loss of hms hood part 4

Loss of HMS Hood Part 4

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The Loss of HMS HoodA Re-Examination

by William J. Jurens

Part 4

Multiple Hits:

Most observers were confident that the fatal explosion seemed to originate in the vicinity of the mainmast, in a positionwell forward of the after magazines. There is, of course, a possibility that Hood was hit by more than one projectile in asingle salvo. If this were the case, then a shell hitting and detonating in the area of the mainmast a split-second beforeanother penetrated farther aft could explain the impression of most observers that the explosion began farther forwardthan it actually did. As will be demonstrated below, however, the chances of such a sequence of events are not high. Asa near approximation, the percentage of hits to be expected on moderately sized normally maneuvering targets in well-aimed naval gunfire can be roughly described by the equation:

Ph = 10(E-TX)

Where:

Ph = Percentage of hitsK = Percentage of hits at maximum range of gunE = 2.00T = 0.02 - (0.01 Log K)X = Percentage of the maximum range of gun

In which we express X as a percentage of maximum range in order to render the equation dimensionless. In theformulation above, 100% hits occur at 0% range and a variable number of hits occur at 100% range. That 100% hitsoccur at 0% range is true almost by definition, but the percentage of hits occurring at maximum range (i.e., at 45elevation) is somewhat more difficult to define. For most normal situations, the equation is most accurate when T isselected as being equal to 0.023, equivalent to 0.5% hits at maximum range.80

The maximum range of Bismarck's guns taken from published range tables is normally approximately of 35,500 meters. This figure corresponds to only a 30 angle of elevation however, as Bismarck's guns could not elevate any higher. Computer simulations however, show that the 45 maximum range would have been in the immediate vicinity of 41,700meters. Taking this figure as the maximum range of Bismarck's guns would mean that Hood was at about 36% ofmaximum range when she exploded. At that range, the equation would yield approximately 15% hits.81

U.S. Navy fire effect tables from 193582 give 0.235 hits per gun per three-minute period for the 14-in/50 gun at 16,000yards [14,630 meters], a roughly equivalent situation. Assuming one round per gun per minute, this is equivalent to a hitpercentage of 0.235/3 = 0.078, or 7.8%.

Other official figures83 give average four-gun pattern sizes for U.S. 14-in and 16-in [350mm and 406mm] guns asapproximately 190 meters at our range of interest. A very simple approximation, giving Hood a beam of 30 meters, wouldrender a hit percentage in the vicinity of 30/190, or 15%.84

Bismarck's actual performance was in fact in rough agreement with these estimates. Up to the time Hood exploded,Bismarck fired five, four-gun salvos, and achieved between one and three hits, giving her a raw hit percentage of about2/20 or 10%. In viewing this figure, however, we must remember that the five salvos she fired included at least two andpossibly three to find the range, and also that Hood and Prince of Wales were making rather frequent course changesduring the action, so that her hit percentage in aimed, well-ranged fire would probably have been somewhat higher.

Taking this and other factors into account, once Bismarck had found the range it would appear reasonable to grantBismarck about a 10% - 15% hit probability during the final salvos she fired at Hood. A statistical analysis of four-gunsalvos with a 10% single shot hit probability shows that about 64% of such salvos would result in no hits, 31% wouldresult in one hit, 5% would result in two hits, and only about 0.27% would result in three. For a 15% hit probability, the



figures are about 5%, 40%, 9%, and 0.8% respectively. Thus the chance of two simultaneous or near simultaneous hitson Hood leading to the visible effects accompanying the blast seem only to be about one in fifteen or twenty. Theprobability of more than two simultaneous hits causing the blast is negligible.

Other Hypotheses:

There remains another alternative, admittedly of low probability, that Hood might possibly have destroyed herself. Evidence is sketchy, but nonetheless does exist.

It is interesting to note that more than a third of the witnesses aboard Prince of Wales actually missed the fatal explosionitself. Further, of the approximately forty-five witnesses who observed the explosion directly, less than a quarterassociated it with a specific fall of shot from the enemy. A further 22% associated the explosion with the firing of one ofthe after turrets, and fully 55% of the observers did not associate the explosion with anything at all - to them the ship justblew up. There is therefore at least a minor possibility that the final explosion had nothing to do with Prinz Eugen orBismarck at all.

