KG 5 class underestimated?

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Bgile
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Post by Bgile »

Duncan,

If you have caused upset here, it is because some of us think you are distorting historical truth, which most of us care about a lot.

I believe KGV could only develop about 115 shp except under very unusual circumstances for a very short period of time. I think that in normal service she was capable of 27 to 28 knots, and Bismarck was capable of about 29 kts. That's what I think from reading many sources over many years. You can point us at things to look at and we will probably go look (I did - cool program!), but you still aren't going to change the actual performance of the ships in real service.

I feel these ships, while satisfactory designs, were not as good for the most part as their competition. I believe most historians would agree with me. I think their heavy gun performance was less than their competition and I feel the same way about their AA capability (Bismarck had worse AA). Their cruising radius was also marginal. As the RN attempted to correct their AA deficiency and their damage control weaknesses, they gained weight and got slower.

Not everyone will agree with me on every point and I accept that, but that's my opinion.

You feel differently about some of these things, and you seem to be on a mission to convert others to this belief. That's fine. I just don't think you are going to convert very many of the people who have spent a lot of their lives acquiring knowledge of this subject.
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marcelo_malara
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Post by marcelo_malara »

Bismarck does have a longer WL length, but her extreme beam tends to counter that, as her length to beam ratio is less favourable than KGV.
Sorry again, but where do you get the idea that the l/b ratio has much influence in the resistante of a ship?
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Post by Bgile »

marcelo_malara wrote:
Bismarck does have a longer WL length, but her extreme beam tends to counter that, as her length to beam ratio is less favourable than KGV.
Sorry again, but where do you get the idea that the l/b ratio has much influence in the resistante of a ship?
Sorry Marcelo, but I'm with Duncan on this one. It is an important factor with high speed ships, and directly effects resistance caused by the ship's own wake.
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Post by dunmunro »

Bgile wrote:Duncan,

If you have caused upset here, it is because some of us think you are distorting historical truth, which most of us care about a lot.

I believe KGV could only develop about 115 shp except under very unusual circumstances for a very short period of time. I think that in normal service she was capable of 27 to 28 knots, and Bismarck was capable of about 29 kts. That's what I think from reading many sources over many years. You can point us at things to look at and we will probably go look (I did - cool program!), but you still aren't going to change the actual performance of the ships in real service.
Just to recap, at the beginning of the Bismarck episode, Captain Leach signaled to Admiral Holland that PoW "was ready for 29knots, but that no more could be achieved without taking risks" so even at full load, Leach felt his ship could steam at 29knots. PoW's log and signals passed between Hood and PoW indicate that PoW did steam at 29 knots for several hours. At the time of the DS battle, PoW's displacement was down to about 41k tons versus about 48K for Bismarck. Under these conditions I believe that there is a reasonable probability that PoW was as fast or faster than Bismarck. I have presented what data I can and even produced data from a computer simulation, which supports my contention. I am making a reasoned argument based upon sound data, obtained from original sources, please tell me how this is "distorting historical truth" ?
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marcelo_malara
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Post by marcelo_malara »

And what about the ammo? The 14" has a 721 kg shell, at a muzzle velocity of 732 m/s. The 15" has a 800 kg shell at 820 m/s. Energy at the muzzle is 19710 kN for the 14" and 27544 kN for the 15". At 25000 yards the 14" has 445 m/s and an energy of 7284 kN, while the 15" has at 25000 m (more than 25000 yards) 473 m/s and 9131 kN. Note that if you compensate for the 2 guns difference, BS would have an added energy of 73054 kN, while the 14" 72840 kN, so BS still has a thin advantage, despite the fact that the numbers of BS are for 25000 m against 25000 yards (22860 m) for KGV.
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marcelo_malara
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Post by marcelo_malara »

Sorry Marcelo, but I'm with Duncan on this one. It is an important factor with high speed ships, and directly effects resistance caused by the ship's own wake.
We had already compared BS and Hood, the former wider than the later and with similar displacements. And Hood still needs more power to outrun BS.
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Post by dunmunro »

marcelo_malara wrote:And what about the ammo? The 14" has a 721 kg shell, at a muzzle velocity of 732 m/s.
I know wiki is not a definitive source but this article seems correct:

http://en.wikipedia.org/wiki/BL_14_inch ... _naval_gun
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Post by Bgile »

dunmunro wrote:
marcelo_malara wrote:And what about the ammo? The 14" has a 721 kg shell, at a muzzle velocity of 732 m/s.
I know wiki is not a definitive source but this article seems correct:

http://en.wikipedia.org/wiki/BL_14_inch ... _naval_gun
It does agree perfectly with Marcelo.
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Post by Bgile »

