1921 firing trials against Baden

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George Elder
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No one owns GKdos 100.

Post by George Elder »

Hi Ulrich:

When I received the document there was no understanding of exclusivity, and the translations you did and that I edited were a bit more elborate than that of the US version. Indeed, you edited sections that went beyound the potted rendition. As far as I am concerned, there is no problem, and the translations we made should be freely shared with the entire community. I frequently give access to what I have on file to anyone who asks, and I cannot imagine any other approach to serious scholarship. It may well be the case that a certain document is incomplete or that an author or coauthor doesn't want a just-completed document released due to copyright concerns, preexisting agreements, etc. That is fine and dandy. But translating a historical document such as GKdos usually isn't a problem in that is is widely known. If it were a specially found secret document that was to form the foundation of a subsequent book or article, that would be another story. But that isn't the case here, and I honestly do not see the problem.

George
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Content of GKdos100

Post by Bill Jurens »

My German is admittedly somewhat sketchy, but here is my interpretation of what GKdos100 contains.

As noted earlier, the armor penetration information in this document is in the form of a series of six or seven-page pamphlets each of which deals with a particular class of German ship that might be faced with one or more opposing vessels, usually armed with similar or identical guns.

The series typically begins with a graphical summary of the ballistic characteristics of the guns of the German ship. This is followed by a couple of pages graphically showing the penetration characteristics of that German gun into (presumably) German face-hardened and homogeneous armor. The last part of the pamphlet consists of a series of 'bar charts' which give the calculated immunity zone of the German ship against the guns of the enemy assuming any one of six to ten typical impact scenarios. This -- as might be expected -- lists accurate information regarding the caliber, projectile weight, and intial velocity of the German projectiles -- though it is not clear why, as the information is not further used, and is in any case given elsewhere -- along with conjectural values of caliber, weight, and intial velocity for the opposing enemy guns. No other information regarding enemy shells or ballistics is given, and predicted striking velocities and angles of fall are conspicuous by their absence. These must have been calculated in order to produce the bar charts, but the actual figures for range vs striking velocity and angle of fall are not given in Kdos100.

This document is therefore of value in reconstructing and understanding the performance of German projectiles against German armor, and also of value in helping us to understand what the Germans THOUGHT various enemy guns were capable of. This information, while useful in illuminating the tactical thinking of the German navy of the time, cannot be associated with any specific mark or mod of incoming shell.

I hope this helps.

Bill Jurens
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Ulrich Rudofsky
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Post by Ulrich Rudofsky »

I wish there were enough space somewhere to post the entire original, the USN synopsis or translation (which I never have seen), and our translation, just to set the record straight and to provide the text to all English speakers.

Also, I have on my wish list a request for the entire series of pamphlets that belongs to the "Unterlagen und Richtlinien........" and the USN coverage of this report. There must be close to a dozen German pamphlets in this series, and we only worked out the details of "Heft a".
Ulrich
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Questions from Marty1

Post by Bill Jurens »

Marty1 wrote:

"I do have one question for you. You mentioned the velocity data for 15-inch APC MkI is not in doubt. Fair enough. I don’t have firing\range tables for this particular projectile. I only have the J.Campbell Data and the Baden Trials data. As far as recreating this data in the absence of actual range tables, what would you choose for a drag function?

In addition what would you choose for a form factor? Personally I’d run with a simple G1 (or KD1 depending upon what part of the world your from) and based upon the nose length I’d guess the form factor to about ~0.75. What would be your inclinations regarding the appropriate drag function and form factor for this projectile? No cheating now – pretend you don’t have access to any range table data.


For the 'old' bullet, I'd use the drag function for Projectile Type 1 with a form factor. The form factor is 1.00 for a 2 C.R.H. but a correction for other values of C.R.H. can be easily derived provided that the actual value is known. (Keep in mind that in most cases the form factor will be found to vary slightly -- and sometimes dramatically -- with angle of departure, and hence range. For newer more streamlined designs, one can usually start with Projectile Type 1 and an initial form factor of about 0.60 for small angles of departure, increasing to about 0.70 at large angles of departure. These will match old range tables well, but one must keep in mind that old range tables often are not very accurate, except regarding range vs angle of departure and range vs time of flight. When calculations were done comparing range vs angle of departure and range vs time of flight, there were usually disagreements. In the 'good old days' all that could be accurately measured were range, angle of departure, initial velocity (sort of...) and time of flight. Nobody could effectively measure angle of fall and striking velocity at long range and therefore these items, though calculated, were essentially 'taken on faith'.

For the 'new' WWII type bullets, I would use the drag function for Projectile Type 8 (or perhaps Type 6) directly. Most of these bullets will run more-or-less 'clean' on Type 8, i.e. with a form factor of 1.00. That's because Type 8 is really based on the British 5/10 CRH design.

