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Quad 15s on a Pre-dread. Working as intended?


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On that note, I LOVE having triples for predreads. Very hurr durr big gun good, fits with the rest of the game very nicely.

 

On that note, because it's so exacerbated by it: why is balacing for predreads so wonky? Even with your twin 11s or what have you, it's impossible to get the ship balanced & have the rear turret in a reasonable-looking location: behind that breakwater. It seems like the CoP/CoB is far past the middle of the ship. Is the bow really that non-buoyant?

 build_Mpi3VCHEWa.png.cca2e56cbbdb7535d7e51b3c781f2131.png

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Well... from a historical perspective hydrodynamics were just in their infancy in the pre-dread era, so although I couldn't say for certain (as it's not a period I've researched a while lot) I wouldn't be surprised if pre-dreads were indeed highly unbalanced, and they simply added balast to trim the vessels back then.

Just food for thought.

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11 minutes ago, Draco said:

Well... from a historical perspective hydrodynamics were just in their infancy in the pre-dread era, so although I couldn't say for certain (as it's not a period I've researched a while lot) I wouldn't be surprised if pre-dreads were indeed highly unbalanced, and they simply added balast to trim the vessels back then.

Just food for thought.

Lord Kelvin was around before the pre-dreads and the major calculations (basics of buoyancy) not to mention sailing and ship design experience was already very mature by then (iterative design improvements is well ingrained in the naval architecture design cycle). Saying that naval architects didnt know how to trim vessels back then is kind of very farfetched. This assumption also seems to completely ignore machinery weight which is a sizable amount and typically located further aft.

This aside, it only further highlights the glaring need for more improved designer otherwise everyone's designs are going to be same without the ability to balance machinery spaces and weights within the vessel.

Edited by coalminer
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Okay so first off, I did not say naval architects didn't know how to trim vessels, please don't put words in my mouth. I said the main solution involed balast rather than hydrodynamic calculations.

Second, there is a BIG difference between basic buoyancy (aka. Will it float at all?) and then to advanced hydrodynamics (how much will the ship's speed and accuracy be affected by weight distribution, water flow, specific hull form, wind direction, varying sea states, temperature ect.)

Don't conflate the two.

Basic buoyancy has been a known factor since the Vasa and the Mary Rose capsized, whereas hydrodynamics weren't fully understood until well after WWII.

In this sense, the game is actually giving us access to information that wouldn't and couldn't be known entirely until well after the end of the game by displaying a stability percentage in the ship builder.

That's all I was saying.

Edited by Draco
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14 hours ago, Draco said:

Basic buoyancy has been a known factor since the Vasa and the Mary Rose capsized

That's pretty much the issue here.  It isn't that we know or don't know exactly how unbalanced the ships are, its that one can easily make a rough guess on paper of how weight is going to be distributed by the game's time period, and as a result the idea that designers couldn't estimate that a design would incredibly heavy towards the bow is preposterous.  And so we get predreads that are ridiculously bow heavy for no easily discernable reason when to the best of my knowledge ships at the time, would if anything, be stern-heavy as a result of it being easier to put things away from the part of the ship that needs to shove its way directly through water.

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Battleship-Mikasa-from-JFS1906-Cropped.p

Here's an image of the Mikasa.
Notice how the majority of the weight is situated considerably fore of the centre point of gravity in the ship.
Perhaps you give long dead designers too much credit?

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1 hour ago, Draco said:

 

Here's an image of the Mikasa.
Notice how the majority of the weight is situated considerably fore of the centre point of gravity in the ship.
Perhaps you give long dead designers too much credit?

Perhaps you can point what where specifically it provides the centre point of gravity on this image? All i see are armaments and armour layouts which also does not include any weight numbers or stability calculations and machinery spaces. This image on wiki is credited to Janes which as far as I am aware would not have access to such (back then) state of the art engineering drawings.

Since we are citing wiki, looking at the preceeding Formidable class which the Mikasa is based off on, these numbers are  provided (Freeboard was 23 ft (7.0 m) forward, 16 ft 9 in (5.11 m) amidships, and 18 ft (5.5 m) aft.) considering that the Formidable class did not have (or had minimal sheer) in the deck from pictures and drawings, this provides that the designers or atleast the sailors knew that ships ought to be trimmed aft to provide optimal sailing conditions, sure they could have been ballasted, but knowing that the hull had X volume and displacement, any engineer of the day would not dedicate such weight to ballast. Why add weight for balance when it could be built from the start for the aft trim or atleast even keel.

They might not have advanced CFD software but they sure werent going in blind like idiots either. I am not going to do a full literature review for you but heres an article from 1880 on Naval Architecture and the basics of ship stability, sure the illustration in the article is calculating for transverse stability but the formulas for longitudinal stability are more or less the same.

https://ia800708.us.archive.org/view_archive.php?archive=/22/items/crossref-pre-1909-scholarly-works/10.1016%2F0016-0032%2880%2990459-7.zip&file=10.1016%2F0016-0032%2880%2990617-1.pdf

The Royal Institute of Naval Architects was founded in 1860s and the theories were demonstrated by William Froude through testing in physical facilities, were they sitting around on their rear ends twiddling their thumbs? Maybe, but the Dreadnought did not capsize immediately upon launch, perhaps they were pretty good at guesswork. Take it however you want it, I am giving credit to those who pioneered the field of engineering and naval architecture.