dunmunro wrote: Just to recap, at the beginning of the Bismarck episode, Captain Leach signaled to Admiral Holland that PoW "was ready for 29knots, but that no more could be achieved without taking risks" so even at full load, Leach felt his ship could steam at 29knots. PoW's log and signals passed between Hood and PoW indicate that PoW did steam at 29 knots for several hours. At the time of the DS battle, PoW's displacement was down to about 41k tons versus about 48K for Bismarck. Under these conditions I believe that there is a reasonable probability that PoW was as fast or faster than Bismarck. I have presented what data I can and even produced data from a computer simulation, which supports my contention. I am making a reasoned argument based upon sound data, obtained from original sources, please tell me how this is "distorting historical truth" ?
You have convinced me that at that time on her displacement then PoW was capable of 29 kts. I have to believe the statement of her commanding officer. This was a brand new ship with a clean bottom, so it makes sense to me. You must be correct that on that day, she could steam with Bismarck.

This doesn't mean the class as a whole was capable of 30 kts except under special circumstances not normally achieved in service, any more than the Iowa class was capable of 33 kts.
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Post by Bgile »

marcelo_malara wrote:
Sorry Marcelo, but I'm with Duncan on this one. It is an important factor with high speed ships, and directly effects resistance caused by the ship's own wake.
We had already compared BS and Hood, the former wider than the later and with similar displacements. And Hood still needs more power to outrun BS.
I'm not sure what you mean. When Hood ran trials in 1920, she was capable of almost 32 kts with about 150,000 shp on 44,600 tons. Definitely faster than Bismarck on that displacement.
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marcelo_malara
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Post by marcelo_malara »

I will quote the great David K. Brown (WI, 3 1994, Powering of Warships):

"For a given displacement and speed, resistance will depend mainly on lenght and prismatic coefficient and to a lesser extent on beam and draft.

Beam in moderation does not affect the resistance directly, but a fatter form will tend to have a lower lenght/displacement ratio.

The prismatic coefficient

Cp = Vi/(L * Am)

Volume of the hull /(Lenght * Midships area)

really tells the designer how the bouyancy is distributed along the lenght: a low prismatic is full amidships with fine ends, whilst high prismatic form has fuller ends and a small mid section. The direct effect of the prismatic on resistance is only important at about Fn=0.3."

The prismatic for BS is 0.595 and for KGV 0.560, not much different.
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Post by dunmunro »

Bgile wrote:

You have convinced me that at that time on her displacement then PoW was capable of 29 kts. I have to believe the statement of her commanding officer. This was a brand new ship with a clean bottom, so it makes sense to me. You must be correct that on that day, she could steam with Bismarck.

This doesn't mean the class as a whole was capable of 30 kts except under special circumstances not normally achieved in service, any more than the Iowa class was capable of 33 kts.
The KGV and PoW, were unique, in that they were commissioned early enough in the war, they did not yet have the masses of light AA that burdened BBs later in the war, plus they did not have some of the refinements, such as strengthened prop shafts, more fuel capacity, and various other additions, that added more and more weight, I'm sure the late war KGV's were much slower, simply because they were far exceeding the design weights. PoW also had the "advantage" of the smallest fuel capacity of any KGV, which, theoretically, made her a couple hundred tons lighter, than KGV.
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Post by dunmunro »

Bgile wrote:
dunmunro wrote:
marcelo_malara wrote:And what about the ammo? The 14" has a 721 kg shell, at a muzzle velocity of 732 m/s.
I know wiki is not a definitive source but this article seems correct:

http://en.wikipedia.org/wiki/BL_14_inch ... _naval_gun
It does agree perfectly with Marcelo.
sorry, what I meant to point out is that the MV = 757 m/s for a new gun.
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marcelo_malara
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Post by marcelo_malara »

It is still a lighter shell with less velocity.
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Post by dunmunro »

marcelo_malara wrote:It is still a lighter shell with less velocity.
of course, but there is still 10 shells versus 8.

14" = 1590lb
15" = 1764lb

14" MV/Energy 15" MV/Energy (kilonewtons)
2475=20565 2690=26977 (muzzle)
1976=13121 2144=17137 (10k yds)
1774=10575 1919=13729 (15k yds)
1614=8754 1735=11222 (20k yds)
1512=7682 1602=9568 (25k yds)

At all ranges the 15" shell has a considerable advantage, but even at the muzzle the total energy for all shells shows only a small advantage for Bismarck, while at 20k yds, it is pretty much even.

I used this calculator:
http://www.billstclair.com/energy.html
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