Chris Caine Bivi Bag test

[Swallow]

When I was at the Wilderness Gathering Chris Caine was talking about kit and saying test it before taking it out. (that talk is on youtube if anyone is interested). His suggestion was to line a Bivi bag with newspaper weigh it down and fill the bath with water (with the opening out of the water). If the newspaper was damp 24 hours later then send it back and get another one.

I just tried this a with a new unused bivi bag and it bombed.

Opinions on whether this is a good test, there are better tests or anything related would be appreciated.

 

[tartanferret]

I would imagine any bivi bag would do the same and wet through. ( at least any breathable one )

Immersion in water for 24 hours seems to be a hard core test as it does not allow the water to bead off the surface.

I wouldn't worry myself,

 

[Andy BB]

Did Chris Caine actually recommend a make? I'd tend to agree with TF that Goretex etc bivvys would probably have a hard time meeting 24-hour submersion tests.

 

[boatman]

What a silly test. I would have thought that only a plastic bag or a fully waterproofed one would pass it. The Bivvy Book suggests that air movement is necessary to reduce or avoid condensation. My own cheap Trekmate bivvy bag's foot end remained dry within from condensation and without from heavy rain outside throughout the night in September.

 

[Swallow]

Did Chris Caine actually recommend a make? I'd tend to agree with TF that Goretex etc bivvys would probably have a hard time meeting 24-hour submersion tests.

For bivi bags no, though his own was ex-army gore-tex I think. The only product he did name was a lowe-alpine crossbow rucksack, which is not made anymore, but had a round bar that made the weight sit properly on your hips. Other than that kit changes by the time you replace it so he did emphasise testing.

With my, not quite on it, test the weights were not sufficient for full submersion so it was only half submersed.

 

[Greek1983]

I agree with boatman, it's a silly test. My uber-expensive Carinthia Observer Gore-tex bivy tent with a 10,000mm water column would certainly fail that 24-hour test because it's not designed for the above reason.

The only reason I can think of this test is if you're about to use you bivy bag over your tarp/basha/poncho as a "backpack cover" when river crossing.

 

[Dark Horse Dave]

Yeah I watched that Youtube vid a while ago, and thought then that it was a daft test.

Many years ago I used one of those heavy duty orange survival bags as a bivi bag. While it would have passed CC's test, I woke up drenched in my own sweat, which of course couldn't evaporate through the bag. Daft I know!

 

[Swallow]

Well if I thought it was a 100% sensible test, there wouldn't be a post on here questioning it.

I don't plan on bivi-ing in a river anytime soon hence the question of what is a sensible test (which doesn't involve getting soaked). No suggestion on that one so far and the obvious one of leaving the shower running for 8 hours seems a hell of a waste of water. That also removes the body heat part of the equation.

Hydrostatic head is defined in a couple of places having a column of water on the fabric and how high that column of water has to be before it penetrates. Though it doesn't say anything about duration of how long the column is there. There's bivis out there claiming to be breathable which also have an HH rating. Does that mean the HH ratings are bogus?

In my case the bag was not weighed down but sitting in an inch of water, which does not seem that unrealistic for a badly placed camp when it is bucketing.

 

[Swallow]

Thanks for all the posts guys. I kind of get what you're all saying which is why I asked the question in the first place, but the Hydrostatic Head thing is still a curve ball for me. I checked the specs for the bag and the HH is 10,000 which is more than my tent. I thought that meant that you can stack 10 metres of water on it before anything comes through, so I don't quite get why under six inches of water comes through. It also has a breathability rating of 10,000g/m2/24hr. I can't quite get the physics to line up between these two. I can get the idea of heat pushing it out like a sort of one way door or something i.e. if there isn't a stack of water on it that it can breathe, but I'm still a bit lost on why it came in.

More important that my lack of understanding of that is if there is any water at all around where you are lying then will that come in?

 

[Greek1983]

Because, and I quote wiki answers:

Hydrostatic head is a fabric's resistance to water pressure equivalent to a column height of water. Whilst a hydrostatic head of 1,500mm will keep out heavy rain, it will not stand up to the increased pressure put on a fabric in general use and by rucksacks etc.

In other words, no, it'll definitely fail any such tough tests. If that was the case, then any type of Nylon (except Cordura) would've obsolete.

About ground water, you don't have to worry that much. Again, it all depends on the pressure you make when you lay down. If you use a sleeping mat, then you rise some mm above ground, thus you protect the bivy. If you're afraid of possible floods from nearby rivers, streams or from heavy rain, then dig 2 trenches around you with an E-Tool so to let water flow away from your stuff. We're doing that during my service whilst trying to sleep in a canvas pup-tent covered from top to bottom with heavy duty Nylon...