15in Up Gunned Gneisenau v 1939 Modernized Renown

[Bgile]

Dave,

I wasn't confusing yaw with trajectory change, and I probably shouldn't have muddied the waters by mentioning the latter, except that it's one reason two plates might be more easily penetrated than one.

I'm still not seeing anything that indicates how much yaw might be induced. Am I missing something? Do we have anything that indicates how much yaw might be induced in a battleship caliber projectile penetrating two inches of armor?

I take it you have the study. How did you obtain it?

[Thorsten Wahl]

Im sorry its a little bit off.

http://www.navweaps.com/index_nathan/Pe ... ermany.htm

Im a little bit confused about the results facehard give us
According the given penetration tables from the link for german facehardened armor it seems the SK 38 is better in belt penetration at any range compared with the Mk 8 1-5 16”/45 (1939-44) 2,700-lb and partly better than the Mk 8 1-5 16”/50 (1943-44) 2,700-lb at distances below 10000 meters

i made a small gfx

Distance in metres, penetration in mm
please check



in addition it seems the penetration data for the german SK 38 against german vertical and horizontal armor doesnt fit the original GKdos100 drawings

[Dave Saxton]

Dave,

I wasn't confusing yaw with trajectory change, and I probably shouldn't have muddied the waters by mentioning the latter, except that it's one reason two plates might be more easily penetrated than one.

I'm still not seeing anything that indicates how much yaw might be induced. Am I missing something? Do we have anything that indicates how much yaw might be induced in a battleship caliber projectile penetrating two inches of armor?

I take it you have the study. How did you obtain it?

Yaw is dynamic depending on several factors. One factor is distance traveled after penetration of the yaw plate before reaching the main plate. If the rate of precession is ralatively rapid, it may reach maximal yaw by the time it reaches the main plate in the case of a relative small inter-space. Or if the rate of precession is relatively slow it may require a greater distance before reaching maximal yaw. As it turns out The British found the distance between plates of the German systems as built were virtually perfect for a slower rate of precession as was found on the blunter nose shells. Another factor with yaw is how much away from the head of projectile the center of gravity is shifted by removal of the cap. Longer and heavier shells will develop significantly greater yaw than a lighter short bodied shell. One can't saw that there will be X amount of yaw after penetrating a two inch plate because of all the complex interelated factors involved.

I was sent the study on British shell research that contains some of their observations on yaw several years ago. Its locked into an old computor though.

[Bgile]

Yaw is dynamic depending on several factors. One factor is distance traveled after penetration of the yaw plate before reaching the main plate. If the rate of precession is ralatively rapid, it may reach maximal yaw by the time it reaches the main plate in the case of a relative small inter-space. Or if the rate of precession is relatively slow it may require a greater distance before reaching maximal yaw. As it turns out The British found the distance between plates of the German systems as built were virtually perfect for a slower rate of precession as was found on the blunter nose shells. Another factor with yaw is how much away from the head of projectile the center of gravity is shifted by removal of the cap. Longer and heavier shells will develop significantly greater yaw than a lighter short bodied shell. One can't saw that there will be X amount of yaw after penetrating a two inch plate because of all the complex interelated factors involved.

I was sent the study on British shell research that contains some of their observations on yaw several years ago. Its locked into an old computor though.

It seems to me that a shell traveling 400 m/s or some such isn't going to yaw very much in 40 feet of travel through air unless the rate of yaw is really, really fast. How likely is it for such a heavy object to start spinning at that rate after travelling through such a thin plate, given the resistance to that from the gyroscopic effect of the spin? Intuitively it doesn't seem like it would have much effect on it, but I'm sure not in posession of any way to determine what would happen one way or another.

Are you sure lighter shells would develop less yaw? It seems like they would possess less inertia and the heavier shell would be more resistant to change in it's orientation, particularly against the same armor thickness. Where did you get the information that lighter shells would develop less yaw?

[Bgile]

Im a little bit confused about the results facehard give us. According the given penetration tables from the link for german facehardened armor it seems the SK 38 is better in beltpenetration at any range compared with the Mk 8 1-5 16”/45 (1939-44) 2,700-lb and partly better then the Mk 8 1-5 16”/50 (1943-44) 2,700-lb at distances below 10000 meters

That doesn't bother me very much. The German shell has higher muzzle velocity.

