Making my own WPB fabric.

Justin, I'm not sure exactly how you are implementing this into your poncho idea. Can you explain a little more on that side? Will the polyester fabric simply lay on top of the tyvek? Using your technique of adding silicone to the polyester, could you theoretically laminate the polyester to the tyvek, while your silicone is still wet. I guess this depends on how large the panel of fabric is. You'd would have to stretch the polyester, add the silicone, very carefully lay in on top of the tyvek, then work out any wrinkles or other abnormalities. The only reason I suggest this is because I would think it would give you even better abrasion resistance that two materials floating free of one another. Soft of like how a very thin mesh fabric is added to WPB membranes in a 3 layer design to add durability.
Either way, good luck in your experiments.

Hi Jesse,

Sure, i will explain a bit more. I will take two rectangular pieces of the polyester organza or one large piece and fold same, and in the middle of the "shell" and "lining" fabric of the polyester organza, will go a similar sized piece of 1443R tyvek. Then the edges will be folded over a couple of times, and i will take small strips of silnylon and sew the edges of the 3 layer within the strips of silnylon. Then all that will be sewn onto the poncho (with a semi long stitch as to not stress the tyvek too much), but leaving the bottom unsewn. Then i will cut out the original fabric via the bottom, close to the edges of the seams. This large rectangular piece of homemade 3 layer WPB, will go on over the front core area, so from my lower chest down to where the poncho ends (around knees).

I like your reasoning behind doing a more true laminate by "gluing" the 3 fabrics all together with the silicone. There are a couple of reasons why i can't do that though. Tyvek is made out of polyethylene, and PE is notoriously slippery and hard to bond things too. The silicone will not bond to the Tyvek material–very little does. Plus, i would not want to inadvertently fill in the tyvek's "pores" which is where the breathability comes from.

However, the good news is that adding silicone to the right and wrong sides (outer and inner) of the polyester fabrics, will make the polyester more slick–e.g. less friction, and so will cause less abrasion damage to the Tyvek, plus will add a little abrasion protection to the polyester itself from outside abrasion sources. It will, and has, decreased the breathabilty a bit, but not much since it's such a breathable fabric to begin with.

Note, this is not an ideal WPB fabric. It will not have high enough HH for many people's tastes, and it's a bit on the heavy side (equivalent to mid weight eVent), and likely will be less durable than a 3 layer eVent or Neoshell type fabric. And the Tyvek will still be prone to some oil contamination (which will reduce it's high hydrophobicity, which could lead to decreased HH levels).

However, it's cheap, and extremely breathable as compared to eVent or even Neoshell (CFM of about 6 vs .5 to 1 respectively). Hence, with a combo of this and an already breathable poncho design, i will likely sweat less (which will decrease oil contamination some). Since i will have the option of wearing a Houdini underneath, and would be anyways during a more heavy or windy rain (for some arm protection), i'm not worried about a non ideal HH or a little water potentially coming through (which could very well happen).

Certainly a DIY, cheap WPB solution and ultimately the proof will be in the pudding–i plan to test it around home before bringing it out on a trip. If i could have found a light weight, and more reasonably priced eVent fabric, i probably would have gone with that instead. I'll put up some pics when i'm done.

Did some testing of 1443R Tyvek fabric.. not sure i want to use it. Such a weak tear strength and low puncture resistance. Seriously there is a tent made out of this stuff? What happens with strong winds with stronger gusts?

Anyways, also did some testing of the 3 layer version–took a rectangular piece of the Tyvek, put in between two layers of the polyester organza (not silicone treated). The two shorter, opposite sides had a thin strip of silnylon folded over the edges and then was sewn.

Tried tearing it at the silnylon reinforced edges, did well, couldn't tear it. Tried tearing it at the non reinforced edges and tore through all 3 layers easier than i thought i would…

This worries me, and more over contaminating the tyvek with body oils worries me more. I have some left over M50 material. If i used that as the inner liner and the poly organza material as the outer, (and still reinforced the edges with a thin strip of silnylon), this might suitably increase tear strength and decrease body oils some more.

However, there will still be poor puncture resistance. What if i walk directly into a sharp branch or graze thorns or the like, likely it will puncture or rip right through the organza and tyvek material easily. I want good breathability, but not if durability will suck royally. Perhaps nylon mesh treated with silicone would work better than the poly organza (but then there will be less UV resistance)?

