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KWAM
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 18th, 2016, 8:49 pm
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BB1987 wrote:
I'm just speculating, but would it be possible, if needed, to fit a sonar inside the shipìs bulbous bow?
Yes, it would be, and Yamato's original Type 0 sonar array was part of her bulbous bow.

Having a lot of belated realizations I should've had a week ago.


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TimothyC
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 18th, 2016, 11:55 pm
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KWAM wrote:
Having a lot of belated realizations I should've had a week ago.
First, welcome aboard, and you've posted a first work that puts mine to shame.

Second, welcome to the shipbucket process. We all find things later that we want/need to change.

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citizen lambda
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 19th, 2016, 10:57 am
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KWAM wrote:
The VL-ASROC wasn't added originally because the ship doesn't carry sonar and I wasn't sure quite sure whether it would actually work without it. But, I just had the (horribly belated) realization that it would be possible for an escort to find the sub, then relay a firing solution to the Yamato through a datalink and have Yamato fire the ASROC instead, almost like an arsenal ship. I'll add it along with the RAMs that I forgot.
That works too provided you have the datalink, but even without ship-to-ship cross-targeting, you can just download target location from the ship's helos, reducing the load they have to carry on close-in patrols. VLA doesn't have range beyond self-defense against modern torpedoes anyway.
You've mentioned adding a bulb sonar, which would probably allow direct targeting of the VLA. You might want to find some space (say on the sponsons near the aft SeaRAMs) for a pair of Mk.32 self-defense torpedo tubes.
KWAM wrote:
About the VLS as a whole, I did check. A 4 cell wide Mk 41 is around 125" or 3.47m. I'm trying to do this thing with 16 cell wide Mk 41s, so it's around 14m wide total. The length of the VLS was never really a concern. The Yamato's hull has a beam of 38.9m (very nearly double that of an Atago-class destroyer, which has a beam of 21m), and the forward section of the ship was also lengthened by 15m so it's not really replacing anything. Even if the forward section hadn't been lengthened, the only thing there is crew quarters which aren't too important with the reduced size of the crew. At the position the VLS is to be added, the hull is wide enough even at the waterline, which is only reached by the 64 strike length cells in the middle anyway (the 64 on the sides are self-defense length). It might be cutting it close, but there is more than enough room for the forward VLS to fit as-is, even without lengthening the forward section.
I did a quick check-fit based on the position of the VLS blocks in your drawing and a publicly available top view (of the original ship without lengthening, of course). Let's not question the advisability of cutting open a 75-year old hull to add a plug made of modern materials, that's your scenario after all.
You have apparently taken blast mitigation into account to an extent, judging by the blast shields between gun turrets and VLS, so for the purpose of this check-fit I have standardized a blast zone of 50px in front of the gun tubes.
Without any lengthening and sticking to your 16-abreast configuration, I pack only two 8-cell blocks less forward than you do, for a grand total of 288 cells. OTOH, barring other equipments, I managed to comfortable fit 24 cells abreast in three lines of 8, with space for two corridors inbetween. With that arrangement, you can pack up to 144 cells forward and 288 aft.
You might go even further by rotating the VLS blocks 90°, but I haven't tested that yet.
KWAM wrote:
EDIT: Has the JMSDF ever operated (or planned to operate) the SM-2ER? If they have I might as well add that one too.
The SIPRI database mentions only SM-1MR, SM-2MR and later SM-3 BLock-3/A/B, all of which are MR missiles. That being said, I don't see what would technically prevent you from adding SM-2 Block-4 or even SM-6/ERAM since you already pack SM-3s.

