SUBSIM Radio Room Forums - Poking holes below the waterline

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- - Poking holes below the waterline (https://www.subsim.com/radioroom/showthread.php?t=131123)

Quote:

Originally Posted by bobchase

Quote:

Originally Posted by JCB

Yes, I have seen many a hit below waterline with HE in my games. But does anyone know if it actually was possible IRL for a HE round to penetrate 2-3 meters of rock hard water (at the speed we are talking here...) and successfully explode upon impact with the hull? :hmm: My gut tells me that it won´t work as it does in game. However; it is still a game, so it doesn´t really matter. Any naval ordanance experts here? If my suspicions are true I will bring AP rounds for waterline shots as flavour. :)

JCB,
In my experience HE shells don't usually explode when they strike the water. (At least not the Russian and Chinese ones.) Whether it explodes when it hits the hull depends on the downward angle of the shot and the depth when it strikes the ship. I used to hear the 105's bounce off the hull all the time. You'd hear a big 'Ker-Plunk' followed by a 'ting' when the shell hit the hull and, maybe, a delayed 'boom' if it did actually explode. However, most of these rounds were shot near maximum range - not close in like your deck gun is. So the angle of the strike on us was nearly vertical. If you were unlucky enough to be on deck when they came in you'd see a 80' high plume of water followed by a huge 'KER - PLUNK'.

Bob

Wow! Perfect! That is what I was waiting to hear! Thanks a bundle Bobchase! :D
Now, as you say, the downward angle of the shots affects the shell. Say I aim to hit a merchant about a meter below the waterline 1200 meters away. At such a short distance the angle would be just a couple of degrees off the horizontal plane making the travel through the water a rather long one. Unfamiliar with the ballistics of the naval 88 used on the VII´s I would guess the shell would act like a torpedo for at least 3-5 meters before actually hitting anything. If your experience is true for the german shells as well we might suspect HE shells not performing the way it was intended to do, hitting and detonating upon impact with the ships hull, when traveling underwater first. A HE shell that don´t detonate is not a wery potent weapon, being relatively light and frangible compared to AP. This is very interesting information indeed, bobchase. The "ker-plunk" sound you heard - was that the sound of the shell hitting the water not detonating? In that case I´m fascinated by the ability of a compact lump of metal making those plumes. :huh:

ker-Plunk revisted

JCB,

Here is a picture of a plunging round (Ker-Plunk shot) that was taken from my ship on its 1st Nam cruise back in '67. (I was on the 3rd Nam cruise in '72)

http://www.uss-newport-news.com/nnpix/1967_69_pix.htm

Click on the upper left picture for a close-up. The upper right picture is a very good picture of a fall storm in the N. Atlantic. In a couple of months the seas would be twice as big...winter in the N. Atlantic is not for the frail and timid.

Another good site for pictures of incoming rounds is:

http://home.att.net/~dgoad/photos3.html

One of the 1st pictures is the USS McCormick taking incoming from a small coastal gun. These rounds are coming in from an angle so they were very close to the NVA gun.

Down farther is a picture of typical 'near miss' where a 105 round prematurely detonated before actual penetration. The funnel of our ship would be approximately the same thickness steel as merchant hull.

Still further down this page is a picture of HMS Perth. If you click on the picture of HMS Perth, you will see a better picture of where she is surrounded by shore battery fire. The Perth took a round in the fantail that day sending some good Aussie's to meet Davy Jones.

As far as far a 'flat trajectory' goes - no - or at least, probably not. Unless you are point blank, running down the side of the merchants' hull, a gun's shot has a trajectory like a lopsided rainbow. When a shot leaves a gun, no matter what the angle of elevation, the shot goes straight out only at first. But it's wind resistance vs. gravity and gravity always wins. As the speed of the shell drops, the forward & upward vectors become less and gravity becomes the largest vector operating on the shell. So the downward side out at far end of the 'rainbow' is always much steeper than nearer, upward side. The very top of the arc is always past the middle of the range and for a very high elevation round (+41 deg) can be nearly at the end. Which is why rounds fired at maximum range are called 'plunging fire' .

