By the time he gets back with seven of his closest friends, the ship is done. Pretty much done. It has a lot of decks and some sails and a rocket engine, at least. You don't know everything that's supposed to be on a ship, but you're certain voidsailers don't actually work like sailing ships, so it doesn't matter. You've used the substantiation domain of Stone to turn silk into something more solid, and you can do more of that later. All you need for now is enough space for everyone to get aboard.