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So in my book, the majority of my society's medieval-era navy is pulled by at least one adult dragon. Adult dragons are huge; their heads alone are about the size of a medium-sized car. How might ship design change in order to accommodate the potential issues caused by a regular ship getting dragged behind a dragon that is the same size or larger than said ship?

These dragons have four limbs: 2 wings (which double as forelimbs when the dragon is not flying), and two hindlimbs. So technically, they are wyverns.

These are fire-breathing dragons. Temperament varies. Ship-pulling dragons would most likely be captive-bred dragons, so they're more tolerant of people and less likely to drown/consume the crew. They are somewhat spiky around the head. They have somewhat long tails with a scythe-like blade at the end. They could be distracted by prey but may have blinders on to prevent that. The dragon itself could contribute to firepower.

These are my dragons. I have them designed and behaving how I want. All I'm asking for is how a ship might be designed differently to be efficiently pulled by dragons, not how the dragons are going to react to it.

The dragons would most likely be flying low over the water instead of swimming, so most likely some sort of stabilization would be needed. They are capable of soaring long distances in the right conditions, so unless it was super windy/storming/etc the wing flaps would be minimal.

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  • $\begingroup$ How do these dragons propel themselves through the water? Do they "fly underwater" like penguins? Do they tuck their wings along their bodies instead? Do they undulate from side-to-side like fish or crocodiles? Do they undulate up-and-down, like whales? Do they kick with their hind legs, like a human swimmer? $\endgroup$
    – Jasper
    Jun 30, 2019 at 23:10
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    $\begingroup$ You may be interested in Naomi Novik's Temeraire serie. Napoleon's wars, from the point of view of a British "airborne" officer. $\endgroup$
    – Matthieu M.
    Jul 1, 2019 at 7:06
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    $\begingroup$ This super doesn’t work, sorry. By mentioning soaring, you seem to fundamentally misunderstand how this works. Things that fly operate under an extremely delicate balance of weight vs power. For anything beyond short flights, most are hard pressed to carry anything beyond their weight, and that’s with a great deal of flapping, generally. When soaring, a few too many extra grams make flight untenable for an albatross. Propelling a boat take a hell of a lot of force. $\endgroup$
    – Daniel B
    Jul 1, 2019 at 7:43
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    $\begingroup$ Soaring does not add any energy to the equation, wing flapping does. Yes, some birds can stay aloft for long periods without moving their wings much, but that is only after a massive expenditure of energy that comes from flapping. After that, they are just really efficient gliders and occasionally take advantage of thermals to get additional lift. That is not going to get you enough energy to move a boat through water. $\endgroup$
    – Paul TIKI
    Jul 1, 2019 at 16:58
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    $\begingroup$ So... wild dragons are called dragons, but dragging dragons are draggins? $\endgroup$
    – Nahshon paz
    Jul 2, 2019 at 11:11

11 Answers 11

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I guess, this will be a Frame Challenge.

By your description, the dragons seem ill-suited to be good swimmers. They are aerial, not aquatic, unless you have a water friendly type dragons. Just because you use dragons extensively, it doesn't mean they are well suited for every single task. Unless they can float passively in water, their range will depend on their stamina. They are living creatures so need to rest, eat, crap... That's not something you want in your long-range vessels.

Historically ships usually built, because you can move more and heavier cargo over water. Transportation, Logistics. With HUGE dragons around who can fly, it is ill suited for them to be used for pulling boats. It would be way more effective to design a flying vessel around them.

Scenario 1: If your dragons are abundant and easy and cheap to keep, flying vessels will be designed around them with almost no ships whatsoever existing and the technology not refined.

Scenario 2: If your dragons aren't abundant or easy and cheap to keep, wind sailing boats will be the mainstream to cut costs.

The military aspect:

They won't invest in developing dragon pulled ships, because they have no reason to. With dragons, they can maintain air superiority and can easily destroy any dragon pulled ship from high up. It would be an easy target, since the dragon would be restrained to pull the ship. HIGH GROUND rulez!

In case of Scenario 2, they will have a standing Navy, but they won't be dragon powered. They will have Navy supported air force ready near the coasts and if their range is limited, especially for the smaller, more agile dragons, they MAY develop huge Dragon-Carriers, to extend their range of operations. Mostly in huge seas or oceans.

Also, flying create a lot of wind, especially if the creature is huge. It would mess up finely the ship or carriage pulled by such a creature. I imagine there wouldn't be long rows of people wanting to travel that way.

In short, dragon lifted AIR ships? Sure, awesome! Boats? Unless the dragons swim, nope.