All of the water plumes you see in the pictures are non-exploding shots. A contact fuses' detonator should not detonate on water. A timed fuse or a proximity fuse could but you wouldn't be using them from a sub's deck gun. When plunging fire comes in, it sounds and looks just like what dropping a very big rock off of a pier only enlarged by a factor of 100 or more. A tight vertical water column 80' high was very common from a plunging 105. 207's made a bigger splash because they reached higher altitudes and weighed more.

I can't really tell you how far below the water line the shells exploded. when I was out on the weather deck and saw incoming, I nearly always went to my general quarters station. The few times they didn't call way GQ was when we already had downed the gun or tank.

When I was down below and heard the 'tink' sound, again, they almost always called away 'NOW GENERAL QUARTERS...' And when there was an explosion, it was almost always delayed from the 'tink' sound.

However, we where a heavy cruiser (CA) and if the shell did explode on contact, the shell would have exploded against the belt armor. Our armor was 8" thick at the water line and tapered down to 3" at the under curve of the hull. So we could have taken a hit from a 207 shell and been OK.

Above the water line is a very different story and a lone 88 could have done some damage, started fires, and killed shipmates. On the other hand, the life expectancy of a surfaced submarine against us would have been measured in seconds...

As far the games' deck gun goes, it seems to me to be a fairly accurate representation of what it might have been like. Yes, the HE shell could explode below the water line and after penetrating a hull. AP rounds have less explosive power than HE rounds because of the thick armor steel that they are made of. (More steel = less space for the explosives.) So an AP round would only be used against armored targets or if all the HE shells had already been expended. The fuse on an AP round is typically a delayed contact detonator. The delay is for armor penetration, not for the water or the thin skin of a merchant. Fired a close range, it might be possible for an AP shot to go through the ship and then explode, doing little or no harm. But it's a sim/RTS game, not an *exact* simulation of the real thing.

Hope this helps,

Bob

Very interesting reading Bobchase, thanks a lot :up:

This is super, bobchase! Couldn´t have asked for a better reply. :D

SH3 is exiting, but real life experience sort of knocks the wind out of it... A very interesting read!

*loading HE-rounds*

By the way: Welcome to the forum! (I´m sort of a newbie myself, but somebody got to say it. :sunny:)

Quote:

Originally Posted by kenijaru

Quote:

Originally Posted by JCB

Since HE rounds are supposed to detonate upon impact, wouldn´t the shells explode upon impact with the water (on its way to hit below the waterline) detonating harmlessly meters away from the hull....
Maybe the AP rounds, being made for penetration rather than fragmentation, will serve my needs better? :88)

what you say makes sense, makes a lot of sense :yep:

but if you hill the side of a merchant with AP, the shell will probably slip through the ship like a hot knife through warm butter and explode harmlessly in the air or water. (thats the same problem argentine pilots had in the malvinas/falklands, the bomb fuse was delayed to protect the airplane from the blast but that made the bombs go through the british destroyers, with some "lucky" exeptions.)*

HE shells arent ment to throw sharpnel, but to open big holes on whatever they touch, the actual sharpnel they throw is a secondary effect (or an evolutionary leftover, like our coxis or apendix) :hmm: anyhow, you dont need sharpnel as you are not trying to kill the crew.

just shoot with HE and then use external camera to make sure you are leaving holes on the bugger.

*please, lets not start a discusion about that, specialy not here, it was just an example that poped into my head.

At least you sunk HMS invincible ;)

In the stock game, I always put a few AP in the areas there the fuel is supposed to be, and after that a few HE shells, resulting in a big fire or explosions.

Or am I imagining things?

Quote:

Originally Posted by Fusek

In the stock game, I always put a few AP in the areas there the fuel is supposed to be, and after that a few HE shells, resulting in a big fire or explosions.

Or am I imagining things?

From what I´ve heard about the game engine so far - the latter...