New shelter

"My experience is that in a major downpour, water will find its way through if there is a way through, even when the way is not apparent to the naked eye. This can occur at a seam, as noted by Lori, or where there is a not easily seen flaw in the mylar (cuben) or the fabric coating (sil)."

I'll go with that theory, although I'm still surprised at how *much* got through. As soon as we get some warmer weather, I'll take the tarp outside and apply a thin coating of diluted silicone to add extra sealing, plus make sure the seam is absolutely sealed.

"So what do you guys think of the scarp? How does it compare to the moment?"

Don't have a Moment, but I do have the Scarp 1 with the new fly. It's a very nice four season tent, with excellent floor space and head room. It looks solid enough to take a fair bit of winter weather, although, of course, it's not designed as a tent for an Everest base camp. Because of the inner fabric liner it should be a bit warmer than any single walled tent, while still having enough (adjustable) ventilation. A nice design.

"Is there a seam on the tarp? Do you use one of those ridgeline setups where the line is strung between two trees and the tarp attached to it, and if so, was the line below the tarp? The only thing I can think of is a scenario in which a seam wasn't sealed or the seam sealing hadn't "took" for some reason. Or a line drawing the water under the tarp. Unless it was some really odd combo of site selection and weather?"

It was an MLD tarp set up over a hammock, with lines running from the middle of each end of the tarp to a tree – no ridgeline under the hammock itself that supported the tarp.

I'm going to redo the seamsealing this spring, and will try applying a very diluted coat of silicone sealer over the tarp itself.

I have been caught in a few >12 hour downpours and can say, IMHO, “misting” is caused by condensation. “Drips” could be caused by a leak OR condensation collecting into drops large enough to fall from above.

My last trip was the worst for condensation I have experienced.

Synopsis:
GoLite Shangri-La over snow with temps around 34 degrees F, and 16 continuous hours of rain with the back of the tarp under high tree branches. The misting I experienced from this heavier (1.7 oz) Sil was when the large drops fell from high above (read: loud!), breaking the condensation loose from the 50+ degree walls. I heard and felt drops on the sleeping bag only to find GoLite’s (you don’t need to seal this because of this awesome thread) malarkey was failing. I just have a hard time swallowing misting caused by rain being driven through the material… but stranger things have happened…
Could it be more so when the fabric starts to stretch maybe?

Misting is not the same as condensation falling from the inside of a silnylon wall. Fact: Most silnylon has a hydrostatic head of only 1000 to 1200mm. Under hard rain pressure the fabric will mist. End of story.

"My experience is that in a major downpour, water will find its way through if there is a way through, even when the way is not apparent to the naked eye.

I'll go with that theory, although I'm still surprised at how *much* got through"

It can be amazing, at least in my experience of dealing with houses and hurricanes or major northeasters; one minute it's dry, the next its pouring. ( usually after many hours of being dry ) There was a very active thread back in 2008 begun by Miguel D Arboleda discussing his experience with a silnylon tarptent. Though my experiece is with houses and not tents or tarps I can add the following apparent observations regarding leakage in fairly major rain/wind situations.

The combination of time and pressure seems to be the key. Water will get pushed into and begin to permeate materials and "channels" it would not seem possible for it to penetrate given enough time and pressure. Once the penetration is complete through the "barrier" a syphoning effect begins to occur. This can be relatively quite pronounced and abrubt. It appears to many local observers regarding buildings that there seems to be some sort of pressure differential at work where the lower pressure inside is literally pulling the water through the established channel. Maybe also there is that quality of water; it's viscosity or whatever ( help me here! ) that also creates a situation where the water that has made the penetration seems to be pulling other water through. Anyway the appearance or experience is that there was no leak and now it's just pouring. I would expect this is what Samuel C. Farrington is observing and I would think it would be the rule in high pressure/long period situations with any fault or "channel".

Miguel's experience would seem to be an outlier; where really large amounts of water can get pushed through fabric that is generally speaking water-proof; that with enough volume and pressure the fabric gets soaked and the circuit then connects; water can begin to travel through the fabric in greater volume.

But of course I'm no scientist or have no particular knowledge of fabric and the associated physics.

A recent post from Whiteblaze on some misting with the TT Moment. With that type of storm – misting is inevitable in certain situations (high pressure rain), but minor. It is a livable fact in exchange for UL materials.

http://whiteblaze.net/forum/showpost.php?p=920980&postcount=63

Hi Don

> My assumption was that there was no way that condensation could form underneath
> the tarp at a rate that corresponded to the rate at which I was being hit by drops of water.

A risky assumption!

Let's look at the meteorological conditions likely in such a case. An abrupt storm is often preceded by warm humid air, while the rain itself comes from a cold front over the top at a much lower temperature. This means that the wet soil and atmosphere under your tarp was warm and moist, while the cold rain chilled the tarp down fairly significantly. To make things worse, the ground sheltered by your tarp stayed warm since it didn't get hit by the cold rain. It was slightly damp from the little bit of rain before you got your tarp up.

