Building a Teardrop trailer?
Seal every single wooden surface really, really well. This means end grain, too. Seal, seal, seal. You want to make it waterproof inside and outside. It's not impossible; you just need to be thorough.
Use paint on the galley side walls, floor and hatch interior. Use a thick, oil paint. Water will most likely find its way in at some point, dripping down a wall and puddling on a flat surface so make sure it's all waterproof.
Caulk every single seam, anywhere two pieces of wood meet. Seal it up.
That's my speech of the day.