No Diesels when decks awash

[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"?

[WernherVonTrapp]

I always cringe when I see a flat statement like this with no corroboration. Uh-oh, someone else in the forums who is just like me. I don't know if I can handle that. I mean, I have a hard enough time just living with myself. http://forums.ubi.com/images/smilies/59.gif

[gamer025]

Originally posted by 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.

WHAT?! LOL are you sure? I've done it in SH4 but NOT SH3. In SH4 you can remain on the watch deck until the boat is almost under, whereas in SH3 as soon as you give the order it forces you inside.

I've gone as deep as 24ft in SH4 with the diesels running. The aft section of the boat was submerged with only part of the bow above water, that is the part that curves upward.

in SH3 I tried to go 1 meter deeper and it wouldn't allow me to stay on the tower. I can't remember now if the ship changed to electric propulsion.

[MWolfe1963]

Originally posted by SailorSteve:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">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"? </div></BLOCKQUOTE>

That was usually the case, running on electrics. Obvious not deep enough to hit the con tower or no one could stand outside.

Game wise, decks awash is rather difficult and confusing. You can be decks awash with the electrics running and you're crew will act dived and not be on watch. It's also hard to get it to hold, eventually the boat will surface and not hold depth, so you have to adjust. The good thing, even though your crew goe's under, you can stay and use the TBT and see better.

[Blowtanks]

It always worked for me running RSRD, but the others mods didn't seem to work as well or at all.

[sneakattacks]

Refer to "DECKS AWASH' in

Useful Links & Information> Tips, Mods,Tools, 100club> SILENT HUNTER 4 TUTORIALS AND SET-UP TIPS> The SHIV Guide> DECKS AWASH.


This part of the SHIV Guide will cover it all and give hints why and when to use this tactic. The main thing is that "decks awash" is not defined by water on your deck (a common misconception), but by the deepest depth the diesels can run continuously. If your electrics are running, you're below your boat's ability to run at "decks awash". And it varies between boat types, don't you know... The 'Guide' lists the maximum depths for the various classes of boat in SH4 v1.4.

(Why the SHIV Guide has gotten buried so deep in layers is a mystery to me. It's a valuable help for this game. By me, it should be up front and visible for the newcomers and old timers alike.)

[Wolferz]

FYI,

Diesel electric boats always run on electric motors. The Diesels are there to turn the generators only.
While surfaced, the diesels handle the full load on the generators and charge the batteries at the same time.
Just like modern locomotives.
If you run the game with the TMO MOD, you can run at radar depth which is essentially decks awash... see signature pic below.

[lordish2001]

You have to understand the design of the Balao class submarine and all other
American boats subsequently. The main induction valve, the valve responsible for providing the diesels with most of their air, was in the conning tower at the same level as the bridge. It was under after AA deck on the tower.

This valve was well above water when the decks were totally under. Yes, speeds were reduced from 20 knots but the boat was far faster than when totally submerged. The men manning the diving planes were trained to maintain trim to minute angles so the boat could keep water from coming over the top of the main induction to prevent flooding.

This was a useful way to reduce the radar cross section of the boat or increase the diving speed in tight situations. Remember, the Balao took over a minute to dive while the German Type VII took less than 20 seconds.

When you're trapped on the surface, I don't think you wanna take a minute to dive when you're forced to set up a down the throat shot on a rampaging Shimikaze destroyer with blood in her eye.

To check I recommend Clay Blair's history of the Silent Service.

lordish

[TheBeastBelow]

You also have to consider, this game was written in the UK and explains why a new American Sub comes with a totally weathered paint scheme. No self respecting skipper would ever allow thier boat to ever get that rusty. Even ship in storage never get that bad. At the same time German boats start out totally clean.
This might explain a lot of the short comings on US boats in the game.
Another thing to take into consideration is, Although the air intake was placed well above the waterline, the exhaust was not. The engine can only take so much exhaust back pressure before bad thing start happening to the engine, like blowing head/exhaust gaskets or even blowing the head right off the engine depending on how many rpm the engine is turning.

[Wolferz]

You also have to consider, this game was written in the UK

Actually, it was produced in Romania.

[KaelNL]

Euhmmmm,... how do I tell if my boat is running on diesels or electric? Is it the sound? The speed gauge? Or is there some nifty light on a panel somewhere that I'm not aware of?

[TheBeastBelow]

If you are submerged, you are running on Electric Motors. If you are surfaced, you are running on Diesel Motors.
There is a Toggle Propelsion command but I think it is just left over from previous SH.

[Wolferz]

Originally posted by TheBeastBelow:
If you are submerged, you are running on Electric Motors. If you are surfaced, you are running on Diesel Motors.
There is a Toggle Propelsion command but I think it is just left over from previous SH.

US fleet boats are/were propelled with electric motors. Both above and below the surface. They were faster surfaced due to the increased amperage output from the generators, as opposed to the lower amperage output from the batteries while submerged. Unlike their German counterparts and earlier fleet class boats, they didn't require a layshaft to run the battery charging enerator off of one screw.

All fleet boats except the S class ran four diesels that were directly connected to four generators, to power the electric motors and charge the batteries.

[KaelNL]

Originally posted by TheBeastBelow:
If you are submerged, you are running on Electric Motors. If you are surfaced, you are running on Diesel Motors.
There is a Toggle Propelsion command but I think it is just left over from previous SH. That's obvious.

The reason I ask is for the 'decks awash' thing: I want to make sure my diesels are still running while I'm partially under. If they quit, I have to emerge another meter or so, while if they run, I'm good or may even dive another meter.