[dunmunro]

Im a little bit confused about the results facehard give us. According the given penetration tables from the link for german facehardened armor it seems the SK 38 is better in beltpenetration at any range compared with the Mk 8 1-5 16”/45 (1939-44) 2,700-lb and partly better then the Mk 8 1-5 16”/50 (1943-44) 2,700-lb at distances below 10000 meters

That doesn't bother me very much. The German shell has higher muzzle velocity.

At 25deg target angles the performance of the 16/45 increases relative to the 38cm. The 16/45, at 15k yds, retains a higher percentage of its velocity after penetrating the same thickness of armour, so that it will have greater penetrating power against additional internal armour. So in actual combat, at non zero target angles the relative differences will be reduced between the two guns.

[Dave Saxton]

It seems to me that a shell traveling 400 m/s or some such isn't going to yaw very much in 40 feet of travel through air unless the rate of yaw is really, really fast. How likely is it for such a heavy object to start spinning at that rate after travelling through such a thin plate, given the resistance to that from the gyroscopic effect of the spin? Intuitively it doesn't seem like it would have much effect on it, but I'm sure not in posession of any way to determine what would happen one way or another.

Are you sure lighter shells would develop less yaw? It seems like they would possess less inertia and the heavier shell would be more resistant to change in it's orientation, particularly against the same armor thickness. Where did you get the information that lighter shells would develop less yaw?

It's more than a matter of spin stablization. The shells center of gravity, and mechanical forces during penetration also have a great effect in induced yaw. Longer body shells do develop significantly more yaw than short body shells. Krupp knew quite about these behavours. They did extensive research using high speed spark photography and observed that yaw is both significant and immediate. 40 feet is plenty of space to develop significant yaw. This includes large caliber shells, and particulary armour piercing capped types. 600mm (less than 2 calibers distance) is all that is required for battleship caliber projectles to obtain a yawed orientation. The shifting of the center of gravity is a major causal factor in induced yaw. Induced yaw is not a minor factor in penetration dynamics and it can not be dismissed as such.

[Bgile]

Then why did every navy except the Germans, who basically copied the Baden design, go with a more or less single thick armored deck? Was this secret yaw defense something only the Germans knew? That seems ridiculous to me. For one thing, the British fired a 15" shell right through Baden's upper deck and MAD, where it then exploded. Yaw didn't prevent this from happening.

Do you have some documented tests you can point to? How much yaw are you talking about? Like a battleship shell goes through this small amount of armor plate and then turns 90 deg sideways? How much angle? Under what angle of incidence? How much armor? In what actual combat did this take place?

What is "significant yaw?" One degree? How much?

[alecsandros]

Dave, Steve,

My understanding of shell dinamycs after first impact is drasticaly below yours
A small input though: when Massachussets hit Jean Bart at Casablanca, the 406mm shell that pierced the 150mm armored deck wasn't deflected to much (a few degrees perhaps) and it blew up deep, deep inside the ship... Even considering a possible poor quality for French homogenous armor, 150mm of steel is pretty thick...

[Karl Heidenreich]

Bgile:

... the Germans, who basically copied the Baden design, go with a more or less single thick armored deck?

The myth of myths! It´s a shame that with my actual obgligations I can´t come up with an adequate asnwer using (again, time after time) the references that are always, very properly, ignored in order to support a nationalistic stance. Bgile: PLEASE READ GARZKE AND DULLIN to dispell that myth; you should know better!

Will try to write this weekend, if possible.

[Dave Saxton]

Then why did every navy except the Germans, who basically copied the Baden design, go with a more or less single thick armored deck? Was this secret yaw defense something only the Germans knew? That seems ridiculous to me. For one thing, the British fired a 15" shell right through Baden's upper deck and MAD, where it then exploded. Yaw didn't prevent this from happening.

Do you have some documented tests you can point to? How much yaw are you talking about? Like a battleship shell goes through this small amount of armor plate and then turns 90 deg sideways? How much angle? Under what angle of incidence? How much armor? In what actual combat did this take place?

What is "significant yaw?" One degree? How much?

Did you read my earlier post about the amount of yaw being dynamic? The value of yaw will vary depending on several variables from the rate of precession to the center of gravity of the shell in question. It can't be condensed to a simple term of yaw is typically X,y or Z degrees. In Krupp engineer, Dr. Kratz's paper, he describes the center of gravity of the shell falling above or below the line of flight. He uses charts and graphs. I'm sorry if I don't know how to express these complex data sets (usually expressed by calculas equations) in an internet forum format off the top of my head.

