New water conservation standards require that at least half of a pool's surface be covered when not in use. But pool covers are ugly at the best of times, and the fear that children can be trapped underneath is a concern to many parents. Easily made from hula hoops and black polythene, Lily Pad pool warmers are cheap, safe, and a heck of a lot more fun than traditional covers.
The polythene film captures and transmits solar radiation directly into the pool, warming the surface of the water. Inventor Edward Hujsak says that since they don't need to cover the entire pool, the lily pads form a "dynamic sculpture" as they nudge each other and form constantly varying patterns across the surface.
Hujsak says that you can swim without removing them: a bow wave ahead of the swimmer causes them to float out of the way. Though we haven't tested that idea, it seems clear that they're a safer option for parents as they are light and easy for kids to push out the way.
Edward Hujsak is a career rocket engineer who helped design and develop the Atlas and Centaur rockets at General Dynamics. Download his Lily Pad PDF file from Make magazine.
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.