Here is my latest creation: a poncho based on the Roger Caffin’s “mountain poncho” design made of cuben (big thanks to Roger for sharing his pattern and instructions).
Material is the CT2K.18 (1.0 oz/sqyd) cuben from zpacks. While it is not the lightest cuben out there, it is the first one with double-thick foil layers what makes it truly waterproof even after some wear. This had been shown here by Richard Nisley and my tests confirmed that. At the time I was buying the fabrics, it was the only really waterproof option at this weight range. My previous poncho was made of 20D silnylon which had claimed HH of 1500 mm – it was waterproof when new but started leaking badly after something like ten days of use. Now there are some nice light sil/PU coated fabrics that are also waterproof enough but I guess cuben will last longer.
Design. I’ve modified Roger’s pattern slightly in some details (rounding some lines) and I make the poncho and the sleeves a bit longer. I’m also using a water-resistant zipper instead of snaps (which I had on the previous one and found it difficult to keep them organized). The zipper closes from top so it’s possible to zip up the collar and leave the rest open “cape style” for ventilation. There is also one snap (see the first picture below) that can hold the poncho in place without using the zipper.
Details. The double-sided tape makes it easy to make neat details – e.g. the drawcord tunel and visor on the hood are laminated from inside without sewing through the outer fabrics. All seams are taped – I made my own seam tape from 0.5 inch wide double-sided adhesive tape (from zpacks) and the fiber-free foil cut from the edges of the cuben. It worked really great and is as light as possible.
Working with cuben. Before I started, I was really worried of sewing the tightly curved seams in a material that has practically no stretch. In the end, it was not that hard, but only because I made a very accurate pattern in computer (which I tested successfully on the silnylon prototype). For things like sewing the sleeves into the oval holes in the poncho, every millimeter matters.
Weight is 177 g (6.24 oz) including a 4 g cuben stuffsack. 20 g lighter than the one made of 20D silnylon.

I have yet to see how it works. I’m sure it will be waterproof and I’m curious how it will handle the condensation – cuben tarp stays much drier inside than silnylon. I am only somewhat concerned about it being noisy but it should get better when the cuben wrinkles more (I’d love to see cuben with TPU membrane instead of PES).



