Rodney + POW v Littorio and Victorio Vento

[Lutscha]

Well, it's a theoratical excersize which assumes 0 degree target angle, of course they could assume many things that put KGV in a better light but they give perfect conditions to everyone... Btw, you see that the shells fail to reach KGVs machinery on some occasions so they take the distance from belt to machinery in account.

Underwater hits are excluded, because the can't be simulated.

I lack a complete armour scheme of KGV but how thick is the longitudal bulkhead in the machinery spaces?

[dunmunro]

Well, it's a theoratical excersize which assumes 0 degree target angle, of course they could assume many things that put KGV in a better light but they give perfect conditions to everyone... Btw, you see that the shells fail to reach KGVs machinery on some occasions so they take the distance from belt to machinery in account.

Underwater hits are excluded, because the can't be simulated.

I lack a complete armour scheme of KGV but how thick is the longitudal bulkhead in the machinery spaces?

It is really a question of simulating the average conditions that would occur in combat. For example, many the the RN shells that hit Bismarck in the final battle would probably have penetrated at a O target angle, but typically there was some target inclination which degraded the performance of many RN hits. I was referring to the drawing on page 3 of the Marinearchiv thread, but I did read through the whole thread and, yes there was some very interesting data and simulations presented.

However, again I am not sure if VV's decapping plate is sufficiently spaced to properly decap an RN 14" AP shell:

If the cap remains intact after being knocked off, there is a minimum distance, the "Decapping Gap", behind the plate that the next plate in line must be located at to get the effect on that plate of a completely decapped projectile. If the plates are too close together, the cap does not have time to free itself from the nose and some, if not all, of the benefit of knocking off the AP cap is not obtained....

For obliquities other than normal, the Decapping Gap for an intact AP cap for both Type 1 and Type 2 AP caps decreases linearly from whatever it is for the decapping plate thickness in use at normal obliquity to a constant 1 caliber at 30° and up obliquity for all decapping plate thicknesses. This gap seems enough for British APC projectiles, since a smaller gap did not work with British 14" and 15" APC projectile tests at 30°, but a very slightly larger gap always worked with British 9.2" APC projectiles.

http://www.navweaps.com/index_tech/tech-085.htm

and the diagram in the article seems to indicate that the cap would remain intact since the decapping plate is only .2 calibres thick, while the decapping plate gap is only .65 calibres wide.

On page 3 of the Marinearchiv thread the KGV cross section seems accurate, but the machinery spaces have 13.7" armour and the TDS bulkhead is 2 x19mm thick, thinning to 19mm at the top.

I realize that UW hits are hard to simulate but this really penalizes KGV, since her armour scheme was specifically designed to defeat UW hits, while the RN 14/45 gun was very effective when scoring a UW hit because of its large, 48lb burster, which was also specifically designed to maximize its fragmentation effect.

[Tiornu]

The longitudinal bulkheads inboard of the KGV torpedo bulkhead have a thickness in the neighborhood of 11-13mm. I don't know if this is D steel or something cheaper, but it will be inconsequential against most large nose fragments. Nor will it have any notable worth against lateral splinters.
The gap between Littorio's decapper and main belt is not a void. The filler will decrease the distance needed to assure separation of the cap and shell body, according to Nathan.

[lwd]

..., while the RN 14/45 gun was very effective when scoring a UW hit because of its large, 48lb burster, ...

I thought hitting the water normally initiated the fuze. If so most shells that would achieve UW hits will either detonate before they reach the target or will have had a fuse failure. Those that don't will typically be hitting fairly close to the waterline which means they may well be on the belt. Or have I got this all wrong.

[Bgile]

I thought hitting the water normally initiated the fuze. If so most shells that would achieve UW hits will either detonate before they reach the target or will have had a fuse failure. Those that don't will typically be hitting fairly close to the waterline which means they may well be on the belt. Or have I got this all wrong.

I think you have it right, but it depends on the depth of the belt. If the belt is too shallow or the shell hits in the low point of the ship's wake, or the ship is heeling in a turn, the hit may occur below the armor. In the case of the PoW hit on Bismarck, one of these things happened, the shell apparently went off in contact with or very close to Bismarck's holding bulkhead, and the bulkhead was distorted and perforated by fragments.

