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I'm currently working on developing the navy for the most advanced faction in my fantasy world and I'm stuck with the design of the largest ship, a sort of a medieval carrier ship.

I'm talking about having a ship that would be roughly the same size and function as a modern aircraft carrier, with the main difference that it would carry smaller ships (Hunters) instead of aircraft because my fantasy world does not and will never have any sort of flying contraptions.

The problem with this idea is to find a way for the Hunters to sail out of and into the carrier while the carrier itself is on the move. The reasoning behind this is that the carrier would be carrying and managing several dozen Hunters, which would have a relatively short range of operation, so the carrier would have to keep up with them at a reasonable pace, especially when the operation demands prolonged harassment of the enemy.

As the carrier sails across the water, it creates a serious wake in its path and that very wake is my main design obstacle. Placing the hangar bay doors at the front of the carrier is obviously not an option, while placing them at the sides would force the Hunters to directly cut across the wake when coming in and going out every single time. Placing the hangar bay doors at the rear would force me to place the engines somewhere else and I honestly have no idea how the physics work when a smaller ship is tailgating an exponentially larger one.

So far the only concept that somewhat resolves the issue is to apply the idea from the Japanese I-400-class submarines that was attempted during WWII. This would mean providing the carrier with several cranes that would lift the Hunters out of the water while they maintain a parallel course to the carrier and bring them in. Carrying the Hunters in and out one by one seems significantly slower than allowing them to enter and leave the hangar bay relying on their own propulsion, but if there really is no alternative to it then I guess I will have to settle with that.

Any suggestions would be greatly appreciated...

PS EDIT: Both the carrier and the Hunters have engines powered by reactors (power cells), so they don't require sails.

PPS EDIT: The ships would be roughly made of the metals available to us during the pre-ww1 era. Since gunpowder and explosives don't exist, the guns on these ships are the first of their kind, basically oversized airguns.

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    $\begingroup$ I'll point out that aircraft on real aircraft carriers can neither take off nor land under their own propulsion - they're lifted to the deck by an elevator, launched by a catapult, and can only land using arrestor cables. So the practice of the carrier participating in launching or retrieving the smaller craft is how it's done now, and might be more feasible than you think (although there certainly may be better solutions). $\endgroup$ – Nuclear Hoagie Apr 6 at 20:06
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    $\begingroup$ It's not clear what this brings to the table. It might be true that an "aerial aircraft carrier" would be useful, because it would still provide a mobile base to refuel, restock, and switch out fresh pilots, nor can the large slow airship be used in the same way as the planes. However, with a regular ocean-going vessel, they would just resort to having the fleet of hunters themselves. They do not need to refuel. The "pilots" can get sleep on their own ships. They can bring everything with them on the smaller ships. The solution to this is simply a fleet. $\endgroup$ – John O Apr 6 at 20:38
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    $\begingroup$ What benefit is the carrier supposed tp provide? real navies have actual uses for larger ships, usually larger guns. Sails would have provided a speed benefits But your's seems to have no benefit. $\endgroup$ – John Apr 6 at 20:50
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    $\begingroup$ Have you looked at whaling boats? They would deploy smaller boats for operations, then retrieved them $\endgroup$ – Gault Drakkor Apr 6 at 22:44
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    $\begingroup$ You have not explained what kind of attacks your hunters do, but I'd have a lot of problems believing that a giant ship carrying dozens of tiny ships is a better solution than a fleet of midsized ships. If you have magical engines capable of propulsing a giant ship to large distances and tiny ships to great speeds you'll have to write a very convincent explanation on why you can't make a middle-of-the-path engine to propel a medium sized ship to a fraction of the speed of the tiny boats and a fraction of the distance of the giant ship. $\endgroup$ – Rekesoft Apr 7 at 9:53
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A giant catamaran.

