Sinking of the Hood- did all the magazines explode?

Discussions about the history of the ship, technical details, etc.

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Re: Sinking of the Hood- did all the magazines explode?

Post by dunmunro »

HMSVF wrote: Fri Aug 06, 2021 2:28 pm
dunmunro wrote: Thu Jul 29, 2021 5:47 pm
paul.mercer wrote: Sun Jul 25, 2021 10:18 am Thanks (as always) Wadinga and Bill for your replies.
Looking at it from the points that you both have made it would seem that Mr Mearns theories are at best incorrect or perhaps out-rightly misleading. However it is interesting to see how some ships exploded as they rolled over while others did not, I have always thought (probably wrongly!) that a shell which was designed to take an extremely heavy impact before exploding would go off by just falling from its rack onto the deck.
Looking at the other part of the film which dealt with Pearl Harbour, it said that the Japanese aircraft used modified 16" AP shells on the battleships, one or more of which penetrated the magazines of the 'Arizona'. did any other nation use large caliber shells in this way as it appears to have been a very good and successful idea?
One other point from the film re the sinking of PoW and Repulse it mentioned that PoW's armour did not extend all the way down and - as far as I could make out, this applied to other capital ships, surely the danger from torpedoes must have been taken into consideration when ships were designed, so was it weight considerations that prevented sufficient armour being placed way below the water line? I realise that in the case of Bismarck and PoW the hits by the rudder and propellers were the two places that could not be adequately protected.
Shell fuzes were designed not to go off from very low velocity impacts.

AP bombs had similar designs to AP shells, but it's best to design the AP bomb to have a larger bursting charge than in an AP shell, to take advantage of the lower striking velocity of an AP bomb and the thinner armour that needs to be penetrated.

The KGV class had a very deep belt - deeper than most contemporary designs, and had a Side Protection System that was designed to protect the ship from UW shell hits and torpedo hits:

https://en.wikipedia.org/wiki/Torpedo_b ... ection.png

AFAIK, 3 of the 4 torpedo hits on PoW struck the ship outside the SPS and the one that did hit the SPS, abreast B turret, appears to have been defeated by the SPS, and very little flooding occurred inboard of the SPS in the vicinity of the torpedo hit.

I was under the impression that the SPS had been compromised by counterflooding and that the hit aside B turret did vent upwards. I believe that it was extended a deck higher on HMS Vanguard. I'm going from memory so I may well be talking bullocks in regards to the last bit.
Yes, the SPS abreast B turret had been degraded because the void spaces had been counterflooded. This allowed for a transmission of shock damage into the hull and probably aided the upward venting of the blast (although this is actually an expected result) but diver inspection of the SPS' inboard armoured holding bulkhead, showed it to be intact.
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Re: Sinking of the Hood- did all the magazines explode?

Post by Byron Angel »

HMSVF wrote: Fri Aug 06, 2021 2:21 pm
Byron Angel wrote: Fri Aug 06, 2021 5:26 am Cordite appears to have possessed some peculiar characteristics. Once ignited, it would continue to combust even underwater in the complete absence of air. That combustion would in turn produce an array of volatile unstable gases which, if confined, would spontaneously deflagrate when a certain pressure threshold had been reached.

See Frederick Noble's lecture on nitrocellulose propellants in "Artillery and Explosives".

Byron

Some of the Japanese battleships (thinking Yamato,Musashi,Kirishima/Hiei) ended up in a right old state. Was Japanese propellant similar to British?

Hi HMSVF,
From what I have been able to quickly determine, Japanese propellant was evidently a cordite formulation (nitroglycerine content of about 30pct) probably equivalent to British post-WW1 Cordite SC. To the best of my recollection, of the IJN BBs you mentioned (Hiei, Kirishima, Musashi, Yamato), none suffered any catastrophic magazine explosions in connection with their losses. Kirishima's experience of suffering 20+ 16in hits from USS Washington at ranges <10,000yds without a magazine explosion (as well as the experiences of Yamashiro and the cruisers Aoba and Furutaka at Cape Esperance) suggest that either the propellant was pretty stable, that IJN ammunition handling practices were very good (or perhaps that these ships were lucky).

