Breathable, Waterproof Material for Quilt Foot End?

i’ve used this on the foot area of a bivy. so not a quilt but similar area and similar purpose. it works well *except* you can/will get condensation on the inner side. if this condensation is inside your quilt in might effect the performance of the down. although all told, it’s probably drier than what’s dripping/touching from the shelter ceiling.

I’ve never used any of the RSBTR WPB material. I was aware they carried it, however I’ve never heard anything about it.

Thru-hiker carries Pertex Shield which is a little heavier at 1.8 oz. It has a good reputation, but whether or not it’s any better I don’t know…..probably is though. Cheaper too at $16.95/yd. http://thru-hiker.com/materials/coated.php

Even though thru-hiker has very few offerings, everything they sell is of the highest quality.

I’ve used momentum 50 from thru-hiker on the foot of my bivy/quilt that touches the end of the tent and gets wet.  Keeps the insulation dry.

I suspect the similar lightweight rsbtr fabric you mention is just as good.

I have found that other lightweight nylons are not as waterproof.  I put a puddle of water on the fabric and it was okay for an hour, but then it “found a way through” and quickly drained through.  The momentum 50 held up for 24 hours until I got bored with the experiment.

That was a few years ago.  Who knows if the momentum 50 they sell now is the same.  You could try the experiment yourself.

I think the foot of your quilt getting wet from inside tent condensation is the least demanding case of water intrusion.  The fabric is vertical and any water will tend to just run down between tent and quilt, to the floor of the tent.  It’s a small amount of water.  Any fabric would be fine.  Theoretically : )

RSBTR’s “Membrane” fabrics are just a brand name — they do not have a membrane. Confusing.

There are at least three current variants of Membrane: nylon and poly that are not intended to be waterproof, as well as Membrane Silpoly which is. More confusing.

Presumably you tested the silpoly, but it might be worthwhile to double-check. One mm Hg sounds more like one of the non-waterproof variants.

RSBTR also sells a 2.5L WPB product, which does have a membrane. Triply confusing. This is the 1.4 osy WPB that Brad asked about in the OP.

Hi Brad,  I used the RSBTR WPB 1.4 material for my bevy sack, works very well.  The breathable characteristic is dependent on there being enough vapor pressure (ie: temperature differential) to push the water vapor through.  Your design may not trap enough water vapor to produce the necessary pressure.  If that’s the case, a lighter weight WP Silpoly might be preferred.  Might consider a polypropylene fish net material loosely attached to your tent to prevent your quilt/bag from having direct contact with the tent wall.  If you try this definitely go for polypropylene, not polyester.  Polypropylene is <u>non-wicking</u> whereas polyesters typically are treated to wick.  I don’t think having my quilt against a wet rag would accomplish the goal of keeping the quilt dry.  Try gluing just the top corners.  If that doesn’t work, add the lower corners.  But don’t glue the whole thing and don’t pull it snug, you want it a bit loose to let the natural drainage to be unimpeded.

Most nights the condensation in my single wall tent (Zpacks Duplex) doesn’t penetrate the Pertex water-repellant covering on my REI Magma sleeping bag (echoing Jerry’s point).

If there’s lots of condensation (e.g. very rainy nights), a little does get through. I’ve solved that by turning the end of my tent into a double-wall tent, using a garbage bag instrerad of  the mesh that Ted suggested: The Duplex has a loop about 18″ up on the inside, at the end. I suspend a corner of my pack liner garbage bag there, and spread the other end loosly under my sleeping pad, forming a triangle.  The folds of the garbage bag form an insulating layer of dead air so that no condensation forms on the side touching my sleeping bag. I worried that moisture from my feet (or wet socks) would condense there, but it doesn’t.

If your tent doesn’t have anything to hang the garbage bag from, you can get stick-on loops from Z-packs.

Bill B,

RE:  “Presumably you tested the silpoly, but it might be worthwhile to double-check. One mm Hg sounds more like one of the non-waterproof variants.”

Looking again at the invoices, the product was sold as Membrane silpoly.  The replacement product, the same, although the results of Stephen Seeber’s second tests were so similar, my guess is that RBTR just cut off more from the same role.  Also, the HH of both products fell sharply the greater the washing, the lowest values being under .5mm HH, and the highest slightly higher than 1 mm HH.

With respect to the WPB fabric spec’d at 1.4 oz/sq/yd, the weight on my scale, following Nisley’s practice of using one foot square swatches multiplied by nine, was consistently 1.5 oz/sq/yd. Not major, but every ounce counts when light weight is a goal.  It all adds up.  Note that I’ve not asked Stephen or others to test the WPB.  The scale is a “MyWeigh.”  I have a second one used to monitor the first from time to time.

Jerry:  Not sure what tent you are using these days, but have found that when moving around in the tent while asleep, the foot end of the bag inevitably rubs against the lower tent wall, which was one reason I’ve used double walls ever since.

Not sure about the Dutchware uncoated silnylons for an inner, as the nylon tends to absorb moisture.  So will continue to experiment with washing the RBTR poly membrane (plain weave, sil coat) to see if it can work as an inner tent wall.  Its measured weight is under one oz/sq/yd, while all the other waterproof breathables (WPB) I’ve found are all at least 1.5 oz/sq/yd or more.  Not a big difference, but am determined to keep the weight down wherever possible.  Weight savings on all the tent components definitely does substantially lower the total weight.  The garbage bag and/or rain jacket do sound interesting.

Note that the goal is a shelter that can keep out the moisture in severe storms when the humidity is high, and the wind and water are striking the tent hard.  Preinstalled netting would probably do fine; but for a taut pitch want a solid inner that will briefly stay dry inside and accessible outside while the outer fly is being pitched.  Not yet sure what fabric the outer wall will be. Found a super strong poly one at 1.08 oz/sq/yd, but it is a very dark color and gloomy.  The membrane for the inner comes in a bright yellow.  Color me fussy.