I wove my own hammock a few years ago and since then I've been very paranoid about leaving it out in the elements. If you put that kind of work into something you get a little protective. If I see rain clouds on the horizon I unhook the hammock and drag it back into the garage. I can count on both hands the number of times I've left it out overnight. In the winter it slumbers in a large plastic bag in my attic. It's excessive. It's compulsive. It's obsessive. It has to stop. And here's the solution - a hammock shed.
Step 1: Alternate Uses
What brings more pleasure than swinging lightly in a shaded summer breeze? Not much. Maybe a small basketball (as see in the picture). But this need not be just a container for a hammock. Think of things you constantly bring in and out of your house, garage, shed and into your yard. Any of these things could fit into a custom made storage box and fitted to a tree in your yard (or to a 4x4 post set in concrete wherever you like). The two big uses for this kind of container that I can think of are for yard games and garden tools. If you and your family have one of those badmiton/volley ball sets, croquet sets, horsehoe sets or whatever then this might be a great storage solution for you. If you enjoy gardening then a well placed box with your shovels, hoes, and miscellany might be a time and energy saver. Could also be used to hold garden hoses, drip irrigation hoses, loads and loads of things.