Battleship Fuso was long thought to have fallen victim to a magazine explosion and broken in two at Surigao Strait, but recent location and inspection of the wreck site suggests that this account is in error. Go here - https://pacificwrecks.com/ships/ijn/fuso.html - for details.

On the other hand, the Japanese battleship Mutsu was lost as a result of a spontaneous magazine explosion in 1943 while anchored in Tokyo Bay; the cause of the explosion remains unknown.


Byron
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Re: Sinking of the Hood- did all the magazines explode?

Post by Bill Jurens »

My thanks to those who have submitted comments on the so-called 'forward magazine explosion' hypothesis. The original formulation of this, was even more bizarre than the version(s) still in circulation, i.e. they claimed -- believe it or not -- that the forward magazine explosion not only took place, blowing off the conning tower, etc., but that the source of this was flame that passed forward through the side protection system from the after magazine explosion. I was, as some may already know, the so-called 'technical expert' on the 2001 Hood expedition, having been recommended by David K. Brown, who could not go on the expedition himself, and representing the Marine Forensics Committee (Panel SD-9) of the Society of Naval Architects and Marine Engineers. As it turns out, the documentaries ignored me more-or-less entirely, presumably because my comparatively mundane explanations were not spectacular enough. Usually, in such cases, the bow detaches because it is essentially uninhabited in action, and all 'buttoned up', so there is no one there to try to escape and leave hatches open, and relatively few ship services in the area which create fairly leaky bulkheads. So the empty compartments collapse in one big go, rather than slowly filling via progressive flooding.

Before the 2001 expedition left I did some Computer Fluid Dynamics simulations which suggested a collapse near the bow due to hydrostatic overpressure as the ship plunged, and we actually made a fairly elaborate 1:100 scale (or perhaps 1:50 scale) model of Hood which was to be sunk on camera to illustrate the implosion. But it was never used as the forward magazine explosion hypothesis -- developoed by Mr. Mearns and Eric Grove -- was adopted instead. My negative comments, expressed on camera, were very carefully edited out during post-production.

The submerged combustion of Cordite and similar propellants is somewhat complex. Insofar as the propellant already carries the necessary oxidants in it, it does not need additional oxygen to burn. It is virtually impossible to ignite when wet, but a stick already lit, via a match or something similar, can indeed be slowly submerged into water and continue to burn slowly, it one can get the hot gasses to form a thin insulating blanket, creating in effect a thin layer of 'steam' keeping the surrounding water away from the propellant itself. This trick is much more easily accomplished with tube-type propellant geometries, as the water has a great deal of difficulty penetrating the small inner tube, which is expelling high-pressure gas from each end. So a submerged tubular grain can burn from the inside out.

Insofar as the pressures of water have to be very low to allow this, the grain will not continue to burn after the grain is submerged more than a few inches, after which the water pressure compresses the steam blanket width to zero. If the propellant is confined, the gas pressure will be higher and the propellant may continue to burn to a slightly greater depth of water. There was a danger if propellant tanks were left closed and ignition occurred inside, as -- regardless of the presence or absence of water outside the tank -- what amounted to an explosion could occur. For that reason, many navies deliberately equipped propellant tank lids with vents which would allow the propellant inside, if ignited, to 'roman-candle' rather than explode. There has been a lot of commentary over the years on excessive 'leakiness' of magazines, etc., but in most cases this leakiness was actually beneficial, and it was often specified that magazine doors be left open in action in order to allow early venting to occur. (The doors almost always opened outward from the magazines in order to allow venting to occur, and in some cases -- in order to prevent flash -- doors could be closed but only held closed by a single clip, which means that they would 'fail open' very early in the game if a magazine burn occurred. This whole idea represented somewhat of a statistical trade-off, while a leaky magazine somewhat increased the probability that an ignition might occur, if it DID occur, a leaky magazine would tend to result in something like a single-turret burnout whereas a heavily-sealed magazine could explode and destroy the entire ship. Most navies preferred the former to the latter...