It doesn't take much of a deviation of the center of gravity from the line of trajectory to cause the shell's interaction with the main armour to become a yawed interaction. This is and was a well known behavour. Indeed some USN documents refer to the thin 38mm upper armoured deck of the new fast battleships as the yaw deck. In it they describe the yaw deck as causing the incoming shell's orientation to become altered enough to cause it to "strike flat", rather than nose on. If you understand yaw (and granted it is a complex concept) you can understand that the orientation only needs to be altered just enough to cause the shell to not strike directly nose on. This will cause the impact to be over a much greater area. The armour plate will still need to be thick enough though (not essentially just a splinter deck as in Baden). Nevertheless, yaw does improve the effective thickness of the main armour. The greater impact area will of course cause the necessary velocity required for penetration of the main plate to become greater. If the necessary velocity for penetration of the main armour is increased by a certain %, that is the same as increasing the thickness of the main armour deck by that certain %.

Yaw is just one of several factors in the German system, and I don't find the German system dependent on yaw to be viable. The overall arrangement of German deck protection was due to a wide variety of sound rationals, not the least of which was to use a protection arrangement with scarps.

The American application of deck armour of the new fast battleships also consisted of a thinner upper deck and a heavier armoured deck below. It is interesting to examine the American application of this concept. The armour tonnage was divided among three plates (thin splinter plates behind the main armour actually contribute very little to effective thickness and can for practical purposes be omitted from the calculation). For example, in NC the structural deck was 36mm STS, with 88mm STS plates inboard and 102mm STS plates outboard, laid in direct contact over this. This laminated deck was one level below the 38mm yaw deck.

The German system differed mainly by extending the distance between the upper deck to two deck levels, and by using single armour plates for decks. By placing the main deck lower it allowed it to back up the vertical protection, and allowed yaw effects time and space to become more manifest, among several factors. The thickness of the German upper deck is thick enough to do some good in terms of de-capping and energy consumption, but not so thick that it will cause unfavorable trajectory changes of significance, or consume too much weight that could be better used by the main armour. The Germans didn't commit the sin of using laminates for the ballistic decks.

[Bgile]

Why do you think the Germans came up with this system, which you obviously consider superior, when none of the other navies embraced it? Everyone else felt that one deck was superior to two of the same total thickness, and that is why they did what they did. I'd also be interested in knowing whether anyone else considered the German system superior, or just the Germans. For example, the British concentrated all of the armor plate in the one thick deck on the newest ships. I suspect the other navies didn't think it was quite as much of a game changer as the Germans did or they would have done the same thing. Of course, the German system does give up a much larger internal area to damage because of the MAD being so low in the ship.

[Dave Saxton]

The American deck protection system is a multi- plate system, and the German system is essentially a two plate system. The Germans were not the only ones who used two plates or more in new construction designs. The Germans also considered a single plate as more desirable in most cases. Hence they didn't use laminated decks. Nonetheless, they knew that a properly engineered two plate system could match or exceed the effective thickness of a single plate of greater overall weight expended. In that case nothing is lost in terms of ultimate ballistic protection and it allows other design considerations to be incoperated.

[lwd]

One has to be careful of that line of reasoning. For instance it does look like the Italians deliberatly designed the armor system of the VV's to decap AP projectiles. It's not clear anyone esle did. In recent years such a decapping system is viewed as superior if it's well designed. Penetration mechanics are very complex and only in recent years with high power computers and very complex computer codes have we started to get a really good idea what is happening. In WWII era an individual getting a good idea that lead to a series of tests might result in a design that was unique to one country and significantly superior to that of others (or not depending on what he got right and wrong). Notice that no one else went down the superheavy path where several countries pushed muzzle velocity to extremes.

[lwd]

.... Nonetheless, they knew that a properly engineered two plate system could match or exceed the effective thickness of a single plate of greater overall weight expended. ....

The other qualifier here is in certain regimes. From what I understand the US multi plate deck protection system was designed to defeat AP bombs. It was not necessarily better at defeating AP shells. It's not clear to me how much benefit the upper deck gave in the case of AP projectiles.