The Ship Model Forum

Hey, guys!!!

I have been looking into below-deck hangers for a little while. Ever since the Spruance-class, we have had a fascination with the above deck hanger. While that is the easiest and is the most reliable, it forces you to forfeit most of (Spruance and Ticonderoga) the back half of the ship and sometimes the entire back half (Arleigh Burke) to a hanger and flight deck. This really limits the ship's armament and capability, and if this can be gotten away from, it should be.

It's alright if we are just going to have ships that deliver a little bit of ordnance (FFs, DDGs, CGs), but if we are going to have ships that deliver heavy amounts of ordnance (BBs/BBGs) we can't forfeit the entire back half of the ship for convenience of not having to maintain an elevator. We need to employ the back of the ship for armament as well. While this is the case, I think helicopters are important enough to put considerable effort into storing helos onboard as well. The below-deck hanger is an excellent way to accomplish both of these requirements at once. So, as a result, I have been doing a lot of research into below deck hangers lately. There is not really a lot of information on these out there, but what is out there weighs both in favor and against a below-deck hanger.

The last "modern" ships to employ below-deck hangers were the Virginia-class CGNs. From what I gather they had a horrible time with water leaking into their hangers. Even then, the hanger was only large enough for a single Seasprite LAMPS helo, because the elevator had to be stored in the elevated position (what a horrible idea anyway). Supposedly the leaking was such a problem that they welded over the hanger and put silly little Mk143 Tomahawk Armored Box Launchers on it instead.

The ships before those, however, were the heavy and light cruisers. They all enjoyed very successful hangers. Instead sealing the hanger by elevating the elevator to the main deck, they had a hatch that covered the hanger and slid forward when they wanted to access the hanger. Those hanger sealed and worked very, very well. They just were not large enough to fit modern day helos inside.

Does anyone have any additional information on both the CA/CL and CGN below-deck hangers that can help with my decision making?

Thanks!

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Proper Preparation Prevents Poor Performance

Seahawk SH-60
Length: 64 ft 8 in (19.75 m)
Height: 17 ft 2 in (5.2 m)
Fuselage width w/attachments: Approx 7'
Empty weight: 15,200 lb (6,895 kg)
Loaded weight: 17,758 lb (8,055 kg) (ASW mission)
Useful load: 6,684 lb (3,031 kg)
Max takeoff weight: 21,884 lb (9,927 kg)

In comparison

SC1 Curtiss Seahawk
Length: 36' 4.5"
Height: 16'
Max Gross Weight: 9,000 lb.

SOC-3
Length: 31' 5"
Height: 14' 9"
Max Gross Weight: 5,437 lb.

So, it appears that the hanger deck would require a height of at least 20', to allow working space for the rotor head. Unlike the cruisers, the weather deck opening would need to be at least 65' long. This suggests a split deck hatch for sliding movement port and starboard. This would allow clear space, fore or aft of the hatch, for the helicopter, to permit closing of the hatch, leaving the bird on deck. The hatch would need seals, pneumatic or compression or both, on all edges to provide a weather tight seal.

Russ

Is this idea for a completely newly-designed vessel or a modification to an existing?

If the former, then I have nothing more to add.

If the latter, however, then you have to think about the stuff that you will have to take out from the space that the hangar will go, and where that stuff will be relocated to.

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De quoi s'agit-il?

Yes, sir. This would be a new design (Montana-class/also to be employed aboard Russ's USS Kentucky build). This is also to keep in mind that the elevated dimensions would be based on an SH-60B with a folded tail. The internal hanger would afford more space for maintenance and work.
I don't quite understand what you mean. What I have in mind is a hatch that would be a single hatch that would slide forward, opening the entire elevator to be exposed. I would so suggest the elevator be big enough for the full 65' SH-60 to be elevated (this sounds like the full rotor and unfolded tail dimension so I will have to look it up), but as a matter of procedure it would go up with its tail and rotors folded.

