Nearly Waterproof Shade Sails!
The main pictures and this picture both show dry ground under shade sails after a shower.
Our sail are showerproof but when it rains properly, providing there is a 20% or more slope, the water will sheet on the upper surface and go to the lowest point but there will be line of drips underneath.
Rain seldom falls vertically and shade sails are usually high off the ground! In most scenarios if you are standing in the middle of a waterproof shade sail your head and shoulders will stay dry - now we are talking about an umbrella (again).
Totally Waterproof Shade Sails!
This picture shows a car under a fully waterproof shade sail. You can see that the car is dry and there is a dryish area to the right of the car. Above the car you will see well over 100 litres of rain "ponding" in the shade just waiting for a gust of wind to dump it on the unlucky person by the door.
Obviously if the shade sail were lower the protection would have been better. usually heavy rain is associated with a temperature drop and wind. That in itself makes staying outside very unpleasant and the need for a waterproof shade sail redundant.