Lutzow vs. US heavy cruiser

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dunmunro
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Re: Lutzow vs. US heavy cruiser

Post by dunmunro » Sun Jan 03, 2010 10:01 pm

RN 8". Note: Time of flight for SAPC Shell with MV = 2,725 fps (830.5 mps)
5,000 yards (4,570 m): 6.2 seconds
10,000 yards (9,140 m): 14.1 seconds
15,000 yards (13,720 m): 24.7 seconds
20,000 yards (18,290 m): 38.4 seconds
25,000 yards (22,860 m): 55.9 seconds
29,000 yards (26,520 m): 78.6 seconds


2) Time of flight for 335 lbs. (152 kg) AP Shell with MV = 2,500 fps (762 mps)
6,000 yards (5,490 m): 8.1 seconds
10,000 yards (9,140 m): 14.7 seconds
20,000 yards (18,290 m): 37.2 seconds
30,000 yards (27,430 m): 77.8 seconds

Note: Time of flight for 260lb AP Shell with MV = 2,800 fps (853 mps)
6,000 yards (5,490 m): 7.3 seconds
10,000 yards (9,140 m): 13.4 seconds
20,000 yards (18,290 m): 35.2 seconds
30,000 yards (27,430 m): 70.6 seconds

Data from Navweaps.

11" 661lb ToF, estimated:
20k yds = 30 sec
25k yds = 43 sec
30k yds = 55 sec

The RN 8" ToF is for a gun with wear = to 80fps loss of MV. The USN ToF = new gun for both. The RN 8" ToF with new gun MV would be about 1 - 3 seconds less than the above. These three 8" guns are very close in their ballistics.

AoF:

20k yds RN 8"=27.6*, USN 335lb= 25.7, USN 260lb = 24.4, KM 661lb 11" = 18. (subtract about 1.5degrees for a RN 8" @ 2800FPS.)
25k yds RN 8" = 41*, USN 335lb = ~40, USN 260lb= ~39, KM 661lb 11" = 27.7

data from NAaB and Navweaps.

When you consider the flatter AoF and shorter ToF, the 11" will be about twice as accurate at 25K yds. The ToF at long range actually gives the 11" the edge in controlled RoF. We have seen how both sides, combined, fired over 2000 rds of 8" ammo at Java Sea yet scored only about a 1/2 dozen hits.

*(subtract about 1.5degrees for a RN 8" @ 2800FPS.)

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Re: Lutzow vs. US heavy cruiser

Post by dunmunro » Sun Jan 03, 2010 10:12 pm

alecsandros wrote:
dunmunro wrote:The official account of the action lists at least six 11in hits on Exeter and several near misses:

http://funsite.unc.edu/hyperwar/UN/UK/L ... /37989.pdf

It makes for a very interesting read.
A good read, indeed. But I only counted 5 direct hits on Exeter..
You might be right. Paragraph 27 is a bit ambiguous and upon re-reading it, it may be referring to a previous hit.

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Re: Lutzow vs. US heavy cruiser

Post by Legend » Sun Jan 03, 2010 11:08 pm

Dunmunro my friend, I believe that for the American Baltimores the second set of numbers you described, the one with a MaxVelocity of 2,500 feet per second, is the most accurate.

http://en.wikipedia.org/wiki/8%22/55_caliber_gun

The Baltimores used a varying mix of Mark 12 and Mark 15 models of the 8"/55cal.
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Re: Lutzow vs. US heavy cruiser

Post by Bgile » Mon Jan 04, 2010 6:22 am

Didn't someone say that over 15 deg AoF most hits are deck hits so hit probability isn't quite as different for low angle. Also, the 11" guns used on AGS were terrible at deck penetration. They could do a lot of damage with contact fuses though.

Byron Angel

Re: Lutzow vs. US heavy cruiser

Post by Byron Angel » Mon Jan 04, 2010 10:13 am

Bgile wrote:Didn't someone say that over 15 deg AoF most hits are deck hits so hit probability isn't quite as different for low angle. Also, the 11" guns used on AGS were terrible at deck penetration. They could do a lot of damage with contact fuses though.

..... Twas I. For a warship target of typical transverse proportions (freeboard versus beam), a 15 degree projectile angle of fall is the approximate crossover point from a majority of side hits to a majority of deck hits.

However, I would not read too much into angle of fall as a predictor of overall gun accuracy. At medium and long ranges the influence of angle of fall declines greatly. A typical WW2 era US or British CA had a beam of about 60 ft and a freeboard (side height) of about 20 ft. Its target pattern (beam + danger space) would be affected (approximately) by projectile angle of fall:

A o F____Beam_______Danger Space______Total Target Pattern
18deg____60 ft__________60 ft________________120 ft
28deg____60 ft__________38 ft_________________98 ft
40deg____60 ft__________24 ft_________________84 ft

Taking into consideration that GRAF SPEE / LUTZOW had a beam of about 70 ft and probably a slightly greater freeboard height, it becomes apparent that there would have been no great difference in their overall target patterns at any given range - 5 to 10 pct at best, depending upon range.

The ability to achieve straddles on target would have been of far greater import. GRAF SPEE / LUTZOW would have had a palpable advantage at long range by virtue of the shorter time of flight of her 11-in shells, assuming equal fire control methods (i.e. - radar FC versus radar FC, or optical FC versus optical FC).


Byron

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Re: Lutzow vs. US heavy cruiser

Post by alecsandros » Mon Jan 04, 2010 8:57 pm

Great posts from Dunmuro and Byron!
Now that the picture of teh guns/shells/salvos appears clearer, can someone say something about the AGS/Baltimore armour and overall durability?

