Bismarck anti-torpedo bulges

[plank10]

I've been reading about anti-torpedo bulges and how many WW2 era warships (e.g. HMS Royal Oak 08) were fitted with them. Does anyone know if the Bismarck was also fitted with these bulges? Any info would be appreciated.

[Sailor Steve]

Bismarck was bulged, but internally. There were void spaces inside the hull, with light armor behind them, the idea being that a torpedo would blow a hole in the side, but the internal armor would stop any splinters and contain damage to the interior void.

[plank10]

Were these bulges part of the original design and built into the ship, or were they installed after the ship was completed?

[Sailor Steve]

Given the work that was done in that area during the First World War, I'm pretty sure by the time Bismarck came along she was designed that way.

[Aktungbby]

Original! but they didn't go aft far enough to prevent the Swordfish hit to the steering and they didn't work against an underwater trajectory fluke 14 inch shell from King George to armor sections XIII and XIV at the beam weld under the main side-armor belt to the inner 45 mm inner armor. This welding, in its infancy technique-wise and the frigid water temperatures made the steel and welds brittle. Subsequent torpedoes from Dorsetshire had little effect and the evidence is clear from a Ballard expedition, much to British chagrin, that the Germans scuttled their vessel as rumored. Moreover Bismark bulge defenses were tested against 500 kg torpedo war heads not 14 in. main battery shells which were expected to land top side ie. cracking fire as opposed to direct fire. In her defeat, HMS Hood (a faster 'battle cruiser with weak deck armor) was attempting to close the distance to get under Bismark's downward 'cracking' fire to a closer position where her own belt and turret armor could withstand 'direct' fire, approx. 11,500 meters...she didn't make it. In my hasty research for your question, oddly enough, Bismark's overall defensive armor rating( deck and side) is about 6 whereas Iowa, Yamato and King George are 9+

[Sailor Steve]

All true, to a point.

Originally Posted by Aktungbby

Original! but they didn't go aft far enough to prevent the Swordfish hit to the steering and they didn't work against an underwater trajectory fluke 14 inch shell from King George to armor sections XIII and XIV at the beam weld under the main side-armor belt to the inner 45 mm inner armor.

True, but it's impossible to armor any ship completely. To do so would require more weight than any hull could carry. Armor is constructed to protect the ship from its own shells (as it's impossible to test it against enemy shells until it's far too late) at certain distances. Too far out and no deck armor will stop incoming falling shells. Too close and no belt armor will keep shells out.

Subsequent torpedoes from Dorsetshire had little effect and the evidence is clear from a Ballard expedition, much to British chagrin, that the Germans scuttled their vessel as rumored.

The problem there is that nobody is sure exactly what effect British torpedoes had. The ship was described by observers on the spot to already be listing to port (the engaged side).1

Any hits at that point would be above the armored belt. What usually goes unmentioned is that most of the hull is buried in sand and mud, and they still haven't been able to count shell holes below that level.

Director James Cameron, who filmed the Ballard expidetion, made the following statement:

Would the wounded Bismarck have sunk without the scuttling? "Sure," Mr. Cameron said in an interview. "But it might have taken half a day."2

That has long paralleled my own opinion, which is that the British torpedoed Bismarck to keep the Germans from towing the wreck home and the Germans scuttled her to prevent the British from having a war prize. The simple fact is that Bismarck was a flaming wreck by that time and would have sunk anyway. That is entirely due to British shellfire.

Moreover Bismark bulge defenses were tested against 500 kg torpedo war heads not 14 in. main battery shells which were expected to land top side ie. cracking fire as opposed to direct fire.

That is always true. You don't test armor against torpedoes and you don't test torpedo protection against shells, mainly because you already assume the protection is useless against anything it wasn't designed for.

1 "The Final Action", John Roberts, Conway's Warship, Issue 28, collected Volume 7, October 1983.

