Best material for MYOG dry bag

use sil nylon and heavily seam the seams. OR use cuben fiber and tape or glue the seams.

-Tim

This is pretty much the cutting edge of lightweight dry sacks:
http://www.trailspace.com/blog/2009/07/24/outdoor-retailer-granite-gear-uberlight-ctf3-drysacks.html

They are 17-19g (2/3oz) for a down sleeping bag size.

They're made from Cuben fibre which you can order from cubic tech but you need to order 9 yards minimum. You might be able to buy a smaller quantity from someone on this site or elsewhere. Cuben is expensive (ie. ~$20/yd)

A silnylon dry sack would still be really light (ie. 1.5oz) so it depends on your priorities and how much you want to spend. MEC.ca sells lightweight silnylon drysacks for $10-$19. Mine is the 7L size for my quilt and it weighs 40g (1.5oz).

http://www.mec.ca/Products/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524442628934&FOLDER%3C%3Efolder_id=2534374302701623&bmUID=1259308570437

I am pretty sure standard silnylon would leak to much, not enough water resistance there.

The cuben could be an interesting idea, but for this circumstance I want something proven.

The last link provided in actually to a PU coated nylon, so maybe that would be the go? Should offer significantly more waterproofness than standard silnylon. Anyone know what is used in 'normal' weight drysacks?

is this for a pack rafting trip or some other trip where the down bag may get fully submerged for longer than a second or two?

If not then i wouldn't get too worked up over having the most waterproof dry sack in the world. It just depends what your priorities are, idiot proof water proofing or ultralight weight. IT isn't often that you can solve the idiot proof problem and the ultralight problem with the same solution, some educated compromises must almost always be made.

-Tim

I put my quilt into a stuff sack made of the same UL fabric as the shell. That gets it into a manageable size. Then I put that into a large (ie not tight) plastic bag inside a silnylon outer bag (almost tight).

As others have noted, the modern silnylon is not waterproof at high pressures, and you may have trouble sealing the top end at a low weight as well. But I can twist the top of the plastic bag shut very reliably.

The combination has never let us down, and a plastic bag is very light!

Cheers

I do similar to Roger C.

Around here the "sandwich" method (plastic bag sandwiched between two fabric stuff sacks) is promoted by Cliff Jacobson … a teacher (retired) and author who has led youth and adult groups on remote canoe trips for several decades … always using a down sleeping bag. The contingency it's designed for is swamping in a large and windy lake where you and your gear might be floating for hours … it works for that.

The idea is that the plastic bag is the water barrier and the two stuff sacks protect the plastic bag from punctures and snags.

The only difference between Roger's and Cliff's advice is that Cliff doesn't bother with "waterproof" fabric for the stuff sacks. His line about waterproof stuff sacks is "how can they be waterproof, they have this large hole on one end!"

Thanks for the advice guys, maybe ill just line the original stuff sack with a tough plastic bag and stuff it in there. Few twists and rubber bands to hold the top shut.

> "how can they be waterproof, they have this large hole on one end!"
Hi Jim

Well, Cliff is right of course.
But I use very very light fabric and I find that it does not hold its seams as well under tension compared to silnylon. Also the silnylon seems to avoid snagging on things, while the very light fabrics can snag a bit. Well, that's been my experience anyhow.

Cheers

You should use some 70D Heat Seal Taffeta. You could make the whole thing using scissors and a iron. Though it wouldn't be as lightweight as a Silnylon or Cuben Fiber version, it would be cheaper, easier to build and bombproof.

Cheers,
Lawson

This Ripstop Nylon claims to be waterproof up to 125psi and weighs 2.6-2.8 oz/yd2.

http://www.rockywoods.com/Fabrics-Hardware-Patterns-Kits/Ripstop-Nylon-Fabrics/Coated-Ripstop-Nylon-Fabric

I have always used Ziplock bags when expecting rain.

Neither Sil nor Cuben will give you a long lasting truly waterproof dry bag.

Try this: https://www.diypackraft.com/shop/merchandise/fabric/lightweight-heat-sealable-ripstop-nylon/