Naval Design Question

[Shawn]

This question concerns the French pre-dreadnoughts such as Charles Martel and Jauréguiberry. Specifically, was there any logical advantage to the excessive tumblehome used in the designs and, in conncetion with that, why mount your secondaries in sponsons? They just seem to be begging for penetrating hit to the magazines.

[Sea Skimmer]

The tumblehome allows for a higher free board by reducing top weight, allowing the ship to fight its gun in heavier seas. It also allowed the wing turrets to fire dead forward and aft. On paper this meant such a ship could fire 3 guns aft and 3 astern, instead of just two. So that’s why the French liked four single gun turrets instead of two twins.

The French were still thinking in terms of ramming tactics when end on fire would be very important. In reality ramming was a nearly impossible tactic against a ship under power, let alone one armed with 12in guns, and blast damage effectively precluded firing heavy guns down the ends of the ship. The French in fact had a bugle call system setup to evacuate various open secondary guns around the wing turrets, as the crews would otherwise risk be killed. Magazines are still below the waterline, and not at much risk from flat trajectory predreadnought gunfire. The real risk was that tumblehome makes it very easy for a ship to capsize, as a great many of them did.

The reduced top weight of tumblehome also helped the French pack on such massively absurd superstructures, which provided better then usual accommodation space. The French logic being that a ship might fight once in 20 years, but the crew would always be on it and might as well be comfortable. French warships also have wine tanks for that purpose.

In the end the 'advantages' do not sum up to being very logical. But the French had some pretty horrendous if cool looking naval thinking in between the US Civil War and WW1, and within that context the tumblehome ships must have seemed brilliant.

[Shawn]

French warships also have wine tanks for that purpose.

Thanks for the answer. However, please tell me that above quote was made tongue-in-cheek.

[Simon_Jester]

Well, if wine is part of the standard naval provisions (analogous to rum in the Royal Navy for much of its history), that would be no stranger and more irrational than having a place to put the rum barrels on British ships.

[LaCroix]

I just took a look at the Jauréguiberry - that amount of tumblehome is ridiculous. The sides are slanted in a way that would be fine in a broadside exchange, but terrible in a long-range exchange. It looks like they designed the perfect ship to fight yesterday's army.

@ Sea Skimmer
I have a question about the capsizing. You said they were prone to do so? That is especially why you use tumblehome in ship construction - to prevent that.

I just ran the numbers on stability, and they show an excellent self-righting moment, even when inverted.
Was that superstructure that badly constructed that it leaked like a sieve or what was the actual reason for capsizing?

[folti78]

I just took a look at the Jauréguiberry - that amount of tumblehome is ridiculous. The sides are slanted in a way that would be fine in a broadside exchange, but terrible in a long-range exchange. It looks like they designed the perfect ship to fight yesterday's army.

@ Sea Skimmer
I have a question about the capsizing. You said they were prone to do so? That is especially why you use tumblehome in ship construction - to prevent that.

I just ran the numbers on stability, and they show an excellent self-righting moment, even when inverted.
Was that superstructure that badly constructed that it leaked like a sieve or what was the actual reason for capsizing?

Stuart summarized the problems with the tumblehome hulls in this post. Look for the paragraph starting with "Now tumblehome.". To add to it, compared to flared hulls, tumblehome has a reduced ability to prevent capsizing if there are flooded compartments. Which happens time to time to warships under fire.

[LaCroix]

Thank you.

Of course the increasing rate of immersion is a key problem with tumblehome hulls.

I was confused when it was stated that a tumblehome would increase roll rate, as that is basically the only thing that tumblehome shape is good for in nautical construction - reducing roll with a massive up-righting moment.

I agree that a tumblehome hull taking over water will fare worse than a regular hull, but taking another look at the pictures of the ships in the OP, I believe the biggest problem are the these sponson guns, which will pull them down faster than a Kraken.

[LaCroix]

At least the French were not as stupid as the latest idea from the Navy designers. Giving a tumblehome ship a wave-piercing bow is definitively not a good idea. Except you are aiming for a submarine, then go ahead...

[folti78]

Yep, those don't help with the stability either*. Tumblehome hulled warships is one of those ideas, which works good on paper, until you start to put on the things that make a ship a warship and also had to conform with various other requirements coming with the job, like seakeeping in less then perfect weather and the ability to take damage.

* silly question: if one of those sponson turrets gets blown off the ship, which problem will sink the ship faster? Imbalance due to lost weight on the side or flooding at the other side? </silly>

[LaCroix]

The trick with tumblehomes is that when they roll, the freeboard is still above the waterline, although they sink a bit deeper into the water. While the submerged volume of the hull is only slightly increasing on the submerged side, the weight being lifted out of the water on the other side shifts the CG, and the self-rightening moment is increased. For that to work, superstructure has to be light, to not counter-balance that moment.

