aircraft carrier design question

Back in the old days it was the requirement to ship thru Panama. And of course speed, with e.g. the Essex having a fineness ratio of around 9 to 1. And with the introduction of deck edge lifts they mounted the lifts in a way that the didn’t protrude into the hangar space. The new Ford class for example is down to 7.7 to 1, and that’s already pretty plump for a fast ship. Certain seakeeping features also don’t improve when going for a lower fineness ratio. The only way to get a wider hangar deck would be a multihull design. If you “taper out” the hull right from the water line, you’ll get all kind of nasty effects in heavy weather and during harder maneuvers.

I wouldn’t worry about it coming into the hangar from the top in quantities greater than the scuppers can handle as that is only really a matter of small leaks around lifts and any other small openings. Any side openings should (must?) have weathertight closures. ROROs have the problem of vehicle decks low in the ship with bow doors that let it in from the front in big chunks – Herald of Free Enterprise, Estonia, etc.

Absolutely agreed on firefighting. SS Normandie/USS Lafayette went over that way: http://en.wikipedia.org/wiki/File:USS_Lafayette_1942.jpg

I don’t think the risk of free surface effects is likely to be the, or even a, main consideration. If you’ve got significant quantities of water that high up, you’re already sinking.

You may very well be correct. However wet stuff can come in from the top AND wet stuff inside is often a side effect of firefighting on board. (To the point that there are (or were) Damage Control chappies who claim that the greatest risk posed by a fire onboard is sinking)

Compare to ferries and large ROROs. Airframes in the hangar aren’t going to impact on free surface – it’s still free flowing around them.

For sure, and that one was a bit tongue in cheek. The amount of floorspace taken up by relatively skinny tyres on flying things is fairly small.

LOL! :p

Brought that on myself really, eh? 🙂

What you don’t want in any floaty thing is ‘free surface’.

I don’t think the risk of free surface effects is likely to be the, or even a, main consideration. If you’ve got significant quantities of water that high up, you’re already sinking. Compare to ferries and large ROROs. Airframes in the hangar aren’t going to impact on free surface – it’s still free flowing around them. Packing a car deck on a ferry with cars doesn’t make it any safer.

I’d say two reasons:

1) Structural – you need to support the flight deck and a single thickness of hull at the sides is insufficient for that. Compare to a container ship – they don’t pack containers right up to the ship’s outer hull, there’s a set of void or other spaces along the whole of the side. You either have compartments along the side of the hangar or webs or pillars somewhere down the middle. The latter will create obstructions that you really don’t want in there.

2) What Al. said about trunking, stairs, lifts, plus workshops, offices, etc. that you want immediately adjacent to the aircraft maintenance space.

* note number of ‘l’s before making smart ar$ed comments

LOL! :p

What you don’t want in any floaty thing is ‘free surface’.

If wet stuff gets inside it can start moving around and affecting the stability of the ship.

A list (leaning to one side) is a pain but usually not a disaster. A loll* (leaning one way and then leaning the other) is much worse.

The larger a single space is the more free surface one has and the greater the risk of ingress of water creating a loll as it sloshes around.

A hangar is a big open single space, the bigger it is the better for movement and maintenance of airframes but also the greater the risk of loll. I would hope and presume that the Naval Architects and fellow number crunchers have a maximum figure for free surface at that height above the wet stuff for that wetted volume of hull and so the hangar space cannot exceed that value.

Presumably the more airframes stored indoors the less free surface as they take up space. But there must be a happy medium between filling the hangar with metal not water and at the other end having room to move and maintain teh airframes and minimising flammables stored indoors in unsafe conditions

On top of this there are bits which need to be alongside the hanger deck (trunking for power, air, water, other fluids), stores, access, stairs, turbolifts (probably not that one), aircraft elevators, possibly trunking for air supply and exhaust from engines buried in the depths (dependent on how tis powered), and so on. At least some of these will need to pass through the hanger deck level up and down to other decks and so cannot be moved elsewhere.

* note number of ‘l’s before making smart ar$ed comments

yeah, like that. as we see, hangar is always a bit narrower than waterline beam, even though in theory theres enough width for a broader one. why is that?

You mean like this?