The start of my new system. You may recognize the label. It made quite a stir approximately a year ago when Mateusz posted his Tyvek bivy in the MYOG forum.
His posting coincided with my reexamination of my shelter system. I wanted a bivy to use in floorless shelter or possibly a minimalist tarp. Other specs were optimal breathability, lightweight, low cost material such as Tyvek and top notch quality workmanship. The ideal bivy would provide peace of mind when the dark clouds roll in and the big drops are blowing horizontally through my shelter or streamlets from a real gully-washer are carving a path right under my bag.
In spite of our long response time between emails due to the distraction of earning a living, I was able to obtain a copy made up to fit my WM bags.
I received the bivy a few months ago but haven’t been able to use it until this weekend. Although storms can thunder through the Sierras any time of year it is hard to plan a trip with full cooperation from God Almighty, especially when testing gear. A small Sil-nylon shelter was chosen hoping to generate a fair amount of condensation. As you can see it worked. In spite of a regular pitch providing fair ventilation, the small space produced generous condensation that was dripping off the walls. Occasionally the foot of the bag would touch the tent walls or I would roll over and touch the side. By morning everything inside was wet with dripping condensation.
Somewhat surprisingly, inside the bivy, my sleeping bag was mostly dry with only a little dampness up around the neck and down at the foot on both nights. The outside of the bivy appeared as though it was parked out in the rain. I expected to suffer a fair amount of wetness inside the bivy considering the conditions. The damp dried out instantly in the sun. This bivy seems to be fully breathable top and bottom while giving full protection.
As some of you might know I tested the Tyvek Sublite and did an extensive review here awhile back. Based on my usage of the Sublite I was expecting good results with the Dusk to Dawn bivy. There was only slight reservation concerning the fact that the bivy is fully enclosed whereas the Sublite is ventilated 360º. This hesitancy was fully discharged on this trip considering the copious amounts of condensation inside the tent and the dryness of my sleeping bag.
Based on this test and my other experience with Tyvek I am now seriously shopping for a lightweight tarp to use with the Dusk to Dawn for a seventeen day hike later this summer.
