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Extending Pack Capacity (On The Side): Part 1: The Problem

Extending Pack Capacity - The Problem with Pouches, Pockets and Dry Bags

The Problem with Pouches, Pockets and Dry Bags


So, you really like your pack but you want to carry extra stuff? Easy ... go out and buy a new, larger pack - the outdoor industry can't wait to assist.

A larger pack is probably not the best solution, for a number of reasons, but what is the solution? And what's the problem with the solution? Confused?

Read on ...

[ Note: If you're tired of hearing about problems and are more of a "solutions" kind of person, by all means skip this snake and climb the happy ladder to Part 2. ]

Side Pouches, Side Pockets & Heavy Duty Dry Bags



Introduction: The stuff we need on the way

When you're trekking for weeks or months at a time, you'll likely notice there's a whole load of kit you don't touch between packing up your tent in the morning and setting it up at night: tent, sleeping bag, sleeping mat, wash-kit, sleepwear, spare clothes, maps not yet required, and of course food rations. In our view, this is what the body of a pack is designed to carry.

At Scramble we like small (30 to 40L) climbing packs. Even though the Predator 30, our favoured trekking pack, is a military "patrol" pack, it's really a climbing pack decorated with MOLLE. It's a stripped down, narrow bodied, single cavity pack with a minimal hip belt. It sits high on the back, has a high centre of gravity and leaves sufficient space for a harness or a large padded belt. Our favourite pack for mountain trekkers that morph into mountaineers when necessary (especially in the winter) is the Blue Ice Warthog 40 (review coming). It looks very different, but in use feels very similar. Both of these packs are very comfortable and well balanced and are tough and durable enough to handle additional loads. As we pointed out in our Predator 30 review, once food supplies dwindle, excess loads can be decantered back into the pack's main body, so the pack integrity and centre of gravity remains relatively constant across the duration of the trek and/or climb.

This post is largely about extending pack capacity, but more than that, it's about access ... or more accurately ease of access to all the stuff you may need between setting off at dawn and setting up at dusk.

Pouches to the left of me, dry bags to the right

There's a good deal of real estate on the side of a pack and most packs have attachment options of some kind or another on their sides, e.g. compression straps. When you add load to the side of a pack, as long as it's approximately balanced (left and right) there's no major negative effect on the centre of gravity, though the lower the weight sits the lower the centre of gravity will be. However, when you add load to the back of a pack, that does affect balance and the lower that weight is, the more the user will notice a significant pull at the shoulder and push into the lower spine. The user will have to lean forward to provide a countervailing force and this causes all sorts of back issues and leads to an uncomfortable and unbalanced ride.

So adding capacity at the sides makes sense.

There's 3 main solutions (with blurry hybrids in between) to adding capacity to the side of packs and each have their pros and cons. At Scramble we've tried and thoroughly tested multiple variants of all three. Ultimately, we're not happy with any of them, here's why:

The pros and cons of current offerings

If you're pushed for time and want a succinct summary in tabular form, click here.

1) Military Side Pouches

Capacity range: 8L - 15L (10 - 12.5L = Standard)
Example: Karrimor SF Sabre Side Pockets

Pros & Cons

Karrimor SF's Sabre Side Pockets attached to a Sabre 45 pack

  • Capacity (good): Ranging from 8 - 15L (10 - 12.5L = Standard), they provide a meaningful amount of extra capacity and more importantly provide sufficient space for a wide range of kit.
  • Compatibility (poor): Don't play well with regular packs, i.e. require PLCE or MOLLE compatible military packs.
  • Centre of gravity (poor): Except on large bergens (big military packs) these side pouches tend to sit quite low (on the 45L model pictured for example).
  • Profile (poor): Large profile, being barrel shaped and quite squat they create a very wide load.
  • Weight (poor): Heavy - most will weigh in at around 250g+ a piece.
  • Access (moderate): Access is generally via a top lid either zipped or clipped or both. Thus stuff at the bottom is harder to access than at the top. Straps may need to be loosened to access these items.
  • Security (good): Their attachment system is very robust (whether via a MOLLE backing or a zipped and clipped attachment system) and generally combines with two compression straps. This makes them exceptionally good at load bearing and very stable.
  • Water-resistance (moderate): Dry bags are required for anything that mustn't get wet.
  • Abrasion-resistance (good): Military specifications for load bearing materials demand that these side pouches are generally made of a 1000 denier nylon, making them a very protective, abrasion resistant outer shell for your gear.


