waterproof packing

[Jim Colten]

This is a fork from

this thread which has was starting to wander from it's initial purpose

Here is a packing method promoted by Cliff Jacobson,
who has been leading adult and youth groups on northern Canada canoe trips for a few decades.
The assumption is that some mishaps leave you with near zero probability of getting outside help.
The objective is to have dry pack contents when you've retrieved it after it's been floating for several hours.
(Cliff uses down insulation)

This does not pretend to be SUL, hardly even UL … but it does not just pretend to be waterproof. I must confess, however, I don't use this for backpacking

The "Sandwich Packing Method"
1) The pack itself need not be made of waterproof material.
Uncoated fabric has an advantage that it does not trap water between the pack body and what I'll describe below.

2) Use a somewhat sturdy pack liner made of a material that'll resist a strong hydrostatic head.

3) Use an "abrasion liner" inside the pack liner. Need not be waterproof.
Folks often use an old pack liner that they've tired of patching.

4) Sleeping bag goes into a stuff sack, need not be waterproof.

5) That bag goes inside a somewhat sturdy poly bag,
purge excess air from the poly bag, twist closed,
fold the twist over double, bind with a shock cord loop or short piece of small line.

6) That assembly goes inside another stuff sack, need not be waterproof

7) Other things you want double protection for get the same treatment, the rest goes into any old stuff sack.

8) all your gear bags go inside the pack-liner-liner sandwich, the abrasion liner gets folded down,
push the excess air out of the first liner and give it the twist/fold double/bind treatment

9) close the pack

This does work. When I give lakeside pre-trip orientations to BWCAW crews I start by tossing my pack into the lake. After about an hour of presentation and Q&A, we retrieve the pack and inspect it's dry contents.
Hasn't failed yet.

[Art Sandt]

Instead of the 4 non waterproof layers (5 including the backpack) and 2 waterproof layers described above (am I counting this correctly?), one could just use 1 waterproof layer of a durable material, and be done with it. Coated nylon tends to be much stronger than 2 mil compactor bags, and if you're going to be using 2-3 compactor bags in varying states of wear, the weight savings won't be so much over a standard dry bag in the fist place.

As I said in the other thread, though, backpacking assumes land travel, otherwise it would be called swimpacking. It does not carry the same water risks as kayaking or canoeing unless you are actually crossing streams that are large enough to fall into. Not all trails cross streams this large, and those that do often have bridges. If you'll notice, the waterproofing method described in your posts is for canoeing rather than backpacking.

That's not to say that I haven't heard of people falling into streams they were crossing and dunking their backpacks, just that not all trails have streams like that…

[EndoftheTrail]

I'm sure it works, Jim, but many others have shown that using just one good layer works too:

1. Line the pack with one big "contractors bag" — basically a large 2-mil garbage bag. Note however, that most supermarket "lawn and garden" trash bags are only 0.8 to 1.1 mil — so look for the heavier duty contractors bags in hardware stores.

2. Pack just like normal.

3. Close and twist the garbage bag end — then point the end down (away from sky, toward ground) — and cinch/zip the pack tight. If pack is only very loosely filled or if canoeing or crossing major streams is part of the day, you can rubber band the twisted end for extra protection.

I have hiked for many hours in hard rain and have my pack dunked in a river (canoe mishap) — and not a drop of water ever made it through a contractor bag.

So it works, but is one layer always the best? No, much will depend on your packing style. For example, I always pack my tent outside the pack — so no need to open/disturb the pack itself. I also place frequently used items and lunch in an outside pack pocket — protected by a ziploc bag — to minimize/eliminate need to open up the main pack compartment. But folks who pack their tents and/or everything else inside may prefer multiple wp bags rather than just one big liner bag.

So one big wp bag or several smaller one — much will depend on packing styles. But IMO, "concentric" layers of bags is not necessary for most hikes. YMMV.

[Michael Davis]

I know that this isn't light either but, I use P.O.E. Pneumo Lightweight bags which are basically kayak bags that have been lightened up a bit. They are still super heavy-duty from a backpacking standpoint. I feel guilty everytime I pack them but I use all down insulation and I sure am happy when everything stays dry.

As a bonus, I have found nothing that can compress like these things. You leave the air valve open as you stuff the sack, then roll down the top (3x min) and connect the buckle. Then the fun starts! Hold the bag up to your chest (or sit on it) and squeeze all the air out and quickly close the air valve. It's like vacuum packed!

So, I justify the weight by considering the volume I'm saving and the confidence that my stuff will be dry.

http://www.pacoutdoor.com/2008/index.cfm?action=product&productID=118&groupID=35&familyID=2

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