All in all, the tumblehome hull allows for a frightening amount of roll without taking over water, something very much needed in a sailboat.

That works fine in four conditions:
1. On paper
2. If the superstructure on deck is small and light. Like, only a boathouse, and no heavy guns and superstructure.
3. There are no guns sitting in straight turrets on the sides of the ship, waiting to be submerged.
4. No holes poked in the hull, or you get a first-hand lesson in exponential math as the flooding occurs.

All of them are not met on a warship.

re: silly question: Actually, Blowing off one of the guns completely will help the ship, as the loss of weight would make it roll to the other side, lifting the hole higher above the waterline... If you only blow a hole into the sponson -> Bouvet

[Sea Skimmer]

* silly question: if one of those sponson turrets gets blown off the ship, which problem will sink the ship faster? Imbalance due to lost weight on the side or flooding at the other side? </silly>

Well it'd take a main magazine explosion to throw off one of the turrets like that, at which point the ship will probably flood at every point within 100 feet of the magazine walls instantaneously, and everything else will follow shortly after. The ship might well sink before it can finish capsizing, that has happened. Ship sinks bodily while halfway rolling over. Now weight imbalance from the turret ejection system functioning alone shouldn't be a serious risk, or else the ship would have been very hard to construct! You have to install one turret before the other.

While such early ships didn't face much of a threat to the magazines from gunfire, because of the flat short range trajectories, the Russo-Japanese war and WW1 showed that mines, torpedoes and fires would easily explode them. Such early battleships had no torpedo defense system, and often had magazines stacked right up against the hull walls. So hot fragments from a mine would hit the ammo before enough water could enter to quench the flames, often causing an immediate explosion. Didn't help that the ammo they used back then was so unstable that numerous ships simply exploded at anchor as late as 1917.

[Shawn]

Thanks for all the great replies. I'm still curious about the ammo supply to the spnsons. There is no barbette trunk to use to hoist the ammo so how is it delivered from the magazine?

[Sea Skimmer]

Instead of a large barbette, the French used a small armored tube just wide enough to hold the ammunition hoists. This ran inside the pedestal which controlled the turret rotation. A number of early steel battleships, and many turret/barbette equipped ironclad battleships used this arrangement for turrets on the ends too. This idea only worked with relatively small main battery turrets. Larger turrets needed a full height of barbette in ordered to hold the ammo hoists needed for more then one gun, and to support all the rotating platforms needed for the men who handled the ammo.

Also such a small armored tube means the people and ammo inside can be roasted by fires very easily. As you can see from the picture of Jaurequiberry below in fact, a shell could explode UNDER the turret without hitting any armor, and then star a fire which burns under the turret! Great design feature. Some treaty cruisers had similar setups in the 1920s though, purely to save weight.





Canet was not a very good designer in general, but he worked for Schneider which had a near a monopoly on construction of heavy artillery, fortress and warship turrets for the French military in the run up to WW1. So you can find his turrets all over. In fact in one set of trials for Romanian Brialmont forts (another designer with more connections then skill), Canet's turret was so ruined by hits that the Romanians suspended the trials before the last shot (which would have demolished the thing) to avoid embarrassment for both parties. Canet won anyway thanks to politics, though he did change that particular turret design prior to arming the forts around Bucharest.

[Shawn]

Looks at the diagram and asks that age old question, What the F_ck were they thinking?

[The Dark]

Didn't help that the ammo they used back then was so unstable that numerous ships simply exploded at anchor as late as 1917.

The last loss I can find from Poudre B dates to 1921, during the salvaging of Liberte. A lighter was loaded with old shells and was going to dump them in deeper water, since the wreck was in Toulon harbor. The shells exploded and blew up the lighter before it could dump them. At least four battleship were destroyed by magazine explosions involving Poudre B - Togo, Aquidaban, Iena, and Liberte. The Admiral Duperre was only saved by flooding her magazines.

[Sea Skimmer]

The last loss I can find from Poudre B dates to 1921, during the salvaging of Liberte. A lighter was loaded with old shells and was going to dump them in deeper water, since the wreck was in Toulon harbor. The shells exploded and blew up the lighter before it could dump them. At least four battleship were destroyed by magazine explosions involving Poudre B - Togo, Aquidaban, Iena, and Liberte. The Admiral Duperre was only saved by flooding her magazines.

