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by Bill Jurens
Sat Mar 17, 2012 10:42 pm
Forum: Naval Technology
Topic: Comparing Montana's bomb deck armor to Yamato's Question?
Replies: 5
Views: 3223

Re: Comparing Montana's bomb deck armor to Yamato's Question

For what it is worth, the actual weather deck plating for the Montana design consisted of two 45# STS plates with no substrate below. The entire weather deck was covered except for a portion forward of the muzzles of the guns of Turret I. There was an irregular transition in thickness for a space of...
by Bill Jurens
Fri Sep 30, 2011 2:54 am
Forum: Naval Technology
Topic: Frame Spacing
Replies: 9
Views: 5417

Re: Frame Spacing

For a variety of reasons you will generally find that the shell construction of merchant ships tends to be somewhat more robust than that of warships of similar size. Hood's side shell plating was typically 25#, about 0.625" thick, about the same at that used on the Iowa class ships and on Bism...
by Bill Jurens
Wed Sep 28, 2011 1:54 am
Forum: Naval Technology
Topic: Question for Bill Jurens on his South dakota pic
Replies: 2
Views: 1720

Re: Question for Bill Jurens on his South dakota pic

This drawing is one of a series I did in suport of Strafford Morss' articles in Warship International magazine a few years ago. Part I of "The Washington Naval Treaty and the Armor and Protective Plating of USS Massachusetts" was published in Warship International No 3, 2006 on pages 273-3...
by Bill Jurens
Tue Sep 27, 2011 4:17 am
Forum: Naval Weapons
Topic: Projectile fire questions
Replies: 28
Views: 5045

Re: Projectile fire questions

Cuttlefish wrote: "I am here with some questions, as I think there will probably be someone here who knows this matter. The subject is (roughly) the venerable Royal Navy 15" gun. What altitude did the shell reach at the top of its loft, if fired at about a 22º elevation angle, for example?...
by Bill Jurens
Sun Apr 10, 2011 1:59 am
Forum: Bismarck General Discussion
Topic: Bismarck: Scuttled or Sunk?
Replies: 206
Views: 59124

Re: Bismarck: Scuttled or Sunk?

Herr Nilsson has it right. I found this particular failure quite confusing when I first examined the wreck in 2001; the stern was broken off very cleanly, but there was a narrow 'shelf' running around the entire perimeter of the break, i.e. the break actually took place a short distance abaft the af...
by Bill Jurens
Mon Feb 21, 2011 3:06 am
Forum: Naval Weapons
Topic: Ranging of guns
Replies: 7
Views: 1318

Re: Ranging of guns

A good point. This is commonly referred to as an error resulting from "trunnion tilt". It's quite difficult to correct for, which is one reason why ships tended to have such low hitting rates in stern chases when the range, if it was changing at all, was typically changing only very slowly...
by Bill Jurens
Mon Feb 21, 2011 2:50 am
Forum: Bismarck General Discussion
Topic: Searchlight Use
Replies: 16
Views: 2810

Re: Searchlight Use

The USN found that seachlights were almost useless in firing against a target that was firing against you; the haze of spray thrown up by enemy 'shorts' quickly reduced one's own visibility to near-zero. And, of course, they also provided an excellent aiming point for the enemy. If an enemy ship usi...
by Bill Jurens
Fri Feb 18, 2011 6:55 pm
Forum: Naval Weapons
Topic: Ranging of guns
Replies: 7
Views: 1318

Re: Ranging of guns

Dispersion in range could be reduced in a number of ways. Dispersion in deflection was rarely large enough to represent a serious concern. In some systems, individual turrets were driven in azimuth so as to converge upon a target at a given range, but this meant slewing the entire turret, not adjust...
by Bill Jurens
Thu Jan 20, 2011 5:03 pm
Forum: Naval History (1922-1945)
Topic: Battleship Vittorio Veneto
Replies: 100
Views: 16832

Re: Battleship Vittorio Veneto

Regarding dispersions, etc., I would recommend reading the lengthy two-part article Brad Fischer and myself did for Warship International about four years ago, which specifically covers the gunnery of the 'fast battleships) (BB-57 onwards). These papers were specifically written to extend my previou...
by Bill Jurens
Sat Nov 06, 2010 4:23 pm
Forum: Naval Weapons
Topic: sectional drawings major naval projectiles
Replies: 4
Views: 1066

Re: sectional drawings major naval projectiles

The 16" Mark 8 was manufactured by three different companies, Midvale, Crucible, and Bethlehem, and was provided in at least eight different 'mods', each of which varied slightly from the others, especially in internal geometry. (External geometry and weight etc. had to be maintained for ballis...
by Bill Jurens
Fri Oct 22, 2010 2:02 pm
Forum: Naval Weapons
Topic: Naval gunnery accuracy - question for M. Jurens
Replies: 24
Views: 5680

Re: Naval gunnery accuracy - question for M. Jurens

There was a 'pencil and paper' version as well, which came out earlier than the computer version. This is still useful for research into the M&F Rules because it described the hit percentage equations in some detail. I don't think the computer version did that.

Bill Jurens
by Bill Jurens
Thu Oct 21, 2010 4:29 am
Forum: Naval Weapons
Topic: Naval gunnery accuracy - question for M. Jurens
Replies: 24
Views: 5680

Maneuver and Fire Rules

The Maneuver and Fire Rules were developed by the U.S.N. Naval War College about 1920. They were re-issued fairly regularly -- about once every five years or so -- and were in use until about 1947. These rules -- a complete set is about 400 pages long -- were specifically designed to model surface g...
by Bill Jurens
Wed Oct 20, 2010 2:45 am
Forum: Naval Weapons
Topic: Naval gunnery accuracy - question for M. Jurens
Replies: 24
Views: 5680

Re: Naval gunnery accuracy - question for M. Jurens

That's probably a book length topic. :-) The equation quoted was for U.S. fire control in the 1920s, no aircraft, good visibility, battleship-sized target, and minimal maneuvering. The Naval War College and other sources developed much more complex equations later on, which degraded the hit percenta...
by Bill Jurens
Wed Sep 29, 2010 2:35 pm
Forum: Bismarck General Discussion
Topic: Bismarck's forward tanks
Replies: 2
Views: 757

Re: Bismarck's forward tanks

Many thanks to Herr Nillson for his comprehensive and useful information on this subject!

As always, his comments are both accurate and incisive.

Once again, he has shown that spectulation is no subsitute for actual documentation.


Bill Jurens
by Bill Jurens
Fri Sep 03, 2010 10:40 pm
Forum: Bismarck General Discussion
Topic: BISMARCK armor scheme = BADEN?
Replies: 157
Views: 13668

Another moment with moments...

For a solid cylinder we have: I (longitudinal), i.e. axis running from end-to-end = (m * r^2)/2. I (transverse), i.e. across diameter I = (m/12) (3r^2+h^2) For a tube, we have: I (longitudinal), i.e. axis running from end-to-end = (m/2) (R^2 + r^2). I (transverse) i.e. across diameter I = (m12) (3R^...

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