Derrigable sailship.

[Knife]

So, for whatever reason we've decided to build a derrigable. We have the technology to build the frame and make and pump the hydrogen/ perhaps helium into the various bladders inside the frame work to make the ship float.

What we don't have is electrical engines, gas-combustion engines or even steam engines to run propellers on the ship. What we do have is good old tried and true sail power.

One, what would be the realistic problems with such a feat and two how would you go about placement and use of sails on such a thing?

All that rigging all on top would probably make the ship flip keel up. Could you put a mast on the dorsal and then another mast on the ventral side of the ship? Perhaps on each side of the ship. Any ideas?

[Gomu Niwatari]

Well, considering it's lack of stabilization, lateen (triangle) sails aren't going to be useful. Really, you'd just have a really big and cigar-shaped version of a hot air balloon.

[Winston Blake]

Over/under sails would probably make it harder to keep stable when landed, and be harder to build (reaching the top side).

I'm sure a lot of experience went into the designs of historical ship sails. An idea would be to use a simplified sail pattern of the ship class closest in size to your dirigible.

One big difference is that there's no water to act against when tacking, so you can't travel into the wind.

[Broomstick]

It won't work.

A dirigible (or balloon or zepplin or any other such aircraft) is not comparable to a ship on the water - it's much more like a submarine under the surface of the ocean.

You don't stick fins into ocean currents to drive a submarine, you have to have a propellor/screw. Same for an airship. Stick a sail on a balloon it won't go any faster in the air than if it didn't have it. A sail/fin might change the airship's orientation with regards to the air mass or ground, but it won't even allow steering.

By the way - all airships (and balloons for that matter) could be equipped with a ballast system, and most are, to maintain up as up and down as down.

Now, in theory, you could have a muscle-driven propeller, but really, why not use steam power to drive the propulsion system? How can you not have steam engines? If you don't have steam engines then boil water and expel it as a jet - which I suppose is a steam jet.

[Simplicius]

If you're envisioning sailing ship-type rigging on a zeppelin, I'd say you should probably forget it. The weight of the masts, sails, standing and running riggging, ironwork, tons of extra structure to step the masts into, and a large crew and their living space and provisions will interfere with the effective operating of your dirigible. Plus, you will only ever be able to go downwind anyway, so it won't be very useful as a proper vehicle. Might as well just bag it and use a hot air balloon instead.

[Knife]

Well damn, I was hoping for a clever way around the various problems. I knew tacking would be non exsistent but... Oh well, steam punk it is I guess.

[The Duchess of Zeon]

Well damn, I was hoping for a clever way around the various problems. I knew tacking would be non exsistent but... Oh well, steam punk it is I guess.

Quite. It is simply impossible to rig a flying machine with sails, sorry.

Steam engines, however, well, that's how the first powered flight in recorded history took place--a Frenchman's steam-powered airship (in the 1850s).

[Beowulf]

The only underwater vehicles that can manage to move horizontally without a propeller are essentially gliders. Probably not quite what you'd want, especially considering you'd have to have a way to change it's buoyancy in the air repeatedly, and you'd have to repeatedly gain and lose altitude as well. Steampunk is by far the better option.

[Jadeite]

There's a guy in Pennsylvania who built his own rigid airship, it uses a lawnmower engine for powered propulsion.