Shipbucket

Another funny one from you....


I will not recommend to be on that ship that get a 76mm shell fired in to it... There are shells for various operation. one of the reason Norway did go for 76mm is because if the have to use the 76mm as an long rang CIWS, they can send up bigger high exploding shells than what the 57mm can. but the 57mm have higher fire rate.

oh it's easy to sink a fishing boat with an 7.62mm. Remember when the old Oslo class once accidentally fired 3" shells in to a target ship (old fishing trawler), well four shells from it's twin 3" guns was enough to sink that vessel, and it was a vessel in the 80 meter size with it's multiple fish-tanks... but an 3" high exploding grenade can do very nice damage.

I was drawing a parallel between trying to sink a large commercial vessel like a container ship or cruise ship with a medium caliber naval gun -- be it a 57 or a 76 -- is like trying to sink a fishing boat with a 5.56 or 7.62mm RIFLE. 7.62 not 76.2!!! The kind an infantry man carries today. An M16, a FAMAS, a G34, an FN-FAL, and AK47, etc. Because those 76mm shells are about 10x the diameter of the 7.62mm bullet and that cruise ship is about 10x the length of the fishing trawler. Punching very small holes in very big things don't sink them very quickly.

That's blatantly untrue...

An object made from a material heavier than water -- steel, aluminum, fiberglass, etc. -- which is filled (entirely with water) is not buoyant. It sinks. An object filled with water is buoyant if and only if the material itself is lighter than water

The sonar pod itself was added after the original geometry of the hull was designed. If the sonar pod is heavier than water it is like hanging a rock from the bow. If it is lighter, it is like hanging a balloon. In most such installations the pod will be designed such that it's total weight for the enclosed volume is about the same as the water it displaces so it doesn't actually require ballasting in the stern for balance. The construction materials and the sonar equipment will be heavier. But, you can easily build in an appropriate air space or two to balance them out. It won't be very precisely neutral, but a little bit of extra weight or lift (say +- 100kg) in the bow doesn't amount to much on a vessel of this size. It'll be like a sailor standing on deck. neat the bow. You wouldn't ballast for that; it wouldn't affect trim tangibly enough to matter.

Wave piercing is not that esoteric. It's actually very simple. At hull speed... roughly 1.34 x sqrt(length_in_ft)... the wave length of the wave made by the ship is roughly the length of the ship. When they happens the ship sits in the middle of a valley with the peaks of the wake it makes near the bow and the stern. To go faster it needs to climb the bow wave, which means engine power has to fight not just hydrodynamic resistance but gravity. Lifting a 5000 ton ship is a lot of work so a lot of power is needed to go a little bit faster. But this is assuming that you are actually climbing the bow wave...

In a ship whose bow is very slender, the magnitude of the bow wave is minimized. This make it easier to climb -- reduces the gradient if you will. In a ship whose bow is very slender compared to the waist amidships and the which has a flat transom stern. The buoyancy is concentrated in the middle and near the nose the ship isn't very buoyant. The bow hence tends to cut deeper into the bow wave as it sinks into it while the ship's middle and stern resists sinking lower. In a tumblehome hull, this is aided further by the fact that you have less and less additional enclosed volume the deeper you sink into the water. We don't have that here, but we do have a very, very, narrow bow with very little flare.

A design like this goes faster and needs less engine power to maintain a good cruise speed. They do get wetter in front in heavy seas compared to ships with a hurricane bow. This is in part mitigated by the fact that the freeboard is about 7~8 m above the waterline depending on the loading, and the gun, VLS cells and all that is very far from the bow. Compared to the Zumwalt, because the bow actually is slightly flared and not a tumble home and the sides are traditionally flared, the ship is less prone to rolling over in heavy seas with waves come from the sides or the rear quarter.

I think that the Oto Melara 76 mm is still better than the 57 mm because it has the capability to fire DART guided antimissile munitions (on a modified mount).

oke, if you design it to be weighing exactly the same as the volume, it does not change the trim. however, it does change the overall CoG, center of bouyancy, wet surface, forward surface, moments of intertia, the spread of volume over the hull and the full hull volume. and thus the way forces on the ship work, the stability, the way the ship moves, the power the engines require, the point the hull turns around, the impacts of waves on the ship........
let me put an example to explain all that simple: if you have an empty bucket floating in the water, or you fill that bucket up with water. if you fill it up, it moves differently, right? and that is all you do here, you add weight and volume to an already existing hull (or remove it) and to check if all still works you have to recalculate everything.

the fact that you add the sonar bulb late in the hull design process is a bad thing as well, btw, as then again you can recalculate the entire forward hull for pressures, weights, etc, something you could have avoided by incorporating it earlier. of course this does not go for your drawing, but it goes that way for real ships, where everything has to be correct.

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Navy inside baseball here, it was the money. Nothing more. Of course the program managers are saying the 30mm is better anyway to justify the downgrade in capability but the actual original reason is dollars.

Interesting Shipright. I'll certainly file that away.

Dwight, something occurred to me while I was posting in another thread. Do you intend to draw either version of your ship in Shipbucket scale and to Shipbucket style? I ask because if not, then the thread is really in the wrong place and I'd request that you request that Golly or Colo move it to the Non-Shipbucket Drawings section of the message board.

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Heh. There's a few youtube clips about the new 30 mm mount out, and in one the damn thing can't even hit a remote controlled semi-rigid inflatable craft... Coming right at the target ship.

57 mm airburst would be a LOT more effective.

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Would you please not eat my gun...

The projetion drawings are pretty close to shipbucket style. They are of the correct scale. The problem is that this started out as a 3D parametric model and I CANNOT render it with zero anti-aliasing. To observe SB style strictly, I'll need to hand trace that in photoshop and manually trim pixels and edges. I didn't get around to it yet.

Speaking of that, those 3P ammo are expensive. For 3~4km range -- which is where most engagements of this sort occur -- they should just make a shot shell for the 57 and 5" guns. Forget tungsten... a few thousand 00 steel bucketshot will work just fine. You can miss by 2~3 m and still pepper the antagonist.