Aircraft Carriers II (Closed to posting)

Thank you, ambivalent. It surely makes sense to look for smaller and cheaper aircraft carriers, but one has to take account of the arguments you mention.
I trained as an aircraft designer, not a naval architect. I am therefore aware of the advantage of having an aircraft launched with a vertical velocity component.
Now compare a monohull and a tricat with the same displacement. The tricat will have a greater length and a narrower main hull, a greater flight deck length and width.
The tricat needs more steel, has a greater wetted surface and a greater friction drag.
The tricat does not need internal bulges to protect the engines and magazines against torpedoes, as that is done by the side hulls.
Let's give both ships electric propulsion, GT or nuclear with GT get home power, and EM cats.
The monohull will have propellers close together, so their propulsive efficiency will be some 10 % lower then for a single screw vessel. I would imagine that the tricat with an propeller under each hull will pay a smaller penalty.
The tricat will have lower wave drag than the monohull, so at the speed for launching and recovering aircraft the power needed and thus the weight of the propulsion plant will be less.
The hangar forms the structure connecting the side hulls to the main hull and is as wide as the outside of the side hulls, with workshops on all sides and with elevators on every corner except the port aft corner.
The tricat will have a moderate ski jump with a pair of cats. Therefore aircraft are launched at about 80 % of the speed with which they need to leave a flat cat. This reduces the energy to be stored for a launch and the length of the cat by about a third.
The end of the landing strip is also a ski jump. so the pilot has, if he misses the arrester cables, more time to decide whether it is necessary to leave his office. The landing strip is also shorter.
So the tricat has a larger deck from which less space is occupied by launch and recovery areas.
It might well be that respotting of aircraft will occur less on the tricat than on the monohull.
The tricat has a larger structure weight but a lower propulsion plant weight, fuel weight,

I would imagine that the tricat configuration will be of no use to super carriers, but that a tricat carrier of halve the size and with halve the number of aircraft would be more effective than a monohull ( think CdG, QE2 ). It is something the Chinese might consider for carriers that start building after 2020.

Judging by some interesting artwork I have seen in the hallways of some military industry office spaces there have been some studies on the subject of wave piercing catamaran and tri-hull aircraft carriers. I have to admit an attraction to them myself. One can obtain a very large flight deck and hanger space on a minimum displacement. It would also be a more stable platform than a similarly sized monohull with no heel at all during turns and almost no bow wave. They are deceptively fast too.
Get over the idea you will have both catapults and a ski jump. It is one or the other. Catapults do not work along a curve, especially an EMALS catapult. If you choose CATOBAR or STOBAR, then there will be an angled deck, which seems perfectly doable on a tri-hull. When landing on a conventional aircraft carrier, the pilot firewalls the throttle on touchdown so if the pilot misses the wire there is enough power and speed to go around. There is absolutely no need for a ski jump to assist this. If you choose STOVL then all you need for landing is a spot. Watch some videos of how it's done. The USN, RN and MMI all have vids on line of STOVL ops. The aircraft pulls into a hover alongside the port side of the ship aft of the takeoff area, stabilizes and then slides right to the landing spot. Western STOVL practice does not use an astern approach to the landing spot like the Russians do.
The side hulls buy you absolutely no underwater protection. Torpedos explode underneath hulls, they don't usually penetrate the sides. If anything, the narrower center hull of a tri-hull degrades underwater protection significantly. If you want the void spaces now used to absorb blows and to store fuel in, you loose hull volume necessary for propulsion machinery and ammunition. If you move some of the propulsion out to the outer hulls, you sacrifice it's protection altogether. The shallower draft cuts into the safety margin for protecting your magazines from missile and bomb hits.
Thinking about this more, you loose any speed advantage over a monohull during flight ops. Wind over the deck has to be exactly down the centerline of the landing area. A couple of degrees either side of centerline creates a high sink rate over the ramp and hard landings. It is a function of airflow over the ramp. If you look at USN carriers, all the cats are angled to port slightly to accommodate optimal landing wind over the deck. The carrier therefore has to choose a course and speed to put the wind over the deck right down the landing line, and this will not be in line with the ship's centerline. This dictates speed, no matter how fast the ship can go. You aren't going to design a shorter landing area because wind and aircraft weight, and how much stress the aircraft can take, will determine the minimum deck space needed for arrestment. It is telling the French PA2 proposal calls for a larger and wider landing area based on experience with the Charles de Gaulle. Also, from personal experience, if wind over the deck is too high, you cannot operate helicopters. There are strict wind limits for blade fold and unfold, rotor engagement and disengagement. I once landed on Nimits with 40 plus knots of wind over the deck in a CH-46D, which normally lands nose high on the main gear, then you set the nosewheel on the deck. This time, with over 40 knots of airspeed to hold a stable "hover" ( we were in forward flight really ) I had to poke the nose gear into the deck and try to hold forward stick as I set the main gear down. Take off was more like a vertical cat shot, no hanging around close to the flight deck. There have been problems with helo ops on the USN's LCS's due their high speeds and turbulence around the hanger.
Extra speed would allow the ship to run fast enough downwind to create a wind over the deck if necessary, something our CVN's can do so they are not always stuck, as with older slower carriers, turning upwind to launch. You can turn down wind and steam (should we call that "turbine" now instead of steam?) so you can turbine, lol, downwind at a speed sufficient to give you a positive wind over the deck.
You could also indent the elevators into the side hulls a bit and buy yourself some dryness in the hanger bay and you would have enough width to have an elevator aft on the port side, something I see missing from modern carrier designs other than those of the USN.