2 http://www.fpp.co.uk/History/General.../scuttled.html

[Aktungbby]

The Bismark sure got the 'bulge' on the Hood. The site I had on google had a great diagram of the armor crossection and the testimony, as well, of some German survivors from the conning station. But my computer smarts aren't up to transferrring it. It seems too, that while the welds might have been impaired, the burning paint fumes killed a lot of sailors not wearing breathing gear; The survivor mentioned was wearing a leather jacket which spared him from shell splinters while his two battle-station mates in t-shirts died of their splinter wounds; his diagram discription of the damage conning area(superstructure) is quite graphic...big holes and lots of them!!! Oddly enough the superior paint and face hardened steel armor is holding up well, including the teak deck, as reported by Ballard compared to Titanic for example. Also the ship's impact with the sea bottom appears to have slightly 'blown out' the armor sides. Odd though that big gun ship shells converted to bombs, as with the Arizona, glancing off turret two and/or travelling underwater below the armor belt on a short near misses can so devastatingly negate the main armor of a capital ship intended to prevent such mighty mishaps!

[plank10]

This is slightly unrelated to my original question, but does anyone know whether the Bismarck received any modifications/changes/upgrades to the hull between its launch and sinking?

[Sailor Steve]

Bismarck was launched with a straight WW1-style bow, but the curved 'Atlantic' bow was installed during fitting out, so she never went to sea with anything else. There were minor changes made during trials, but no major ones involving armament or armor.

[Aktungbby]

No modifications except the bow and anchor chain plates were made after the design was settled upon, in keeping with the limitations of the post Versailles treaty limitations to 35000 long tons displacement. As Japan(YamatoBBY??) refused to sign a subsequent limitation treaty, this limit for Bismark and sister ship Tirpitz was raised to 45,451 tons. Welding allowed the rivet weight saved to be converted for armor weight. Some consideration was made for an increase in armament to keep up with the French Richelieu but would have entailed major alterations to cope with the armament weight/speed/armor weight ratios and in any case German naval construction and the limits of the Kaiser Wilhelm Canal kept the hull from being altered and the main battery at four turrets: 15" guns. The German navy always anticipated combat close to the North sea against superior forces (British) and thus favored superior defensive armor and watertight compartmentalization. Essentially, prewar politics and WWI battle doctrine rendered the modifications!!! Oddly enough it was HMS Rodney's 3 turret 9 gun 16" battery which did most of the damage, 340 shells fired (2 turrets KO'd on Bismark) and not the 14" guns of HMS King George V (one 2 gun and two 4 gun turrets) which had numerous misfires in the battle. Additionally, at 3,000 yards, Rodney launched 12 torpedoes while crossing Bismark's 'T' and one struck, making HMS Rodney the only battle ship to torpedo another battleship in naval warfare! The Swordfish torpedo damage to the unarmored stern had been ultimately fatal however as any speed to the vessel created a harmonic disconvergence between the unarmored stern and the forward armored hull and the severe vibration caused increasing weld/plate destruction, fuel loss and forced Bismark to a relative 6 knot crawl in the force gale of the sea battle and pursuit. Correction to my above post: Leather clad Mr. Statz was the reliable witness who survived the battle and the torpedo bulge tests were with 240 Kg warheads(500 lbs.).

[plank10]

I see. I was looking at images of the Bismarck wreck, and I noticed that the bridge and mast were missing along with other parts of the superstructure. How did they come off? Surely they weren't held in place by gravity like the turrets.

[Sailor Steve]

The ship slid down a long underwater slope. Did it roll during that slide? If the ship was upside-down during any of that big chunks could easily have been ripped off. For sure? I don't know.

[Jimbuna]

Originally Posted by plank10

This is slightly unrelated to my original question, but does anyone know whether the Bismarck received any modifications/changes/upgrades to the hull between its launch and sinking?

You'll find a wealth of information on the link below (click on the Bismarck tab):

http://www.bismarck-class.dk/index.html

For many a year it has been debated whether she sank as a result of Royal Navy gunfire and torpedo damage or as a result of scuttling.

I subscribe on the side of the latter but she would not have been sunk without the former having taken place.

IMHO there is only one major fact of relevance...Churchill did not order that she be captured or immobilised but rather ordered "SINK THE BISMARCK" and that is precisely what the outcome was.

Another link for your perusal:

http://www.hlrgazette.com/2011-artic...-bismarck.html