Hope this helps...

Bill Jurens
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Post by marty1 »

It’s page 36 and 37 of Unterlagen und Richtlinien zur Beftimmung Der Hauptkampfentfernung und Der something something. Its gothic lettering so my spelling may be off a notch or two. It looks to be a low dpi scan of a photocopy, of a photocopy, of a microfiche print-out. It's definitely made the rounds if I can claim to have a copy. Sorta' like Kathy in my senior year of high school -- she'd been around the block way too many times. But hey, all the boys still liked her -- for her brains of course. Enough with the sailor talk.

Best Regards
MKS
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Post by marty1 »

Bill:

Thanks for your thoughts on exterior ballistics for these big shells. I had not come across the variation of form factor relative to launch angle before. I’ll give it a whirl and see if I can creep a bit closer to Campbell’s data.

Do you have any opinion on where Campbell derived his Vdrop material in "Naval Weapons"? Do you reckon these are primarily from Range Tables, or do you think he has crunched some of these numbers himself using common drag functions?

Regards
Marty
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Post by marty1 »

Tiornu wrote:i would think that the 'old' shell is the jutland type, 1920 lbs, as depicted in your drawing; its cap is so unlike a modern shells that i couldn't even identify it when i first looked. the revelations of jutland prompted a makeshift upgrade, the installing of a new cap on the same old shell body. i don't know if the filler and fuze were the same, and i don't know the weight. then came a whole new shell, the mk 3 greenboy 1919-lb. the mk 5 first appeared in 1923, weghing 1917 lbs. i believe the stanard shells at the start of wwii were the mk 13 1920-lb 4crh and the mk 17 1938-lb 6crh.
Getting back to page one of the thread, are you of the opinion that the NavWeps Penetration data I posted represents the Jutland 15-inch APC Old Type (old penetration cap)?

Range (yrds)-------Velocity (fps)-----------Penetration @ 0-deg
8629----------------1853--------------------------16"
14853---------------1537--------------------------12"
19707---------------1329--------------------------11"
23734---------------1178---------------------------9"

The more dramatic Vdrop referenced above would seem to fit the bill for the shorter nosed 15" MkIa Old Type.
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Campbell's data

Post by Bill Jurens »

Marty1 wrote:

"Thanks for your thoughts on exterior ballistics for these big shells. I had not come across the variation of form factor relative to launch angle before. I’ll give it a whirl and see if I can creep a bit closer to Campbell’s data.

Do you have any opinion on where Campbell derived his Vdrop material in "Naval Weapons"? Do you reckon these are primarily from Range Tables, or do you think he has crunched some of these numbers himself using common drag functions? "

A rather significant variation of form factor vs range is (sadly) the rule rather than the exception. This makes recomputing a complete range table from a single range and elevation and intial velocity set rather difficult.

By "Vdrop" data, I assume you mean the tables of striking velocity vs range in Campbell. If that is the case, I don't understand why you are diddling around with form factors and re-computation at all. Just make a big graph of the data you have, e.g. range vs striking velocity, join the points with a smooth curve, and pick any data you need right off from that. That's how they made the range tables in the first place. Usually, they took most data from the angle of departure vs range testing, and let the angle of departure vs time of flight data (which usually didn't match), 'float" when computations were being performed. In the old days, trajectories for range tables were only rarely computed from scratch; most of the time actual range firing tests were used to determine the most important variables directly, with the numerical exterior ballistics boys primarily concerned with computing differential effects.

NJM Campbell was a very meticulous researcher and had access to all of the official range tables. I'm sure that his data is taken directly from the original range tables. He would have had no need for recomputation.

Keep in mind that Vdrop vs range is dependent upon intial velocity and angle of departure in a rather complicated and messy way. For an initial velocity of 2400 f/s for example, you might you might find, the range/sv pairs 18000 yards, 1800 f/s and 24000 yards, 1600 f/s. It does not follow, however, that the initial velocity were decreased by 200 f/s, that the new striking velocities at the same ranges could be computed by just subtracting 200 f/s from them as well. Also, keep in mind that the test firings such as the ones you are observing on Baden are very typically done at much reduced initial velocities, so that the actual trajectory etc., including values of striking velocity vs range may be quite different from those found in a regular range table. For test firings, you only need to get one specific range and striking velocity pair right at a time.

It's important to not that the record of these firings -- at least the record as reproduced in this thread -- is somewhat incomplete, so one must proceed with caution. This is complicated stuff even after a lifetime of study.

