Westwood wrote on Jan 5^th, 2013 at 10:34pm:

I have a couple of Paul Bunyan Duluth packs.  Packs don't get any bigger.  As pointed out previously, the canvas packs are surprising water proof.  Leave the packs out all day in a rain and the inside will not be wet.  My packs are not waxed.  This doesn't mean you can leave the packs in standing water, but if they are hung up, the inside will stay dry. The life time guarantee on Duluth Pack is not all inclusive.  The life time guarantee refers to the hardware and the straps.  The guarantee does not include wear and tear.

I've also got the #4, Northwoods, and Timber Cruiser canvas packs.  I use the 6 mil liners as well, and have never had water inside the packs except for the time my son and his buddy swamped on the Nina Moose river. 

Also had the canvas start to tear near a rivet on my Northwoods so I stopped by the Duluth Pack factory in West Duluth (?) prior to a recent trip.  They hesitated to fix it under warranty saying that it was normal wear and tear but when I told them I had only used the pack for about 6 trips up to that point, they went ahead and fixed it for free in about an hour.