Tarp "misting", "leakage", condensation etc.

[Jsaults]

Couldn't find the original post, but there was a bit of discussion about sil-nylon "leaking" or "misting through" some time ago.

This past Saturday, during a hang in the wilds of northern Pittsburgh PA (my Father's back yard!) I awoke to find the underside of my WB SuperFly lightly coated with moisture. There were a few light showers overnight, nothing to get excited about, and my WBSF is pretty new (only a few nights out).

But the conditions were very humid, with temps falling from the 80s down to the mid-60s. I simply wrote it off to condensation due to the atmospheric conditions. I wonder how many complaints of "leakage" or "misting through" are due to simple condensation?

Jim

[Shug]

I feel sure it was just that.....condensation. All my silnylon tarps do that.
Shug

[JerryW]

I've had condensation under my tarp, even heavy frost, but never had rain "mist through" no matter how hard it poured.


Jerry

[Cranky Bear]

Also have to take in consideration that Silnylon can become saturated because of the humid and wet conditions which can cause the wet inside of the tarp as well!?!? I think it all comes into play at some time or another, but no matter what having a soaked tarp over you is better than having no tarp (at least that is how I look at it)!

[gargoyle]

yep, just like a glass of water on a warm day.
The fabric is cooled by the rain, making it cooler than the air, and allowing for condensation to happen.
Then the following rain drops hit the collected condensation on the fabric, and causes the droplets to fly off, creating a misting effect.

At least that is my theory

[Hawk-eye]

Another one for the condensation aspect ... no misting, no leakage (but I seam seal). I have had rain run the ridge line and even jump a Dutch biner. So I always run my ridgeline on top and use drip strips.

[Tendertoe]

I have experienced this same phenomenon in those conditions with my Spinn tarps too.

It has to be condensation as Spinn supposedly does not "mist though".

[BillyBob58]

I have had that about a bazillion times. I have it often when it has not even sprinkled.

So I'm pretty sure it's just some form of dew/condensation. Just to throw another monkey wrench into the discussion, I'm pretty sure every time or at least most times I have ever had this was in my backyard. I cannot say for sure if I've ever had that happen on a backpacking trip. But if it has, it has been seldom for me.

[Jsaults]

the Solar Still concept, but I guess that is not really correct. Warm, moist ground is going to be giving off water vapor, and the tarp is the obvious cool place for it to condense.

Speaking of nylon becoming saturated, I guess that is a possibility as sil-nylon ages and loses some of the silicone treatment. It will be interesting to see just how long it lasts (that is, causes water to bead and run off). But I still like sil-ny better than urethane-coated fabric.

Jim

[Rug]

What is hard for me is pitching the tarp steep enough to allow the 'big' drops to run down the tarp and not drip on me. That is why I like the big tarps, enough room to get in & out, and still big enough to pitch it low.