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Subject: Trimaran Carrier Concept
perfectgeneral    7/25/2004 10:34:58 PM
Given the drop in drag it offers and the large ratio of deck space to hull required a tri-hull carrier is bound to come off the drawing boards and into production soon. Something all electric or nuclear. Magnetic catapalt. loads of lifts and decks. Huge. I did wonder about a row of four 40 metre wide decks, each 230metres long, running diagonally in parallel along a 400 metre deck. Islands fore and aft would occupy the opposite diagonal corners. The port hull supports the front of the aft two decks and the starboard hull the rear of the foreward two decks. The four lifts alternate between optimised for take-off and landing on each deck. This is too big for existing facilities but could be assembled from modular hull and deck units. The three hulls would be launched separately. Then the hulls would be joined with additional superstructure and decking in the water. The central hull would have to be partially flooded to attain the correct level. Any comments on the feasability of all this? Any Trimaran Carrier ideas of your own?
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USN-MID    RE:Trimaran Carrier Concept   7/25/2004 10:47:03 PM
The main problems I can foresee possibly coming from air operability. How's this thing going to work? One really big deck with multiple landing strips? B/c that's the only way you'd copy the efficiency and safety of current angled deck carrier designs. And I'd think that a massive deck that big might lead to seakeeping qualities. Too bad RB hasn't posted recently, he could tell you how well that would work.
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perfectgeneral    RE: Angled multiple landing strips   7/26/2004 12:02:07 PM
I thought that alternating strips would allow quicker through put than waiting for deck crews to clear the last jet before dealing with the next. The approaches and exits would be staggered in time as well as space. Forty to eighty metres not enough margin of error? As for seakeeping, you've got me there. The trimaran shape is supposed to be pretty stable and as long as the outer hulls are shorter and centrally mounted I can't see turning being much problem. However only somebody with RB's background could have an educated guess. I'm not sure what such a large zigzag edged deck would do when a gale caught it either.
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RM-Nod    RE: Angled multiple landing strips   7/26/2004 3:09:26 PM
I've discussed this with RB before, here's the link... It goes on from there. Very interesting, unfortunatley the MoD thought it was too risky and didn't go any further.
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Mark F    Internal Volume   7/27/2004 8:48:59 AM
Trimaran concepts were looked at for CVF. Presumably they were canned because they lack the one thing a carrier really needs above all else - internal volume. The Trimaran concept has a whole seems to have lost much of its steam since the British have conducted their Triton experiments.
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RM-Nod    RE:Internal Volume   7/27/2004 12:14:05 PM
"Presumably they were canned because they lack the one thing a carrier really needs above all else - internal volume." The design put forward was capable of carrying the same airwing as the current CVF concept but with nearly 20,000 tonnes less weight and have better sea keeping capabilities and speed. "The Trimaran concept has a whole seems to have lost much of its steam since the British have conducted their Triton experiments. " What gave you that impression? The Triton program ended on schedual and the result are now under consideration by teh FSC IPT. We won't hear anything for a while but it's still going.
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perfectgeneral    RE:Internal Volume   7/27/2004 9:03:25 PM
I guess with MOD being so timid this technology will gradually creep up through the ship classes until it reaches the flagship. If any state embraced this approach successfully they would outclass all current ships in other fleets. There is risk in not trying it too. Thanks for the link RM-nod, I'll check it out with interest.
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hybrid    RE:Internal Volume   7/31/2004 3:54:05 PM
Actually several factors led to reasons it got killed in the US Navy's planning and development for future carriers. Of those two of the most critical were damage control. If one of your hulls got damaged (especially for catastrophic damage) there was a major possibility of listing to one side of the ship..making launches difficult if not outright impossible, then there was the issue with out to transfer troops, cargo, weapons, and other essentials between the different big of a passageway or thruway is enough or too small, toss in no one has built a trimaran of that size and you get issues with how to build the joints and other elements that need to bridge the 3 hulls together (they need to be able to flex but only to a certain degree). Finally to cap off all those problems have you ever noticed why an aircraft carriers forecastle is placed where it is? Its because of turbulence thats caused by the ships passage. Placing it in the middle of a ship as would nominally be warranted in a trimaran design causes landing aircraft to experience anywhere from moderate to severe turbulence. NOT a good thing in an aircraft carrier. The disadvantages from all those toss in with the costs associated with R&D to fix those said problems would drive the price of any supercarrier sized trimaran aircraft carrier design insanely higher than our normal carriers already are.
