Yamato with several more knots

Dalekiller · Jul 1, 2015

Recently I finished a book about the Yamato's last voyage, A Glorious Way to Die: The Kamikaze Mission of the Battleship Yamato, April 1945 by Russell Spur.

However I read an interesting tidbit about Guadacanal, Yamato was considered several knots too slow for that voyage due to massive armor and thus Kirishima was sent instead and ended part of Iron Bottom Sound.

What would have happened had Yamato had several thousand tons of armor removed for speed?

Saphroneth · Jul 1, 2015

You also need a LOT more Ship Horsepower.

Dalekiller · Jul 1, 2015

Saphroneth said:
You also need a LOT more Ship Horsepower.

Apparently the ship only needed 2-3 knots more.

RodentRevolution · Jul 1, 2015

Dalekiller said:
Apparently the ship only needed 2-3 knots more.

I want you to think very carefully about just how much weight you are going to need to take off to gain 2 knots on the same hull. Because I think you are about to piss Jackie Fisher off by giving the Japanese the world's largest large light cruiser.

It will involve an enormous amount of yard work as armour is never easy to cut and will still result in the USS Washington sinking the Yamato in a night action because you can bet the butterflies are going to take the night off to giggle at this one.

Saphroneth · Jul 1, 2015

Dalekiller said:
Apparently the ship only needed 2-3 knots more.

Yes, that's what I mean.
The Hood and the King George V were about the same mass. Hood was longer (which aids speed) and had an extra 16% ship horsepower on top of that, and that earned her 3 knots as-built. Age of machinery eroded that entire advantage.

Dalekiller · Jul 1, 2015

I mean what if the ship had been built with 2000-3000 less tons of armor from the get go. Which is not unreasonable as the Yamato was a first to be armored like a Western Battleship.

Gudestein · Jul 1, 2015

A funny thing though is that the 150000 shp is not really impressive for a 65000 tons ships. GZ had 200000 shp for half the mass. One do wonder if some design changes could have been made from the beginning?

I guess the OP means in the original design?

Dalekiller · Jul 1, 2015

Gudestein said:
A funny thing though is that the 150000 shp is not really impressive for a 65000 tons ships. GZ had 200000 shp for half the mass. One do wonder if some design changes could have been made from the beginning?

I guess the OP means in the original design?

I should've made that clear from the start but yes. Actually the Japanese might have to give Yamato more flexible armor and thus make her actually better than in OTL.

Saphroneth · Jul 1, 2015

Dalekiller said:
I mean what if the ship had been built with 2000-3000 less tons of armor from the get go. Which is not unreasonable as the Yamato was a first to be armored like a Western Battleship.

Still not enough change to get that many extra knots.

Insider · Jul 1, 2015

put atomic power plant aboard, with enough power to make it steam 40 knots. You would also get rid of that fuel consumption issues.

BlueTrousers · Jul 1, 2015

Okay, folks. Time for the Dummies' Guide to Ship Powering.

To a first approximation - and this is a very rough approximation to a very complex situation - power requirements vary as displacement to the power of two-thirds and as the cube of speed. The ratio of the product of these two figures to power is known as the Admiralty Coefficient.

For Yamato, with a displacement of 69,100 tons, a speed of 27 knots and a machinery plant generating 150,000 shaft (not ship) horsepower, the Admiralty Coefficient is 221.

Turn the formula around, and we can calculate the displacement for a given speed. If we want to strip weight off the Yamato to get her to 30 knots, we need to get her down to 43,000 tons from 69,100 tons. That's a weight saving of 26,100 tons. She only carried 21,266 tons of armour, so as well as leaving off all the armour, you still need to find another 5,000 tons of weight. Losing a turret, along with the associated magazines and auxiliary machinery, might do it.

In other words, doing it requires constructing a monstrosity that would make even Jackie Fisher say "Hang on a minute..."

Getting the desired speed by increasing horsepower is a bit more feasible, only needs another 54,000 shp. Though the extra machinery weighs more and takes up more space... Going from a South Dakota to an Iowa cost 30% of displacement; getting half the speed increase out of Yamato might cost 15% of displacement. Taking us to, oh, 80,000 tons or so.

This is getting silly again. And we haven't even thought about where the fuel comes from. Maybe we'd better just send Kirishima.

CalBear · Jul 1, 2015

RLBH said:
Okay, folks. Time for the Dummies' Guide to Ship Powering.