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KWAM
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 19th, 2016, 4:10 pm
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citizen lambda wrote:
That works too provided you have the datalink, but even without ship-to-ship cross-targeting, you can just download target location from the ship's helos, reducing the load they have to carry on close-in patrols. VLA doesn't have range beyond self-defense against modern torpedoes anyway.
You've mentioned adding a bulb sonar, which would probably allow direct targeting of the VLA. You might want to find some space (say on the sponsons near the aft SeaRAMs) for a pair of Mk.32 self-defense torpedo tubes.
Yeah, I've added the bow sonar and SVTTs. Not too sure about what sort of vulnerability these tubes would pose if they were hit by enemy fire, but we're both here adding a few hundred VLS cells outside the armored citadel so clearly none of us care too much about that.
citizen lambda wrote:
I did a quick check-fit based on the position of the VLS blocks in your drawing and a publicly available top view (of the original ship without lengthening, of course). Let's not question the advisability of cutting open a 75-year old hull to add a plug made of modern materials, that's your scenario after all.
You have apparently taken blast mitigation into account to an extent, judging by the blast shields between gun turrets and VLS, so for the purpose of this check-fit I have standardized a blast zone of 50px in front of the gun tubes.
Without any lengthening and sticking to your 16-abreast configuration, I pack only two 8-cell blocks less forward than you do, for a grand total of 288 cells. OTOH, barring other equipments, I managed to comfortable fit 24 cells abreast in three lines of 8, with space for two corridors inbetween. With that arrangement, you can pack up to 144 cells forward and 288 aft.
You might go even further by rotating the VLS blocks 90°, but I haven't tested that yet.
Here's what I was going for:

[ img ]

The light blue is the shape of the hull at the waterline and the green is the citadel (both are taken from Janusz Skulski's Battleship Yamato).

I deliberately tried to avoid cramming every available square foot of deck space with VLS cells. The 144 fore and 288 aft seems powerful on paper, but would probably look pretty silly in execution. Plus, most modern Aegis ships don't actually devote that much deck space to VLS anyway. The number I ended up with seemed like the largest number of VLS cells I could fit while still maintaining some semblance of practicality (not compromising the hull integrity more than it already has been, leaving room for other equipment, etc).
citizen lambda wrote:
The SIPRI database mentions only SM-1MR, SM-2MR and later SM-3 BLock-3/A/B, all of which are MR missiles. That being said, I don't see what would technically prevent you from adding SM-2 Block-4 or even SM-6/ERAM since you already pack SM-3s.
I want to stick to weapons that the JMSDF actually use. The MCLWG in the early versions was an exception because it was used in the original image that inspired this whole thing. The 46cm guns are also an exception since Yamato isn't Yamato without Yamato's guns. Outside of those two though I'm keeping it to actual JMSDF weapons.

Also found out that that self-defense length cells can't actually launch the SM-2MR and only work with the Aster 15, Sea Sparrow and ESSM. Japan doesn't use the Aster and I'm pretty sure they no longer operate the Sea Sparrow, but they do use the ESSM on their newer second-line destroyers. Guess it's time to fill all the self-defense cells with ESSM quad packs, because who wouldn't want 256 ESSMs?


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erik_t
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 19th, 2016, 5:08 pm
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Frankly, I think I'd abandon the stretch, land the aft turret, and use the volume saved for VLS (probably with several feet of concrete in the bottom of the barbette for stability). Maybe sit the SSM box launchers above it, rather than several decks up where they're hard to get at. Heck, sit the VLS entirely above deck a bit forward, and now you have a helo hangar. And the VLS can have big blow-out panels like an Abrams turret or something, so we can lie to ourselves and say we're not really all that vulnerable to ship-killing damage.

But it's your drawing, of course ;)


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KWAM
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 19th, 2016, 6:09 pm
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erik_t wrote:
Frankly, I think I'd abandon the stretch, land the aft turret, and use the volume saved for VLS (probably with several feet of concrete in the bottom of the barbette for stability). Maybe sit the SSM box launchers above it, rather than several decks up where they're hard to get at. Heck, sit the VLS entirely above deck a bit forward, and now you have a helo hangar. And the VLS can have big blow-out panels like an Abrams turret or something, so we can lie to ourselves and say we're not really all that vulnerable to ship-killing damage.

But it's your drawing, of course ;)
I know one of the Iowa-class (USS New Jersey?) was originally going to get its rear turret removed for a VLS. But, I don't really feel like making such a massive change to the armament. Like I said before, Yamato isn't Yamato without Yamato's guns.

The stretch serves several purposes right now: it adds additional room for the VLS and other equipment if needed. It also streamlines the hull a little to improve hydrodynamics (length to beam ratio is a bit closer to the Iowas) so it can hold up a very small portion of the paper-thin reasoning for how a ship this massive somehow manages 30 knots.