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On 9/19/2021 at 10:28 PM, Draco said:

Okay so first off, I did not say naval architects didn't know how to trim vessels, please don't put words in my mouth. I said the main solution involed balast rather than hydrodynamic calculations.

Second, there is a BIG difference between basic buoyancy (aka. Will it float at all?) and then to advanced hydrodynamics (how much will the ship's speed and accuracy be affected by weight distribution, water flow, specific hull form, wind direction, varying sea states, temperature ect.)

Don't conflate the two.

Basic buoyancy has been a known factor since the Vasa and the Mary Rose capsized, whereas hydrodynamics weren't fully understood until well after WWII.

In this sense, the game is actually giving us access to information that wouldn't and couldn't be known entirely until well after the end of the game by displaying a stability percentage in the ship builder.

That's all I was saying.

Yamato's bulbous bow was extensively tested in towing tanks and she was built before the end of WW2, advanced hydrodynamics was a well known subject and further improved upon by the availability of advanced CFD. The Iowa classes were also completed before the end of WW2. Why bring up the Vasa and Mary Rose where actual first hand documentation is scarce for wooden sail boats when the Turbinia was built, tested and improved upon by well known methods in 1890s?

on the 2nd, the term "fair winds and following seas" has probably been around for a long time (since the age of sail at the very least) which meant the effects of sailing into head seas was atleast known to affect vessels. Without basic buoyancy there is no advanced hydrodynamics, they are interlinked concepts.

And what I'm saying is the designer is a poor representation of how ship design is done with the limitations as is. Balance (weight distribution) and a number of items are abstracted very poorly (and has been demonstrated in numerous other threads).

Edited by coalminer
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1 hour ago, coalminer said:

Why bring up the Vasa and Mary Rose where actual first hand documentation is scarce for wooden sail boats when the Turbinia was built, tested and improved upon by well known methods in 1890s?

To emphasize that I am not challenging the ability of 1900s naval designers to build ships that don't sink upon contact with the water, which you still seem to be suggesting (and correct me if I am mistaken on that).

 

1 hour ago, coalminer said:

And what I'm saying is the designer is a poor representation of how ship design is done with the limitations as is.

And I never challenged that either.

 

1 hour ago, coalminer said:

Yamato's bulbous bow was extensively tested in towing tanks and she was built before the end of WW2, advanced hydrodynamics was a well known subject and further improved upon by the availability of advanced CFD.

Bulbous bows were invented after the advent of capital ships such as HMS Hood which lacked ram-bows, which in turn proved to have poorer hydrodynamics than some dreads and pre-dreads who had them, forcing engineers to go back and come up with equations for why they weren't getting the calculated amount of knots for their horsepower... Thus discovering that ram-bows could have benificial hydrodynamic properties, which could then be further improved by being built specifically with that in mind, hence the bulbous bow.

Again I never said it wasn't a known field of factors by WWII, I said it wasn't a fully understood field of factors, which means, in case anyone here wants to twist my words again, that there were still "a few" lessons left to be learned come the end of WWII, rather than "nobody knew anything and half the ships launched just straight up sank when they hit the water".

In case anyone needs further clarification, ballast doesn't nessecarily mean a stack of bricks at the bottom of the ship.

It can and often does involve a tank or series of tanks along the keel with direct access to the sea that pumps water in or out as ammunition, fuel, food or other consumables that also affect a ship's trim are expended/consumed, precisely to maintain optimal trim at all times.

Think of it less as useless weight and more as counterflooding's refined sibling.

Naval designers that do not employ such ballast are therefore much more likely to see their ships sink due to inflexible distributions of weight that cannot be rectified on the go.

Therefore, when we talk about stability in this game, we assume that the trim of a given vessel is already near-enough on a perfect keel, regardless of the arbitrary stability % displayed in the designer.

What the % marker indicates is how much of the ship's "static" weight is as close to the centre of the ship as possible, and how much of the non-centered weight is offset by similar weights on it's opposite side.

The reason that this is shown at all is because the more weight you have at the ends of a ship, the more effort you have to expend adjusting your trim, not to mention that this complex process is impossible to relay directly to your gun crews in real time, and therefore affects accuracy, and potentially floatability aka buoyancy (once you start taking hits at least). And it is this aspect of hydrodynamics that were still coming into light in the 1890s.

Furthermore, to determine this %, you don't need Froude's formulas, you just need to grab a trusty old ruler, hold it up to your screen over the Mikasa image, and conclude that the unarmoured bow section of the ship is a good 1/3rd shorter than the unarmoured stern section. You also don't need Froude's formulas to realize that the centre of gravity is likely very close to the centre of that armoured section. It thereby follows that ballast trim in the aft of the ship was most likely involved in maintaining an even keel, either in the form of fuel, food, fresh- or seawater tanks as described above, and quite possibly all of said categories.

I hope that all that clarified that I neither disagree with your statement that this aspect of the ship designer could use improvement nor that I am suggesting that naval designers in the 1890s were complete morons.

I was simply voicing what I thought to be a less considered point of view on the matter.

Edited by Draco
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On 9/19/2021 at 12:05 AM, neph said:

Just for comparison: (and this isn't just this hull, it's uniformly all predreads & pre-dread cruisers)

4Fv1RiBKIn.png.9e31e82fdfc75079aa28645eeb43b835.png

 

With the new armor system you can always add some additional armor to the aft to balance the ship.

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5 hours ago, davidt_man said:

 

With the new armor system you can always add some additional armor to the aft to balance the ship.

I reckon I may need a bit more than "some"!

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