Several witnesses noticed - and chose to mention unusual events aboard Hood during the action. P.O. George HenryGoff, a layer-rating in the port battery in Prince of Wales ' port-after director, testified that he saw the third salvo fall ". . .on the starboard side of the 'Hood,' very close. The next thing I remember was seeing flames from 'X' turret. 'A,' 'B,' and'Y' were firing at the time and I noticed that 'X' turret was not firing. . . . The next thing I noticed was that the 'B' turretwas firing but belching out flames. After that 'Y' turret fired on its own and 'Hood' went up." When queried in detail aboutthe belching flames, he replied, somewhat opaquely, "When a gun fires the flash licks slowly round the muzzle of thegun. But there was no straight flash and the flames licked slowly round." The board dismissed his testimony with thestatement "This witness is rather inclined to be imaginative."85

But others had noticed a similar phenomenon. Through his periscope, Petty Officer James Crowley, captain of Prince ofWales ' P.4 turret, noted ". . . when I looked through the periscope again I saw a flame come from 'B' turret through one ofthe guns. Not many moments after that she blew up."86 P.O. Edgar Holt saw the same thing through the periscope ofP.5. turret. ". . . a fire broke out abreast 'X' turret on 'Hood' [sic] port side," he said. "About two minutes later I saw aflame about 10 feet long shoot out of 'B' turret muzzle and about a half to one minute later 'Y' turret on 'Hood' fired herfirst salvo. About a second later, 'Hood' blew up."87

Others also observed something unusual with 'Y' turret. Petty Officer Lawrence Sutton saw the action from the port sideof the Admiral's shelter deck on Prince of Wales. ". . . Hood was firing with her foremost turrets," he said. 'Y' turret hadbeen trained fore and after during this time. 'Y' turret then trained towards the enemy and before firing there was a flashabaft the mainmast of the 'Hood' which appeared to be a fire on the boat deck. 'Y' turret then fired," he continued, "andat the same time a huge flash came up all around 'Y' turret. The flash rose to well above the mainmast of the ship and allI heard was a tremendous roar and I could not see anything until the smoke had cleared away. That was all I saw of the'Hood'." The court considered the memory of what he saw "very confused."88 A number of other witnesses confirmedSutton's observations. At least one clearly saw Y turret train toward the enemy, return again to its fore-and-aft position,and train upon the enemy again.

To what can we ascribe this unusual performance? Could Hood have been encountering internal difficulties with hersupply of powder and shell? Could some failure have disrupted the notoriously complex and often unreliable sequence ofanti-flash mechanisms installed after British experience at Jutland?89 In the urgency of combat, might someone in theturret have over-ridden a balky anti-flash interlock in order to bring the turret back into operation? Might there have beensomething wrong with Hood 's propellant? Could a failure of her gas ejection system have caused a flare back into 'Y'turret which thence blew up the ship? Are these scenarios all merely wild speculation? These possibilities, thoughunlikely, cannot be positively excluded.

Probable Cause:

The exact origin of the explosion is now, and shall probably always remain, somewhat in doubt. An examination of theactual testimony of witnesses shows that although a preponderance felt that the explosion came from forward of Hood 'smainmast, this opinion was by no means universal. Statistically, about 42% saw the explosion as originating forward ofthe mainmast, 16% saw it originating at the mainmast, and 21% either saw it originating aft of the mainmast or someplaceelse entirely. Some witnesses associated the explosion with a fall of shot from Bismarck, but, as we have seen, a verysignificant proportion did not.