A top view:
   ____________________________________________________
  /                                                    \
 /                        Starboard hull                \
| Bow                                             Stern  |
 \    ____    ____    ____    ____    ____    ____      /
  \__/    \__/    \__/    \__/    \__/    \__/    \____/   <-Hunter bays along
                                                              inside of both hulls
   __      __      __      __      __      __      ____
  /  \____/  \____/  \____/  \____/  \____/  \____/    \
 /                                                      \
|                         Port hull                     |
 \                                                      /
  \____________________________________________________/

A side view:
             Structure connecting the hulls  
                             |
                             V                      Rope towing hunter through the wake
  ____________________________________________________    |
  \  /====\  /====\  /====\  /====\  /====\  /====\  /`-. V 
 __||______||______||______||______||______||______||____`-.    |\                 
|                                                        |  `-__|_\_  <- Arriving hunter
~\                                                      /~~~~~\____/~~~
  \____________________________________________________/

The ship has two long hulls, structurally connected above and possibly below the waterline -- above, high enough to clear the masts/highest points of the hunters. If below, deep enough to not interfere with the hunter's keels.

The inside-facing sides of the two hulls have the docking bays for the hunters, which can be closed off via sliding doors in heavy weather. A system of pulleys and ropes attached to the structural supports above can assist in launching, catching and docking the hunters.

Getting past/through the wake

The connecting structure over the two hulls can function as a network of cranes/tracks. It may be unsafe/unfeasible for a hunter to successfully navigate past the wake by itself, but if it's being held by one or more ropes from above, you should be able to keep it steady until it's been let out far enough behind for it to navigate. To pull it back in, the catamaran can toss a floated cable/rope out from between the two hulls. Make the rope as long as it needs to be to drag a safe distance behind the wake. This rope could be caught by a hunter, and then it can be towed forward into the between-hull space where it can be more easily handled and docked.

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    $\begingroup$ Couldn't a hunter coming in from the front of the catamaran and snag a line lowered down at the front of the cat, avoiding the wake before it forms under the vessel? Otherwise, the only other thing I could think of is a kind of thin underwater sloped platform the (flat-bottomed) hunters would kind of wash up on to until they were out of the water. $\endgroup$ – DWKraus Apr 6 at 20:44
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    $\begingroup$ A catamaran would also solve a couple of critical engineering issues I can think of based on the limitations of medieval ship construction. Short of the carrier being a glorified barge (Nemi ship)/giant raft. $\endgroup$ – DWKraus Apr 6 at 20:47
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    $\begingroup$ @DWKraus Well, I think JBH is right in his answer that this would be challenging if we were constrained to wood/"medieval" materials, but with the OP's fantasy setting and the statement that "Both the carrier and the Hunters have engines powered by reactors (power cells), so they don't require sails", I was assuming their engineering tech might be more flexible. $\endgroup$ – Qami Apr 6 at 20:50
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    $\begingroup$ Wake is always behind the ship, not in front. The ship can slow down to minimize wake, and the effects of wakes are lessened in deep water. A boat coming up at the front of a ship experiences no appreciable wake, and if you had some sort of guide rails for pushing a hunter to the middle, you could easily loft one out of the water on rails covered in wheels (like on a boat trailer). $\endgroup$ – DWKraus Apr 6 at 21:09
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    $\begingroup$ The Sea Shadow, the real world skunkworks stealth missile boat, solved the catamaran wake issue by using drive "screws" one in each pontoon that turned in opposite directions, directing the wake inward where it hit the opposing wake and canceled out. $\endgroup$ – OhkaBaka Apr 8 at 15:17
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Surely you are just thinking of something like this?

enter image description here

That there is an Amphibious Assault Ship.
A large part of its role is to carry, launch and service a fleet of smaller ships (and helicopters)

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  • $\begingroup$ I can't seem to able to find any mention as to whether thay can embark amphibious craft or boats while mobile, which actually made me curious as to whether they are able to. I have only ever seen these manuevers performed from a stationary ship in any sort of videos or pictures. $\endgroup$ – JANXOL Apr 7 at 13:16
  • $\begingroup$ Amphibious assault ships fall entirely within their own category. The carriers I intend to create would strictly operate out on the open seas. Instead of carrying smaller ships designed to themselves carry land troops, my carriers would be having smaller ships dedicated for open seas combat operations, such as Gunboats (and maybe even Destroyers if I eventually decide it's worth the scaling) $\endgroup$ – Argent Hellion Apr 11 at 9:12
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Torpedo boat carrier

These things were actually done in real life with torpedo boats and larger ships which carried them out to sea. One example of such vessel would be the La Foudre (later converted to a sea plane carrier.