To a first approximation - and this is a very rough approximation to a very complex situation - power requirements vary as displacement to the power of two-thirds and as the cube of speed. The ratio of the product of these two figures to power is known as the Admiralty Coefficient.

For Yamato, with a displacement of 69,100 tons, a speed of 27 knots and a machinery plant generating 150,000 shaft (not ship) horsepower, the Admiralty Coefficient is 221.

Turn the formula around, and we can calculate the displacement for a given speed. If we want to strip weight off the Yamato to get her to 30 knots, we need to get her down to 43,000 tons from 69,100 tons. That's a weight saving of 26,100 tons. She only carried 21,266 tons of armour, so as well as leaving off all the armour, you still need to find another 5,000 tons of weight. Losing a turret, along with the associated magazines and auxiliary machinery, might do it.

In other words, doing it requires constructing a monstrosity that would make even Jackie Fisher say "Hang on a minute..."

Getting the desired speed by increasing horsepower is a bit more feasible, only needs another 54,000 shp. Though the extra machinery weighs more and takes up more space... Going from a South Dakota to an Iowa cost 30% of displacement; getting half the speed increase out of Yamato might cost 15% of displacement. Taking us to, oh, 80,000 tons or so.

This is getting silly again. And we haven't even thought about where the fuel comes from. Maybe we'd better just send Kirishima.

There is also the specific hull form to be considered. a different hull shape might give slightly more speed. Not three knots, but maybe a half knot, with a clean bottom. Of course that also changed to armor requirements, the protection scheme, and everything else about the ship.

Yamato and her sisters were white elephants. Designed for a war that over five years before they were commissioned, so huge that they used resources that could otherwise have been used to build half a dozen 16" gunned ships, and with armor that had vast variances in quality from plate to plate. Even if all three had been completed that would have faced insurmountable odds as the USN put as many as 16 fast BB, 10 of them with the 16"/50 which fired a shell that could defeat the Yamato's armor at vitually combat ranges (the penetration curve of the MK 8 2,700 pound AP is remarkable, it gives a ship armored like Yamato no safe zone, had the Americans had her design blueprints in front of them they could hardly have designed better)

Also, the excuse regarding speed was just that, an excuse. There is no way the IJN sends its flagship into that sort of knife fight in 1942, not when the Decisive Battle was still to be fought.

phx1138 · Jul 1, 2015

RodentRevolution said:
I think you are about to piss Jackie Fisher off by giving the Japanese the world's largest large light cruiser.

LOL.

Yeah, to make this credible, you'd have to, what, remove her turrets & replace them with 6"?

(Turn the extra space over to carrying men & fuel to reinforce Guadalcanal?

)

CalBear · Jul 1, 2015

phx1138 said:
LOL.

Yeah, to make this credible, you'd have to, what, remove her turrets & replace them with 6"? (Turn the extra space over to carrying men & fuel to reinforce Guadalcanal?)

I like it.

Instead of a destroyer transport you have a battleship transport. Of course with a 36 foot/11 meter draft, you better have lots of lighters to run stuff to the beach from a couple miles out.

NOMISYRRUC · Jul 1, 2015

RLBH said:
Okay, folks. Time for the Dummies' Guide to Ship Powering.

To a first approximation - and this is a very rough approximation to a very complex situation - power requirements vary as displacement to the power of two-thirds and as the cube of speed. The ratio of the product of these two figures to power is known as the Admiralty Coefficient.

For Yamato, with a displacement of 69,100 tons, a speed of 27 knots and a machinery plant generating 150,000 shaft (not ship) horsepower, the Admiralty Coefficient is 221.

Turn the formula around, and we can calculate the displacement for a given speed. If we want to strip weight off the Yamato to get her to 30 knots, we need to get her down to 43,000 tons from 69,100 tons. That's a weight saving of 26,100 tons. She only carried 21,266 tons of armour, so as well as leaving off all the armour, you still need to find another 5,000 tons of weight. Losing a turret, along with the associated magazines and auxiliary machinery, might do it.

In other words, doing it requires constructing a monstrosity that would make even Jackie Fisher say "Hang on a minute..."

Getting the desired speed by increasing horsepower is a bit more feasible, only needs another 54,000 shp. Though the extra machinery weighs more and takes up more space... Going from a South Dakota to an Iowa cost 30% of displacement; getting half the speed increase out of Yamato might cost 15% of displacement. Taking us to, oh, 80,000 tons or so.