***A reactivated Des Moines, though, would go up with tail and rotors folded, because the elevator is a little smaller but should still be able to accommodate a 60 folded.***

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Proper Preparation Prevents Poor Performance

Ok,Lets say you a hatch with dimensions of 40'x60'. It will logically be on the centerline with the long dimension running fore and aft. Now what is the weather deck space requirement for the system?

I haven't located a scaled diagram of an SH-60 but working from the BB-62 plans on the HNSA site, it appears that the SH-60 with tail and main rotors folded is roughly 7'x 30'

WWII Cruiser sliding style: (35') for hatch + (36+') for hatch cover slide area + (60+') for the bird to roll onto = 131+'

Modified (side) sliding: 35' x 10' for hatch + (12' port or starboard of the opening for hatch cover to slide onto) + 60+' to roll bird onto = 95+' length of system,


Modern breakbulk cargo ship hydraulic or electric hatch cover system: In this system, the hatch cover is split into sections which are "piano hinged together" and fold up onto each other. 35' hatch + 65' bird pad. I would suggest the hatch cover fold to both port and starboard which would require perhaps 5' to one side of the hatch.




This website has typical mechanical and weather proofing diagrams. http://www.macgregor-group.com/?id=11602

i'm presuming the elevator comes up onto more flat deck in order to allow the helo to unfold and launch, not to mention the amount of relatively level real estate it'll need to land?

i honestly don't really see how the cost-benefit on this one works out... the only places i envision there being the requisite amount of flat deck area (presuming your design is reserving superstructure space for weaponry, which i understand to be the entire point of this exercise) is way forward or way to the stern, and either case the below-decks hangar, roof equipment, and elevator gear are interfering with machinery spaces.

i presume you're envisioning a big gun ship (for NGFS)? if so, why not have two gun turrets up forward, and leave the stern superstructure for an abovedecks hangar/flight platform? i'd say two turrets with two-three large caliber advanced tubes each should be way more than sufficient for any envisionable NGFS needs? especially if the turrets are capable of being independently targeted.

Actually, on the Iowa class, given that you would need a 20' hanger deck with a 20' high overhead, the only place to put the hanger is aft of Frame 166 to Frame 181. If you placed the elevator in ths space but to Port or Stbd of the #3 mount gun tubes (or both) the hanger would intrude into the second deck and the 1st and 2nd platform decks. I suggest a hanger measuring 44' beam (22' to either side of the centerline) 40' fore and aft with the elevator(s) on the outboard ends and as far forward to Frame 166 as possible.

This would take out the center 44 x 40 feet of the crews mess (part of the table area) on the 2nd deck, the same area of crewberthing on the 1st platform and the cold storage on the 2nd platform.

On a Montana, there would presumably be an easier fitting of the space, aft of #4 turret.

For what it's worth as a comparison, Kirov class ships have a sub-deck hangar accessed by a split door system that opens upward to the vertical.

Bob

These are all fascinating methods you guys have suggested! The best way to do it, I think is exactly like the old heavy cruisers and light crusiers did it. It was very simple. A large hatch slid forward, the elevator came up, and the aircraft was readily available on the deck. Check out the legendary USS Salem done by Keith Bender. This is an excellent deptiction of the below-decks hangers on the heavy cruisers.

Of course, I would elevate the deck for AFFF plumbing, but I would make sure it is tall enough to be level with the top of the hatch. The hatch would be smooth and uniform instead of a bubble like on the heavy cruisers. This way, the helo can land directly on top of the hatch and taxi off it and into a storage area, or the hatch can be open and the elevator platform up when the helo lands, and once it was spun-down and folded up, the elevator could simply go down into the hanger, and the hatch can close.

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Proper Preparation Prevents Poor Performance

Far from it. Its never been a problem. The below deck hangers use a large amount below deck space and displacement. The below deck hanger also very limited and has a much higher operating cost than an above deck hanger.

The Spruance class and the Oliver Hazard Perry class didn't loose any capabilities because of the above deck hangers. Both classes over their service lives have had their hangers enlarged and reconfigured, this would not have been possible if they were below deck. Below decks hangers require either a large crane or a heavy lift elevator to function. These items are very heavy and encroach on valueable below decks space.