In any case, once submerged, the propellant gasses are to all intents and purposes innocuous insofar as the propellant is usually formulated to release all of its chemical energy during the burning process itself. One could, in a dry environment, have these gasses, if they remained at a high enough temperature, re-ignite, but the effect -- what was often called a 'flash-back' or 'blow-back', though visually spectacular enough was usually not very dangerous insofar as the actual amount of material re-burning was relatively small.

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Re: Sinking of the Hood- did all the magazines explode?

Post by paul.mercer »

Hi Bill,
Once again many thanks for your detailed description of what happens to cordite and the need to keep the magazine doors open - as i said in one of my posts, "this puts the forward magazine theory to bed" - once and for all I hope!
On the part about the magazine doors being left open, presumably if an order came to 'flood the magazine' the crew would have time to escape, I always thought (obviously wrongly) that once battle commenced the crew were effectively sealed inside the magazine. If we recall the 'Sink the Bismarck' film (which was just that) when the order to flood was given someone said 'But what about the men' but the order was carried out anyway.
On a slightly different topic concerning cordite explosions, have a question about a 'flashback' occurring in a turret, after the breach has been opened caused I believe by un-burnt cordite igniting or after a failure to fire, My Dad was on the Queen Elizabeth in the late twenties/early thirties and he recalled that if there was a failure in one of the 15" guns the procedure that had to be carried before opening the breach was quite long and very comprehensive in case the cordite was on a slow burn and would ignite when exposed to air. I have often wondered if this was the cause of the explosion in the turret of the New Jersey some years ago. Also, if a failure happened in battle, would it put that particular gun out of action for as similar length of time or would the procedure be 'speeded up'?
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Re: Sinking of the Hood- did all the magazines explode?

Post by Bill Jurens »

@ Paul Mercer:

I am pretty sure that the turret explosion you referred to occurred on USS Iowa, not New Jersey. This sort of thing did not occur on Iowa, as the breech door was never closed in the first place, i.e. the explosion there occurred during the loading process itself.

There are only a few situations where provisions are not made for the crew to escape from lower compartments. Whenever possible, at least two egress routes are provided in normally-manned compartments, although the second one may not be the most convenient, i.e. may require some wrench work. The danger is that in escaping they may leave doors and hatches not securely clipped, or closed at all, and this might result in potentially dangerous progressive flooding.

Treatment of hangfires in big naval guns was tricky. My recollection of USN practice near the end of this era was that whenever guns that 'hung' were to be left alone for twenty minutes to ensure that everything was really 'dead' in the chamber. Then they would be reprimed and fired again. After three or four unsuccessful tries, the turret would be cleared and the breech opened by a small unloading crew.

Explosions, etc. don't occur when the breech door opens and lets in air as the propellant itself doesn't really care about air in the first place. What might happen is a slow ignition where the propellant is actually smoldering in an unstable state and can go off anytime. That's why repriming early, or immediately was frowned upon insofar as it required removing the ignition cartridge -- basically a small-arms type rifle blank -- and during the time the primer was being removed, the propellant could spontaneously combust and shoot the cartridge out with some force along with a large jet of flame. So the primer vent, which could be opened or closed with a small sliding latch cover, was -- for at least a short time -- a source of anxiety. Usually, the primer was replaced via long forceps which prevented the potential of a crew-member being trapped behind the gun should it recoil without warning.

Rules, as they say are "..for the control of idiots and the guidance of wiser men...", so in practical terms the treatment of any particular hangfire remained a matter of judgement and experience, where rules were sometimes bent a little.

The type of flash-back your father refers to is probably due to hot gas within the breech reigniting when air gets back in. In unburned state, the propellant contains it's own oxidizers and doesn't need air at all. The residual gasses still do contain some energy, however, and DO need oxygen to re-ignite. So, if the gun is fired and the breech door is opened too soon afterwards, a 'flashback' can occur. For that reason most big guns employed an air-ejection system which would inject high-pressure air into the breech during the interval between firing and re-opening the breech door. This would result in some flashbacks, of course, but they were of no danger insofar as they vented out through the muzzle rather than back through the breech.