Given the conflicting and confusing evidence that has been presented, is there nonetheless a "most probable" explanationfor the loss of Hood that reconciles the observations of witnesses with the geometry of the ship, and with the course ofthe action? I believe there is. The first significant bit of evidence is that to most witnesses the blast was essentiallynoiseless, or at least lacking a noticeable "bang." The "bang" of an explosion is caused by the creation of a supersonicshockwave, and is necessarily absent when burning occurs, even very rapid burning indeed. The noiselessness of theexplosion constitutes strong circumstantial evidence that the fatal blast was caused not by the detonation of Hood 's shellsor torpedoes but by the more or less rapid combustion of her propellants. It is probably no coincidence that a very similarnoiselessness was associated with the explosion of USS Arizona 's propellant magazines at Pearl Harbor. This conclusionis in accordance with the findings of the original boards. Assuming that a shell or shells from Bismarck precipitated thedisaster, this also explains the short delay that witnesses noted between the arrival of Bismarck's fatal salvo and the firstevidence of the blast, and may in fact explain why many did not causally connect the two events. The burning rate oftypical gun propellant is closely related to the surrounding pressure and temperature, and except in a very tightly enclosedspace - such as the breech of a gun - take a considerable time to "build up steam." In fact, if venting is adequate, mostgun propellants are surprisingly hard to ignite and unspectacular in their combustion.

In the absence of any other possible energy source, like the boards, I have concluded that it is most probable that Hoodwas relatively slowly rent apart over a period of perhaps a second by the uncontrolled burning of the propellants in herafter magazines. Although the actual position of the hit and the subsequent path of the projectile through the ship areproblematical, it is clear that there are several routes by which one of Bismarck's 380mm shells might have reached theafter magazines. Again, like the boards, I have also concluded that the most probable cause of the final blast was a hitfrom a single 380mm projectile from Bismarck.

The general consensus of witnesses was that the explosion seemed to originate in the vicinity of the mainmast, somedistance forward of the after magazines. The orthographic diagram shows that there is one place where a shell fallingslightly short could have passed through the after engine room and detonated in or near the magazines locatedimmediately adjacent to its after bulkhead at station 280. Yet another possibility is that it passed through the 178mm beltbefore detonating in essentially the same place. If this occurred, and ignition of the propellant in the magazines followedfrom it, then a large part of the rapidly expanding gas bubble would have taken the path of least resistance and ventedinto the engineering spaces immediately forward of this area. For a time the sheer inertia of Hood 's structure would haveslowed expansion in any other direction. Once the expanding gasses had reached the engine rooms, the quickest exits tothe outside would have been the series of massive exhaust vents located on the centerline immediately forward and aft ofthe mainmast. These huge ducts, changing in size and shape as they rose through the ship ended in roughly squarevents 1.8 meters on a side on the boat deck. It was as spectacular, near-vertical columns of flame from these vents nearthe mainmast, foreshortened to observers on surrounding ships, that the explosion first became visible. Shortly thereafter,the entire stern of the ship exploded.90

At the time of the blast, the Boards of inquiry calculated the "X" 15-in magazine contained about 49 tons of cordite, "Y"magazine contained 45 tons, and the 4-in magazines contained about 18.5 tons. The uncontrolled burning of this quantityof propellant in the after magazines might have slowed briefly as the volume of the engineering spaces served as a spaceinto which the gasses could expand, and as the vents directed much of the combustion products outboard. But althoughthis expansion and venting could temporarily relieve the pressure, it could never be enough to prevent an explosion fromeventually tearing the ship apart.91 Ironically, the chemical energy stored in the battlecruiser's after magazines - enoughto lift her enemy over a kilometer in the air had it been employed to do so - had instead destroyed the Hood herself.

1) The fatal projectile explodes, probably somewhere in the 4-inch magazine. There isas yet no sign of trouble from outside the ship.



2) As the propellant ignites, pressure builds up and the forward magazine bulkheadblows out, flooding the engineering spaces with high pressure gas. Compressed airbegins to move up the engine room vents.

3) As uncontrolled burning proceeds, flame bursts from the engine room vents on theboat deck. Within a second or so, the stern of the ship has completely disintegrated.

Click on any of the above sketches for a larger image.

4) A model of Hood showing the engine room exhausts through which the final explosionprobably first vented itself. The model is Tamiya kit no. 7827-950.