Poudre B is a propellent, not a shell filling. The two kinds of explosives are not the same, though they can have similar base compounds. Propellent makes more gases at lower speeds since the idea is to push the shell, not shatter the gun into a million pieces. So an explosion of the shells would not be the result of Poudre B. I'm not sure what shell filling the French would have been using in 1911. Propellent tends not to work or present any real hazard after it gets wet, though you can dry it out latter. Sealed up shells with integral fuses however could remain operational on the sea floor for years.

Keep in mind BTW that the French changed the composition of Poudre B a bunch of times, and some of the later ones are basically totally unrelated to the original compounds and lacking the unstable guncotton base. But it took until after WW1 for it to evolve enough to be really safe.

[LaCroix]

Another thing that was as dangerous for yourself as for the enemy were the torpedoes. The Jauréguiberry's torpedo air chambers/air flasks exploded at least three times, always during exercises. That is as critical a flaw as the barbette, especially as these tubes are probably located near or below waterline.

[Marcus Aurelius]

Poudre B is a propellent, not a shell filling. The two kinds of explosives are not the same, though they can have similar base compounds. Propellent makes more gases at lower speeds since the idea is to push the shell, not shatter the gun into a million pieces. So an explosion of the shells would not be the result of Poudre B. I'm not sure what shell filling the French would have been using in 1911.

Probably melinite, which is a derivative of picric acid and quite unstable by modern standards, since it tends to corrode the shell walls and form more unstable picrates. Another possibility is amatol, but it's relatively stable and much more unlikely to cause troubles unless the shells are really old. Picric acid was much cheaper than TNT in those days, and although TNT based compositions like amatol were less expensive, picric acid was still commonly used in WW1 as the 'cheap and cheerful' ( ) high explosive.

[The Dark]

I'm not sure what shell filling the French would have been using in 1911. Propellent tends not to work or present any real hazard after it gets wet, though you can dry it out latter. Sealed up shells with integral fuses however could remain operational on the sea floor for years.

They were using either black powder or Melinite (picric acid and guncotton). Melinite was used for AP and some HE shells, while black powder was used as an HE bursting charge.

[SilverHawk]

Not to veer too much off topic I hope, but what where the advantages of battleships switching to an in-line armored turret design instead of the old dreadnought set of having them on the starboard and portside rims of the ship?

I would assume an easier profile to armor and higher speeds because of the streamlined hull.

[Questor]

Not to veer too much off topic I hope, but what where the advantages of battleships switching to an in-line armored turret design instead of the old dreadnought set of having them on the starboard and portside rims of the ship?

I would assume an easier profile to armor and higher speeds because of the streamlined hull.

My understanding is that it, at least partially, has to do with the structures necessary to distribute the weight to the keel. Stuart mentioned that in one of the articles on NavWeaps.

I think that efficiency also has a lot to do with it. In line weapons can bear to both broadsides.

[SilverHawk]

Roger that, perhaps you have a link to Stuart's site? I loving reading about military history. (Though I much prefer Air Force instead of the Navy, nobody can deny the allure of Battleships and Aircraft Carriers.)

[Thanas]

It's not really his site, but here is the link.

[SilverHawk]

Awesome, thank you much.

Edit : I loved the article on the CIWS, a lot of stuff I already knew about, but the indepthness (Is that even a word?) of the article was amazing.

[The Dark]

Not to veer too much off topic I hope, but what where the advantages of battleships switching to an in-line armored turret design instead of the old dreadnought set of having them on the starboard and portside rims of the ship?

I would assume an easier profile to armor and higher speeds because of the streamlined hull.

My understanding is that it, at least partially, has to do with the structures necessary to distribute the weight to the keel. Stuart mentioned that in one of the articles on NavWeaps.

I think that efficiency also has a lot to do with it. In line weapons can bear to both broadsides.

The latter's a good part of it. The British were originally wary of superimposing turrets because of concern that the blast from the upper turret would damage the lower turret. Since they didn't want to be limited to 4 guns (2 fore turret, 2 aft turret), they originally did the hexagonal design, so that three turrets could fire in each direction. They tried to reduce it to 4 turrets and have the midships turrets able to fire to either broadside or fore-and-aft, but they tended to damage the superstructure if firing on the opposite broadside (i.e. port turret firing to starboard). So, a hexagonal ship would have 12 guns, with 6 able to fire fore, 6 on either broadside, and 6 aft. A superimposed ship would have 8 guns, with 4 able to fire fore, 8 on either broadside, and 4 aft. However, it would also be using less displacement for the quantity of guns, allowing for either larger guns, more armor, or a faster ship. Additionally, it would have less beam, generally meaning it would be quicker for the same engine power. Once it was determined that the superimposed turret would not damage itself, it became standard.