Cheers,
Alex

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Legend
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Re: Lutzow vs. US heavy cruiser

Post by Legend » Mon Jan 04, 2010 11:39 pm

Heavy Cruisers of the USN had little or no TDS, besides compartmentizing of course, so a hit beneath the waterline would prove very destructive to the ship's innards. I am not sure however of the armor and defensive capabilities of those upper works above the waterline.
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Re: Lutzow vs. US heavy cruiser

Post by Bgile » Tue Jan 05, 2010 12:19 am

Legend wrote:Heavy Cruisers of the USN had little or no TDS, besides compartmentizing of course, so a hit beneath the waterline would prove very destructive to the ship's innards. I am not sure however of the armor and defensive capabilities of those upper works above the waterline.
The USN philosophy was that it was impossible to provide a CA with a good TDS because they lacked the necessary beam. Instead, engine rooms and boiler rooms were alternated so it was unlikely for a ship to lose power from one hit, and diesel generators were provided at the extreme ends of the system. Major bulkheads between engineering spaces were made as resistant to fragmentation damage as reasonably possible on the displacement. A TDS doesn't protect a ship much against AP shells. Belt armor does that. If an 8" shell penetrated or passed below AGS's belt armor, then IMO it would probably also penetrate whatever "vital" space was behind it.

Edited out incorrect "longitudinal" reference.

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Re: Lutzow vs. US heavy cruiser

Post by Gary » Tue Jan 05, 2010 10:20 pm

Hi Hammy
Junkyard dog " is a little bit harsh on Exeter as a design

I wasnt so much criticisng Exeters design but rather the fact that she seemed to be nearly always in need of a spare part for one thing or another.
Was her sister HMS York the same?

Having said that, the Exeter was by all accounts a happy ship that was liked by her crew dispite her faults.
Maybe its time I stopped comparing all Royal Navy cruisers to HMS Belfast :whistle:
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Re: Lutzow vs. US heavy cruiser

Post by RF » Wed Jan 06, 2010 9:01 am

Gary wrote:
I wasnt so much criticisng Exeters design but rather the fact that she seemed to be nearly always in need of a spare part for one thing or another.
Was her sister HMS York the same?

Having said that, the Exeter was by all accounts a happy ship that was liked by her crew dispite her faults.
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Re: Lutzow vs. US heavy cruiser

Post by hammy » Fri Feb 05, 2010 5:55 pm

Exeter and York were attempts to "cut down" the Washington cruiser to something smaller , but the logic for this escapes me because you'd be better off with another pair of "Towns" , unless this may be part of the old 1930s 6inch vs 8inch debate , ie which was better , and these two are trial ships to prove the case one way or the other .
As neither was to get into an action that proved the performance of one gun over the other , I suppose the point is a bit moot still , although , interestingly , a lot of the players over on the " Navyfield " game are putting triple 6 inch into their C As in preference to the twin 8 inch .
( Yes , I know , that game is not a realistic representation of actual gunnery , but it is a pointer towards what works in there , ie greater quantity at faster rate is preferred over greater hitting power and better range .)

And I dont like Belfast much , that gap between the hangers and the fore funnel is unattractive , and the armour belt/torpedo bulge is clumsy too .
I think the smartest of the Big British cruisers was "London" after reconstruction . Pity the lightly built "county" hull couldn't take the extra weight , so they left the rest of the class alone . But aesthetically , that was a smart looking ship .
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Gary
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Re: Lutzow vs. US heavy cruiser

Post by Gary » Fri Feb 05, 2010 7:20 pm

I love the British Town class, they probably dont have to much wrong with them (for CL's)
Give me 12 X 6inch over 6 X 8 inch anyday (sorry but I just dont like York/Exeter)

The Gloucester sub class had improved Turret armour over the Southamptons - I assume Belfast/Edinburgh also had this?
Belfast was orginally intended to carry 4 quad turrets but this idea was shelved
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Re: Lutzow vs. US heavy cruiser

Post by hammy » Sun Feb 07, 2010 1:46 am

Yes , the two "Ugly sisters" were bigger , and so could carry the aft Lighter-than-originally-intended triple inch turrets a deck higher , and there was a margin left to harden them too , but I haven't the armour detail to hand at the moment .

As a 16 year old lad in my first job I was a trainee machine fitter in a factory making tin cans ( no hearing protection then so I've been a bit "luggy" ever since ) .
I well remember the Foreman there telling me one day that he had been a gunner leading seaman aboard "Belfast" in the early 1950s , and his vigourous demonstration of how you punch-thrust the cordite charge bag up into the breech with a clenched fist , after the chain rammer had put the shell in .
As my juvenile nose would have been relatively only about four inches up the barrel from the shell's nose during this display , and as his fist appeared to be about the size of a football , you can see why the memory has stuck ! :dance:
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Re: Lutzow vs. US heavy cruiser

Post by RF » Mon Feb 08, 2010 2:29 pm

Gary wrote:I love the British Town class, they probably dont have to much wrong with them (for CL's)
Give me 12 X 6inch over 6 X 8 inch anyday (sorry but I just dont like York/Exeter)
The only thing is the shorter reach. At the River Plate it was Exeter that was able to put AGS under fire at maximum range, and land two hits before being clobbered. Can't see 12 x 6 inch as being able to do damage to AGS that early in the action....
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Re: Lutzow vs. US heavy cruiser

Post by Bgile » Mon Feb 08, 2010 4:29 pm

At long range 8" has the advantage due to better ballistics and easier to spot shell splashes. 18,000 yds is about the max for 6" and 8" is around 26,000 yds if I recall correctly. Cruisers in general are hard to hit at steep trajectories though because they are so much narrower than battleships.

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