Trunks, thanks for posting these graphs and figures. I'd seen them before at BPL, but had trouble taking them all in and relating them to real-world tarp use. I admit I still have trouble making meaningful generalities from these specific facts. The question of static versus dynamic water pressure/impact is especially mystifying ("mist"-ifying). I plan to keep using both silnylon and CTF3 tarps, though the old urethane coated nylon is (I think) the clear winner if hydrostatic head is the the best way to measure how waterproof tarp fabric can be.

Other people's accounts of tarp performance in the rain may not be rigorously scientific, but they are easier to relate to, so I'll just keep on paying attention to what works and what doesn't work, for myself and for others. Then, I'll implement what I've learned (if I remember to) and try to figure out if I learned it correctly. Thanks to all who are contributing to this dialogue. (I know, a great man once wrote, "The plural of anecdote is not data," but what the heck. )

Now, just so I can add something useful myself, let me state that I learned that it's better to have a tarp ridgeline under the tarp than over it, because without the ridgeline supporting it my tarp can form a pool of water overhead ....