[Dave Saxton]

I don't think British RFC was nearly as good in 1941 as it was late war. I know US RFC sure wasn't. I really doubt it was good enough to make a decisive difference at 30k yds or more. IMO no-one would be hitting much at that range.

These are good points.

In 1941, the 50cm Type 284 in service was the early production model. This early model did not have lobe switching, so it was limited to being an electronic rangefinder in practice. The British often refered to these as "electronic range finders", but really that is the most important function of any firecontrol radar. As a range finder it was far superior to the optics, with a range accuracy of +/- 150 yards, but the typical max distance that it could be used for this function was considered to be about 20,000 yards. It's true that KGV's early model 284 detected the Bismarck at about 25,000 yards, (and the Suffolk's 284 could track Bismarck to 26,000 yards) but it could not be used for spotting until the range closed some. The operator latter stated that this was the best range performance that he ever obtained from this particular set. Tests of the KGV's 284 determined that it could range a destroyer at 14,000 yards and cruisers at 20,000 yards.

In 1942, new construction, and large warships without firecontrol radar already, began to recieve the Improved Type 284. The BB to BB range was rated as 29,000 yards, and this model used beam switching that allowed the bearing of the target to be accurately fixxed. Historically Duke of York's Type 284M first detected the Scharnhorst at 35,000 yards, but the bearing could not be fixxed, and held, until the range had closed to about 26,000 yards. The newer models used an improved ranging panel and indicator that improved range accuracy, but the range accuracy degraded a percentage of the range with increasing range, nonetheless.

During 1942 those warships already with the early model Type 284 had to in most cases soldier on, and did not recieve the modified model upgrades until 1943.

The 10cm replacement, Type 274, first began to be phased into service in the spring of 1944. It had some teething problems including an inability to spot for bearing, however.

[dunmunro]

Dave, there was also some suggestion that the Type 281AW unit could be used for RFing as well, and that it would have a longer range than the 284, but with less accuracy in range, and very poor bearing discrimination:

"The second set was the air warning system, the aerial of which was situated on top of the mainmast. Although primarily an air warning set, it was possible to feed ranges from a surface target into the 14 inch Transmitting Station.

This set had a more or less unlimited range."
http://www.hmshood.com/history/denmarks ... letter.htm

and this account is verified here:
"My position was in the 281 receiving office and I personally manned the display tube. In those days we had no gyro repeats; we had to give the bearings by red or green [port or starboard], but we did have two M-type transmission units, little counter-drums on which we could transmit range. The transmission counter-drum that I controlled had as its counterpart a receiver on the bulkhead of the Transmitting Station - the TS. This had to be read and placed by someone into the calculations which were being carried out on the plot. Unfortunately, despite the fact that I transmitted these ranges, no one even knew they were coming in on the counter-drum and no radar ranges were used by our gunnery people. We had only one previous shoot and had not developed any drill."
http://www.navweaps.com/index_inro/INRO_Bismarck_p1.htm

[Dave Saxton]

One of the characteristics of meters wave length radar is potentially great range. Type 279 had a wave length of 7.5 meters and Type 281 3.5 meters. These extra long wave radars have the ability to see beyond the radar horizon through multi-pathing. Decimetric and centimetric radars can not see beyond the horizon. (There is some slight down ward bending but it's not enough to be significant). Transmission pulses of long wave radar could in some cases propagate for hundreds of miles. This is the most likely reason as to why Lutjens still thought he was being tracked in the case of the Bismarck.

The British used Type 279 at Matapan. There were no 50cm sets in the Med at that time. The account of Valiant's Type 279 is given in the official report:

"Shortly before this action, telephone communication between the 15" TS and the RDF (radar) office..to a range reciever in the TS had been fitted by the ship's staff......the first ship to be picked up was at a range of 9 miles and this ship was later sighted at 4 1/2 miles on the bearing indicated by the RDF....the guns and the RDF were put on the right hand target and fire opened, the AFC was set to the RDF range. This broadside was seen to hit... fire was shifted to the left hand target ..all these five broadsides were seen to hit..."

Naval Ordnance later poo poo'ed this, because the range was so short, and because Warspite and Barham (without RDF) also obtained first salvo hits.