Thank you, Ambivalent. This ids a very interesting subject and I expect to see some, mostly probably less than successful, experiments in the next twenty years.
Turbines in CVN's use steam, so it is alright to for a CVN to steam downwind. I wouldn't want her to "sail" downwind.

I didn't mention torpedoes exploding under the ship, because that is no different from a mine doing the same. You need the same defense against both.

If we build the tricad wide enough the landing area can be parallel to the center line on the port hull. That would be a pretty large tricad I suppose.

By fitting hydrofoils between the side hulls and the main hull fore and aft you can reduce pitching, thus preventing the propellers milling air except in very extreme conditions when you would have reduced propeller revolutions very considerably.

bd popeye said:

Sure thing...

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Thought I would post a couple of pics here regarding the progress on a couple of critical new US Navy ships, the USS Gerald Ford, CVN-78, and the USS America LHAR-6:

Wow they are looking good Jeff. I am surprised they weren't axed buy the Obama administration. Do you have any new pics on the progress of India's new carriers. There seems to be no pictures of Vikramadatiya or the Vikrant. I do know that Russia has started testing the Mig-29K Prototype on her deck for something.

tomcat21 said:

Wow they are looking good Jeff. I am surprised they weren't axed buy the Obama administration. Do you have any new pics on the progress of India's new carriers. There seems to be no pictures of Vikramadatiya or the Vikrant. I do know that Russia has started testing the Mig-29K Prototype on her deck for something.

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These are the latest I have on my :





I'll look for more. But the Russians are flight testing the Indian Mig-29K on the Kuznetsov. Here's an article:



There's speculation that the Russians themselves may switch over to the Mig-29K and the two-seat version of the same now that a good production is going to go for the Indians. Here's a pic of the Indian aircraft on the Kuznetsov:



BTW...what do you think of these couple opf PS jobs I did for a more realistic look at what will look like?







Notice how CVN-78 will have two Phalynx CIWS, two ram luanchers and two NATO Advanced Sea Sparrow launchers. In fact, it looks like all the CVN's are being upgraded to that standard, as is the new America class LHAR. Pretty strong.

Interesting secondary mast behind the island of the Vikramadatiya. i have to wonder about the fatigue life of that long bow overhang. Will we read a few years from now about cracking from wave slamming?
Looks about as far along as China's, eh.

The construction photos of the Ford here and on the Northop-Grumman site give some idea of the carrier's under water protection.

Wow very nice. Any news on launch date? Plus I like the link to the testing of the Mig-29K. I saw a photo in my airforces monthly magazine recently with a Mig-29K on Vikramaditya. They were testing arresting gear or something. I would love to see new stuff on Vikrant though. I also wonder how soon they'll test the Naval LCA. With the Mig-29K in service its probably not to far we'll see the Naval LCA being put into service.

tomcat21 said:

Wow very nice. Any news on launch date? Plus I like the link to the testing of the Mig-29K. I saw a photo in my airforces monthly magazine recently with a Mig-29K on Vikramaditya. They were testing arresting gear or something. I would love to see new stuff on Vikrant though. I also wonder how soon they'll test the Naval LCA. With the Mig-29K in service its probably not to far we'll see the Naval LCA being put into service.

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There are videos of the Indian Navy flying their MiG-28K's off Kuznetsov, including an interview in Russian of an Indian pilot. Poke around YouTube a while and you will find them.

With a deck load of F-35B's and MH-60S's an LHA becomes a pretty potent offensive naval weapon in it's own right, at least as good as the STOVL carriers in other navies.