SilPoly Tarp Condensation

[LowTech]

Here in the desert we don't usually get dew except, right after we have rain. Not the light rain that falls and then returns almost as fast, but the all day storms that rain multiple times in a 24 hour period . . . those kind of rains. After those it's guaranteed that everything will be wet in the mornings.
Anyway, when I moved to SilPoly tarps over the tougher SilNylon ones that I started w/ condensation on the inside started to become an issue that I'd not really had before. Of course pitching the walls steep helps shed it since poly doesn't absorb. Unfortunately I like space and hang pretty constantly in a windy environment so I've gone to using interior poles to pitch my tarps sort of quonset hut style. Of all the things I've expermented w/, shock cord on the guy outs, no shock cord, exterior poles, cat cuts, angles to the wind, etc, nothing has worked as well as running interior poles. Problem w/ that is that its not a steep pitch and if I get a morning wind . . . it rains on me from the interior of the tarp.
These storms that have been flooding places NW of me have created a situation where I've had about a week of wet mornings. After a few days of mornings where I had to pull all my quilts out if the hammock before morning winds started, the whole time trying not to brush my head on the tarp and start a dripping line, I came up w/ an experiment . . . I was going to pitch a small hex tarp that I had inside my big 12'×14' base camp tarp.
This started when I noticed that there was not interior condensation where I had the corners folded to the outside making that part of the tarp double walled. I knew how doubled walled tents work and was interested in how double tarping would work .
I didn't have enough pole sections to do an interior pole setup on the big tarp so I did an exterior pole one and then I pitched the small tarp in a basic A pitch inside it. The next two mornings when I got up there was not a drop over my head. I was able to sort out my bed w/o worrying about brushing against the tarp. The outer tarp still had it's condensation but the inside of the inner tarp was totally dry. Then the winds pushed me inside w/ over 24 hours of > 20mph winds w/ regular gusts over 30mph and 36moh being the top so far. I wasn't willing to subject my tarps to that unless it was a survival situation. Hopefully it'll still be wet enough after tonight that I can get a couple more nights of testing in before its too dry to dew.

For me I think optimum would be having both tarps w/ interior pole setups.

 

[cougarmeat]

Thank you for conducting the experiment and providing the report. Just last night, I was musing about traps. The ThunderFly was my last SilNylon - because I couldn't think of a redeeming feature over SilPoly (aside from a bit more toughness). I soured on SilNylon after I had to wrangle three wet tarps at Honeyman State Park (coastal and wet). They do get heavy.

I've never had a "mist" problem in my Hammock years, but I definitely recall a morning on Vargas Island where every exterior surface was wet with dew. I wondered how a hammock - and by hammock I mean quilts - would fare under a tarp in that situation.

 

[LowTech]

I see that I should be referring to them as SilPoly and SilNylon so as to be clear on the types of tarps I'm using. Too much assuming on my part.

 

[LowTech]

Well the wind is going to be here for a week or so and it's already dried everything enough that there's nothing more I can do at this time to experiment more.

 

[Alan]

Found anything new the past 2 weeks?

 

[LowTech]

Condensation and dew have been nonexistent since then. We did just go through a couple winter storms w/ rain but didn't get anything from them. Now winds . . .? I've had no shortage of them. Some nights w/ 20-25mph sustained and gusts up to 50mph. So experimenting in the wind never stops around here.