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doggtag    multi-hull strength vs monohull   7/31/2004 8:32:38 PM
A trimaran is not going to "tip over" like some have suggested: the sheer weight of ship equipment and superstructure, coupled to the multi-hulls extra stability, will very easily prevent such an occurrence. A trimaran will have to take back-breaking damage to "roll over" like monohulls do (effectively, shearing off the complete secondary hull on one side would be required to roll a trimaran). And the extra "outrigger" hull sections can effectively shift ballast between them to stabilize a multi-hull far more effectively than monohulls. A trimaran could effectively survive a critical central hull compromise which might sink a monohull, just because the secondary hulls offer additional flotation and protection for the central hull. Multi-hulls such as Triton and SWATH (Small Waterplane Area Twin Hull) like the US Sea Shadow have pursued the multi-hull idea just because it affords greater stability than monohulls. And there is a considerable increase in usable deck and internal space because multihulls have a greater beam than monohulls of the same length. The only real drawback being that very large multi-hull vessels will be too wide to be able to use the canal systems throughout the world (Panama, Suez, even St Lawrence). Multi-hulls are not going to look like Hawaiian outrigger canoes: the multi-hull form will effectively be a large hull structure with a large central and two secondary hull extensions which extend into and below the surface. There was an article in Jane's Defence Weekly several months ago in which was proposed by UK shipwrights a "pentamaran", a main hull with 4 mini-hull extensions. The benefit of having such multi-hull vessels, in addition to considerable internal and deck space increases, is that overall displacement (draught) will be shallower. With greater flotation from additional hulls, a ship will not sit as low in the water. This could prove valuable in several littoral operations: whereas a typical monohull destroyer-size ship may set 7m in the water, a multi-hull may effectively be able to set at a shallower draught of 4-5m, but still maintain considerable stability. And another benefit of multi-hulls: there was a SWATH-type proposal for a USN frigate/USCG cutter several years ago that could effectively deploy its ASW torpedoes from between the hulls, as opposed to over the side. Not so much as being "underslung" like ordnance on aircraft, but more like they exited the underside of the hull crossover. The disadvantage of SWATH-types is that they have a considerable-sized submerged hull section, whereas multi-hulls would (ideally) use "standard" hulls (as opposed to the submarine-looking submerged pontoons of the Sea Shadow. There are considerable pluses, and certainly minuses, to multi-hulls. But the extra structural gains they have will make the ship more tolerant of the flexing, hogging, and sagging that naval vessels experience. But the damage level would have to be truly catastrophic for the vessel to roll over on its side like we've seen monohulls do for centuries..
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hybrid    RE:multi-hull strength vs monohull   8/1/2004 3:04:47 AM
doggtag I fully agree that when you get down to destroyer/cruiser sizes cat designs and trimaran designs may be an efficient way of increasing space (surface area PLUS extra volume on the outriggers). However when you get to supercarrier sizes thats where the problems start happening. No one has built to those sizes trimaran designs. Semisubmersibles (such as some oil rigs) are the closest things in comparison. Hence the Navy doesn't know how the structure would flex and the pressures and stress exterted on such a craft. This one of the reasons they are looking at monitoring the Triton craft the RN is looking to produce. Data gleaned from that will help the Navy with its own ship designs. As for tilt over..I did mention it would be catastrophic damage that would cause the problems. But another issue is the volume versus surface area used/gained. Lets say you use a trimaran design supercarrier, you got 3 smaller hulls compared to one large hull. You give up a LOT of volume to get that extra surface area. You also end up with the forecastle issue (placement of it is critical for landing craft) plus the issue that one of your outriggers might have to be oversized compared to the other or have more ballast in it to compensate for the weight. Anyways thats my 2 cents on multi-hull carrier designs. Now if we're talking about multi-hull warships of much smaller tonnage and non-aircraft carrier type then thats a whole different ball game.
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USN-MID    RE:multi-hull strength vs monohull   8/1/2004 3:24:33 AM
Seeing as how CVNs are already too big for the canals, the multihull width shouldn't be an issue.
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