3 but not SH4. I agree, it's a useful tool, it would be nice to get it to work properly.

[Wolferz]

Looking at your sig pic there Mush,
Is that diesel exhaust from the Stingray? If it is, that's the approximate location of the muffler and exhaust pipe. Could it really run with decks awash and exhaust partially submerged?

[mush1960]

Wolferz, I agree, exhaust would be a problem. Unless you had a really, really, high pressure exhaust plume!

[lordish2001]

The exhaust could be re routed through a pipe next to the main induction. Almost the next best thing to a snorkel.

lordish

[lecek]

I have had no difficulty running decks awash in SH4. While on the surface just click on 25 feet down. The sub will sink to 22 feet, run on deasels, and still have the watch crew up.

22 feet is more like "decks level with water" then decks awash but it works and it is still about 6 feet or so deeper then surface draft.

[lordish2001]

Hey thanks!

[TheBeastBelow]

A diesel engine exhaust could easily function while submerged 5'-10' without any modification. Diesel Engines are very high compression, much higher then a standard gasoline engine. 12.5:1 compression is very high for gasoline and is about as high as the compression can go for gasoline without having predetonation before the spark even fires, but 12.5:1 is on the low end of the compression scale for diesel fuel.
Obviously, the deeper the exhaust gets the more it will start effecting power output because it will start to hinder the engines ability to breath properly.

-TheBeastBelow

[realoldephart]

I Don't remember the footages for all boats but a while back here on the forum somebody had them all listed. I do remember you can run the Balao at 28 feet and remain on diesels. That however is in a calm sea. If you're in a rough sea it would be much less. Hope this helps.
John

[SailorSteve]

Originally posted by lordish2001:
A common tactic used by US Sub skippers in WW2 was to run at high speed with decks awash.

I always cringe when I see a flat statement like this with no corroboration. It was always my understanding that decks awash was a tactic for a close-in attack running on electrics. It is also my understanding that the hull of a WW2 submarine was designed to cut through the water at high speed, and the conning tower was not.

Could someone please provide evidence that this was indeed a "common tactic"?