Epilogue:

Until relatively recently, this paper might have been considered definitive. But today, there is still more work that might bedone. We live in a marvelous age, an age when men have once more set foot upon the Titanic. It is therefore entirelypossible that curious - and we hope considerate - men will gaze upon shape of "Mighty Hood" again. No one can knowwith certainty what they might find. But only then, if ever, will it be possible to write the final chapter in the checkered life,and the spectacular death, of H.M.S. Hood.



Addendum I: Hood's Deck Thickness

A number of authors have attributed the loss of Hood to insufficient deck armor, stating in effect that she was lost due toan excessive vulnerability to plunging fire. The results of a recently developed computer program, however, seem tosuggest that rather than being too thin to adequately protect her, Hood 's deck armor was in fact at or near the thicknessthat would have granted her maximum protection at normal battleranges.

This program, which I have developed myself, and which is still in the developmental stages, analyzes the entire gunfireproblem from the muzzle to the post impact behavior of the projectile on the target. The program uses a series ofcomplex and accurate algorithms to compute the percentage of hits to be expected on the target at various ranges, theproportion of hits on each exposed surface of the target's armored box, and the number of penetrations based on theU.S. Navy's WW II armor penetration equation given in ORD SK78841 [More details on this equation and its derivation aregiven in Nathan Okun's article '"Armor and Its Application to Warships - Part III," Warship International No. 2, 1979, pp.284 et. seq.]. At this preliminary stage, the program assumes the armor suit of the target to be a simple box with singleplate sides, ends, and deck.

Assuming the initial values for Hood 's armor to have been 200mm, 178mm, and 127mm, respectively, it is easy to varythe thickness of the deck armor and compute equivalent values for the thickness of the belt and ends while keeping theoverall displacement the same. This results in the values shown below in Table V.

Table VArmor WeightDeck Thickness(mm)

Side Thickness(mm)

End Thickness(mm)

Total Weight(tons)

100 229.2 143.0 8,789 120 205.8 129.0 8,789 125 200.0 125.0 8,789 140 182.5 114.0 8,789 160 150.2 99.0 8,789 180 135.8 84.9 8,789 200 112.5 70.3 8,789

Computing the hit percentages and the number of penetrating hits that Bismarck might be expected to score on Hoodover the range band from 15,000 - 25,000 meters at 1,000 meter increments, using optical fire control, and target anglesfrom 0 to 90 in 30 increments, results in the graph shown below. What is important here is not the absolute number ofpenetrations that are scored, but the relative number of penetrations that occur as deck thickness varies.

The graph clearly shows that in this particular situation the minimum number of penetrations occurs with deck thicknessesbetween about 125 and 150mm. It is also interesting to note that increasing the deck thickness beyond this value isactually counterproductive. Even though the algorithms used for armor penetration are admittedly approximate, they doindicate that rather than being too thin, Hood 's decks might have been just about ideal for the situation in which she foundherself on the 24th of May. Incidentally, the program also predicts that Bismarck would have been expected to score

93



approximately 10.1% hits on Hood at a nominal range of 18,000 meters and a target angle of 60.

Addendum II: Twelve Years on:

This article was first published in 1987. In the period since this article was originally published, there have been severaltentative plans made, and abandoned, to utilize modern technology to dive to Hood s wreck. Although such an expeditionmight be interesting from an historical viewpoint, it is unlikely that it could do more than to confirm that the aftermagazines exploded - a point which is universally acknowledged already. It is, in any case, extremely unlikely that anexamination of the wreckage would reveal any significant details regarding the exact circumstances surrounding the loss. The Naval Institute Press has recently published a book The Bismarck Chase by Robert J. Winklareth which covers theloss of Hood in some detail. The bibliography reveals no reference to primary sources and - in the absence of furthercoorborative evidence - the authors conclusions might best be viewed somewhat skeptically. Although Mr. Nathan Okunhas somewhat refined the armor penetration algorithms originally used in this analysis, it does not appear likely that theapplication of the updated equations would substantively change the conclusions previously reached.

