Denmark Strait hits on HMS PoW

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Cag
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Denmark Strait hits on HMS PoW

Postby Cag » Wed Dec 28, 2016 8:32 pm

Hi All

I am opening a new subject (first time for me!) in the hope that someone will be able to help with a question I have.

As part of the Denmark Strait battle map thread I decided for my sins to try help in working out the positions of the participating ships which has ballooned into trying to resolve other matters surrounding the battle.

One such matter is the hits received by PoW and their relationship to the sinking of HMS Hood. I understand the hits to the compass platform the hacs tower and the crane hit which all landed before PoW turned away and came towards PoW from a forward direction.

My problem is with the 15 inch underwater hit to PoW (the one where the shell was discovered whilst in dry dock). I have a full set of builders plans and have used them together with the damage reports in adm 267/111 to attempt to put things together. According to the report the shell hit 12 inches above the bilge keel at frame 187. This frame corresponds in line with the rear rail of the catapult and the shell ended up between frames 190-192 with the nose of the shell facing forward toward the bow.

The angle of entry was 10° from forward and the angle of decent was 2-4° from the perpendicular. The shell was deflected approx 20°forwards whilst passing through the outer bottom plating that formed the lower ships side and a further 15° forwards by the longitudinal bulkhead of the oil fuel compartment which may explain it's forward facing resting place. It's trajectory was rising relative to the ship as it passed through (12 feet inside the ship).

Put simply was this hit similar to the others, from a forward direction or as is shown on the Hood website from aft?

The shell hit at frame 187 and yet landed at 192 which is further aft, this seems odd even for an underwater travel and a deflected path as it seems more logical for the shell to carry on its path toward the bow despite any deflection than be 'bounced' back toward the stern especially when it was apparently deflected forwards?

The only reference I know of is the hit felt by the crew of PoW around her salvo no 12 which coincidentally was when the range to Bismarck was 17100yds which is just over the estimated range of the hits to PoW compass platform and hacs tower.

Any assistance would be most gratefully received and much appreciated

Many thanks in advance
Best wishes
Cag.

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paulcadogan
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Re: Denmark Strait hits on HMS PoW

Postby paulcadogan » Thu Dec 29, 2016 4:17 am

Cag wrote:Put simply was this hit similar to the others, from a forward direction or as is shown on the Hood website from aft?


Hi Cag,

...I think you need to look again. The Hood website diagram shows the hit coming from forward, just as described in the damage report. See hit #5 in the diagram below from http://www.hmshood.com/history/denmarks ... damage.gif.

Image

Paul
Qui invidet minor est - He who envies is the lesser man

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Re: Denmark Strait hits on HMS PoW

Postby dunmunro » Thu Dec 29, 2016 4:22 am

Perhaps Bill Jurens will comment, but IIRC shells that take an UW path often tumble end over end in the water and thus may change their trajectory somewhat.

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Re: Denmark Strait hits on HMS PoW

Postby Cag » Thu Dec 29, 2016 9:11 am

Hi All

Thank you very much for your help it is most appreciated!

Thank you Paul I see what you mean, that does seem slightly less shallow than the 10° from forward though? But it does show the hit coming from just forward of the beam as you say my mistake!

Hi Duncan yes I thought that too only the report does say that the shell did not yaw too much and that it burst it's way through the SPS compartments until it hit the torpedo bulkhead which stopped it although it too was damaged. It went through 30lbs of D steel then 17lbs of D steel and a further 17lbs of D steel plus brackets and stiffners before the torpedo bulkhead (2×30lbs of D steel) stopped it. The hole in the ships side was a diameter of 14.875 inches which also suggests no yaw.

It apparently travelled some 80 feet underwater and then 12 feet within the ship the only deflection occurred upon hitting the ships structure.

I'm just wondering if this was the immediate heavy hit felt and mentioned by Captain Leach or whether it was part of the salvo that hit the crane which would mean that PoW was in fact hit 4 times whilst manoeuvring to avoid Hood. Quite a few witness testimonies including Mr Hunter-Terry state that the crane hit occurred as the bows of Hood passed by the PoW.

The hit that passed through the boat deck I understand and the other two hits astern I'm still working on especially the hit at frame 315 that exploded and punctured two additional holes at frame 317, an explosion would be in every direction but again why would this pierce the hull toward the stern and not also toward the bow? But I guess that has a lot to do with the ships shape at that point.

I'm trying to work out which cabins and compartments were flooded etc.

Thanks again for all the help much appreciated
Best wishes
Cag

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Re: Denmark Strait hits on HMS PoW

Postby dunmunro » Thu Dec 29, 2016 5:45 pm

What I mean to say, is that the shell may tumble just after it hits the water and loses it's ballistic cap and at that point it may change direction.

http://www.navweaps.com/index_tech/tech-041.htm

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Re: Denmark Strait hits on HMS PoW

Postby Cag » Thu Dec 29, 2016 6:21 pm

Hi All

Thanks Duncan yes I see exactly what you mean. I too thought this was the only explanation and it still puzzles me.