Heavy handwavium and Fantasy territory

Scenario 3:

If you really, really, really want dragon pulled ships, you have to scale it right. With the huge sizes of the dragons in question, it would be the equivalent of oil tankers, huge barges. The dragon would be "high" up in the air with long chains connecting it to the ship. The ship should be huuuuge and/or heavy, to make it practical. Something the dragon can't lift up. Which require a whole lot of fantasy to work and for the ship to not sink. The dragon would function as something like a high altitude sail. This setup would be very slow and would mostly focus on material transport over long distances. Like oil-tankers. Maybe mobile fortresses.

And momentum would still be a bi...!

Scenario 4: (Because we already crossed to significant handwavium territory with the ship's properties)

Dragon-propelled ships, the unconventional way. For this to work, dragons must have the proper wing type (scaly? Not sure) or be an aquatic sub-species of your common dragons. Just like penguins to other birds. Yes, you may have guessed already. The dragons will be partly or fully submerged, with only their heads out of the water. They will use their wings to swim, well row in water.

This would be way more effective than flying, as they don't have to spend energy on keeping themselves afloat. This type of propelling also allow for a whole lot of fantasy possibilities, almost anything goes. The Navy may invest in developing submarines, depending on dragons lung capacity or with only their noses out of the water.

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    $\begingroup$ Scenario 2.1: You have waged war against a country using ships, but really want the ships to reach their destination quickly, So you use the dragons to pull the ships to some extent, cover a 2 days journey overnight then when you are about to hit the beach, release the dragons for air support and capture the beach. (for these cases ships need to have some kind of structure to be pulled by dragons). $\endgroup$
    – V.Aggarwal
    Jul 1, 2019 at 4:55
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    $\begingroup$ @V.Aggarwal If they would swim or on land, sure. But unless FULL ON handwavium, flying doesn't work that way. Flying low altitude and with constant pulling require much more energy than going up, gliding and down. No point pulling ships, just transport everything in air. Ships would still be easy picking, costly to implement, etc. $\endgroup$
    – Lupus
    Jul 1, 2019 at 5:28
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    $\begingroup$ With enough handwavium, you can just have floating wood and make dragons pull flying boats instead. We don't make planes to pull boats because it is extremely inefficient. At best we will have something like a hovercraft, but we don't try to make the engines generate lift and suspend themselves. That's what we're turning the dragons into; jet engines that are pulling boats and keeping themselves in the air.. $\endgroup$
    – Nelson
    Jul 2, 2019 at 3:06
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    $\begingroup$ If you wanted the 'boat' could be just a dead weight and act as a dragon-propelled mass driver! Smashing that into a harbour would be a good way to lay siege $\endgroup$
    – AncientSwordRage
    Jul 2, 2019 at 11:34
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    $\begingroup$ And now with scenario 4, I imagine penguin dragon. And my life is beautiful. $\endgroup$
    – Ted Pwyll
    Jul 3, 2019 at 6:51
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Speaking as a lifelong sailor, dealing with medieval construction, you would have to hugely overbuild a ship's prow to do it, the working life of ships would be really short, and sailors would be really seasick. Consider:

Dragons aren't sparrows. They wouldn't realistically do level flight: instead, they'd bob up and down as they flapped their wings. This would create a pronounced, repeated, and rapid pitch of the ship, unless you had the cabling go far far out to reduce the effect, and we're talking about maybe ten times the length of the ship or more. (You can just imagine how much fun this would make sailing in a heavily trafficked harbor or shipping lane.)

Short of "I don't care, I'm handwaving it 'cause it's cool to have ships towed by dragons," this isn't readily solvable.

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    $\begingroup$ I don't see why they wouldn't go with really long cabling. Not in harbour of course, but the nice thing about rope is that it can be winched up very efficiently, no? The dragon can swim in harbour, like a tug-boat, then on the open sea the ropes are extended and it takes off. $\endgroup$
    – leftaroundabout
    Jul 1, 2019 at 7:39
  • $\begingroup$ There's also the speed issue: a dragon, even one flying as slow as possible, is going to be dragging the ship through the water extremely quickly. $\endgroup$
    – Mark
    Jul 1, 2019 at 8:12
  • $\begingroup$ Couldn't this be solved by dampening with springs, elastic cables or some sort of elastic hooks made from wood, which would translate the bumping impulses into a smooth constant acceleration ? $\endgroup$
    – Falco
    Jul 1, 2019 at 8:38
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    $\begingroup$ @leftaroundabout -- Your comment could the core of a good answer. $\endgroup$
    – Jasper
    Jul 1, 2019 at 16:56
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    $\begingroup$ @Nelson so the solution is two-dragon towing, then? Have them well-choreographed so they flap to a beat, with one dragon on the "downstroke" while the other's on the "upstroke"? :D $\endgroup$
    – Doktor J
    Jul 2, 2019 at 19:21
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This answer assumes that the dragon propels the ship by moving through the air.