To Part 3

Acknowledgments:

Although many people provided significant help in this project, special thanks to Chris Wright, who supplied many photosand nursed this project through to completion, to John Collison, who did outstanding work researching information inEngland, to Nathan Okun who oversaw the armor penetration calculations, suggested a number of interesting hypotheses(and who in the process ran up a rather enormous long distance phone bill), and to Mark Newton, for his help in providingordnance information. Very sadly, Paul Schmalenbach passed away just as the first draft of this manuscript arrived.

Many thanks are also due to Mr. Harry Purdue, Chairman of the Hood Association, and to Mr. James Brown of Cheshunt,Herts, who were able to answer many questions, and who supplied, amongst other things, a complete list of those lost inthe tragedy.

Select Bibliography

ADM 116/4351, "CASE 6762 - Loss of H.M.S. Hood in action with German Battleship Bismarck in the Atlantic on 24thMay, 1941." 440 pp. Public Record Office, Kew, Richmond, Surrey. The official record of both boards of inquiry.

ADM 116/4352. A continuation of the above record, primarily comprised of duplicate illustrations and the actual shorthandnotes of the court reporters. 467 pp.

Bradford, Ernie, The Mighty Hood, Hodder and Stoughton, 1959, 224 pp. A readable, if popularized, account emphasizingthe operational history of Hood from her construction to her loss.

D'Eyncourt, E., H.M.S. Hood, Engineering, March 26, 1920. Detailed technical description, with many interestingillustrations, but dated when compared with modern sources.

Grenfell, Russel, The Bismarck Episode, Faber and Baber, 1960. A well-written, basic account of the entire sortie ofBismarck and Prinz Eugen.

Kennedy, Ludovic, Pursuit - The Sinking of the Bismarck, William Collins Sons & Co. Ltd., 1974. Probably the best "allround" account for the hunt for the Bismarck.

Mllinheim-Rechberg, Baron Burkhard Von, Battleship Bismarck - A Survivor's Story, U.S. Naval Institute, 1980. Aninteresting personal narrative of the German side of the action [Transcriber's Note: This book was revised and re-issuedby the U.S. Naval Institute in 1990].

National Maritime Museum, Greenwich, England. "As Fitted" drawings of H.M.S. Hood 1/8 in = 1 ft 0 in (1/96) scale,corrected to c. 1931. Extremely expensive to obtain, drawings from the N.M.M. tend to be of inconsistent scale and areoften poorly reproduced and incomplete. Sadly, in spite of the greatly increased quality of service which would result from



such a move, the N.M.M. still refuses to supply microfilm copies of drawings in their collections.

Newton, R.U., Practical Construction of Warships, Longmans, Green and Co., London, 1939. A top-notch descriptivetextbook describing the nuts and bolts detail of British construction methods between the wars. Although neverspecifically mentioned, many of the illustrations describing capital ship construction are actually of Hood.

Northcott, Maurice, Hood: Design and Construction (Ensign Special), Bivouac Books, Plaistow Press, London, 1975. Main focus on design and construction of Hood. Includes a separate eight page compilation of abstracts from the officialboards.

Oberkommando der Kriegsmarine, Unterlagen und Richtlinien zur Bestimmung der Hauptkampfentfernung und derGeschoswahl ("Basis and Guidance For the Determination of the Best Range and the Choice of Projectiles"), Berlin,1940. Enclosure (A) to U.S. Naval Technical Mission to Europe report No.37245. Operational Archives Branch, U.S.Naval History Division.

Raven, Alan, and Roberts, John, British Battleships of World War II, U.S. Naval Institute Press, 1976. Chapter 4 dealsspecifically with the design of Hood, with many other references throughout. An excellent source of design information

Roberts, John, Anatomy of the Ship: The Battlecruiser Hood, U.S. Naval Institute Press, 1982. 127 pp. A comprehensivetechnical description, with many outstanding illustrations.

Schmalenbach, Paul, Kreuzer Prinz Eugen . . . unter 3 Flaggen, Koehlers Verlagsgesellschaft MbH, Herford, 1985. Anexcellent account by the Assistant Gunnery Officer of Prinz Eugen. In German.

Vielica, Ron, "Who Sank the Hood?" Sea Combat magazine, Spring, 1979, pp. 16-23 et. seq. Highly speculative andtechnically weak account which investigates the possibility that a shell from Prinz Eugen actually caused the sinking.

