Please help me find a good backpack

Joe might make you a larger Arc Haul if you asked. I too see the allure of the Arc from a weight standpoint but I question it's ability to carry 40lbs comfortably.

The Unaweep is probably your best bet. I have one that I am about to take to Alaska for two weeks and could tell you more when I get back but so far I like it. The frame and concept is the best that I have seen.

I also have a McHale but it was too small for my Alaska Trip (LBP 36) and it does have some positives and negotiates. First off the construction quality is head and shoulders above everything else I have used including other packs I consider to be very high quality (MLD, Zimmerbuilt, Seek Outside). You simply will never have a sewing failure. The McHales are also very polished. He has lots of small design details that you can tell have been honed over 30 years of pack making. The water bottles pockets are the best I have ever used. My LBP has the simple suspension but the demo I had came with the bayonet and "bypass" suspension which looked like a real winner (I took mine off for the demo because I didn't want it on my production pack. The McHale hipbelt is also fantastic.

The negatives to the McHale are the cost and the weight of the pack. I suspect what you want will be every bit of $1000 and be 4lb or more. I chose the Unaweep for my Alaska trip over a second McHale due to those two reasons. It also gives me the chance to see a different style pack.

Dan was great to work with and really knows his stuff.

To summarize: the McHale is heavier and more expensive but is more polished and has a great hipbelt and water bottle pockets. It is also the best made pack in the world. The Unaweep is lighter has great x-pack fabrics, probably has a better frame, but it isn't as polished and things like the water bottle pockets are serviceable but nothing to write home about. (For reference I felt the Exped Lightning pockets were terrible – even on the new strap under version)

I think I would at least try an Unaweep before I shelled out the $$$ for a McHale but I don't think you would be disappointed with either.

Another option might be a custom specta HMG Porter 4400. I hear varied reports on how it carries however.

One more thing – the x pack fabrics are much better in the rain than dyneema grid.

Thanks Bradford that is exactly what I needed to hear! Thanks especially for your feedback and comparison between McHale and Unaweep. I agree I think it does make more sense for now to choose the Unaweep, at least until I can afford the Spectra.

The thought did cross my mind, very briefly, if Joe could make the Arc Haul a bit larger. But the same concern – whether, especially if it is larger, it would be sufficiently comfortable to carry the weight – stopped me from taking it further. What reviews are there appear all positive but it is still very early days as the pack is so new, I haven't seen a report of more or less prolonged use to its full capacity.

I know several people who have a Unaweep pack, both 3900 and 4800, and they simply couldn't be happier with them.

If you need a heavy duty winter load hauler, I don't think you will find a better pack for the price. Don't overthink it too much.

They will stand up to the extreme environmental conditions you specified.

The zPacks packs are great but if you need to carry 40+ pounds, I would say the weight of the pack itself becomes irrelevant and all that matters is durability and load carry ability.

One thing to keep in mind is that 40 pounds is well inside the capabilities of the Unaweep, rather than at the edge of packs like the Arc Haul, Porter, Catalyst, etc. If that sort of load is at all normal the Paradox will really come into it's own.

Thanks David that's a good point. My pack's weight doesn't normally exceed 30lbs but I wanted a hauler capable for a little bit more. I figured if would help with the carying comfort and longevity of the pack of I don't load up to its limits every time I'm out.

@Andrew I think I'm going to press the "buy" button;) I half-hoped someone would chime in praising the suitability/strength/comfort of Arc Haul but really Unaweep does seem the best option right now. I'll just have to work hard and shave weight elsewhere (less "just in case" and luxury things..)

Take a look at one of the 4400 ci packs from Hyperlite Mountain Gear. They're light (around 2.25 pounds), solidly built, and waterproof. I have the Porter 4400, and found that it's very comfortable for multi-day hikes. The cuben fiber is probably a good choice for wet and windy conditions.