2) Heavy Duty Dry Bags

Example: Ortlieb PD350 Mediumweight Dry Bags

A fully loaded Predator 30 with 13L and 22L Ortlieb PD350 Dry BagsA Karrimor SF Predator 30 fully loaded for 8 days in the mountains (looks ugly but is surprisingly balanced)

Pros & Cons

  • Capacity (good): Being dry bags they come in a range of sizes. However most (if not all) are cylindrical and this makes for a less efficient use of space. The Ortlieb 13L (which, securely closed = 12L) is 42cm tall with a 19cm diameter. A cuboid 42 cm tall with a 19cm square base would have more than 3L extra capacity.
  • Compatibility (good): Dry bags will work with any pack that has compression straps, i.e. the vast majority of 30L+ packs.
  • Centre of gravity (moderate): This is very much based on the diameter of the circular base. If the dry bag is tall and slender it will have less of a negative impact on the pack's centre of gravity. This is also somewhat dependent on the position of the pack's compression straps.    
  • Profile (poor): Generally dry bags are "sensibly proportioned" and due to their cylindrical shape, this tends to mean that a 10L+ dry bag is quite fat and will have a significant impact on a pack's girth.
  • Weight (poor): Any external dry bag will be made from a tough heavy duty nylon or polyester with an equally substantial waterproof coating. If they're a good quality, effective dry bag, they'll be anywhere between 200 and 300g (Ortlieb 13L = 220g), but not everything we want to store on the outside of our pack may require waterproofing - so they're not the most efficient, weight-wise.
  • Access (poor): Obviously, this is the major weakness. They're awkward to access when on the go. If you've got stuff at the bottom, you have to take everything else out to get at it (not good in heavy rain).
  • Security (moderate): A good dry bag will have some kind of attachment method at the top and bottom and though these won't be load bearing they can ensure that gear is not lost should the compression straps fail and aid stability by preventing the top leaning outward. Generally these bags when strapped in are very secure and their load is directed by the compression straps into the body of the pack.
  • Water-resistance (good): Obviously this is their forte. Not just resistant, but waterproof.
  • Abrasion-resistance (moderate): Depending on the make and model, a heavy duty dry bag will take a good deal of punishment and scraping over rocks and undergrowth. Ortlieb, Sea To Summit, SealLine all make bags that are certainly tough enough for civilian environments where shrapnel is a novelty.


3) Large Capacity Side Zipped "Pockets"

Example: Bach XL Side Pockets

Few outdoor brands have tackled this issue - they'd rather you buy another packLow profile but no room for cooking kit, crampons, tents etc (the Bach, left, look fat - they're actually just 8cm deep).

Pros & Cons

We've so far found just two products that provide a meaningful capacity extension. There are add-on "pack pockets" out there, but these tend to be around 4L max capacity and so not relevant to this post. The two products that are relevant are Tatonka's Expedition Side Pocket (8L) and Bach's XL Side Pockets (6.5L). We're going to take the best of these, the Bach XL Side Pockets and score them (since the two vary quite a bit in terms of design and materials).  

  • Capacity (poor): The Bach, though 54cm tall provides just 6.5L of additional capacity. The emphasis has clearly been to make them as low profile as possible and this has meant they have a smaller capacity than the dry bag and side pouch options above.   
  • Compatibility (moderate): The Bach and Tatonka models both work with any pack that has compression side straps. Though it should be noted that not all packs' compression straps can be unclipped. With Blue Ice's Warthog 40 for example only the top strap has a quick release clip. This would make it somewhat incompatible with the Bach version which expects the compression straps to thread through the back loops.  
  • Centre of gravity (good): Because this type of side pocket is tall, the centre of gravity is intentionally shifted up and this is one of the virtues of this design.
  • Profile (good): These pocket present a narrow slimline profile. However, this comes at a substantial cost - there's a great deal of gear that won't fit inside them due to their shallow depth: 7cm and 8cm respectively.
  • Weight (good): The 500D Cordura Bach design comes in at a very respectable 150g (the Tatonka is heavier and uses a lower grade material).
  • Access (good): The Bach provides a full length zip running from top to bottom. If access is king, this has to be the right approach.
  • Security (poor): The Bach, which only attaches at the back of the pouch, relies solely on the compression straps and doesn't make use of their inward pull (as the straps don't go around the outside) this results in the pouches rolling on the vertical axis which negatively impacts the pack's balance during sudden changes of direction.   
  • Water-resistance (moderate): Dry bags are required for anything that mustn't get wet.
  • Abrasion-resistance (good): The Bach's 500D Cordura provides excellent abrasion resistance (note: the Tatonka's 600D polyester is probably the least convincing of all the offerings here).



So let's look at how these all stack up:


Zpacks' Tall Dry Bag (image copyright

And Finally ...

In a sense Zpacks' offering (pictured right) is a great example of a company trying to solve this problem but, in so doing, crashing directly into many of the issues we've highlighted above.

Yes, it's lightweight (and that's Zpacks' thing), but with their Tall Dry Bag, they offer a low profile, tall, ultralight (20g) waterproof roll-top side appendage with nightmarish access, limited use (loads of kit won't fit - but great for a down jacket) and a low capacity (5.7L). And that, right there, is the problem.

This has been something of a negative, complainy post. In the follow-up, we'll be far more upbeat and talk about a genuine solution.

Click here for Part 2.


Last Updated: 25/10/18


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