A Tardis, Folding Space: Sea to Summit Ultrasil Compression Sacks

How to Fit More in Your Pack: ‘Ultralight’ is not just about weight. It can also be about how to do more with less. In this case I am thinking eg of using a 13 litre Sea to Summit compression sack to compress my clothes to 1/3 of their previous volume, thus saving 8.7 litres of space at a weight penalty of <50 grams. http://www.seatosummit.com.au/products/storage-bags/ultrasil-compression-sacks/?ref=


If I do the same thing with my sleeping bag, eg compressing it from 6 litres to 2 litres I save another 4 litres. Now the 12 litres saved (at a weight expense of approx 75 grams) will allow me to carry perhaps 6 kilograms of extra food – or enough for a journey of an additional 12 days in the same volume pack. If I go to the same trouble with my food – though it may only compress (carefully) in half, I think I would be able to carry all my gear plus perhaps a month’s food in an approx 50 litre pack.

The addition of a ‘pack lid’ attachment such as this one from Zpacks http://www.zpacks.com/accessories/backpack_lid.shtml  will add a further 3.5 litres of food storage as well as providing a bum bag for excursions from camp along the way at a further weight penalty of from 47 grams. This addition will certainly mean that I can carry a month of food in a smallish backpack such as the Gossamer Gear Gorilla with its excellent suspension system, Zpacks Arc or Blast, or Mountain Laurel Designs Exodus. See http://www.theultralighthiker.com/ultralight-pack/ & http://www.theultralighthiker.com/a-gorilla-in-the-hand/


This valve-free dry sack uses a breathable base made of waterproof eVent® fabric, which allows air to be pushed out, but keeps water from entering. Waterproof seams are double stitched and fully taped for excellent durability and resistance to moisture A roll-top Hypalon® closure with lid and 3 straps evenly compresses and maintains compressed size. The Sea to Summit Ultra-Sil Compression Dry Sack is roughly half the weight of the original Sea to Summit eVent Compression Dry Sack.


6 litre = 6 x 14 inches – 2.3 ounces/65 grams (really 53)

10 litre = 7 x 16 inches – 2.6 ounces/74 grams (really 63.5)

14 litre = 8 x 18 inches – 3.2 ounces/91 grams (really 75.5)

20 litre = 9 x 20 inches – 3.4 ounces/97 grams (I expect less than 91)

NB: Just ‘discovered’ that the weight info may be wrong on S to S’s website so that the product may actually be lighter than the specs indicate. The weight for Medium is apparently 78 grams (not 91) and the Extra small 58 (not 68) and so on ie someone transposed the weights into the wrong row. I will know more when I get the product in my hands. If this is true I may not have any weight penalty from the switch as i will be able to jettison some of my inner bags eg that i stuff my clothing in if I use these.

NB2: I bought the three smallest of them. The XS (6 litre) weighs 53 grams; the S (10 litre) 63.5, and the M (14 litre) 75.5.

Further: I was able to easily compress my Montbell UL Super Spiral #3 (http://www.theultralighthiker.com/montbell/) down to 2 litres. It and all my clothes then fit in either of the other bags and compress down to approx 6-7 litres, so the 12 litres of space saving is definitely real! The compressed sleeping bag plus clothes will now fit in one of the Ultrasil dry bags http://www.theultralighthiker.com/dry-bags-sea-to-summit-ultra-sil-nano/ to make the whole package completely watertight.


Sea to Summits UltraSil Dry Sacks Specs for comparison:

Base x Height             Volume           Weight

11 x 24cm       1L        20g

13 x 29cm       2L        23g

15 x 33cm       4L        26g

17 x 46cm       8L        30g

22 x 53cm       13L      40g

25 x 61cm       20L      50g

30 x 70cm       35L      65g

The Sea to Summit eVent Compression Dry Sack.are awesome if somewhat heavier. Tis is a waterproof compression sack which makes (compressible) things take up 1/3 of the space. Great for your sleeping bag especially  but you can slip the Ultrasil one into one of their dry bags once your stuff is compressed.

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