TECH QUESTION , About decks awash !

[Stormfly]

Originally Posted by misha1967

Ah, the Handbuch is still around! Highly recommended read!

Yes, it will help a new Kaleun in this sim too. Only thing is that you can be a bit more "daring" in the early years than it recommends since it was written in '43 where a lot of things had changed.

...as i wrote above, but i should have wrote "if" in bold letters using a higher sized font maybe

(edited my post above)

[misha1967]

Originally Posted by Stormfly

...as i wrote above, but i should have wrote "if" in bold letters using a higher sized font maybe

(edited my post above)

Not a critique at all, Stormfly. As a matter of fact, I highly commend you for linking the Handbuch. It's all too easy for us old hands to forget that we constantly have new fellow simmers joining our ranks who haven't already heard of all of the resources out there

Besides, on the topic of whether or not "decks awash" was ever used, I'm fairly certain that there were some Kaleuns out there using the tactic whether it was documented or not. After all, "invisibility" is the first, second, third and fourth commandment of a sub skipper, and surely all of them knew that the lower your profile to the enemy, the harder you were to spot.

[Stormfly]

Originally Posted by misha1967

I'm fairly certain that there were some Kaleuns out there using the tactic whether it was documented or not. After all, "invisibility" is the first, second, third and fourth commandment of a sub skipper, and surely all of them knew that the lower your profile to the enemy, the harder you were to spot.

you`re maybe right yes, i renember there was also a stupid "Kaleun" who sank the boat by not knowing how to operate the new sea toilet system which was useable while the sub was at dept.

If you compare the hight and size of a german sub`s cunning tower or the boat`s mass with the american version, you see that a pre flooded german sub only need a little mistake done by one of the dive plane operators to sink it then. If you have the cunning hatch closed, the advantage of a faster dive is maybe gone in that case. I dont think that a smart Kaleunt would take such a risk for the little advantage having a allready invisible small cunning tower 1 meter deeper. If you follow the handbook, you see that a german sub using the right "stern trim" was nearly invisible while approaching in a "dog`s curve" from the dark side at night. Last by not least, running decks awash is only a replacement of risc`s, visual detection was not the only problem. Why should they trade a maybe 5% lower visbility against a 20% higher sonar signature, keeping the same speed running pre flooded means higher rpm.

[misha1967]

Originally Posted by Stormfly

you`re maybe right yes, i renember there was also a stupid "Kaleun" who sank the boat by not knowing how to operate the new sea toilet system which was useable while the sub was at dept.

If you compare the hight and size of a german sub`s cunning tower or the boat`s mass with the american version, you see that a pre flooded german sub only need a little mistake done by one of the dive plane operators to sink it then. If you have the cunning hatch closed, the advantage of a faster dive is maybe gone in that case. I dont think that a smart Kaleunt would take such a risk for the little advantage having a allready invisible small cunning tower 1 meter deeper. If you follow the handbook, you see that a german sub using the right "stern trim" was nearly invisible while approaching in a "dog`s curve" from the dark side at night. Last by not least, running decks awash is only a replacement of risc`s, visual detection was not the only problem. Why should they trade a maybe 5% lower visbility against a 20% higher sonar signature, keeping the same speed running pre flooded means higher rpm.

I agree completely personally. I never use decks awash for that very reason. Too many things can go wrong in exchange for very little gain. The German boats were designed to have a very low silhouette even when surfaced and, if you ask me, if lowering that silhouette by 1m is enough to make a difference, then you shouldn't be surfaced at all.

[jason210]

I know that decks awash was a configuration regularly used by British Submarines in the Second World War, both to facilate fast diving and keep a low profile. I don't know about german U-boats, but in SH5 I use decks awash when in dangerous areas - with the hatch closed. It can quickly opened and the boat can be submerged in less than 20 seconds in that configuration, if the speed is decent.

I think WW2 British submarines are a neglected area in submarine simulators. Which is a pity because there were a lot of them and they saw quite a lot of action, particularly in the mediterrean. There were over 270 deployed during the war, all over the world.

I find them fascinating because of their design. Some of them were enormous - for example the River Class was 325 feet long; while the T-class submersibles 275 feet and had an impressive armament of eight forward torpedo tubes and one aft.

http://home.cogeco.ca/~gchalcraft/sm/

[jason210]

Originally Posted by misha1967

The German boats were designed to have a very low silhouette even when surfaced and, if you ask me, if lowering that silhouette by 1m is enough to make a difference, then you shouldn't be surfaced at all.

