Design "feature" of R-class

[marcelo_malara]

I think the limit to the speed of the QE is mostly a hull form and displacement issue. The original design displacement is 27000 tons without fuel. With ~ 3500 tons of fuel, the deep load should be under 31000 tons. As built, HMS QE already displaces 33260 tons at deep load at 1916!. That is without bulge and post Jutland armour.

The reconstruction has the potential to perhaps push 100,000 shp by raising steam pressure and using the additional boiler room.

However, if we keep in mind that KGV achieve 110,000 shp for 28.5/29 knots with 35000 tons design (~40000 tons deep), QE is really draggy even before bulging.

Yes, she was quiet beamier for her length.

[paul.mercer]

I think the limit to the speed of the QE is mostly a hull form and displacement issue. The original design displacement is 27000 tons without fuel. With ~ 3500 tons of fuel, the deep load should be under 31000 tons. As built, HMS QE already displaces 33260 tons at deep load at 1916!. That is without bulge and post Jutland armour.

The reconstruction has the potential to perhaps push 100,000 shp by raising steam pressure and using the additional boiler room.

However, if we keep in mind that KGV achieve 110,000 shp for 28.5/29 knots with 35000 tons design (~40000 tons deep), QE is really draggy even before bulging.

Yes, she was quiet beamier for her length.

Would that have made them more stable gun platforms? Bismarck had a very large beam

[marcelo_malara]

Yes, she was quiet beamier for her length.

Would that have made them more stable gun platforms? Bismarck had a very large beam

More beam means more stability to roll, it would need higher waves to roll the ship and the responding righting moment would be more powerful. But, in the first page of this thread has been disputed that this means a better gun platform, the great D K Brown has been cited for this. It could be that the righting response was violent and that disturbed the sights, or that the velocity of the response in degrees/second is higher than the velocity of the gun barrels in elevation and that would prevent continuous aim.

[wmh829386]

Would that have made them more stable gun platforms? Bismarck had a very large beam

Not really. For battleship, long range fire means salvo firing with director control. So the effect is not significantly as far as I can tell. German battleships tend to have even higher stability, but their long range gunnery doesn't seem to be affected.

[wmh829386]

the great D K Brown has been cited for this. It could be that the righting response was violent and that disturbed the sights, or that the velocity of the response in degrees/second is higher than the velocity of the gun barrels in elevation and that would prevent continuous aim.

In the "Grand Fleet" DK Brown basically said it's complicated and GM is not the only variable in determining how much the ship roll in a sea state. Inconveniently things like the period/size of ship, direction of wave and amplitude of wave all matters.
But generally speaking, ship with high GM rolls more quickly with a shorter period.

[marcelo_malara]

I am curious about QE´s rpm at max power before and after reconstruction. Does anyone have this data?

Regards

So I think the Shaft rpm for max power stays about 300 rpm before and after reconstruction. No idea about the turbine rpm after the reconstruction though

Back from holidays! With my books! In AOTS´s Warspite the numbers are:

Originally 275 rpm 75 000 hp
After reconstruction 300 rpm 80 000 hp

Not much different, bearing in mind that:

hp = torque * 2 * pi * revs per second

...looks like the torque was the same before and after, and that the additional power comes just from more revs. There is no data of the reduction gearing. But the range raised dramatically, from 8000 to 14000 nm at 10 knots. The propellers were changed along with the machinery.

Back to the Rs, I had a look at Burt´s, strangely there is no internal plans of the class. A question arises. The QE class had above armoured deck two full decks plus the forecastle. But the Rs with their higher armoured deck had just one full deck above it and the forecastle. That gives two possibilities:

-internal living space was much reduced
-some living space was afforded below armoured deck.

[marcelo_malara]

Correction, I found R´s cross sections in Burt´s, and yes, there were some crew quarters below the armoured deck.

[wmh829386]

Back from holidays! With my books! In AOTS´s Warspite the numbers are:

Originally 275 rpm 75 000 hp
After reconstruction 300 rpm 80 000 hp

Do you have any information about the R-class's and Tigher's Machinary. It is interesting that the R-class can make 22+ kts with 40 000shp while just about 2000 tons lighter while Tiger can make 29 kts with 104 600 shp.

[marcelo_malara]

Back from holidays! With my books! In AOTS´s Warspite the numbers are:

Originally 275 rpm 75 000 hp
After reconstruction 300 rpm 80 000 hp

Do you have any information about the R-class's and Tigher's Machinary. It is interesting that the R-class can make 22+ kts with 40 000shp while just about 2000 tons lighter while Tiger can make 29 kts with 104 600 shp.

At hand I have this compilation. Numbers look good for me.

28kt /23kt = 1.217

1.217^3 = 1.802

1.802 * 40000 hp = 72000 hp

A 21.7% increase in speed would demand an 80.2% increase in power, and that applied to 40.000 hp gives 72000 hp, and TIger being heavier would demand a little more. Amateur engineering

[wmh829386]

At hand I have this compilation. Numbers look good for me.

28kt /23kt = 1.217

1.217^3 = 1.802

1.802 * 40000 hp = 72000 hp

A 21.7% increase in speed would demand an 80.2% increase in power, and that applied to 40.000 hp gives 72000 hp, and TIger being heavier would demand a little more. Amateur engineering

Oh, It wasn't that the numbers on Tiger or Revenge that is strange, I find the numbers for the QE strange. You see, 72 000 shp is still less than QE as-built.

[paul.mercer]

Gentlemen,
I know thar battlecruisers were designed for speed but I'm surprised that Hood had almost 3,500 tons more armour weight that Nelson and that some of the battlecruisers built between 1909-1912 had almost double Nelsons HP - is that correct or did the RN designers go backwards with their engines?

[marcelo_malara]

Oh, It wasn't that the numbers on Tiger or Revenge that is strange, I find the numbers for the QE strange. You see, 72 000 shp is still less than QE as-built.

Oh now I see what you meant. Yes, for me it was strange too that 40% more design power (40.000 vs 56000 hp) did not buy a single additional knot in QE. It deserves a little digging in my books, I will take care of it. A quick calculation shows that 40% more power should have bought 10% more speed.

[marcelo_malara]

Gentlemen,
I know thar battlecruisers were designed for speed but I'm surprised that Hood had almost 3,500 tons more armour weight that Nelson and that some of the battlecruisers built between 1909-1912 had almost double Nelsons HP - is that correct or did the RN designers go backwards with their engines?

Hi Paul. I have always wondered that the RN honored world´s most famous admiral with that....ship. Nelson class was a big compromise, the designers tried to accommodate 9 16" guns and good protection in just the 35000 t allowed by treaties, something needed to suffer and it was propulsion, with just 2000 t allowed to it. Higher power would have needed more machinery space and in turn that would mean more protection weight. Personally I think the Japanese did better with Nagato.

[marcelo_malara]

This is from Burt´s. It looks that the 23 kt I compiled was a design speed not achieved, the actual speed was closer to 20/21 kt, so it makes sense the 23 kt of QE with 56000 hp.

[wmh829386]

This is from Burt´s. It looks that the 23 kt I compiled was a design speed not achieved, the actual speed was closer to 20/21 kt, so it makes sense the 23 kt of QE with 56000 hp.

Thanks, this makes more sense now! However, I think the actual speed from the QE is still quite disappointing. From actually trials, I think the best speed made for QE is barely above 24 kts.

The R-class though, they are just pretty dreadful in WW2 in overweight conditions... They are making 18/19 kts like the pre-dreadnaughts...