Under these conditions the amount of evaporation from the ground and condensation on the underside of the tarp can be astonishingly high – enough to function very well as a water collection device. This method has been used to get drinking water in some parts of the world (eg deserts).

Cheers

Hi Sam

> a pin hole (or a tiny slit), when exposed directly to driving rain, will
> allow water to drip through.
I am not going to argue with you there! I have experienced that myself too – a ridge seam leaked under a huge storm on one of my early tents. yes, it had been proofed too – but with the 'wrong stuff'.

> Think the urethane coating finally lost its effectiveness,
Yes, this happens. The coating sticks to the fibres still, but microscopic holes develop in the gaps between the threads. Time for a new tent.

Cheers

Hi Cola

> where the water that has made the penetration seems to be pulling other water through
I understand what you are driving at, but the physics is a bit different.

Let's imagine we have a simple (tiny) hole in a sheet of Teflon. Water won't get through because of 'surface tension'. The surface of the Teflon doesn't want to get wet, so the water just bulges at the hole but does not get right through. Despite the hole, the Teflon seems waterproof.

Now let's imagine the water is pushed through the hole somehow. Technically, that means enough pressure was applied to overcome the surface tension in the water across the hole. Now you have water on both sides of the hole – so where is the surface tension now? Well, gone. Without that barrier water can pour through the hole with very little resistance. Your comment that 'the circuit then connects' is remarkably accurate in a way.

So guys – sing the praises of a good DWR coating! Don't let the fabric wet out!

Cheers

To repeat what others have said, Cuben fiber is made of two solid films
of polyester (mylar). Think plastic bag. There is no misting
with this unless the material is destroyed by the pressure.

Since heavy condensation can happen with Cuben, which people attribute to "misting", is it not
possible that "misting" on silnylon is from the same cause?

A steeper pitch to the roof will both lesson the impact force
of snow or rain and increase the likelyhood the condensation
will run down the inside of the fabric rather than
dripping off onto the inhabi-tents.

In the effort to reduce weight of shelters, many have very
shallow roof lines, which may not be suitable for all
climates.

Roger, you want to make it clear that DWR=Teflon.

Many DWR solutions are fluorocarbon-based, so they make fabric into a Teflon-slippery-nonstick surface.

OBTW, environmentalists are very anti-fluorocarbon these days.

–B.G.–

David, totally understand as were my thoughts when I posted, before FamilyGuy's reply.

Maybe it is my misunderstanding in what "misting" is; hence it is in quotes. When a drop of water hits the shelter over your head and you feel a misting of cold spray on your face, but cannot actually feel the water that hit with your hands is what I meant. Did the water get pushed through at over 2psi on a 50+ degree slope? Doubtful, as I felt nothing until the buildup of condensation occurred.

Of course my assumption of falling condensation came based on when I wiped my tarp down each hour, the misting ceased, for that hour.

"Misting is not the same as condensation falling from the inside of a silnylon wall. Fact: Most silnylon has a hydrostatic head of only 1000 to 1200mm. Under hard rain pressure the fabric will mist. End of story."

On reflection, I'm not sure that I can actually describe what I experienced as "misting." I think of misting as more of a fine spray, and I was being hit with larger drops of water than that. Perhaps the top seam had been penetrated, the high pressure of the rain was able to force water through the fabric, or the condensation accumulated fast enough to produce the steady rain of water drops on my face.

What I will do in the future is attempt to add an additional thin coating to the entire tarp, and to try pitching the tarp itself at a greater angle, so that if water does form under that tarp, it will be more likely to run down to the edge rather than being dislodged onto my face. All good thoughts.

Hi Bob

> Roger, you want to make it clear that DWR=Teflon.
Definitely not in this case. The good DWRs are mainly fluorocarbon (not silicone).

> environmentalists are very anti-fluorocarbon these days.
Not true.
There have been well-known problems with some of the precursors which used to be used in the manufacture of Teflon, but those have been phased out.

The manufacturing industry does not get everything perfect the first time around, but in general I find most ethical companies are willing to change their processes to eliminate problems which are validated.

Cheers

in terms of gross generalities, and in particular as related to backpacking fun, Goretex=PTFE=Teflon. GTX is basically thin teflon, a laminate. Not a spray-on, or a coating, etc… I have seen "Teflon" chain lube for bikes in the past, but have no idea how that stuff works. (Teflon is used for tons o' stuff, even non-glare coatings on optics/glasses.) Most DWRs used on backpacking fabrics though are not Teflon. The reason I make this distinction here is that in the case of shelters, any "teflon" would likely be the goretex of a canopy, which provides the primary waterproof/breathable layer. The DWR is independent of the primary waterproof layer/laminate/coating.