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║ Seasick║
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I still don't think you'd get the needed hanger height if you put it all the way back at the stern.

As to Seasick's comments, Use a large amount of displacement? Is the cube of the hanger greater than the compartments it replaces? Is its weight greater? I can't see it

Are the replaced compartments integral to the ship's mission or to crew space. The crew space can be configured around the the hanger, especially since the crew is to be reduced from 1,921 to 900.

I know you don't like guns, but you need more than 1 gun on a ship, and they need to be spread out across the length of the ship so if one end of your ship gets messed up or one mount goes down you can at least fight with the other one.

See above. The Sprucans only had two 5" guns. The Perry only had 1 missile launcher and 1 gun. If the front of the Spruance got messed up its forward gun and ASROC launcher/VLS was gone. Oh, wait, but the helo hanger is okay. Yeah. No problem there. It would, however, still have a 5” gun for basic self defense. For a large ship like the Spruance that is a problem. For the Perry, well, it's a compromise ship anyway, so for the cheaper platform you have to do with less, and your available space is less.


The DDs and FFGs were ASW ships, so modifying their hangers made sense. We changed from a really small helo (Seasprite) to a moderately large helo (Seahawk). Those helos had missions that needed a little more room. A battleship would have utility helos with torpedoes just in case your ASW ship needed one or 2 more birds. So, unless we are going to shift from the Seahawk to a super huge helo, I don't understand how the hanger would need to be expanded much if at all.

So, the below deck hanger could stay the same size as long as we use the same size helos. Is there something wrong with that logic?

Concerning the size needed for a helo, look at how retarded narrow the hangers on Perry FFs are. Super, uber narrow. Even the ones on the Burkes are jammed into the ship, so while I would have a pretty decently large hanger on the battleship, the Perrys and Burkes show how very, very small the hangers can be if they need to be.

Yep they sure do. More weapons for a capital ship in need of delivering high volumes of ordnance is more important than the convenience of an above deck hanger. There are ways to get an elevator up to the main deck without its main hydraulic drive.

Here is a very rough size comparison. I took the length of the full line drawing and divided it by the length of the folded SH-60. The ratio of the Seahawk is 1/30.7ish. So, I made a little rectangle 1/31th the length of the ship's line drawing. So, this is for the purposes of this preliminary level of discussion, no real dimensions yet.

So, here you can see the general relationship. Now for the depth necessary, if a level on a ship is 8' (which is true for the DDGs and LSDs I have been on) you get 16' for two levels below decks. Like in a well-deck, if you need 20', you make a 20' box and put a step latter making up the difference if you are going from the standard level into the deeper compartment. So, here in the battleship, the bottom of the hanger would actually be on the armored 2nd deck. If we have the opportunity to build a new ship or to start at the armored deck and not have to cut through everything to get down to that armored deck, all we would have to do is take the slope out of the armored deck that follows the upward sweep of the stern and make it level, giving us another 2' for the length of the hanger. That gives us the 20' we would need, and if we need more than 20', we just cut into Kentucky's armored deck the foot-print of the hanger and make the deck a little deeper.

Great question. The internal area is another advantage to a battleship. You have so few people on such a huge ship.

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Proper Preparation Prevents Poor Performance

I'm glad you decided to put the floor of the hangar at the second deck. On the Iowas, the level below contains the steering gear, which would, I think, not appreciate being adjusted. Everything above is mainly crew quarters and aviation stores, so that would be ok

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De quoi s'agit-il?

Hey, Timmy! Yeah, if that depth is an issue, the hanger can still move even further forward to where the forward most part of the hanger is against the face of the armored box that ends just behind Turret 4....in fact, I think that's how it is going to have to work. Also, I am not suggesting this being done to an existing Iowa, just the Kentucky build and a new-construction ship.

Now, here is such an AWESOME way to build this hanger by Wayneb. This guy...man, what an awesome approach.
Here is his Majestic Class light aircraft carrier HMAS Melbourne build.

I cannot wait to start building parts and pieces to this. How much fun! Yeay!
viewtopic.php?f=59&t=52204

Awesome.