The British did consider Types 279 and 281 as back ups for ranging, but they did not consider using them to extend the range of gunnery beyond the range limits of Type 284, or as primary systems for gunlaying in place of Types 284 or 274. Refering to Type 284M's limit of 29,000 yards, Howse was told:

"The 14" guns of the KGV class battleships had a max range of 36,000 yards, so the improvement with Type 284M was arguably not enough. In point of fact , the disadvantage was more theoretical than actual, because for various reasons, fire would seldom be opened over about 28,000 yards..."

In 1942 the Admirality ordered that non-GS radars were not to be used in place of GS sets.

[dunmunro]

I managed to find Paddon's article in Salty Dips (how fortunate that many RN radar officers were Canadian). In it he gives a very detailed account of tracking and ranging on the KM at the beginning of the DS battle, at 26000 yds, but he notes that there were 3 targets at 26k yds: "This was unfortunate because I had 3 distinct echoes of 3 ships at 26K yds, clearly portrayed on the radar screen, an "A" scan with a linear blip. I was able to follow them with complete accuracy and complete detail, religiously giving the range as I have described" Paddon speculates that there was 3 ships in the KM force, which is nonsense, but he may have been ranging on Suffolk or Norfolk, or perhaps he was getting a 3rd, false echo from the back scatter caused by the proximity of Bismarck and PE. I would speculate that the Type 281 signal was hitting Bismarck and then reflecting onto PE, and back to PoW, causing the 3rd blip ( Paddon also mentions being able to detect long wave radar signals from Bismarck).

This may be at the root of the problem, where "interference" was blamed for PoW not getting any usable radar ranges at DS. It is possible that the gunnery officer disregarded the ranges due the the extra blip, as being unreliable. Still it seems likely that the Type281 could range on a BB out to the LOS.

Dave, I wrote this before your last post, so it's not really a reply to it but it does illustrate the Type 281's potential.

[dunmunro]

The RN Radar motherlode!:

http://www.rnmuseumradarandcommunicatio ... E%2019.htm

[lwd]

... These extra long wave radars have the ability to see beyond the radar horizon through multi-pathing. Decimetric and centimetric radars can not see beyond the horizon. (There is some slight down ward bending but it's not enough to be significant). Transmission pulses of long wave radar could in some cases propagate for hundreds of miles. This is the most likely reason as to why Lutjens still thought he was being tracked in the case of the Bismarck.....

The problem with mutli pathing is that it leaves gaps in your coverage. There is also a phenomina known as "ducting" that can effectivly extend the radar horizon quite a ways. I also would not carachterize the difference between the radar horizon and the visible horizon as insignificant. For instance if you look at http://radarproblems.com/calculators/horizon.htm and plug 20 meters into both the hieght of the observer and the target the horizon goes from a visual one of ~32km to a radar one of ~37km.

[dunmunro]

I used NAaB and simulated a hit on VV's belt with a RN 14/45 with the MV=2475fps, O deg target angle, range =20,300yds SV=1607fps and assuming no decapping as per Nathan Okun's "Decapping Revisited" article. The result was complete penetration of the decapping plate, 11.1" belt, and both splinter bulkheads. However, I did not calculate fuse timing so it is possible that the shell would detonate before the 45mm bulkhead which would protect the machinery spaces from splinters, but if this bulkhead is penetrated then even if the shell bursts before the 25mm bulkhead, the machinery spaces would suffer splinter damage.

If we assume a 20 deg target angle then the 11.1" belt is still penetrated but it is unlikely that the 45mm bulkhead would be pierced. However a 20 deg target angle would also increase the effective gap between the plates and increase the chances of complete decapping. So VV would also be wise to maintain some degree of target angle to enhance her protection.

I read through all of Okun's material in the article on the Combined Fleet website and he does not state that the gap was anything other than a void, but he does state that the decapping plate was held in place by many fasteners and that a shell striking these would suffer accelerated decapping, so any round striking the decapping plate would have some probability of being decapped, and logically this probability would increase with an increase in target angle.

[Tiornu]

What angle of inclination did you assign the belt?

[dunmunro]

What angle of inclination did you assign the belt?

8 degs as per Axis BBs

[dunmunro]

I see that I assigned the first splinter bulkhead a thickness of 45mm, when it should have been 36mm, and the final bulkhead 25mm instead of 24mm, but doubt this would change the outcome much.