This is getting silly again. And we haven't even thought about where the fuel comes from. Maybe we'd better just send Kirishima.

Could they have got more horsepower from the same weight and volume of machinery if higher pressure boilers had been used? I was thinking of the type fitted to the destroyer Shimakaze.

Though I can think of two problems with that (and there are probably more). The first is that Yamato and Musashi were ordered in 1937 while the Shimakaze was ordered in 1939. To paraphrase Oscar Goldman the Japanese might, "Not have had the technology," in 1937.

The second problem is that the use of a new and untested technology on such important ships carries the risk that the ships will be ruined if the new technology fails. Look at the problems the Germans created for themselves by fitting their cruisers and destroyers with high-pressure boilers before the prototypes fitted to minor waships and auxiliaries had been properly tested.

phx1138 · Jul 1, 2015

CalBear said:
I like it.

Instead of a destroyer transport you have a battleship transport. Of course with a 36 foot/11 meter draft, you better have lots of lighters to run stuff to the beach from a couple miles out.

TY.

NOMISYRRUC said:
Could they have got more horsepower from the same weight and volume of machinery if higher pressure boilers had been used? I was thinking of the type fitted to the destroyer Shimakaze.

Though I can think of two problems with that (and there are probably more). The first is that Yamato and Musashi were ordered in 1937 while the Shimakaze was ordered in 1939. To paraphrase Oscar Goldman the Japanese might, "Not have had the technology," in 1937.

The second problem is that the use of a new and untested technology on such important ships carries the risk that the ships will be ruined if the new technology fails. Look at the problems the Germans created for themselves by fitting their cruisers and destroyers with high-pressure boilers before the prototypes fitted to minor waships and auxiliaries had been properly tested.

My guess is, had Japan's shipwrights been able to do it, they would have. AIUI, the Yamatos only achieved 27kt because Japan couldn't build a powerplant with high enough horsepower. Judging by Ship Powering for Dummies,

tho, it may've been a space issue.

OTOH, stupid design decisions like making a 70,000 ton ship you hope is invulnerable to enemy guns & not making sure the armor is actually any good

had something to do with it...

bsmart · Jul 1, 2015

I remember reading that the USS New Jersey could make 25 knots with half her powerplant. The other half was needed for the final 8 knots to get to 33 kts. Speedis expensive.

Astrodragon · Jul 1, 2015

CalBear said:
There is also the specific hull form to be considered. a different hull shape might give slightly more speed. Not three knots, but maybe a half knot, with a clean bottom. Of course that also changed to armor requirements, the protection scheme, and everything else about the ship.

Yamato and her sisters were white elephants. Designed for a war that over five years before they were commissioned, so huge that they used resources that could otherwise have been used to build half a dozen 16" gunned ships, and with armor that had vast variances in quality from plate to plate. Even if all three had been completed that would have faced insurmountable odds as the USN put as many as 16 fast BB, 10 of them with the 16"/50 which fired a shell that could defeat the Yamato's armor at vitually combat ranges (the penetration curve of the MK 8 2,700 pound AP is remarkable, it gives a ship armored like Yamato no safe zone, had the Americans had her design blueprints in front of them they could hardly have designed better)

Also, the excuse regarding speed was just that, an excuse. There is no way the IJN sends its flagship into that sort of knife fight in 1942, not when the Decisive Battle was still to be fought.

Actually that's slightly unfair.

The reasoning behind the Yamato class was that the USN couldn't build comparable ships and transit the Panama canal with them.

Which was a bit daft, since there are other ways to get to SE Asia or Hawaii, but there you go.

Zheng He · Jul 1, 2015

Highly unlikely Yamato would be sent to Guadalcanal. The purpose of the IJN's battlewagons was to fight the decisive battle against the US Navy and they were not be employed in subsidiary missions.

The four Kongo class ships were considered expendable which is why they were used in subsidiary missions like covering the landings in Malaya, escorting the carriers, and going down the slot to Iron Bottom Sound.

Scotty · Jul 1, 2015

Zheng He said:
Highly unlikely Yamato would be sent to Guadalcanal. The purpose of the IJN's battlewagons was to fight the decisive battle against the US Navy and they were not be employed in subsidiary missions.

The four Kongo class ships were considered expendable which is why they were used in subsidiary missions like covering the landings in Malaya, escorting the carriers, and going down the slot to Iron Bottom Sound.

Plus the Kongos got used alot because they did'nt drink fuel like an irishman drinks guiness