See also:
Hyybrid IKs

There are a lot of full or hybrid Dropstitch IKs coming out now, but Idaho-based Aire are sticking with traditional bloat technology with their 2020 Tributary Sawtooth upgrade which gets an extra two feet and ‘bold new graphics’, as they call it in motorbike world. Along with with NRS down the road and with whom they seem closely tied, they’re among the US’s more serious IK makers (both come from the rafting game). Before the Seawave came along I’d considered an Aire IK but was put off by:
• Price (US-made models)
• Excessive width
• PVC shells with slow drying bladders
• Self-bailing

In other words, as far from a high-end Gumboat as you can get. It was long-extinct Sears IKs who are said to have originally come up with the idea of ‘inner tubes‘ supporting a sewn or welded PVC shell in the early 80s. It works like a bicycle inner tube supports a tyre. Aire adopted the idea a few years later which may explain why this method is common in North America but unknown in Europe. The benefits of this type of assembly are primarily economic: quicker, less laborious assembly, although bankside repairs using sticky tape on the bladder are near-instant.
As explained on the IK Construction page, the bladder system involves easier sewing or welding of the shell (all shown in this Aire promo video – stills below). No glues or solvents needed, unlike ‘tubeless’ Gumotex or Grabners. Aire spins this as ‘double layer’ but of course they are co-dependant: without one the other is useless. For a recreational packboat user, bladder boats have drying issues because inevitably water seeps in between the two layers and stays there. Owners often complain about this and certainly in a temperate climate like the UK, proper drying would be a pain. It’s a lot of extra faffing to clean and dry than a quick wipe of a tubeless boat. Being rot-free plastic, leaving an IK wet won’t ruin it, the worst might be some mildew or staining, but as with all outdoor gear, storing wet is bad form and may affect durability, especially around sewn seams.
Whether heat-welded or sewn, the tough 1000D PVC hull casing doesn’t have to be watertight. It’s just there to protect the much tinner AireCell bladder which is accessed (and repaired or replaced) via long zippers (see boat below) which is the main way water seeps in between the layers. Other downsides include grit getting in between the shell’s floor and bladder. All-round, it adds up to more maintenance than a tubeless IK which dries in minutes after a wipedown.

• 

• 

• 

You’ll struggle to tell on Aire’s website, but this budget ‘Tributary-branded’ range is ‘imported’: a presumable euphemism for ‘China’. That’s a word that’s even more tiptoed around in packboating world than PVC which, in the US, requires a health warning (left) to be sold in California.
As always, TheBoatPeople tell it like it is. They had a hand in designing the original 13-foot Sawtooth. US-design with cheaper Asian textiles and manufacture explains the reasonable pricing. It also explains the 1-year Tributary guarantee compared to the mammoth 10 years you’ll get on Idaho-assembled Aire-branded boats with urethane (not vinyl) bladders.

Numbers (with help from the reliable theboatpeople are said to be:

Weight: 19kg (42lbs)
Length: 4.65m (15′ 3″)
Width: 84cm (33″)
Payload: 201kg (440lbs)
Construction: 500/1000D PVC with vinyl bladders
Pressure: 0.17 bar (2.5psi) (PRV in floor bladder)
Price: U$ 999

Don’t ask me to explain the hydrodynamics, but a longer boat in the water is a faster boat, providing it’s not ridiculously wide or high or made from concrete. Longer, narrower and lighter than Aire’s US-made $2000 Super Lynx, the 2020 Sawtooth’s length-by-width factor is a pretty good 5.53 – near identical to a Seawave. (Compare other LWF’s here).

Obviously rigidity has an influence on speed and response, but up to a point a thick PVC IK (like my old Incept) is innately stiffer than more pliable rubber-based fabrics like Nitrilon. This may explain why the Sawtooth need run only 2.5psi (0.17 bar) even in a 15-foot IK, while a Seawave runs 3.6 psi and a Grabner even more. Or perhaps the vinyl AireCell bladders (right) can only safely take that pressure?

No footrest is included even though one is needed to brace against for a good paddle stroke. But Aire IKs can have have over two dozen attachment points along their full lengths (left). So besides positioning the seat/s exactly where you want them, you can easily clip-in a bit of sawn-down plastic drainpipe, which anyway is better than the mushy inflatable footrests which come with other IKs. While you’re at it, thread in some thigh straps which further improve your connection to the boat for more efficient paddling, especially at sea and in rougher conditions.

Many Aire IKs have an unusual dropped floor (right), partly because it has to be thick to work as a self-bailer. This design also means it acts like a fat keel to help tracking while its buoyancy lifts the side tubes out of the water to produce less drag and so increase speed. The Sawtooth comes with a clip-on skeg (useful at sea) and the Boat People reckon the Sawtooth is one of the fastest IKs around.

The principle of drop-floor/high sides may work, but in a self-baling boat the floor has to be thick anyway sit you up high above the water level. That means you’re less stable unless the boat is extra wide, but the Sawtooth’s width is pretty good (certainly compared to the Super Lynx).
I can see the value of self-bailing in a whitewater IK – I’d sooner have that than a deck. Not so sure in a touring IK. When heavily-loaded or two-up and passing through swell, the boat may fill from below with water. You’re getting soaked anyway, but that’s not really wanted. It’s the other thing Aire owners grumble about.
Aire IKs are unknown outside the US and certainly in the UK, and although the numbers and the price of the Sawtooth 2020 are great, for the same $999 in the US, I’d sooner choose a Seawave. In fact I did.
Owners’ reviews (old model).