Eagleships are the most common vessels of the High Elf fleet. Armed with broadside Eagle Claw batteries, these craft are huge, sleek and streamlined, making them both fast and deadly. They are able to out-race even Bretonnian Corsairs and are far more maneuverable than any ship of the old world.[1a]
Their hulls are made from a single curved mighty Starwood tree, grown specially for this purpose by Masters Shipwrights of Ulthuan. Those shipwrights lovingly tend groves of Starwood for a time equal to many men's lives. They sculpt the shape of the trunk as it grows, working with the wood to maintain its strength and integrity. They then carefully select the strongest, most flawless of these magical trees before they are uprooted. Mighty spells are then used to keep the plant alive and the masts are actually branches grown out of the trunk that will become the hull.[1a]
Its sails are works of art in themselves, woven from the hair of several shriven priestesses and spiderwicked in a tapestry of enchanting beauty and finally ensorcelled.[1a]
Trunks are bled just before the ship is launched and the sap of the living tree is tapped and allowed to flow out and over the hull. The resin is hardened until it is a strong as steel and remains watertight. The ship is then blessed by the High King himself and allowed to go to sea.[1a]
Source
Man O'War: High Elves -- pg. 48