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Re: Sinking of the Hood- did all the magazines explode?

Post by Steve Crandell »

In a lot of the films you see of major caliber guns being fired you will see a puff of smoke from the muzzle shortly after the gun fires, and this is presumably the high pressure air being used as Bill described.
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Re: Sinking of the Hood- did all the magazines explode?

Post by paulcadogan »

For that reason most big guns employed an air-ejection system which would inject high-pressure air into the breech during the interval between firing and re-opening the breech door.
In a lot of the films you see of major caliber guns being fired you will see a puff of smoke from the muzzle shortly after the gun fires, and this is presumably the high pressure air being used as Bill described.
Is this the explanation for the flames that were seen shooting out of B-turret's barrels on Hood during the battle, but with the residues igniting for some reason?
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Re: Sinking of the Hood- did all the magazines explode?

Post by paul.mercer »

Hi Bill,
Many thanks once again for taking the trouble to answer my queries, I believe you are correct in that it was Iowa and not New Jersey that had the turret explosion.
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Re: Sinking of the Hood- did all the magazines explode?

Post by HMSVF »

Byron Angel wrote: Sun Aug 08, 2021 4:48 pm
HMSVF wrote: Fri Aug 06, 2021 2:21 pm
Byron Angel wrote: Fri Aug 06, 2021 5:26 am Cordite appears to have possessed some peculiar characteristics. Once ignited, it would continue to combust even underwater in the complete absence of air. That combustion would in turn produce an array of volatile unstable gases which, if confined, would spontaneously deflagrate when a certain pressure threshold had been reached.

See Frederick Noble's lecture on nitrocellulose propellants in "Artillery and Explosives".

Byron

Some of the Japanese battleships (thinking Yamato,Musashi,Kirishima/Hiei) ended up in a right old state. Was Japanese propellant similar to British?

Hi HMSVF,
From what I have been able to quickly determine, Japanese propellant was evidently a cordite formulation (nitroglycerine content of about 30pct) probably equivalent to British post-WW1 Cordite SC. To the best of my recollection, of the IJN BBs you mentioned (Hiei, Kirishima, Musashi, Yamato), none suffered any catastrophic magazine explosions in connection with their losses. Kirishima's experience of suffering 20+ 16in hits from USS Washington at ranges <10,000yds without a magazine explosion (as well as the experiences of Yamashiro and the cruisers Aoba and Furutaka at Cape Esperance) suggest that either the propellant was pretty stable, that IJN ammunition handling practices were very good (or perhaps that these ships were lucky).

Battleship Fuso was long thought to have fallen victim to a magazine explosion and broken in two at Surigao Strait, but recent location and inspection of the wreck site suggests that this account is in error. Go here - https://pacificwrecks.com/ships/ijn/fuso.html - for details.

On the other hand, the Japanese battleship Mutsu was lost as a result of a spontaneous magazine explosion in 1943 while anchored in Tokyo Bay; the cause of the explosion remains unknown.


Byron
Hi Byron,

I was thinking more along the lines that all four I believe, suffered magazine explosions at various points of sinking - Yamato as she rolled over,Musashi, Hiei, Kirishima after they had submerged. Certainly Yamato and Musashi are in pieces and Hiei/Kirishima lost their bows.

I suppose I was thinking that perhaps Mearns et al thought that the upending of cordite and shells caused the supposed 2nd explosion. Seeing as several Japanese battleships suffered flaguration (? right word) in the process of sinking and whether there were similarities between Japanese and British propellant.

That said I believe that Scharnhorst suffered a similar occurrence (underwater detonation) when she sank in the Arctic.

Best wishes


HMSVF
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Re: Sinking of the Hood- did all the magazines explode?

Post by mstary1 »

HMSVF wrote: Wed Aug 11, 2021 11:15 pm
Byron Angel wrote: Sun Aug 08, 2021 4:48 pm
HMSVF wrote: Fri Aug 06, 2021 2:21 pm


Some of the Japanese battleships (thinking Yamato,Musashi,Kirishima/Hiei) ended up in a right old state. Was Japanese propellant similar to British?