If the ship were simply pulled by a free-flying dragon, the ship would have to be small. For example, think of someone parasailing. Much of the dragon's effort would go into keeping the dragon aloft.

So instead, the ship supports much of the dragon's weight. The fo'c'sle of the ship would be a modified dragon-nest or dragon-hammock. The dragon's chest might be pitched slightly downward (compared to its free-flying orientation). The nest would have a built in harness, so that the dragon could pull the ship. There would be an area at the front of the fo'c'sle for feeding the dragon.

Dragons are arsonists, and ships are made out of flammable or meltable materials. When the dragon is not eating or drinking, its head would be suspended in front of the rest of the ship. This implies that there would be a pair of masts behind the fo'c'sle. Ropes would extend down from the masts to support the dragon's hammock(s). The two masts would be cross-braced, and held up by ropes attached to the rear of the ship.

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    $\begingroup$ The dragon is in front of the ship, head tilted downward, into the water, glug glug glug. $\endgroup$
    – Muuski
    Jul 1, 2019 at 18:31
  • $\begingroup$ @Muuski -- No, the dragon's shoulders are high enough that the wings usually stay out of the water. This is high enough to cause stability problems for the ship. Since the wings are much longer than the head, the dragon's head would usually not touch the water. Also, the dragon's neck will have some flexibility, so the head will not be at the same angle as the chest. $\endgroup$
    – Jasper
    Jul 1, 2019 at 18:36
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Note: This answer assumes that the dragons propel the ship by swimming, not flying.

The ship's design combines features of a stage coach, a catamaran, and a horse harness.

The ships are catamarans. The dragon's body and tail are between the two hulls of the catamaran, and the dragon's head and shoulders are in front of the hulls.

The ship's hulls and deck(s) act as a shield for the dragon's body and tail. They also prevent the dragon from turning around to face the ship. Effectively, the dragon's head acts as the ship's prow, and the dragon's legs and/or tail act like the propeller of a modern ship.

There is a great big harness around the dragon's shoulders, which is used to pull the ship. Heavy-duty ropes connect the harness to the ship's deck, perhaps via holes in the deck. Crewmen on deck can adjust the tightness of the various ropes, or even release the ropes. In an emergency, the ropes can be severed to quickly free the dragon. Smaller ropes that connect to control surfaces on the dragon can be used to transmit commands to the dragon.

The ship's weapons include a catapult with a modest range. The catapult can toss supplies forward, so that the dragon can eat and drink without having to turn its head around.

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To me the advantage of using Dragon-power is that you aren't restricted to staying in one element. If you rigged the ship on the dragon's back as @Stelpa suggested you could swim, fly and even move on land. The ship would need to float independently of the dragon (the dragon could be lost in a fire-fight or just need to sleep / hunt etc. so the ship would have to function without it).

A catamaran design would work (built to fit the dragon's back). I would make it schooner-rigged with two masts of equal height, deck-stepped onto a rotating plate. When in the air, the plate could be rotated so the two masts were side-by-side, then the masts lowered to the deck for dragon powered flight or rigged horizontally to allow the ship to glide down from the air. It would need very strong well-battened sails to achieve this.

Schooner-Rigged Catamaran

There would probably not be any propulsion when in the air, the sails would just be used as a landing option if the dragon's incapacitated or temporarily if the dragon was detached to take on a different opponent before re-engaging. The sails could be used for alternative propulsion when in the water. This would allow the ship to enter small river estuaries etc. that couldn't be accessed by a very large dragon. The sails would need to fold to the deck when under dragon power as they would create a lot of drag.

I see the Dragon's tail being the main means of propulsion when in the water so the ship could have retractable dagger boards and rudders when operating under dragon power.

The combination of foldable sails, retractable foils and a quick system of attaching and detaching the dragon in flight and on the water would create a lot of action during a battle and maintain the need for a strong crew who work together well and make solid tactical decisions to succeed in battle.

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You don't have to pull them. Put the ships on dragon's back.

I'm assuming your dragons are water type like Chinese ones, which would mean they don't have wings and their bodies are long and snake like. In that case, you can put ships on their back and dragons can carry them while swimming on the surface. Maybe those ships would have to be a bit train wagon-like in design.

Or perhaps you could put some water mill "wheels" on the sides of the ship, or hire people to row/paddle the ship to help the dragon drag it.

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It's hard to imagine how this would work but I'll try.

