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Author Topic: aircraft carrier  (Read 5981 times)

regiment

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aircraft carrier
« on: May 29, 2009, 11:42:45 am »

silly question how much of an aircraft carrier is under water thanks as i said a silly question
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furball

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Re: aircraft carrier
« Reply #1 on: May 29, 2009, 11:48:56 am »

Depends on the carrier I suppose...e.g. 1937 Ark Royal - all of it - but that's probably not quite what you wanted to know... {-)

Lance
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madrob

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Re: aircraft carrier
« Reply #2 on: May 29, 2009, 01:10:39 pm »

When i got my plans for hermes, i was suprrised just how little of it there is underwater
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andyn

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Re: aircraft carrier
« Reply #3 on: May 29, 2009, 03:31:19 pm »

A surprisingly small amount, as they are large, but comparative to their size they don't weigh much, being flat bottomed and thus more stable, they can get away with it.
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Leaky

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Re: aircraft carrier
« Reply #4 on: May 29, 2009, 03:57:41 pm »

And most weight is fairly low down with hangers etc being below the flight deck and fuel,ordnance etc being kept in the bowels of the ship.Big saving in superstructure as well :-)
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Bryan Young

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Re: aircraft carrier
« Reply #5 on: May 29, 2009, 06:59:31 pm »

"Flat bottom" has nothing to do with it. A flat bottom is a weak bottom (I'm still talking about ships).
Until you start talking about large tankers and so on, I would posit that the heavy Warships will draw between 30' and 35'. It takes an awful lot of "deadweight" to go beyond that. Warships do not, in general, change their draught significantly. Not like a cargo ship does. "All" a warship does is expend fuel and sometimes ammunition. This is possibly why warships are rated on "net" tonnage and not subject to the various sorts of tonnages that apply to non-warships. BY.
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Notes from a simple seaman

Bryan Young

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Re: aircraft carrier
« Reply #6 on: May 29, 2009, 07:08:06 pm »

Sorry, I forgot to add to the previous post a thing called "TPI". This is Tons per inch immersion. If, for instance, a General Cargo ship has a TPI of 50, you can fairly easily work out how many tons of deadweight she can carry. I would imagine that a large (US) carrier would have a TPI closer to 200. Hence not much change in draught. Sorry for the omission. BY.
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Notes from a simple seaman

regiment

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Re: aircraft carrier
« Reply #7 on: May 29, 2009, 07:54:11 pm »

yer but to an oap how much is below the water  line.. in feet and inches please
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andyn

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Re: aircraft carrier
« Reply #8 on: May 29, 2009, 08:15:51 pm »

30' and 35'

A flat bottom boat may be weaker, but it reduces the total amount of boat in the water, because there is no pointy low volume bit sticking down...
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craftysod

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Re: aircraft carrier
« Reply #9 on: May 29, 2009, 08:22:26 pm »

I disagree with you on one point Andy,after serving 3yrs on Invincible and another 2yrs on challenger,the flat bottom ships roll like a pig.
Bit like a cork on water
Mark
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andyn

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Re: aircraft carrier
« Reply #10 on: May 29, 2009, 08:26:48 pm »

I have two kayaks, the playboat is flat bottomed and slab sided, and the tourer is rounded, the playboat rolls a lot, as you say, but takes one hell of a lot of effort to get it to go over, the rounded one with boat shaped fore and aft does not roll in general, but goes over without an effort at all...

Scale it up by a few hundred feet and you will have the same charecteristics
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dougal99

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Re: aircraft carrier
« Reply #11 on: May 29, 2009, 08:34:10 pm »

yer but to an oap how much is below the water  line.. in feet and inches please

According to Wikipedia (and I know it can be horribly wrong) Invincible has a draught of 28ft 10.8" (28.9ft)

http://en.wikipedia.org/wiki/Invincible_class_aircraft_carrier

HTH

Doug
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Bryan Young

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Re: aircraft carrier
« Reply #12 on: May 30, 2009, 07:48:09 pm »

yer but to an oap how much is below the water  line.. in feet and inches please
I did say between 30' and 35'.
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Notes from a simple seaman

Bryan Young

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Re: aircraft carrier
« Reply #13 on: May 30, 2009, 07:59:17 pm »

30' and 35'

A flat bottom boat may be weaker, but it reduces the total amount of boat in the water, because there is no pointy low volume bit sticking down...
How on earth do you come to that conclusion? Weight is weight, and weight alone decides the draught at which a ship floats. Square, Round, Triangular or whatever shape you can dream up...it's weight. Didn't Archimedes teach you anything!
The reason I said really flat bottoms were weak bottoms was mainly because the outer shell plating of the hull does have a slight upward bias from the centre outwards. The double bottom is, however, horizontal. This combination gives a cantilever effect that is stronger than a stright forward box section. OK now? BY.
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Bryan Young

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Re: aircraft carrier
« Reply #14 on: May 30, 2009, 08:18:31 pm »

I'll try again!
The sort of rolling that has been mentioned has nothing whatsoever to do with the shape of the hull (except in extreme cases). Are you tryng to tell me that HMS "Victory" didn't roll much because she had (has) a rounded hull?  No. It's all down to "static stability" (not "dynamic stability" which is another subject altogether). Static stability depends to a large extent on "metacentric height". An example of this would be the LSLs ("Sir Tristram" etc) that could have a metacentric height of up to 14ft. Most ships would aim for about 3ft. This height (measured upwards from the ships centre of gravity) really determines the ships ability to revert to the upright condition after being shoved over by an external force (a wave for instance). Therefore it follows that a ship with a small MH, while still being stable, will have a lower period of roll than one with a high MH. It's all to do with "righting levers" that we learned at school. "Give me a lever long enough, and a fulcrum, and I can move the earth". (Was that Atlas?.....).BY.
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Bryan Young

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Re: aircraft carrier
« Reply #15 on: May 30, 2009, 08:21:24 pm »

I have two kayaks, the playboat is flat bottomed and slab sided, and the tourer is rounded, the playboat rolls a lot, as you say, but takes one hell of a lot of effort to get it to go over, the rounded one with boat shaped fore and aft does not roll in general, but goes over without an effort at all...