Bill Jurens
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Post by marty1 »

I think you misunderstand my intentions. My interest is in estimating down range velocity for projectile in which range table data is not readily available. It is not as simple as interpolating between two known points on a graph. Any monkey can draw a line between two points. I am talking about a scenario in which no range data is available. Moreover the hypothetical scenario is: I have is a sectional drawing of a projectile. I can therefore determine projectile geometry with some level of confidence.

I have examined a fair number of firing tables, and side-by-side calc'd down range velocity when using modern versions of common drag functions and an estimated form factor using the various rules outlined by the late Robert McCoy. If range table data is not matching up well with predictions when using a common drag function and a ‘guesstimated’ form factor, then little confidence is developed when one is attempting to predict velocity drop when no range data is available as a cross check.

As far as this being "complicated stuff", I promise I won’t wee-wee my pants even if you decide to start yakking on about triple integrals and polar coordinates. :D It wouldnt be worth talking about if there wasn't some level of complexity to the subject.
Last edited by marty1 on Thu Mar 17, 2005 4:23 pm, edited 1 time in total.
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Post by marty1 »

For example -- I asked about choice of drag functions and form factors for either of the two 15" APC images posted on page-1. You recomended use of i = 0.6 for small launch angles and i=0.7 for higher angle fire. Neither of these two values seems readily obvious for the nose length involved. Even from your own material on the subject I would have expected a choice of i1 ~0.89 to 0.9 for the MkIa Old Style Cap, and an i1 ~0.84 to 0.85 for the MkIa New Style Cap. Your not suggesting that these are secant ogives are you?
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Post by Dave Saxton »

FWIW, The British 6 crh 15" projectile was introduced in 1937. The V drop is obviously much less compared to the 4 crh models, as the range is increased about 10% at porpotional gun elevations. As The GkDOS 100 materials are from the 40's it could well be an V-drop estimate of then current British projectiles, and be mislabeled as a MKI projectile. Much data in GKdos100 and others are Generic for appoximating, and may not lend it's self to such exact specific models
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To Marty1 re Drag functions, etc.

Post by Bill Jurens »

I guess part of the problem -- and our confusion -- is that I still don't quite understand exactly what you are trying to do.

If you are just trying to do velocity drop vs range for a hypothetical bullet, then -- provided the trajectory remains relatively flat -- even old Siacci methods will do just fine. The new methods introduced by Pejsa are even better and apparently work quite well even for fairly heavily curved trajectories. I think McCoy is a bit of overkill.

Sadly, creating a complete and accurate range table directly from scratch, especially for older projectiles for which data is scanty, remains a relatively difficult task. The bottom line is that matching trajectories to range tables for old projectiles remains more of a 'black art' than a true science. There are a lot of twists and turns in this particular maze, not all of which are intuitively obvious.

The form factors I gave you in the previous memo were generic ones to be used as jumping-off points for the changes typically to be expected between older non-streamlined WWI vintange projectiles and newer WWII secant ogive types. I don't like form factors, and try to avoid them whenever and wherever possilble. It's much better, usually, to use the proper drag function right off the hip-hop.

The form factors I suggested did not refer directly to the projectile images posted in this thread because I did not know that you were specifically trying to do these. Choosing the proper drag function for these by visual matching alone might be tricky, but it's probably the best place to start. I would not assign either of these to Projectile type 1 with a form factor, although that's probably how the range tables would have been computed in the first place. Let me have a look at this later tonight and I will see if I have a better match. Very often projectiles that are visually nearly identical range quite differently in practice.

Hope this helps...

Bill Jurens.
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Post by Tiornu »

"As The GkDOS 100 materials are from the 40's it could well be an V-drop estimate of then current British projectiles, and be mislabeled as a MKI projectile."
the document actually specifies which projectile it is referring to, or just the gun? what projectiles does it give for other foreign weapons?
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Post by Dave Saxton »

Tiornu wrote:"As The GkDOS 100 materials are from the 40's it could well be an V-drop estimate of then current British projectiles, and be mislabeled as a MKI projectile."
the document actually specifies which projectile it is referring to, or just the gun? what projectiles does it give for other foreign weapons?
I'm wondering the same thing. I take it as an "estimate" for the typical contemporary performance of the MKI 15" gun, or am I wrong? The document was intended to help tatical commanders choose the right ammo, battle ranges, and to better handle their ships, for various potential battle situations. It was not created to provide exact ballistic performance data (such as exact ballistic limit velocities) on nurmerious projectiles vs specific armour materials. Usually such data sets give general, worst case scenario, performance estimates, hence to find abnormalities from more presise data expectations, are to be expected.
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Post by Tiornu »

can someone who has the appropriate pamphlet confirm that it specifies the british 15in mk 1 projectile and not simply the british 15in mk 1?
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