The same principles can be applied here, provided the Hunter ships are small enough in relation to the carrier and the cranes you have available.

The Hunters would be stored on deck in manner similar to ship's boats and in absence of sails the deck would be full of crane assemblies used to move the hunters in and out of water on either broadside. The motion of the ship isn't that big of a problem as long as you can slow down a little. Take for example floatplane recoveries, where scout planes would land on water and pull up alongside the ship while it was moving at relatiovely low speeds (about 10 knots) and be pulled up onto the deck with a crane. Arguably the more dangerous part would be launching, as with planes it turned out that speed needs to be much smaller, but in case of boats the situation shouldn't be as severe. You should however make sure your cranes can lower the Hunters into the water with enough clearance from the carriers hull to avoid collissions.

Here's a photo from the La Foudre, you can see a torpedo boat being hoisted up (or down) and another one stored on deck.

La foudre torpedo boats

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    $\begingroup$ Currently this is the best concept on the list for the combat variant of the carrier :) $\endgroup$ – Argent Hellion Apr 7 at 17:15
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Forget the wake by avoiding it altogether

The idea of having a huge, hollow ship is unrealistic even in a fantasy setting. Aircraft carriers are made out of steel and not English Oak because ships that size require the advantages of steel and mighty engines to exist. You didn't say whether or not your ships are made of steel or depend on combustion.

So let's assume your fantasy setting is akin to the Golden Age of Sail. Your hunters are, I assume, fast short-range ships. It's implausible (frankly unbelievable) that your carrier would have dock or bay doors that would open to let them exit and enter. To do so would require a power source other than wind and sail.

I recommend long, skinny, and cranes

Let's assume a very long, quite skinny ship that has cranes along both sides of the ship for lifting the hunters out of the water. This not only provides access for repair and resupply, but keeps the hunters out of the water to reduce drag, holding back the carrier. Cross-beams could be moved into position to lock the hunter in place, which would have the advantage of adding the hunter's sails to the overall propulsion of the carrier.

A pair of cranes mid-ship have the unique ability to lift up-and-over, thereby bringing very damaged hunters into an onboard dry dock for extensive refit.

The long carrier would have the advantage of speed due to a minimum water cross-section, which would also allow for a lot of keel-aligned sails, but would have the disadvantage of turning a bit like a lead brick. Good! There should be disadvantages to outweigh the advantages.

An average carrier might host eight hunters with cargo capacity to allow for 3-7 year patrols. Do I have any stats to support that? Nope. It just feels believable to me.

But what about that darn wake?

Since the hunters are always working along side the carrier and never behind it, the wake is a non-issue.


Post edits answer

The OP has since edited his/her question to indicate the ships are made of metal and have powered engines.

In this case, I don't advocate a carrier. I advocate tethers. All the hunters can move under their own power so long as supplies and fuel are available. This minimizes the size of the carrier and improves both its defense and its economy. Rather than being a huge, lumbering clunker when the hunters are deployed, it's a small supply ship... fast and maneuverable. A single "bay" at the back (not actually covered, but a forked portion of the stern) would exist where a hunter can be brought in and parked for repair and maintenance.

Curiously, this reflects an answer I gave to Optimum Shape for a Space Dreadnought.