Scale it up by a few hundred feet and you will have the same charecteristics
No you won't. Centre of gravity is all wrong in a kayak. Thats why the long paddle is used like a tightrope walkers pole. BY.
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Notes from a simple seaman

andyn

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Re: aircraft carrier
« Reply #16 on: May 30, 2009, 08:29:32 pm »

I have two kayaks, the playboat is flat bottomed and slab sided, and the tourer is rounded, the playboat rolls a lot, as you say, but takes one hell of a lot of effort to get it to go over, the rounded one with boat shaped fore and aft does not roll in general, but goes over without an effort at all...

Scale it up by a few hundred feet and you will have the same charecteristics
No you won't. Centre of gravity is all wrong in a kayak. Thats why the long paddle is used like a tightrope walkers pole. BY.

Actually no it isn't, a paddle is a liability and adds instability. Thats why if you get the angle slightly wrong you end up having to move to correct yourself. All the stability in a kayak comes from the paddler leaning. I think you'll find the charecteristics are exactly the same whether you're in the boat or not. Infact in the case of the square playboat, even more so.

Another thing, the paddle is not long at all, you want one that is as short as you can possibly allow, so that when you have your upper arms oustretched, and forearms bent at 90 degrees, you have around three inches between the end of your hands and the start of the feathers. Any longer and you will tire far too quickly.

I'm afraid an arguement in kayaking with me is a complete waste of time. I've been doing it for nigh on 3 years now.
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BarryM

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Re: aircraft carrier
« Reply #17 on: May 30, 2009, 08:40:04 pm »

I'll try again!
The sort of rolling that has been mentioned has nothing whatsoever to do with the shape of the hull (except in extreme cases). Are you tryng to tell me that HMS "Victory" didn't roll much because she had (has) a rounded hull?  No. It's all down to "static stability" (not "dynamic stability" which is another subject altogether). Static stability depends to a large extent on "metacentric height". An example of this would be the LSLs ("Sir Tristram" etc) that could have a metacentric height of up to 14ft. Most ships would aim for about 3ft. This height (measured upwards from the ships centre of gravity) really determines the ships ability to revert to the upright condition after being shoved over by an external force (a wave for instance). Therefore it follows that a ship with a small MH, while still being stable, will have a lower period of roll than one with a high MH. It's all to do with "righting levers" that we learned at school. "Give me a lever long enough, and a fulcrum, and I can move the earth". (Was that Atlas?.....).BY.

Archimedes, I think, Bryan.

Cheers,

Barry M
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Rex Hunt

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Re: aircraft carrier
« Reply #18 on: May 30, 2009, 10:00:46 pm »



Actually no it isn't, a paddle is a liability and adds instability. Thats why if you get the angle slightly wrong you end up having to move to correct yourself. All the stability in a kayak comes from the paddler leaning. I think you'll find the charecteristics are exactly the same whether you're in the boat or not. Infact in the case of the square playboat, even more so.

Another thing, the paddle is not long at all, you want one that is as short as you can possibly allow, so that when you have your upper arms oustretched, and forearms bent at 90 degrees, you have around three inches between the end of your hands and the start of the feathers. Any longer and you will tire far too quickly.

I'm afraid an arguement in kayaking with me is a complete waste of time. I've been doing it for nigh on 3 years now.
[/quote]

I have been a canoeist since 1973 (although they do seem to be a lot smaller these days!)

Paddle choice depends on the type of canoeing being enjoyed.

Short for Slalom and Polo
Long for long distance endurance type events........(would hate to have to paddle with a diddy one on the Devizes to Westminster!)

As usual......horses for courses.


Rex
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andyn

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Re: aircraft carrier
« Reply #19 on: May 30, 2009, 10:09:10 pm »

Quote
Short for Slalom and Polo
Long for long distance endurance type events........(would hate to have to paddle with a diddy one on the Devizes to Westminster!)

Thats true yes, but I wouldn't want to try playing with a six yard paddle...
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Navy2000

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Re: aircraft carrier
« Reply #20 on: May 30, 2009, 10:54:03 pm »

Nimitz class CVn are between 37.7 feet and 38.4 feet in draft. It just depends on each CVN's displacement that they have.

Duane
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Arrow5

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Re: aircraft carrier
« Reply #21 on: May 31, 2009, 06:29:11 am »

Euclid, long lever and place to stand ?????????
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..well can you land on this?

BarryM

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Re: aircraft carrier
« Reply #22 on: May 31, 2009, 09:19:51 am »

"Give me a fulcrum and a place to stand and I'll move the world" - Attributed to Archimedes of Syracuse.

Barry M
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Bryan Young

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Re: aircraft carrier
« Reply #23 on: May 31, 2009, 05:48:17 pm »

Euclid, long lever and place to stand ?????????
Thank you. Just proves my lack of a classical education. BY.
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Notes from a simple seaman

BarryM

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Re: aircraft carrier
« Reply #24 on: May 31, 2009, 05:56:23 pm »

You were closer Bryan; at least you knew it started with an "A".

Barry M
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