My design would start with the envelope/solar propulsion system.
This may take a little effort to wrap your head around but here goes.
This is a Stirling engine. A closed system, lower temperature "cousin" to the steam engine. Now imagine this model turned to use solar heating from the top of a transparent gas bag. The gas bag would be separated by a diaphragm with the lower cell providing the required cooling from shade and air cooling. This would slowly turn a drive shaft through the length of the airship to a large, efficient propeller. This could provide virtually endless travel with the fewest components to fail. It would sound like a breathing beast as it steered through the day sky.
There are many potential ways to improve this ship's efficiency starting with reading the different winds at altitudes. Mooring, drifting, or alternative propulsion would be needed at night but she should average 400+ miles each day.
Solar balloons and model airships already exist in different forms. This could help produce lift as well as airspeed.
I am still a fan of plentiful Hydrogen as a lift gas. H2 can be made as inert and safe as expensive, non-renewable, Helium by adding a small amount of Halon or other extinguisher gas. Sadly, the Zeppelin staff was developing this technology just as the Hindenburg burnt up.
I suppose that theoretically turning on a conventional balloon heater into the lower cell at night would both compensate for the lost solar lift and the engine would still work with the top cell doing the cooling. This would require fuel of some sort though.
The next requirements would be storm detection. Storms killed most of the great airships.
So any way, a smooth envelope with 3 rudder/stabilators (less drag), a large tail mounted prop, a control similar to a boat hull, and top gun/maintenance platforms like a WW I zeppelin.
Most of the romantic deck and rigging would be internal among the girders and lift gas cells.
Heat engines are always, to me, an interesting concept. They do have one great disadvantage, in that they are not self-starting. (Or has that issue been dealt with, somehow?)
Did the Zeppelin company actually discover halon? Or just something similar? And if so, than what? I know that a mixture of hydrogen and helium can be used, but, from what I've read, it doesn't offer much of an advantage over just helium as a lifting gas.
I ask because I want my (ficticious) airships (in my stories) to be as safe, and also as efficient as possible. I already use the concept of auxiliary gasbags (ballonets?) using steam as a lifting gas to gain fast ascent. And the American models are already using helium, but if there's a "safe" way to use hydrogen, it could really make my Prussian airships terribly scary.
I cannot find the article written on the previous Atlantic crossing by an American journalist but he rants about the US refusing to sell Helium to Germany (but we sell it to China now) or even enough to fill the outer gas bag cells, designed to make the Hydrogen safer. They ended up just filling the outer safety liners with air instead. He went on to discuss how the German scientist were working on some sort of additive to make Hydrogen inert. Probably not exactly Halon but Halon proves that the idea works. Halon is not ideal since even though it appears to stay mixed with Hydrogen it is a heavy gas and lowers the Hydrogen lifting power by about the same 8% as Helium. Now if you could figure out how to keep H2 split into a less flammable gas with nearly double the lift of Helium you would bring on a whole new age of airships. Who knows, with all of this sustainable fusion research.....
Unfortunately I cached this article in SPE.
As for the Stirling engine, I have seen them self start but you are correct that some sort of way to add toque would be wise. It could be as simple as a giant lawn mower pull cord. Crew sized. A nose dive might work too or, if still moored, just turn the nose into a reasonable wind.
If you have steam to fill ballonets you could just make Hydrogen which has much greater lift: https://en.wikipedia.org/wiki/Steam_reforming
Ah, I postulate the use of steam because it is a byproduct from the boilers that fuel the bladeless turbines. Sure, hydrogen can be generated by simple means, but isn't weight the enemy of all airships? I figure to just decrease the weight, since steam is lighter than air, and already available.
I hadn't considered the idea of "jump starting" a heat engine by crew action. I like that!
Jump starting the engine could make good story text. The reality would be that a dew covered rig each morning at sunrise, in rain and snow, would be a miserable form of PT for the crew. ;-)
If you are using a fossil fueled boiler there seems to be some potential to create hydrogen with exhaust gasses and steam(?) Weight is always an issue in any aircraft but superior lift helps to offset this. Steam (and hot air for that matter) are mediocre lifting gases and cool while hydrogen is the lightest. Managing all of these variables is why the bridge crew gets the big bucks.
Ah. I do a little thing in my steampunk universe, such that natural gas is available (It's lighter than air, so is close to the surface of the earth), but (most of the) petroleum has sunk to depths that cannot be reached with the drilling technology of the time (1905 - 1908). In fact, it gets a bit more complicated than that. But anyway....
Yeah, I can see how using a big pull cord to start a heat engine would make a good plot device.
And yes, hydrogen is certainly as light as a lifting gas gets, but its volatility is a definite drawback from a safety factor in commercial service. At least for me. My "North Star Lines" gained plenty of investors when they announced they were going to use helium, exclusively. Heh.
Your investors might realize more profits if the airships floated on much less expensive "safety Hydrogen."
Imagine a series of cheap wave powered hydrogen generating buoys as little filling stations.
As opposed to a relatively rare non-renewable gas: http://www.independent.co.uk/news/science/why-the-world-is-running-... Deeper petroleum reserves might have the side effect of releasing more helium which could be extracted from natural gas lines.
The ONLY Airships destroyed by the hydrogen they carried were the US Army Airship Roma (Which crashed into powerlines because of poor navigation) and the Hindenburg, which was caused by a number of human errors stemming from the ground crew and flight crew rushing to land her.
All the other airships that "came to earth" suffered structural damages that tore the bags open, or were intentionally destroyed in war.
One US Zeppelin (USS Los Angeles, ZR-3) had a perfect operating record. (save for one incident where she was stood on her nose at the mooring mast, and that was caused by her use of helium. Ironically Had she been hydrogen filled, the incident never would have occurred.[see picture above]) She served for almost 15 years before being dismantled. And her dismantlement was the military deciding her aluminum could be put to better use.