First, flying things tend to be relatively fast, and large flying things very fast. Even light aircraft cruise at 100mph, and the minimum speed for large planes is usually higher. You can build aircraft that fly more slowly (like gliders and ultra-lights) but we don't because it's easy to generate a lot of power in a combustion engine, and cars are more useful for lower speed transport.

Your dragons are the size of a small airliner, if they flew at the same speed they'd need to eat at an equivalent rate to an airliner's fuel consumption - probably their own body weight per day, or half a dozen cows for a flight of an hour or two. They'd also need runways or high cliffs for take off and landing. I think that means that dragons must fly more slowly than airliners, say light aircraft speed, with 50mph stall speed and 100mph cruise.

That's still much, much faster than most boats. 10-20mph is fast enough for most boats to start skipping across the top of the water like a speed boat, rather than pushing through it. 50mph boats would look like off-shore speed boats - very long and thin, and deeply Vee'd at the bow, to cut through waves and spread out the impacts.

At 100mph, boats don't need to touch the water as the airflow is enough to support the weight. The biggest engineering challenge is maintaining stability and not flipping over. I think your boats would look more like 1930/40's flying boats: long and thin, with wings and a tail for stability. Or possibly ekranoplans - seaplanes that fly very low to trap a bubble of air under the wing to improve efficiency.

TL;DR - they would be more like a DC3 towing a Horsa glider on D-Day than any historical boat.

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Use the Dragons as high altitude kites. (Eg. Jet stream altitudes) Give them a tether, let them climb on their own up to very high altitudes, and have them surf the wind the way hawks/birds of prey do. You get a smart kite that can reach airflows that would be very difficult with a plain old kite, --like ones blowing in the opposite direction of lower winds-- plus, you know.. you've got a dragon.

Otherwise keep all the other plain sailing constructs. Just use the dragons for tapping jet stream energy.

Optional Equipment: If the dragons are real big, give them a small crew that would rig them out with actual kite / sailing material when they get up there, so the dragon's wings wouldn't need to bear the strain all the time.

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  • $\begingroup$ Ropes long enough to reach the jet stream will be heavy. You might need balloons along the length of the ropes to offset most of the ropes' weight. $\endgroup$
    – Jasper
    Jul 2, 2019 at 15:07
  • $\begingroup$ Or lower the jetstream with the same imagination that created the dragons. ; ) $\endgroup$
    – aaronP
    Jul 3, 2019 at 16:11
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@Stelpa have the right idea but I say - get the ship to be tied below the dragging dragon (a dragin, for short). That way you're not restricted with the ship design, and can place it wherever. A simple net harness with hooks would take care of attachment and release to and from Draggy the dragin.enter image description here

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In our world, we do have boats which are tugged by a force that is strong enough to create quick movement, and also tries to tug the boat upward. They are called moths.

enter image description here

I admit that this design is not meant for transporting cargo, or soldiers. But with enough strength, the dragons may be able to lift up a heavy ship.

The main point of the design is that you want as little of your hull in contact with the water as possible, to reduce friction and all the other forces the water works on the ship. So you kinda put the boat on stilts. With sufficiently straight-flying dragons (do the blinders really work?) you should be able to do it. And when the ship needs to stop, or the dragon is distracted, it falls down onto the water on these wide, flat projections (they may have to become huge to actually support the top-heavy ship in such situations).

In the interest of simplicity, I will suggest that the most straightforward thing to do is to strap the dragon where the moth's sail is, and control it by tugging, similarly to how the sailor operates the moth's sails, and how a rider controls a horse. So the dragon will be above the boat, as opposed to in front of it. A sailor may recognize drawbacks to this though, so consult them. Also, be aware of killed dragons crushing their boats - although in a puling behind scenario, the boats will still likely sink once the dragon does.

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A boat is a big, heavy thing. Standing still in the water, it has a lot of inertia. No matter what is propelling the boat (wind, dragon, jet engine), it will take some time to get up to speed.

To put it another way, whatever is pushing or pulling the boat will be moving at the same speed as the boat. That means starting from a dead stop. So, lets assume the minimum airspeed for a dragon to stay aloft is ten knots. In order for the boat to go from zero to ten knots, the dragon will also start at zero and have to propel itself, and the boat it is towing, from a dead stop up to ten knots before it can take to the air. Can your dragons float on the water like ducks and tow a boat up to dragon-flight speed before taking to the air?

Now, if the boat has an alternate means of propulsion (sails, small motor, oars) and can get itself up to dragon-flight speed, then a dragon could fly over, match the boat's speed, and hook up to the boat somehow. Then, it could gradually ramp up its speed.

There is also the problem of hydrodynamic drag. As speed increases, drag increases proportional to the square of the speed. So, as speed goes up, drag goes way up. In order to resolve that problem, might I suggest a hydrofoil?

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