Hi Brad

> GTX is basically thin teflon, a laminate.
Well … not 100%. Actually, the waterproof membrane in Gore-Tex fabric is PolyUrethane (PU).

It's a long story, but in brief Gore found that the Teflon in V1 got dirty and wetted out in the field, so these days in V2 they use the Teflon layer just as a smooth base for a very thin layer of PU coating – thinner than would work on plain fabric.

> The DWR is independent of the primary waterproof layer/laminate/coating.
Absolutely! In fact, I reckon the DWR is as important as the coating – in the field.

Cheers

I wrote > Roger, you want to make it clear that DWR=Teflon.

Roger wrote > Definitely not in this case. The good DWRs are mainly fluorocarbon (not silicone).

Roger, Teflon is Poly Tetra Fluoro Ethylene, or PTFE, and it consists solely of carbon and fluorine. I think you contradicted yourself. This is chemically similar to the stuff that is in DWR fabric treatment.
–B.G.–

Alright guys so I'm brinking it back to the original topic.

After much investigation, reading, and suggestions I've decided that I'm not ready to fully jump into the ultralight world. That being said I still want to carry less that what I currently have. I'm not ready to part with double wall tents yet that offer better protection.

What does everyone think of the Hubba, Hubba HP, Copper Spur, Fly Creek, Scarp? How does the hubba and the hubba hp compare and which one would be better for New England?

Thanks

The Fly Creek comes in a 2-person or a 1-person version. I'm not tall, so I got the 1-person version. However, if I were any taller, the 1-person version wouldn't make it. It certainly has plenty of inner netting.

–B.G.–

I agree with Roger's caution. I've frequently gone to bed in/under a floorless shelter (teepee/tarp) only to find the underside soggy from condensation. This most commonly happens on cold, still nights and has no regard for what material the shelter is made from.

I find a steep-walled shelter typically directs the water away from me, while a flat one can drip on me directly. Of course, knocking into it sends down a shower no matter what shape it is!

Cheers,

Rick

Roger wrote:

"Let's look at the meteorological conditions likely in such a case. An abrupt storm is often preceded by warm humid air, while the rain itself comes from a cold front over the top at a much lower temperature. This means that the wet soil and atmosphere under your tarp was warm and moist, while the cold rain chilled the tarp down fairly significantly. To make things worse, the ground sheltered by your tarp stayed warm since it didn't get hit by the cold rain. It was slightly damp from the little bit of rain before you got your tarp up."

"Under these conditions the amount of evaporation from the ground and condensation on the underside of the tarp can be astonishingly high – enough to function very well as a water collection device. This method has been used to get drinking water in some parts of the world (eg deserts)."

Hi Roger-
Yes, I'm aware of the V1 problems… but the GTX is still the "Teflon" base, topped w/the PU coat. Too bad they couldn't figure out how to make the material oleophobic like eVent did… V2 necessitating moisture to actually condense and pass through as water rather than water vapor thru the PU part of the layer…

I think the DWR is as important as the coating in terms of breathability… a saturated shell won't "take on" extra moisture so well, and breathability suffers. Breathability of the WPB is pretty dependent on a good DWR, but the actual waterproofness of the GTX/WPB layer is not affected by the DWR. You might get more wet because a jacket doesn't breathe as well, but you're not going to have a catastrophic failure of the WPB layer if the DWR's worn off.

Adam, of the tents you mention I really like the Copper Spur. Great tent, huge doors, covered well by fly, lotsa space for little weight. Between the Hubba and HP, you pay an extra $100 for the HP and gain a solid-ish nylon interior, reinforced guy-out points on the fly, and save 3 ounces. The 2-P version adds vents on the ends of the fly. The solid inner (a couple of non-closable mesh vents in the top of the canopy) better for colder weather, blowing snow/sand… but also somewhat less breathable than the mesh of the standard version. If you're doing normal 3-season stuff, I'd just get the standard Hubba (betwixt that and the HP).

Brad,

Josh Wagner is selling a Big Agnes Fly Creek 1 on this forum.

FS/WTT big agnes fly creek UL 1 on 01/16/2010 12:15:56 MST

I have a Big Agnes SL1 and I love it because it is roomy and it really holds up in the rain. The Fly Creek 1 is basically the same tent 4 inches less in length and 1 inch narrower. I am going to get one when my SL1 wears out.

Hi Bob

> Teflon is Poly Tetra Fluoro Ethylene, or PTFE, and it consists solely of carbon
> and fluorine. I think you contradicted yourself. This is chemically similar
> to the stuff that is in DWR fabric treatment.
Ahhh… that's a bit like saying glucose is chemically similar to methyl alcohol or diesel fuel: all three are hydrocarbons.

Cheers