That extra one metre allows you to get about 3km closer to your target, before you are visible.

[Stormfly]

Originally Posted by jason210

That extra one metre allows you to get about 3km closer to your target, before you are visible.

...ohh, that explains that iam able to close in below 2000 meters without beeing detected while not using "decks awash" at night using diesels not more than half ahead.

[misha1967]

Originally Posted by jason210

That extra one metre allows you to get about 3km closer to your target, before you are visible.

Listen, I'm not saying that there's no advantage to be had (although I'm not sure that the sim models it accurately since I've found that they spot my scope if I'm at anything but at a complete stand still no matter how much I make sure that it's barely peeking above the water), I'm just saying that I don't find whatever advantage there is to be worth the trouble.

Trouble meaning that, no matter how much you're decks awash, you're still going to be facing an additional few possibly critical seconds getting your watch crew below before you can dive as opposed to already being below a periscope depth where you can dive pretty much instantly.

I just haven't found it ever to be worth the trouble in the sim. If the visibility is against me and I'm close enough to be spotted (with somebody on the surface who can hurt me), I'll be below the water.

[jason210]

Originally Posted by Stormfly

...ohh, that explains that iam able to close in below 2000 meters without beeing detected while not using "decks awash" at night using diesels not more than half ahead.

I'm not sure how the simulator is modelled, but a small change in the height of an object above sea level makes a big difference to the range at which it sticks up over the horizion, so keeping a low profile is useful in cirumstances, for example, where you are trying to intecept a convoy on an interecption course. With the decks awash you can be on the surface longer and thus travel towards the interception point at a higher speed before you risk being visible to the target.

At least that's my excuse. I just like decks awash because it's cool

[thoomsn]

Ahoj Folks.

This "decks awash" thing was called "Vorfluten" in the Kriegsmarine and it's aim was mainly - as mentioned before - to show the lowest possible silhouette in surface attacks at low speeds (otherwise the big wake would have been seen by the enemy). In SH5 you have to click on 6.5 meters depth to get the boat "half dived". Decks awash was part of the official training as well as crash diving and other tactical skills. It was also used when a boat was supplied at sea: To get the eels on upper deck, the boat was "vorgeflutet" (partly submerged) so that the eels only had to be moved over it's deck. Then the ballast tanks were blown out, the boat raised out of water and the eels was laying on the deck.

that's (historically) all.

[jason210]

Originally Posted by thoomsn

Ahoj Folks.

This "decks awash" thing was called "Vorfluten" in the Kriegsmarine and it's aim was mainly - as mentioned before - to show the lowest possible silhouette in surface attacks at low speeds (otherwise the big wake would have been seen by the enemy).
that's (historically) all.

Where did you get this information from about low speed being a requirement? According to Gordon Williamson in his book "U-boat Tactics in World War II", in a scenario where it is trying to get close to a convoy, the U-boat would often travel with the decks awash in order to present a low profile and at the same time take advantage of diesel engines and surface speed. The wake is only dangerous if spotted from the air and it's not going to be that much different than it would be if the boat was fully surfaced.

[BIGREG]

Hi

Uboat (VII a/b/c/41)
Personally, I think it was not possible to use the diesel with the submerged bridge, since the exhausts to find her submerged (except with a snorkel) therefore have to sail with the electric engine + waves resistance = slower

BigReg/BigRegOne



"Any advantage has its disadvantages and vice versa."

Proverbe Shadock

[jason210]

Originally Posted by BIGREG

Hi

Uboat (VII a/b/c/41)
Personally, I think it was not possible to use the diesel with the submerged bridge, since the exhausts to find her submerged (except with a snorkel) therefore have to sail with the electric engine + waves resistance = slower

The bridge wasn't submerged in decks awash. The air intake for the engine was inside the conning tower, which was above the water line and also shielded from waves by the conning tower plating.

[BIGREG]

I talking about exhausts,I think the system can withstand a little pressure water (wave) but not to be completely under water (too much risk of engine flooding or excess pressure)



if you want a good book with lots detail : http://dl.dropbox.com/u/8655607/2357...Vii-U-Boat.pdf

BigReg/BigRegOne



"It is better to pump even if nothing happens that is going to risk something worse and do not pumping."

Proverbe Shadock

[jason210]

Thanks a lot! That's much appreciated. I don't have that book - although I have Robert Stern's book of the same title.

The exhaust outlets were not a problem since the exhaust manifold pressure kept water out. Also, take a look at the VIIC on page 32 - the exhaust outlet is below the waterline. I wonder why they did this?