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3F UL GEAR Tyvek bivy bag

$27 USD 3F UL GEAR Tyvek bivy
Hood cinched
The 3F UL GEAR Tyvek bivy is available for $26.99 USD delivered on Aliexpress.

  • Protects sleeping bags / quilts from water, dirt or damage
  • Made from lightweight, breathable and water-resistant 1433R Tyvek
  • Hood with cinching drawcord and a zipper
  • Open: 230 x 90cm
  • Packed: 16cm x 8.5cm diameter
  • 200g + 8g stuff sack

Discounts (USD):


This bivy bag is made from 1443R "soft structure" Tyvek - a lightweight, water-resistant and breathable material with a soft, cotton-like feel.

Some potential uses:

  • To protect sleeping bags / quilts (esp. down) from getting wet, dirty or damaged
    • Eat / drink within your bag with less worry of spills
    • Mitigate rain splashback under a tarp
    • Lets you safely use your bag outside your shelter

  • To boost a sewn-through quilt like the Aegismax Wind Hard Tiny
    • Reduce heat loss by covering gaps, the sewn baffles and the zipper
    • The hood keeps warmth from the head contained
    • Nicer feeling material than 15D nylon

  • Use standalone as a bug or wind barrier outside your tent, or as a sheet on warm nights

This kind of Tyvek is different from the "Homewrap" Tyvek used at construction sites - it is not stiff or loud, and is more breathable (but less waterproof).

1433R is used commercially for disposable clothing (e.g. overalls) and for kitemaking, but also for lightweight hiking items, such as this one.

Other examples:

    Specifications:
    • 1443R Tyvek (white)
    • Open: 230 x 90cm
    • Packed: 16cm x 8.5cm diameter
    • 200g + 8g (stuff sack)
    • Cinching hood with linelocs
    • Zip that goes halfway down the bag, with pull loops inside and out
    • Sewn footbox 
    • Red trim around the hood, zipper and near the neck

    Pros
    • Protects expensive / fragile ultralight sleeping gear
    • Use as part of a modular system that can be varied, depending on expected conditions
    • Good quality stitching
    • Packs to the size of a 375ml drink can
    • Better than DIY solutions
      • Materials alone would cost more
      • Would also require skills, tools and time
    • Multipurpose into a picnic mat or vestibule footprint
    • Easily cleanable by wiping
    • Could turn the hood inside out and stuff as a pillow
    • Fits a 6 ft+ tall person

    Cons
    • Water resistant, not waterproof
    • Unsealed seams
      • Water could get in if used outside
      • Could seam seal with silcone sealant or Tyvek tape
    • White colour shows dirt easily
    • Tyvek lacks ripstop reinforcement
      • Relatively easy to tear if handled roughly
      • A washing machine could pull the seams apart
    • 200g of weight + another thing to pack up each morning
    • The zipper comes up to your nose, and there is no flap covering it (cold will transmit through it)
    • While a full size sleeping mat fits within (tested with long Thermarest Prolite Plus) - it does so tightly
      • Won't leave much room for your feet to move around
      • Probably fine with a 3/4 mat
    • Stuff sack is a tight fit

          180cm slit back version

          Specifications:
          • 1443R Tyvek (white colour)
          • Open: 180 x 80cm
          • Packed: 16cm x 8.5cm diameter
          • 130g + 8g (stuff sack)
          • Slit back
          • No zipper
          • No hood
          • No footbox

          Pros
          • 130g is 70g lighter than the hooded version
          • ~$7 USD cheaper than the hooded version
          • Slit back better fits around a sleeping mat, and is less constricting
          • More minimal, with less aspects to fail or tear

            Cons
            • No way to tighten it around you - no elastic straps/snap locks to secure it around a mat
            • Doesn't fully enclose you - heat leakage
            Hooded version
            Red trim, zipper and cinching cords
            Footbox
            Packed dimensions
            Slit back version (Front)
            Rear
            Foot


            Further Resources

            Randonner Leger forum

            Youtube
            3F UL Tyvek Bivy Bag reivew.. (foreign language with subtitles)

            Reddit
            Quilt cover to avoid condensation/dew?

            Terra Rosa Gear bag cover
            Sectionhiker writeup

            Misc
            Breathability of Tyvek 1443R
            Dupont Tyvek 1443R product properties (pdf)

            Youtube
            Tyvek Fabric 1443R - stiffness test
            DIY Budget Tyvek Ultra Light Bivy Bag - Part 1