This is probably a REALLY stupid question but isn't the VLS kind of its own blowout panel? The internal containers are designed to withstand the stresses involved with the launch of a missile anyway and there are systems to vent the gases out. If the VLS is hit and the missiles explode in their tubes, wouldn't most of the explosive force simply be vented out through these systems or out the missile hatch?


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erik_t
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 19th, 2016, 6:48 pm
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Regarding the stretch, it would be beneficial (in some senses) if it were added as a parallel midbody section, but as it is right now, you'd have to reshape the entire front half of the ship to take full advantage of the lengthening. Recall that (at least for our purposes) one of the goals is to minimize the rate of change of cross-sectional area as one moves from bow to stern, because this is the primary driver of wave drag (the Sears-Haack body is the analogous problem in high-speed aerodynamics). It would require detailed study to be sure, but I suspect the higher-order derivatives of cross-sectional area would be harmful rather than helpful if a bow stretch were added in this way.

Note the USN studied several Flight III Burkes (in the early 1990s) that would receive stretches; as far as the outer mold line is concerned, all these stretches were at the midsection, IIRC, with entire compartments moving as "rafts" in order to preserve weight and balance.

Regarding VLS and blowout, Mk 41 is designed to survive a single hang-fire (that is, a motor burning out on a stuck missile) without external damage. The dynamics of a bunch of solid rocket motors being hit by some sort of warhead is beyond my purview, but it is interesting to note that much of the justification for the Mk 57 PVLS was to move the VLS blocks to the edge of the hull, out through which they could expand in the event of serious damage. This test illustrates the problem (I don't remember the source, but I found it on the public internet).

[ img ]

It's... well, certainly not great for a ship if the VLS goes up in smoke.


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erik_t
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 19th, 2016, 6:50 pm
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I think the VLS question is really the following one: what is it for? Are you seeking an extremely robust self-defense capability, aiming to provide area air defense, hoping to duke it out in a missile duel with Kirov, something else...?

Even 32 or 64 cells, dedicated exclusively to Standard or ESSM, would be more than enough for many of these tasks.


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acelanceloet
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 19th, 2016, 6:54 pm
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viewtopic.php?f=13&t=4705 this topic might interest you, actually an real proposal for the iowa class.
what this and other real proposals make me wonder, is what the VLS might do when presented with the blast of one of those guns. the hatches are indeed partially blowout hatches, but what about external blasts?

as for the lengthening, keep in mind 3 things.
- the ship already is longer then the hull speed of 30 knots requires, so there will be no real difference in the resistance done by waves.
- just lengthening one part works in 2D, but you will have to change a lot of the bow to make the parts in front and aft of the lengthening fitted together again. (as these are the same beam at that point, while the new fitted part is not straigth at all
- because of the above, unless the entire forward half of the ship is reshaped, you will have no advantage at all from the additional length, because the ideal shape has not been reached.

that said, getting her to the speed of 30,75 knots while unchanged in hull shape would take, in my estimation, 143 MW, or 194560 shp. the bulges will add somewhat to that, but an new sonar dome, more effective (computer generated) propellers and possibly an more efficient coupling between engines and shafts might do the trick with your 200000shp.
that again said, I still believe an modernised steam powerplant could do an far better job at this then the gas turbines, which require an rebuild of the entire superstructure (large air intakes and the channels for them), might have trouble with the length of the exhaust channels (requiring an much larger funnel) , new internal arrangement (if only because the stability lost because of the loss of weight down in the ship, you could leave away your bulges if your engines are heavy if the current setup works) and need to be removed completely for maintenance instead of being serviced in the ship itself. but hey, your ship, your choices ;)

also, sniped by Erik, however, the Sears-Haack body is IIRC not usable here....... as those rules only apply in near supersonic speeds, which are not reached under water by ships. the waves forming around a ship work somewhat different, but an sharp, non-bumpy bow and stern shape are still what is required of an ships hull.

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erik_t
Post subject: Re: Battleship Yamato Aegis Modernization and RebuildPosted: August 19th, 2016, 7:10 pm
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The governing equations are certainly different, but the idea of smooth variation of derivatives is broadly applicable, I think.

A better question, IMHO, is what purpose a 30+ knot BBG serves that a 20 knot BBG would not.

In any case this takes us far afield of what is in a beginner's drawing section, and we are probably giving Colo subliminal fits talking about this crap ;)


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