Sailing

Many technologies have been invented or rediscovered in the decades before the arrival, but none fundamentally altered our world as much as sailing did. Because of it, the arrival took place. Ships existed before the invention of the sail, but travelling from modern day Velamare to Meiteikoku was considered to dangerous and slow when using oar powered ships. Sailing changed everything and allowed for trade between both people. - Inventions that Changed History, A. Almecci

Utility

The sail is useful for propelling ships. It also allows for larger vessels that can carry a lot of trade goods, as barely any manpower is required for it. The biggest issue with the technology is that it's largely dependent on the weather (wind to be more precise), but that's why most ships still have oars on board to be able to keep moving, although at a lower pace. .

Access & Availability

Sailing is used as the main propulsion method for ships ever since its invention over 500 years ago. Even for ships that don't use it as its main source of propulsion, sails are often present. While the cloths and fabrics to make sails can be relatively expensive, small sails are often available for everyone. Only very small vessels don't have some form of sail on board.

Complexity

Sails in their most basic form are very simple and only require fabric/cloth and rope to make. Therefor it's easy to manufacture in large amounts, which helped the technology spreading.

Discovery

While many technologies around that era where merely rediscovered or borrowed from the city states, some like the sail (and thus sailing) were completely new. The people of Velamare decided that they needed a way to travel to the main continent for trade and considered the journey to dangerous and slow on regular, oar powered ships. Therefor, a solution was found and thus the idea of using the wind for propulsion was launched. This eventually lead to the development of the sail.