Weldon, D.G., "H.M.S. Hood," Warship International, No.2, 1972, pp.114-157. An excellent overall account with a goodmixture of technical and operational details.

Footnotes for Part 4:

80 For 0.1% hits at maximum range, K = 0.03, for 1% hits at maximum range, T = 0.02, and for 10% hits at maximumrange K = 0.01. This encompasses the range of normal probabilities.

81 Copies of the official German tactical gunnery manual Unterlagen und Richtlinien [Basis and Guidance for theDetermination of the Best Range and the Choice of Projectile], secret at the time, give us a check on this figure. Thenecessary computations are too complex and voluminous to reproduce here, but give an estimated 45% hit percentage. This is obviously too high when compared to Bismarck's observed gunnery on the day in question. This is likely becausethe German manual implicitly assumes that the Mean Point of Impact (MPI) of the salvo is centered on the target. This israrely the case in real life, and results in a considerable overestimate of the hit percentage, especially at longer ranges. For those readers who might be interested, the probable error for single gun fire for the guns of Bismarck and PrinzEugen is given in the range tables reproduced in this paper. Multiply these values by about 1.5 to give probable errors forsalvo fire.

82 "FIRE EFFECT TABLE - BLUE 14-in/50, 2577/6-31, Department of Operations, Naval War College, Newport, R.I., c.June 1935.

83 U.S. Navy, Bulletin of Ordnance Information 2-45, pp. 29-30.

84 I have assumed in this computation that the Hood would normally lie at least somewhere in the pattern, and that theaverage displacement of the MPI is roughly compensated for by the effect of the substantial danger space.

85 ADM 116/4351 pp. 205-206.

86 ADM 116/4351 pp. 207.

87 ADM 116/4351 pp. 216. Petty Officer Harold Pickard in the port forward H.A. Director saw it too. "The 'Hood' was stillfiring with all turrets," he said, narrating the action, ". . . when a peculiar thing happened, it seemed to me. It appearedas if 'B' gun had opened her air blast. Flames came out of the muzzle and instead of stopping like an ordinary air blast



they carried on." Other witnesses described the delay as from one to five seconds.

88 ADM 116/4351 pp. 212-213.

89 One author lists no fewer than thirty-seven safety interlocks controlling the operations of the 15-in Mk I. See Hodges,Peter, The Big Gun, Conway Maritime Press, 1981 pp. 133 et. seq. In fairness, the British 15-in twin mount wasconsidered one of the most reliable in service, however, and most difficulties seemed to revolve around other installations.

90 A similar phenomenon was noted in the loss of U.S.S. Arizona, which was also marked by an obvious vertical ventingof gasses through the engineering spaces. while the decks directly over the magazines remained substantially intact. Formore details, see the survey of Arizona recently completed as a joint project of the Arizona Memorial MuseumAssociation, the U.S. National Park Service, and the United States Navy, and published in 1985 a series of drawingsprepared for the Arizona Memorial Museum Association.

91 From a series of tests using cordite, the British developed a rough formula for the non-explosive venting of powderfires, making A = (W0.666)/8 where A is the vent area in square feet, and W equals the weight of exposed powder inpounds. Assuming the total area of the vents to have been approximately 140 square feet, therefore, indicates that theycould have handled some 37,500 pounds or 17,000 kg of burning powder before overloading. These tests are reported inN.A. London Serials 558-1940 and 678-1940. In metric units the formula is A = (W0.666)/50.84 where A is the area insquare meters and W equals the weight in kilograms.

92 Prince of Wales cut in front of Hood after she exploded, and turned away to port shortly thereafter, and her coursesafter disengaging, first 160 then 250 degrees, would not have brought her around behind the Hood again from theGerman point of view. The black smoke usually attributed to Prince of Wales in photographs is in fact most likely fromNorfolk, which was in the appropriate position during the action.

93 For further details on all weapons carried on the Hood, Prince of Wales, Bismarck, Prinz Eugen, Norfolk and Suffolkplease see Naval Weapons of the World.

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