Any thoughts? I'm thinking of either silicone treating some more Maxima ESD fabric, or just using the EPIC fabric i have (but heavy). These might be less breathable and/or less WR, but the durability will likely be significantly higher..??

what about using a polyester ripstop as the outside layer. Add a dwr (like your diluted silicone) and you'd have something a little more sturdy and it would have more UV resistance than a ripstop nylon. Ripstop Polyester doesn't seem to be as readily available but I have seen some around, in fact I found a bolt at my local walmart. As a reference it weighs a little over 1oz/sq yrd.

It's too bad that tyvek is so fragile. I agree, it's hard to imagine trusting that kind of material in a shelter.

Hi Jesse, that's certainly an option. Unfortunately, more robust polyester does tend to be on the heavier side. The pertex micro light stuff on Thru hiker might work ok, but even that is 1.7 oz sq/yd and that's considered a pretty light and thin polyester. The specific gravity (density measured in relation to water, which is 1) of polyester is around 1.38 and nylon is 1.14 so the latter is significantly lighter weight per similar volume.

Wouldn't it be so convenient, if polyester and nylon just switched their hydrophobic and UV properties with each other, or more simply their density?!

Since that won't happen, guess i will check out some more opaque and tightly woven, but still thin and light polyester fabrics for the face at least. I do think the M50 could work well for the lining. But now we're talking about a combo that is going to weigh at least 3.5 oz per sq/yd, and will have a reduced CFM. I don't know how to calculate CFM of 3 fabrics together.

On the other hand, Maxima fabric weighs about 2.7 oz sq/yd, and with a light silicone coating probably around 3. The EPIC fabric i have is 3.5 oz sq/yd with i'm assuming a pretty high HH, but is pretty tough and the DWR will be more uniform than i can do at home and being silicone encapsulated, just need to keep it clean and it will last a very long time–occasional spraying with silicone before it gets significantly degraded might help a bit.

Did some testing of the Maxima ESD fabric with silicone. I did a crappy job of applying the silicone the first time around. Tested it out during a heavy'ish rain, and it wet through fairly quickly.

Re siliconized it and did a much better job. Mixed a thin slurry using paint thinner and silicone adhesive and a handheld blender to mix it–yeah baby!, mixed it very well.

Applied with a foam brush, then pressure wiped with a smoothly woven microfiber cloth. Did this to both sides.

Water repellency now awesome. Breathability not so great. Can suck a very little bit of air through, sucking very hard. Good news, better breathability than silnylon, which i can't suck air through no matter how hard i try (i knew this, but tried anyways). Bad news, no idea what breathability this actually is though. If it has some air permeability, it has to have some CFM even if only .3 to 1, right?

In any case, still much better than most WPB fabrics out there. Super cheap and likely will be super durable too! Just wash well and touch up with cheap silicone spray every now and again–theoretically should last a VERY long time.

Still looking to improve this some for the other poncho. Been thinking about combining a siliconized polyester lining material i just bought from Joann's (couple of bucks with a coupon) with M50 material i have left over.

Siliconized polyester lining would go on the outside and M50 on the inside. However, have some doubts. If the M50 fully wets out, whether from sweat or rain, it will become very non breathable being so tightly woven (this apparently is the newer stuff with lower CFM?).

This would weigh less than the siliconized Maxima fabric, and likely provide a bit more HH and a bit more breathability. However, the wetting out part concerns me. So, alternative is calendared, but non Down proof, 1.1 oz nylon ripstop. Siliconize it as i did the Maxima. Since it's more breathable than the Maxima fabric off the bat, should be definitely a bit more breathable than the Maxima after it's treated.

Combined weight of siliconized rip stop with polyester lining would come in around 3 oz per sq/yd, and have more breathability than either of the above. The siliconized polyester lining fabric is still highly breathable with the silicone coating.

I WILL beat the system so to speak! Who needs a HH of 20, 000 to 30, 000mm?! Ah, but who wouldn't like a CFM of .5 to 3 without paying the high cost for eVent or Neoshell, but heck of a lot more durable than Propore? Even if the materials leak a little under heavy, sustained rain, with a Houdini underneath the poncho and ready to zip up at the moment's notice, i doubt i have anything to worry about. Plus the crucial areas of the poncho, like shoulders etc will be still be fully waterproof.