Hi HMSVF,
From what I have been able to quickly determine, Japanese propellant was evidently a cordite formulation (nitroglycerine content of about 30pct) probably equivalent to British post-WW1 Cordite SC. To the best of my recollection, of the IJN BBs you mentioned (Hiei, Kirishima, Musashi, Yamato), none suffered any catastrophic magazine explosions in connection with their losses. Kirishima's experience of suffering 20+ 16in hits from USS Washington at ranges <10,000yds without a magazine explosion (as well as the experiences of Yamashiro and the cruisers Aoba and Furutaka at Cape Esperance) suggest that either the propellant was pretty stable, that IJN ammunition handling practices were very good (or perhaps that these ships were lucky).

Battleship Fuso was long thought to have fallen victim to a magazine explosion and broken in two at Surigao Strait, but recent location and inspection of the wreck site suggests that this account is in error. Go here - https://pacificwrecks.com/ships/ijn/fuso.html - for details.

On the other hand, the Japanese battleship Mutsu was lost as a result of a spontaneous magazine explosion in 1943 while anchored in Tokyo Bay; the cause of the explosion remains unknown.


Byron
Hi Byron,

I was thinking more along the lines that all four I believe, suffered magazine explosions at various points of sinking - Yamato as she rolled over,Musashi, Hiei, Kirishima after they had submerged. Certainly Yamato and Musashi are in pieces and Hiei/Kirishima lost their bows.

I suppose I was thinking that perhaps Mearns et al thought that the upending of cordite and shells caused the supposed 2nd explosion. Seeing as several Japanese battleships suffered flaguration (? right word) in the process of sinking and whether there were similarities between Japanese and British propellant.

That said I believe that Scharnhorst suffered a similar occurrence (underwater detonation) when she sank in the Arctic.

Best wishes


HMSVF
Kongo suffered a 14" Forward magazine explosion too as she sank. And there was no record from survivors of any fire in or near the magazines.
http://www.combinedfleet.com/eclipkong.html
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Re: Sinking of the Hood- did all the magazines explode?

Post by Bill Jurens »

There are certainly a number of cases where magazines have when large warships capsize. HMS Audacious and Barham are two good examples of this. These explosions seem to usually happen when the ship is still on, or very near, the surface. The probability of magazine explosions after the ship has submerged to any great extent is much more problematical insofar as the ingress of water during the sinking process would, in most cases, flood the magazines quite early on, which would preclude any possibility of a magazine explosion entirely. Very destructive hull collapse during sinking is, of course common -- a good example here is Titanic, where there was obviously no possibility of a magazine explosion at all, but it is often very difficult after the fact to determine if the destruction was caused via an internal explosion, external collapse due to hydrostatic pressure, or some combination of the two. In order for a magazine to explode, the propellant must be ignited before any water arrives, and burn quickly enough for pressures to build up to catastrophic levels. The impulses created by magazine explosions submerged and hydrostatic collapse would seem to be quite similar in magnitude, and it would take a good deal of experience -- which almost nobody actually has -- to be able to discriminate between the two via simple physical perception.

It would, I would suspect, be necessary to inspect the wreck in detail to examine failure modes in order to tell one from the other with any degree of reliability, but again, magazine explosions pe se seem to be more-or-less limited to situations where the ship is still on, or very near the surface. As the ship sinks farther, the probability of hydrostatic collapse increases. The forward section of Hood certainly looks like hydrostatic collapse to me.

The problem with some of the previous speculation on Hood is that the claim has been made that the destruction forward was initiated via flame travelling forward from the after magazines forward. This possibility can be discounted without further discussion -- a lot of ship hulls that have suffered magazine explosions have been salvaged over the years and NONE -- or at least none that I have been able to find -- have shown any significant propensity to propagate fore and aft at all. In reality, the usual situation is to find the hull more or less neatly 'snipped off' nearly transversely a few meters away from the main magazines; in fact I presented an equation set that would explain this phenomena in my paper on the loss of Hood published in the Transactions of the Society of Naval Architects and Marine Engineers in 2002. Further examination of the HOOD video tapes by SNAME engineers since that time has revealed no evidence that my initial findings were significantly in error.

