[pct-l] Using the Ursack without the aluminum

[Barry Teschlog]

The challenge in this case would be to define, in engineering terms, what defeating a "Bear Intrusion" is (or what "bear resistant" is, if one wants to look at the issue from the other side).  Specifically, define how much force, for how long, applied in which way and in what combinations to the container which, by the way, shall not have edges or gaps larger than such and such which would allow the bear to get it's claws under them, unless they could then whithstand an even larger set of forces applied in a different manner.  Somehow, I don't think it's possible, without a lot of testing (e.g. getting bears to claw and chomp at strain / force gages) and then to define a bunch of forces, etc to design to, all of which I suspect is impractical.  

As such, it falls back to empirical testing - e.g. take a production representative prototype, fill it with good, smelly food, and throw it out for the bears to try and get into.  If the bear suceeds, the product fails the test.  If that bear fails to get in, go and repeat the test with other bears until you've passed enough tests to reasonably determine that the container is 'bear reisistant'.  It doesn't get more objective than this.

In the case of the Yosemite bears, empirical evidence has shown that the typical counter balance method is ineffective - the bears have learned how to defeat this defense, hence it's no longer an approved method in Yosemite.  Empirical evidence also indicated that the earlier Ursacks weren't effective (enough), be it from user error or fundamental design issues (Curtis LeMay would state that the root cause is irrellevant - in the end, the net result was the bear got the human food, mission failure).

So, bottom line - what you seem to be asking for, a standard defined in the sense that a bear resistant food storage container shall whithstand XXX pounds of force, applied in YYY manner for ZZZ period of time, I would suggest, is really impractical in this particular context.

YMMV, HYOH, 2 cents, yadda, yadda, yadda.

TC


Message: 4
Date: Thu, 22 Apr 2010 14:12:12 -0700
From: "Matt Thyer" <matt_thyer at hotmail.com>
Subject: Re: [pct-l] Using the Ursack without the aluminum
To: <gwschenk at socal.rr.com>,    "'PCT MailingList'"
    <pct-l at backcountry.net>
Message-ID: <COL109-DS1655CD47A099B7AEA152FBEE080 at phx.gbl>
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Gary, et al.,

You're missing the point.  All of these products are engineered to withstand a bear intrusion.  However, as far as I can tell, there is no standard for this kind of engineering, and thus the rules *are* arbitrary.  A DM can point to a list of "approved" canisters but can't tell anyone why that list is approved and why another list is not.  Worse, in the absence of an engineering standard I can find no regulation.  I see plenty of references to regulation, but not that actual rule.  I'm guessing here, but I find it unlikely that a rule would name specific manufactures of bear food protection.  Rather there is most likely a stated goal (like "will protect food, or prevent bear access") with some basic rules for compliance.  There may be guidance offered which indicates how compliance should be tested as well, but beyond that and a fee schedule the rule probably says little.

Think of it this way, the National Highway Traffic Safety Administration won't tell you that you can't drive a car you made in your backyard.  They will tell you the following 1) what the rules are in place that you must meet for you to drive any car on shared road surfaces 2) how you can test for compliance regarding these rules and 3) what your options are if you want to do something else, up to and including what the penalty might be if you chose to disobey these rules.

While I am trying to save myself some weight (13 ounces in particular) I'd also like to take an engineered approach to prevent bear intrusion.  Otherwise, why would I bother with the 9 ounce sack at all (I can carry my food in something much lighter)?  Regulation should have an object measure that can be reached by way of engineering.  Brand name shouldn't *ever* play a part; I might be cooking something up in my back yard.  Without an engineering standard any attempt at regulation becomes a kind of product endorsement and this lacks objectivity which may result in litigation.

Matt