This is from adm 267/111 and is from a report from S V Goodhall from the DNC representatives examination

"The shell referred to within struck the ship slightly forward of 186 station and about 12 inches above the bilge keel. At the point of impact therefore the shell had travelled a distance of about 80 feet underwater and was about 28 feet below the water surface.
It was still stable and travelling nose first with little yaw as is evidenced by its path within the ship. From the point of first impact on the ship to point of impact on the protective bulkhead the shell travelled 12 feet"

It goes on to say that the shell was only deflected once it hit structures within the ship. Other reports say there was damage to the oil fuel tanks (holding roughly 23000 gallons of fuel) and the diesel tanks in the ships bottom (with again roughly 13000 gallons capacity). I presume PoW would also have leaked oil as did Bismarck?

It is also the angles I'm wondering about, the '10° from forward' in particular. Does this mean the shell struck at an angle of 10° or, as with the descent angle that was given relative to the perpendicular of the ship, it was 10° from the relative fore-aft line of the ship? This is obviously quite important to understand the angle from which it was fired.

Sorry for the questions it just goes to show how hard it is to reconstruct the battle map as there are so many variable considerations to well...er...consider!

Many thanks for the contributions and advice
Best wishes
Cag.

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Re: Denmark Strait hits on HMS PoW

Postby dunmunro » Fri Dec 30, 2016 6:10 am

Here's a thread on UW hits:

viewtopic.php?t=1647

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Alberto Virtuani
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Re: Denmark Strait hits on HMS PoW

Postby Alberto Virtuani » Fri Dec 30, 2016 10:01 am

@all: my best wishes to everybody here !


Cag wrote: "....I'm just wondering if this was the immediate heavy hit felt and mentioned by Captain Leach.... "

Hi Mr.Cag,
I was always puzzled as well by Capt.Leach statement about a "heavy hit aft" just before the compass platform hit.

However, looking at the damage report and at Paul's posted drawing above from Hood website, my 2 cents opinion is that the only hit that could have reached PoW before the compass platform one (hit No.1) is the one on the fore directors support (hit No.2), that would have been felt from the bridge as coming from aft, bouncing over the roof of the chart room just behind the compass platform. Possibly this came very few seconds before the No.1 and it was probably a PG 8" one or even a Bismarck 6" one (as per damage report conclusions).

The UW 15" hit looks too much from a different direction to have hit when the ship was on course around 280°, even accounting for a deflection due to the travel under the water. I also strongly doubt that such a shell (traveling under water, hitting low in the ship, piercing thin bulkheads and resting without exploding) could be felt at all from the bridge during the battle. :think:


Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

Cag
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Re: Denmark Strait hits on HMS PoW

Postby Cag » Fri Dec 30, 2016 11:32 am

Hi All

Again thank you for your help, everything I've read so far makes me expect the shell to have tumbled but in this instance (I think there are pictures of the hole on the Hood association website that show a clean hole) from what the SV Goodhall report says it went in nose first without yaw.

Personally I'm of the opinion that it may have hit the ship nose first but agree with Duncan that this is not to say it did not tumble prior to this but I'm no expert!

Thanks Alberto, I do know the hit was felt in the diesel dynamo room inboard of the SPS and we know something was felt in the TS which is just forward of the forward boiler room.

This hit I agree may have been associated with the crane hit (both 15 inch) but if this is the case we know from witness testimonies that the crane hit occurred as the PoW passed the Hoods sinking bow so these four hits happened within a very short period of time (the time it took to pass the Hood) no doubt whilst Leach was coming round and descending to the conning tower position.

The range estimate for the bridge hits was 16500-17000yds which does match salvo 12 but Rowell himself admits his map timings may be up to two minutes out which makes a big difference when trying to match timed bearings!

Thanks again
Best wishes
Cag

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Alberto Virtuani
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Re: Denmark Strait hits on HMS PoW

Postby Alberto Virtuani » Fri Dec 30, 2016 1:48 pm

Cag wrote: "...these four hits happened within a very short period of time..."

Hi Mr.Cag,
I do agree with you !
According to the drawing above and to the damage report, even ALL the seven hits happened with the ship on a course between more or less 280° (perhaps just 290° for the No.2) and 200° / 210°.

Therefore, according to PoW own maps (and to her turning data), they all happened surely before 6:02:30. However, the last three 8" hits (No.4, 6 and 7, coming from behind the beam) happened quite later than the first 4 hits. This means that the three 15" hits all happened in a much reduced timeframe, probably between 6:00:50 (No.1) and 6:01:40 (No.5), while the ship was passing the remains of Hood, possibly in 3 or max 4 consecutive BS semi-salvos.


Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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Dave Saxton
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Re: Denmark Strait hits on HMS PoW

Postby Dave Saxton » Fri Dec 30, 2016 3:29 pm

With an underwater hit, the angles of entry probably become divorced from the pre-impact trajectory angles. The trajectory, both decent and bearing, will likely be altered a little, or a lot, following impact with the water, and I don't think there is any way to calculate by how much, and it's probably not repeatable case to case. I think the Japanese determined that usually the trajectory flattens some after entering the water. A lack of key holing doesn't necessarily mean the trajectory wasn't altered, but only indicates that procession wasn't manifest at that moment.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Denmark Strait hits on HMS PoW

Postby Cag » Fri Dec 30, 2016 5:25 pm

Hi All

I tend to agree Mr Saxon, it's the report that puzzles me as they say the path through the ship denotes it's nose entry but from everything I've read it did seem odd, also the meaning of the angle of entry being 10° from forward this would not necessarily denote it's origional trajectory would it?

I see what you mean Alberto, it just seems an awful lot of occurrences packed into such a short time. According to the GAR PoW last full salvo was about 06.01:50 and we know Bismarck fired a sixth salvo at Hood which was in the air as she exploded which narrows that time down again.

Does it seem more likely that due to the diversion around Hood, the compass platform hit, Leach's regaining consciousness and the time it took to reach the conning tower that the decision and opportunity to break off was later than that first proposed as just after the compass platform hit?

PoW also still had 5 full salvos to fire too, and we know at the official turn away at 06.02 Y turret jammed, which begs the question were the 3 local control salvos of Y turret fired from a jammed turret or did Y turret jam after the local control salvos meaning then the actual final decision to withdraw was at this time?

Thanks again
Best wishes
Cag

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Re: Denmark Strait hits on HMS PoW

Postby Bill Jurens » Fri Dec 30, 2016 6:37 pm

I would agree with Mr. Saxton's comments.

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Re: Denmark Strait hits on HMS PoW

Postby dunmunro » Fri Dec 30, 2016 10:57 pm

Alberto Virtuani wrote:@all: my best wishes to everybody here !


Cag wrote: "....I'm just wondering if this was the immediate heavy hit felt and mentioned by Captain Leach.... "

Hi Mr.Cag,
I was always puzzled as well by Capt.Leach statement about a "heavy hit aft" just before the compass platform hit.

However, looking at the damage report and at Paul's posted drawing above from Hood website, my 2 cents opinion is that the only hit that could have reached PoW before the compass platform one (hit No.1) is the one on the fore directors support (hit No.2), that would have been felt from the bridge as coming from aft, bouncing over the roof of the chart room just behind the compass platform. Possibly this came very few seconds before the No.1 and it was probably a PG 8" one or even a Bismarck 6" one (as per damage report conclusions).

The UW 15" hit looks too much from a different direction to have hit when the ship was on course around 280°, even accounting for a deflection due to the travel under the water. I also strongly doubt that such a shell (traveling under water, hitting low in the ship, piercing thin bulkheads and resting without exploding) could be felt at all from the bridge during the battle. :think:


Bye, Alberto

A 1700lb shell that punches through multiple bulkheads will be felt as it involves a considerable transfer of energy. It seems very likely that this was the hit felt in the transmitting station and recorded on the AFCT plot. I suspect that the bridge would resonate in sympathy with the hull after an UW hit.

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Alberto Virtuani
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Re: Denmark Strait hits on HMS PoW

Postby Alberto Virtuani » Fri Dec 30, 2016 11:03 pm

Cag wrote: "Does it seem more likely that................the decision and opportunity to break off was later than that first proposed as just after the compass platform hit? "

Hi Mr.Cag,
even if the sequence of events seems to be very fast, here I'm afraid I have to disagree with you. If this was the case, Capt.Leach would have phrased in a very different way his report. Instead, he was crystal clear that he ordered the disengagement after the hit in compass platform, before the turn around the Hood and before that Y turret fired (and jammed).

Capt.Leach on June 4th (my bold and underlined): "Course had to be altered starboard to avoid remains of Hood; meanwhile Bismarck shifted main and secondary fire quickly and accurately to Prince of Wales.
A heavy hit was felt almost immediately and at 06.02 compass platform was hit, and majority of personnel killed.
Navigating Officer was wounded; Commander Officer unhurt.
Same salvoes put both 5.25 directors out of action.
Considered expedient to break off action and consolidate position and ship, after being manoeuvered round remains of HMS Hood, turned away behind spelt smoke screen.
Y turrets fired in local during turn as smoke disagreed with after director.


I don't think there is any space to speculate about a "later" decision to break off action.

Perhaps we can debate whether the decision to break off the action was taken after the hit in CP or even immediately after Hood explosion, as Leach's comments in his own report indicate:
"......Prior to the disaster to the Hood, I felt confident that together we could deal adequately with the Bismarck and her consort. The sinking of the Hood obviously changed the immediate situation and there were three further considerations......In all the circumstances I did not consider it sound tactics to continue single-handed the engagement..... Accordingly I turned away and broke off the action......



Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)


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