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Question on AP for DM

Posted: Fri Feb 09, 2007 3:21 pm
by seldon
I am turning to your advanced knowledge in the subject to ask about armour penetration in naval combat.

What are the real drivers for armour penetration in Naval combat.

I understand the plunging shot effect that represents the hit being on the deck and not on the belt armour at long range, however I was wondering if the AP characteristic also whould apply in long range or if in the case of the projectil arriving to the target on the deck still benefits from the velocity of the gun firing it.

In the same regard, is there no grounds for damage modifiers at short range ?

And also, I've read a couple of times about the Italian guns having higher muzzle velocity than other Med. fleets, should this have no impact at all in damage modifiers?

thanks for your help. It is great to have your extensive knowledge engaged in this project.

We are all looking forward to getting your WWI and pre-dred. version of the rules :)


Posted: Fri Feb 09, 2007 3:24 pm
by DM
I'm about to head off to see about buying a house - I'll try to get back to you on this tonight or tomorrow.

Posted: Fri Feb 09, 2007 3:26 pm
by seldon
Thanks, I'll be waiting...

Good luck on the house, make sure it has a good gaming room ;)

Posted: Fri Feb 09, 2007 3:29 pm
by Wulf Corbett
I can give one simple answer - yes, there are grounds for modifiers to penetration (and accuracy) at various ranges both long & short, but they are abstracted out as a simplification.


Posted: Fri Feb 09, 2007 3:41 pm
by seldon
thanks for your answer. I understand what you are saying but I am trying to understand which drivers are considered, which ones are not and which ones are simply meaningless.

In fact, accuracy and range is taken into account, and the plunging shot could also have been simplified so I am trying to understand which effects are being simplfied.

thanks !

Posted: Fri Feb 09, 2007 3:57 pm
by Wulf Corbett
One other thing (while I fill in time before quitting work...), AP effects are often not a matter of velocity, but of projectile shape or construction. While they'll always penetrate better at higher velocities, if you abstract that out, one 12" shell can have a better penetrative shape or material construction than another for penetration.


Posted: Fri Feb 09, 2007 4:06 pm
by captainsmirk
Very true, during the First World War German 11" guns had better penetration than British 12" ones (and German 12" were a match for British 13.5") simple because their shells were made of better materials and didn't tend to shatter on impact like the British ones did.


Posted: Fri Feb 09, 2007 4:47 pm
by Chernobyl
I've seen some websites that claim the American 16" 2700lb shells were equivalent to or even better than the Japanese 18" AP shells...


Posted: Fri Feb 09, 2007 6:04 pm
by seldon
I agree. I have done some reasearch on this on my own.
That is why I am trying to get some of DM's expertice on the subject to
see what are his opinions in the matter since I had him in high regard on this subject even before VAS.
I like the system and I like to understand the drivers behind the engine of the game.

I've also seen some statements on US 16" as well on Italian guns. Of course you'll probably find arguments pulling in different directions all the time :)

Thanks for the attention to this thread!


Posted: Tue Feb 13, 2007 5:27 am
by seldon
Any updates on this :) ?

Posted: Tue Feb 13, 2007 6:02 am
by DM
Sorry, it slipped my mind (RL quite hctic at the moment).

The principle drivers are:

The mass, shape and impact velicity of the shell
The material from which the shell is made
Angle of impact, including any yaw that the shell has picked up (so ballistic qualities are another factor)

The thickness of the target armour
The materia properties of the target armour
The material (if any) that the shell has to go through before it reaches the armour and the effects on velocity, shape, impact angle etc. that passing tbrough that material has.

There are a host of additional factors but these are the main ones.

Armour penetration should therefore drop off as range increases, although at longer ranges (as the rules try to model) shots at longer range will, by virtue of their steeper impact angles, tend to strike the decks in preference to the sides of the ship and hence deck armour comes into play (generally MUCH thinner than side / belt armour but then the impact angles tend to be much higher so the apparent thickness of the armour is increased, plus the armoured deck is generally not the upper deck but some way below it so the shell has to pass through layers of relatively lightweight structure before it gets to the deck armour and (presumably) all te rally important stuff is below the armoured deck).

Sorry thats a bit rambling.

Posted: Tue Feb 13, 2007 7:57 am
by Chernobyl
I hadn't thought about shell tumbling...interesting. makes you wonder how smart thos guys were! :lol: