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Colosseum
Post subject: Re: North PointPosted: September 7th, 2010, 5:44 am
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[ img ]

Slightly updated, there were some discrepancies from the original drawing that I had to correct, such as the odd position of the bridge wings, which didn't seem to make any sense.

Make sure to hard refresh (hit F5). Also placed the helicopter off the deck to signify the lack of hangar since there's no space for it apparently. Also deleted the top Mk19 mount that would have its gunner fried by the radar emissions.

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TurretHead
Post subject: Re: North PointPosted: September 7th, 2010, 6:02 am
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OK I had a look at the original drawing which had some more data as well. Anyway a typical 2,000 ton LST type merchant ship (and there are a few in service around the world, especially in south east asia) would cost around $30 million.

Vossiej's original ship has stuff in it that makes no sense. Like the Gas Turbine. Even with a gas turbine you aren't going to power a ship with a bow door and ramp able to be beached over 20 knots. The shape of the hull so it can be beached just doesn't make it possible unless its a planning vessel which this is not. The bow looks pretty suspect like its a very sharp bow but in which case the bow door would be very narrow. Like too narrow for any thing wider than a jeep. The bow is too deep as well for any kind of clsoe to shore beaching.

Electronics like that air search radar and the Phalanx would add a fair bit of cost as well. I don't know about people getting fried by radars as the only one big enough to do anything is on top of the mast. Without a gas turbine I would estimate overall cost at $50 million. With high power engines like the gas turbine you are probably looking at $75 million.

My source for this has been the list including costs or all ships built in Australia since 1995.


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Colosseum
Post subject: Re: North PointPosted: September 7th, 2010, 6:38 am
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Good, I've been basing a lot of my decisions off the navies of small countries, specifically Australia, New Zealand, and Japan.

I suspected that the bow was too deep. I'll have to make it shallower a la the original LST:

[ img ]

Would a slowly sloping hullform like that make sense on this ship?

I'll also make the bow doors a bit wider, I had suspected that they were too small.

As far as engine suggestions go, really not my area of expertise. I'll revise the price once I find a little bit more out.

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Colosseum
Post subject: Re: North PointPosted: September 7th, 2010, 7:09 am
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OK, updated it. Refresh again.

[ img ]

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TurretHead
Post subject: Re: North PointPosted: September 7th, 2010, 7:27 am
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Colosseum wrote:
Would a slowly sloping hullform like that make sense on this ship?

I'll also make the bow doors a bit wider, I had suspected that they were too small.

As far as engine suggestions go, really not my area of expertise. I'll revise the price once I find a little bit more out.
Yeah the slope is literally there for the ship to match the slope of the beach which extends under water. All the LST types have that slope. So if you have a deep hull at the bow the ramp will be up in the air and need to be really long to reach the surface.

PS I've been reading a lot about ship design recently because apparently the future of employment for aerodynamicists in Australia is in submarine design.


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Colosseum
Post subject: Re: North PointPosted: September 7th, 2010, 7:39 am
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OK, so it looks alright? What are my options for engines etc?

Kind of makes me realize that not much thought was put into the original design. Come on guys, just drawing a nice ship isn't all there is to this hobby... it also needs to be realistic.

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Gollevainen
Post subject: Re: North PointPosted: September 7th, 2010, 8:36 am
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Diesels for egnine room.
If my mememory serves me correct (without my libary at my reach) most LST size ships have actually rather strong engines by output, needed to move the hydrodynamically inferior bow shape in desirable speed.

Japan, South Korea, France have build ships of this size, also Iran and Libya operates(ted) with similar size British build ships. Also Turkey, Philiphine and Indonesian navies have considerable size LST fleets of western composition. Should seek from there to find good data. www.hazegray.org migth be best place, if their old "world navies today" section is still visible.

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TurretHead
Post subject: Re: North PointPosted: September 7th, 2010, 8:47 am
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I think you've made it look a lot better. The propellers are protected as well which one would think is pretty important when you intentionally bottom your ship on the ocean floor all the time.

As to engines just a couple of diesels should be fine. The problem with LSTs is the bluff bow needed to hold a ramp produces turbulent flows at lower speeds. So now matter how much power you put into your thrust you are going to run into the ‘hump’ at the 10-15 knot mark in which you need to exponentially increase thrust to get through it. So to drive a bluff bow ship at 27 knots is going to require a huge increase in power over a similar sized piercing bow ship. Even with a sharp bow the lack of depth to the bow needed to bottom on a beach floor creates problems.

The real solution to making fast LSTs is big ramps or in this case an extendable pontoon as a ramp:

[ img ]
http://www.nps.edu/academics/gseas/tsse ... ect_2.html


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Vossiej
Post subject: Re: North PointPosted: September 7th, 2010, 1:08 pm
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Colosseum, is it allright if I use your modifications on my Indonesia variant? The new bow etc.

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Gollevainen
Post subject: Re: North PointPosted: September 7th, 2010, 1:26 pm
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As to engines just a couple of diesels should be fine. The problem with LSTs is the bluff bow needed to hold a ramp produces turbulent flows at lower speeds. So now matter how much power you put into your thrust you are going to run into the ‘hump’ at the 10-15 knot mark in which you need to exponentially increase thrust to get through it. So to drive a bluff bow ship at 27 knots is going to require a huge increase in power over a similar sized piercing bow ship. Even with a sharp bow the lack of depth to the bow needed to bottom on a beach floor creates problems.
Another solution would be sort of arragment that the USN Newport class used. Thougth they were considerably larger ships (but still classed as LST). In USN, I recall reading that the 20 something knot designed speed for ambhipious assault task force gave most of the speed proplems, but In smaller navy designing homebuild ships, the speed requirment should be naturally looked from their own strategy perspective. Naturally all other aspects like defensive armament and the vessels capacity to act as seccondary logistical support ship should be seen against wheter the Navy wants to use them? In large massed beaching assaults of strategical level, or in lot smaller scale landings?

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