Had Hood's forward magazines exploded on the surface, or nearly on the surface, then this would have been obvious to many observers. None noted any substantive explosions forward -- Briggs' 'flash of flame' around the bridge is almost certainly due to the explosion of the after magazines, but this represented more of a visual effect than one representing a substantive amount of physical energy, and occurred well before the ship actually sank. While it is possible that some sort of minor magazine explosion occurred forward on Hood after the bow submerged, other than the fact that the bow actually separated from the rest of the hull, there is no evidence whatsoever to support such an hypothesis. The failure forward was almost certainly due to hydrostatic implosion, with some plating clearly showing the sort of 'two-phase failure' which is typical in these sorts of overload events.

Of course the idea that the conning tower was blown off and sent flying through the air is completely nonsensical. Had this sort of even occurred on the surface, it would have been noticed by many and almost certainly have killed Briggs and his shipmates. The idea that some sort of explosion could have propelled the conning tower any distance at all underwater is simply silly.

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Re: Sinking of the Hood- did all the magazines explode?

Post by paul.mercer »

Hi Bill,
Thanks once more for all your input to this thread. One thing that puzzles me is the implosion of a ship due to water pressure as it gets further down,
I can understand why the stern of Titanic is completely wrecked as it presumably broke off near the surface and did not have anything to stop it spiraling down with water pressure forcing the deck upwards unlike the bow which,I understand basically 'planed away'. But with regard to a battleship, I would have thought (obviously wrongly!) that the thickness of the hull would prevent any implosion as it would be far greater than on a merchant ship. Did Bismarck show any signs of implosion as it is even deeper than Titanic?
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Re: Sinking of the Hood- did all the magazines explode?

Post by Steve Crandell »

Bismarck sank slowly, and many of her compartments were filled with water due to a long period of accumulated combat damage. Also, I believe there are survivor accounts of sea cocks being opened towards the end, which would fill engineering spaces. Compartments already mostly filled with water aren't likely to suffer catastrophic implosion.
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Re: Sinking of the Hood- did all the magazines explode?

Post by Bill Jurens »

Mr. Mercer wrote:

"One thing that puzzles me is the implosion of a ship due to water pressure as it gets further down,
I can understand why the stern of Titanic is completely wrecked as it presumably broke off near the surface and did not have anything to stop it spiraling down with water pressure forcing the deck upwards unlike the bow which, I understand basically 'planed away'. But with regard to a battleship, I would have thought (obviously wrongly!) that the thickness of the hull would prevent any implosion as it would be far greater than on a merchant ship. Did Bismarck show any signs of implosion as it is even deeper than Titanic?"

For normal hull structures collapse would usually occur at less than 100 foot depth, perhaps considerably less. In the case of Titanic, the stern probably collapsed (and separated) quite near the surface, and flooding was probably complete very soon after the stern submerged. As Mr. Crandall noted, with Bismarck the situation was different, as scuttling orders were given which probably meant that many hatches, etc. were deliberately left open as the crew attempted to leave. This was exacerbated by the fact that the hull had been very heavily riddled by shell fire during the final action, so relatively few internal compartments of any size were still patent when the ship went down. It's likely, still, that Bismarck suffered a fair amount of implosion damage as deep tanks low in the hull failed, but most of this was probably erased as the ship struck and subsequently skidded down the slope on the bottom. So the bottom of the hull, where this sort of damage would have been visible, has been either scraped off or buried in the mud.

The strength of the hull -- and due to service requirements, merchant ship hulls of that period were commonly structurally stronger than many warship hulls -- has little to do with it, insofar as almost any practical hull structure would structurally collapse at depths exceeding a hundred feet or so anyhow. Very little except things like gas bottles would make it deeper than 4000 feet. Maximum depth, provided it is over three or four hundred feet is of little practical consequence, as little would survive to even that depth unless specifically designed to do so.

Bill Jurens
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