Here’s another idea I don’t want to bother patenting.
I’ve owned 2 motorhomes so far, and the roofs always leak. There are lots of holes in the roof for vents, wires, etc., and with all the jostling a motorhome gets on the road, after a while lots of invisibly small cracks open up (despite sealant) and the roof leaks – even if you apply more sealant every year.
Make the roof a hollow structure with air pressure inside. It could be a flexible inflatable structure, or rigid but with a hollow air-tight space inside.
Then pressurize the inside of the roof with air from a pump or tank.
When tiny gaps appear in the roof, the air will escape outward (being replaced by the pump or tank) and will push away water, instead of letting it in. So the interior will stay dry.
The pressure doesn’t have to be high – a few PSI (tens of kPA) should be enough to prevent water from coming inside.
How often the pump runs (or the tank empties) is a measure of how many leaks there are in the roof – when there are enough to bother with, you go and apply sealant. When the leak stops, you’ve found the spot.
You could even pump in colored smoke to help find leaks.
This would be a cheap solution – a molded (or inflatable) roof doesn’t cost much and a $20 electric air pump are all you need.