Ship

Summary

The airship (commonly referred to as just "ship") is the most ubiquitous form of transportation in Seven Skies.
Ships range greatly in size, from small single-passenger skiffs to behemoths with thousands on board.
They're composed of two main sections: the "hull", which is the rigid wooden structure that forms the primary part of the ship, and the "envelope", a soft balloon (usually made of silk) containing the elevator gas that keeps the ship aloft. These two sections are usually roughly the same volume, but that can vary depending on how how the elevator gas can get, what type of wood the hull is comprised of, and many other factors.
Most ships of a size or purpose that require a powerplant make use of one or more Elevengines. Their power is used primarily to turn large sweeping propellers, whose blades are made of angled silksails. These propellers provide forward propulsion (and on some more maneuverable ships, can be reversed). Vertical movement is achieved through the manipulation of the envelope's temperature, or by pumping elevator gas in or out of the envelope.

Societal Impact

Ships are a transformational technology. Their advent as the principal form of transportation ushered in the Age of Exploration, which has completely changed the nature of international relations. What was once a slow trickle of messages or trade goods carried by unreliable means has now become a raging river of information and commodities borne by fleets of mighty ships.
As international relations have changed, so too have the people. The doors unlocked by ships have opened up a new world of opportunities for the daring. A great need for skilled sailors, navigators, cartographers, survivalists, merchants, and more erupted. Lured by the call of the sky, many left their homes and sought a new life of adventure and treasure, to mixed results. Some were lucky and "struck it rich", others settled for positions not as glamorous as they hoped but serviceable, and others met more unfortunate fates: through being taken advantage of by more cunning folk, contracting foreign diseases, or falling victim to the many mysterious dangers of the uncharted skies.
The sudden departure of so many young, able-bodied people also impacted societies still on solid ground. In some cases, villages or entire regions lost more than half their workforce over a decade to the wild blue yonder. They were forced to deal with starvation resulting from a lack of farmers or ranchers, infrastructure decay, crime, and more. Some survived by joining with adjacent communities, others scraped by through force of will, and some simply vanished.
Conversely, some communities exploded overnight with growth. Those who were on natural trade routes saw rapid expansion as merchants and venturers flowed through them. Again not without consequence as crime skyrocketed and the sudden urgent demand for infrastructure took a toll on their governments, but the flood of tariff money helped ease those growing pains.

History

Dangers

Early ships were incredibly dangerous, for many reasons. Early elevator gasses were inefficient and required significantly hotter temperatures to keep ships aloft, as well as larger envelopes. Larger envelopes had their own troubles, as silk was not as common, and silkweaving techniques had not yet been perfected. Thus, envelopes tended to tear easily, either from poor material or poorly woven silk. They bigger the envelope, the greater the risk of a tear.
Pioneers of ship travel also faced the issue of navigation. Severe winds were difficult to detect until you were caught by them, sky maps were nonexistent, and no one knew what to expect beyond their homelands. Of course, this was seen as a positive by many adventurers. Explorers who sought out the risky and unknown became known as Venturers.
Airborne fauna posed another danger for ships. Many predators welcomed these defenseless, slow-moving, crunchy snacks into their hunting skies with voracious glee. Other fauna were simply unintentional dangers: many a ship's envelope fell victim to the sharp talons of birds who used it as a rest stop.
Of course, many of these dangers are still relevant today, but sailors have learned how to mitigate many of these risks. Maps are beginning to be commonplace, sailors learn the hunting skies to avoid, envelopes are made with better techniques and material, etc.

Origins

Many nations claim to have invented the ship, but the true answer is that it depends on what you define as the first ship. Sea-faring ships certainly came first, but there is no way to determine their chronological origin as they've existed since history has been recorded. The Torlohalds claim the first airship was invented when their own Lemwist the Mad strung a small canoe to a pair of pigs and used it to lift his prized seaweed collection up to his cliff-side home.
The Valstralians of course dispute the legitimacy of this claim as less of an "invention" and more an abuse of local wildlife. They claim that the first airship was invented when Baldrich Gage came up with a brilliant solution to traversing waterfalls by tying a large sheet over his craft, lighting a fire underneath it, and burning dreamer's grass (which released the earliest known elevator gas).
Any true Wuljent, however, will point out that this ramshackle contraption A) only worked going down a waterfall and was not powerful enough to go back up, an important requisite for ships, and B) was clearly not that brilliant an invention as Gage would meet an early fiery death when his own contraption caught fire on the fourth demonstration of its capabilities. No, the real first airship by their estimation would be the one constructed by Emalie Copenwaller, complete with a proper enclosed envelope and filled with an elevator extracted from dreamer's grass (extracted safely away from the flammable hull, of course), for the purpose of trading with the Vulfrents below them more efficiently.
At this point another would point out that Ms. Copenwaller only perfected the basic ship design, not invented it, and then the argument would return once more to Lemwist the Mad and begin anew.