General tech level is medieval. There's a smith and a smithy on the ship, which is a wind-powered sailing vessel. I need a throwaway line to explain why the crew is not able to condense water, such as "We don't have any _______ aboard," because if they're able to make water half the rest of the plot becomes impossible. I remember from the Voyage of the Mimi that you could use plastic sheeting, but this is not Ye Olde Medieval Plasticke, so that won't work. I can find a hell of a lot on the fact that I WANT to build a condenser, but not HOW. Air wells and fog fences and dew ponds are not going to fit on a boat.
EDIT: Got what I need, thanks! And now I feel like an idiot for not remembering that plastic replaced glass.