[pct-l] Testing of Bear Cannisters / URSACK

[Matt Thyer]

If you get a chance give a dog a chew bone that's too big for it to fit all
the way in its mouth.  Dogs will gnaw at the side of the bone until the
tooth-on-bone friction abrades the surface of the bone enough for them to
gain leverage on the now roughened surface.  While they're gnawing they'll
usually hold the bone between the front paws and the ground.  This action
does not require them to possess an opposed digit and the action is
generally easier the larger diameter the bone happens to be.  Most of the
abrading action is the work of the canine teeth, but they can and do engage
teeth further back along the jaw including molars.  The upper jaw is rested
on the top of the bone and the bottom is leveraged against this fulcrum
until the surface is weakened.

The top of the Garcia Bear looks a lot like the bottom of a big femur.  The
lid has a pair of recessed locks and a stationary hinge, but there's still
weak points where the lid sits within the canister's upper portion and where
those milled aluminum recessed locks are.  Now imagine a big bear head
resting in the shade of a long needled pine tree with a Garcia Bear
canister.  It would rest its upper jaw on top of the canister and begin
gnawing at the wall and top of the canister until it created a weak point
which it could exploit.

A hinge is a type of bearing that connects two solid objects, typically
allowing only a limited angle of rotation between them.  The recessed milled
aluminum "locks" are actually hinges in disguise.

I've been thinking it would probably be helpful to categorize encounters at
some point since there are a lot of variables that might result in a
problem.  It's extremely hard to be objective about encounters because
reporting is, as best as I can tell, completely anecdotal.  Something like a
range from "Bear sighted in area, but ran away" to "Bear broke into camp
entered <brandX> canister."  As I sort through encounter reports I'm seeing
what appears to be a lot of successful bears, but I'd wager that most bear
encounters aren't even noted which makes it impossible to calculate efficacy
of canisters.

2 cents,

MT 

-----Original Message-----
From: pct-l-bounces at backcountry.net [mailto:pct-l-bounces at backcountry.net]
On Behalf Of Scott Bryce
Sent: Wednesday, April 28, 2010 2:22 PM
To: pct-l at backcountry.net
Subject: Re: [pct-l] Testing of Bear Cannisters / URSACK

Matt Thyer wrote:

> I'll take a look at the Garcia Bear as well, hadn't heard of that one 
> until you mentioned it.  I'd point out that REI says it weighs 2 lbs.
> 12 oz. and it's made of ABS which will break if enough pressure is 
> applied.

The idea is that it is too large for a bear to get its mouth around it.

> The hinges probably aren't going to be the failure point that a bear 
> is able to exploit,

Hinges?