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  • $\begingroup$ So like a clipper ship on steroids? $\endgroup$ – DWKraus Apr 6 at 20:49
  • $\begingroup$ Maybe a hybrid model, with an outrigger (minimal wake) supporting a structure with cranes/docking scaffolds that can dock hunters or lift them out of the water as needed? $\endgroup$ – DWKraus Apr 6 at 21:02
  • $\begingroup$ So you're basically telling me to give up on the hangar bay doors entirely and focus on the cranes. In that case copying the torpedo boat carrier seems to be the best option. $\endgroup$ – Argent Hellion Apr 6 at 21:24
  • $\begingroup$ @DWKraus Yeah! Other than the OP's edit that the ships are powered, which means there's tech beyond wooden beams, which means it's just another troop carrier. That's disappointing. I was really diggin' all those sails. Aargh! $\endgroup$ – JBH Apr 6 at 22:52
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    $\begingroup$ @ArgentHellion Yes. As an author, you have two routes and you kinda have to pick one. You can embrace the fantastic - in which case you can do what you please and should focus on the aesthetic to garner the greatest emotional response from you reader. Or you can embrace realism - in which case your carrier is bound by physics, engineering, and economics. There's never really money to waste when building ships. In your case, we all made assumptions due to lack of details (note that for future questions). So I'm going to add an epilogue to my answer. $\endgroup$ – JBH Apr 6 at 22:56
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Like a whaling fleet?

The question reminds me of the whaling fleets during the first half of the 20th century.

Both the factory ships (big, lumbering, sturdy, lots of space) and whalers (small, nimble, rough, cramped) would journey together. At times along the way the factory ship resupplies the whalers if necessary. Considering that for a navy there is no need to conserve space for a captured product this space becomes useful for power cell storage / reload, ammunition and food and water.

As the whalers were ocean-going vessels there was no need for these to be carried or towed by the factory ship. Only restricted by the space for food, water and fuel the whalers were capable of independent operation away from the factory ship.

Use of resources

If this nation is capable of producing big ships like a "carrier" then there is plentiful available metal.

Also these big vessels are capable of operating in open seas. So navigation is mastered.

In turn why would this nation restrict itself to product smaller vessels requiring carriers? It is more sensible to have smaller ocean going vessels that have the additional benefit of operation along the home coast as patrol crafts. One design, two functions. Can be used where needed.

Modus operandi

Why would a carrier carry ships? In a way this only makes sense to beat another nation's navy. However this does not fulfil the objective of projecting military or political power over another nation.

Food and water in the late industrial age where metal ships with screw propulsion became dominant were not as restrictive as fuel capacity.

So the hunters in this question have a limited fuel capacity which limits their effective range reach. In contrast a big ship (tender) can carry lots of fuel (besides food and water) to extend that range of hunters. However this big ship requires protection which a small / big fleet of hunters can provide.

Maritime transfer of resources between ships in open sea is not a preferred option. Having said this it depends mainly on equipment (ropes, maybe cranes) and training. Any navy big enough to create big tenders tends to have at least a professional core of sailors.

Final thought on modus operandi of tenders: These ships require a dedicated effort of a nation to build and operate. Just using these to extend the range of smaller hunter vessels to fight other ships "for the glory of sinking ships" makes only sense if this supports the other big and medium ships that land troops to conquer other nations or parts of the world providing scarce resources.

The wake problem

A big ship only makes a big wake if it sails fast. Ships and boats going alongside each other requires protocols of communication and coordination that professional navy personnel gets training for.

A fast moving ship deploying small vessels at fast speed into up to medium open seas is cool. And if possible by physics we would have historical examples.

Conclusion

I just fear this carrier question is impractical for the reasons above. The idea however is cool.

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    $\begingroup$ This is a well-thought-out answer. Welcome to the site, you started out strong! $\endgroup$ – Alendyias Apr 8 at 13:56
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The US Navy did have such a ship class. Made out of metal, and when launching, the ship was partially sunk. They were LSD, known as Landing Ship Dock. How they work is beyond me, as they are now part of the mothball fleet. The one I know of is the USS Thomaston, LSD-28. I could not comment on PcMan's post.

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  • THE ANSWER

After more research and an in-depth comparison of speeds and sizes, I had arrived to the conclusion that the Catamaran build is the best one when it comes to providing speed, size and stability. I would take the torpedo boat carrier design and widen it into the Catamaran build, providing the carrier with 6 cranes spread on the sides so it could service 6 Hunters at once. The Catamaran design with the hangar bays being underneath the main deck simply isn't feasible due to such a large vessel being forced to sit as low in the water as possible for the sake of stability.

As far as speed is concerned, I've locked the carrier's speed for operations at 10 knots (20kph) and I've locked its maximum speed at double that number. The Hunter's speed are still something I'll be working on...

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