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Proper Preparation Prevents Poor Performance

Are you talking about a super Montana what-if or are you going for an all-new BBX?

I personally don't see any benefit to putting the hangar in the stern and quite a few drawbacks*, some of which have been mentioned. BUT, if you're going with a completely new ship, then I would imagine that using podded propulsion would free up space for you.

* For example, how much deck space do you lose by needing to allow that hatch to slide forward? You're talking about a nearly 70' long plate. You could lose a turret out of that, which negates your implied benefit.

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Tracy White -Researcher@Large

"Let the evidence guide the research. Do not have a preconceived agenda which will only distort the result."
-Barbara Tuchman

Both the Kentucky build Russ is doing and a Montana I will do one day.
Why should it be so big? If one helo is 7' x 30' folded, the hatch does not need to be more than 40' at most.

The only draw backs I see are:
Loss of internal space: For that, there should be plenty of internal space in the ship and structure for the displaced Chief's mess (unnecessary) and berthing. No mechanical elements would be influenced by the hanger. It would not be deep enough to penetrate the main armored deck (2nd deck), and all of the steering gear and such is well behind the aftermost part of the hanger.

The necessity of an elevator: You are absolutely right. Maintenance will have to be performed.

Size: I think you guys are assuming this hatch and elevator would be significantly larger than it would need to be. See above.

The hatch would slide forward (over the length of the hanger itself), the elevator would come up, the helo would fly off, and if the second helo needed out, the second helo would drive onto the elevator and be taken to the flight deck the same way.

Does that clarify things a little? I understand the best thing needed here is a drawing. The one in one of my last posts illustrates the internal space taken up. Now I need to do one of the overhead looking down.

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Proper Preparation Prevents Poor Performance

Mainly because I brain farted and combined the 7' with the 30' and came up with 70' for some weird reason.

My main deal is that I disagree with your statement that you would be voiding the aft half of the ship for helo support. If you're working on a Montana hull, well you've already got that space back there that would be wasted otherwise, but I firmly believe you'd suffer from weather related downage more with that design than with a platform mounted higher. I'd just as soon rip out Turret #3 and build a hangar and deck there.

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Tracy White -Researcher@Large

"Let the evidence guide the research. Do not have a preconceived agenda which will only distort the result."
-Barbara Tuchman

GlobalSecurity.org lists the SH-60 series helo as being 40' long in its folded configuration. The operating height is 17'2". The folded height (due to the tail) is 13'. Thus, for two 8 foot decks (16' total) it would not be possible to have the helo unfolded in the hangar due to height limitations. Even with the 13 foot folded height, is a 16 foot high hangar sufficient to allow maintenance on the rotors mechanism, for instance?

The hatch opening for a 40 foot folded length would have to be 45 feet or so to allow a little space fore and aft. So, the 45 foot opening plus the fully opened (slid forward) hatch cover, also 45 feet, requires a total of 90 feet of dedicated deck space.

Regards,
Bob

Am I hearing an echo or is it just me?

However if it folds or if it slides to port or stbd...

I understand...I almost put grease where it was not needed today on a Mk46 REXTORP.
I don't get why people think eliminating weapon systems is such a good plan. But that's okay! Turret three would only give you the landing area. Then you would need to "rip out" the range finders, associated structure, and aft stack (?) to build your hanger . If the ship were nuclear powered with no stacks and stuff, I would have a Spruance-style hanger amidships.

Now, the reason why I like the hangers that the heavy cruiser had vs the Virginia style is because their hatch is literally a cap that sits on top of a lip. That keeps water out. Unlike the hangers of the Virginias that relied on the elevator to be raised all the way up to close the hanger, elevators that need a whole bunch of really clever seals and packing. If you instead have a cap on top of a lip that goes all the way around, only flood water would penetrate, but even then, that’s what seals and rails can accomplish. The only impressing thing about this cap would be that it needs to slide forward.

However, I really like the challenging input, guys. Thanks so much so far.

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Proper Preparation Prevents Poor Performance