Kayak hull design explained for first time buyers.

With the explosion of choice in the kayak market in recent years, sifting through the options can be a pretty daunting task for new comers to the sport. Here is a quick intro to the basics to help you with the big decision.

A few terms to get your head around first:

Tracking: the ability of a kayak to maintain a straight course while paddling. If a hull tracks badly it zig-zags while you paddle causing a lot of the power from a forward stroke to be lost to side-to side motion.

Freeboard: the height of the side of the kayak measured from the waterline to the deck. Generally kayaks with more free board offer a drier ride, but the trade-off is that there is more of the kayak out of the water to catch the wind. This will increase your drift speed when soft plastic fishing or squidding and will make paddling or pedalling into a headwind that bit harder. To counter the effect of the freeboard, you can use a drogue/sea anchor and Hobie kayaks can also increase their water resistance by keeping fins vertical in the water.

Rocker: the amount of curvature in the keel line of a kayak. Kayaks with large rocker will be seen to have an upturned nose and stern and be banana shaped. They sacrifice a little hull speed but are very responsive and handle surf/chop very well.

Stability: There are two types of stability, primary & secondary. Primary stability is the initial steadiness a paddler feels when the kayak is on flat water. Secondary stability is a kayak’s ability to stay stable when rolled over on its side. Secondary stability gives the paddler the ability to roll a kayak back upright easily from a tipped over position (think of the no-spill baby cups that roll back up when knocked). Most kayak designs are a balance of primary and secondary stability to suit a particular use. In trying conditions such as choppy swell, secondary stability allows the hull to rotate on the wave keeping you vertical whereas primary wants to stay parallel to the surface of the wave and you have to counter it with your weight, leaning into the swell.

Stability

Kayak Design

There are a raft (pun intended) of different sizes and shapes of kayaks out there, the following guide is designed help you match a kayak to your needs. The general perception is that short & wide = stable, long & thin = fast. Unfortunately there is a little more to it than that.

When you hit the stores in search of your first kayak there are four common hull designs features you will encounter. It is very common for modern manufacturers of fishing kayaks to use a blend of these types in their designs. The following diagram and explanation by Austin Kayak sums up these hull features well:

hull_design

Joseph Dowdy – Austin Kayak

1)Rounded Hulls – These hulls, as their name implies, have rounded edges giving the kayak a ‘torpedo’ shape that results in increased speed because of less water resistance. Rounded hulls usually make for more manoeuvrable kayaks as well and commonly have more secondary than primary stability.

2)V-Shaped Hulls – Compared to rounded hulls, these hulls have a sharper ‘V’ shape that allows the hull to better cut through the water making them more effective at tracking in straight lines. These hulls are generally fast as well and sometimes considered ‘tippy’ as they offer more secondary than primary stability.

3)Flat Hulls – Flat hulls are used for a surprising variety of purposes ranging from play boats to fishing kayaks. The reason is, based on other factors like length, width and curvature, flat hulls combine stability and manoeuvrability. Flat hull also offer great primary stability.

4)Pontoon Hulls – Stability is the key feature of pontoon hulls. Kayaks with these types of hulls combine the primary stability of a flat hull with the secondary stability of a rounded resulting in the the greatest stability available. While these hulls generally lend themselves to decent tracking they aren’t known for their speed.

What other considerations are there?

Chines:

The chine of your kayak is the shape of the transition of your kayak from the bottom to the side edge. These transitions can be rounded (also known as a ‘soft’ chine) or square (also known as a ‘hard’ chine). Both types of chine have their advantages and disadvantages.

chine2

Joseph Dowdy – Austin Kayak

Hard Chines 

Hard chines improve the primary stability of a boat and help with tracking but are more prone to capsize in choppy conditions and in surf launches and landings. The hard chine gives oncoming water more of an edge to push against. Kayaks with hard chines are more prone to broaching in waves. Very common on fishing kayaks particularly those with raised seats and standing areas.

Soft Chines

Soft chines in contrast provide better secondary stability and improved speed. This is ideal for ocean swells and choppier conditions. Soft chines are a common feature on sea kayaks and fishing skis for this reason. Paddlers looking to cover distance will generally go down this road.

Multi-chine

As kayak manufacturers strive to find the perfect balance of primary and secondary stability they often end up producing hulls that are a combination of the four types of hull outlined above. This leads to hulls being multi-chined giving a blend of soft and hard chines and a combination of their features.

Length: 

Short Kayaks (~2.5m)

Short kayaks are very manoeuvrable and responsive but tend not to track well and have slower hull speeds. This makes them ideal for fresh water creeks and rivers with skinny water. Their smaller size makes them easy to carry down banks with poor access and their plastic hulls will handle dings from underwater snags/rocks with ease. If chasing natives is your thing then these are probably the boat for you but bear in mind if you are fishing rivers with a bit of flow, its better to organise separate launch and exit points so you are always paddling with the current.

Medium kayaks (~12ft)

This size boat is good for bay and estuary use as they have enough length to track reasonably well and are usually still wide enough to offer good primary stability making them well suited to beginners. The extra length of say a 3.5m boat gives better hull speed which will give you more speed to get off the water quickly if the weather changed out in the bay. The other advantage for bay use is that they will track better into a headwind allowing you to cover more distance to your fishing spot. These boats are ideally suited to fishers who want to drift fishing soft plastics or paddle to a spot to anchor and bait fish. They also tend to offer the best storage for fishing gear.

Long kayaks (~5m)

Boats in this category are usually long and narrow with excellent secondary stability but less primary usually just enough to fish from. Paddlers transitioning to these boats are initially unsettled by the ‘tippyness’ but soon learn to move with the boat. These boats are designed for covering distance so offshore and bay trolling of hard bodies and live baits is where it’s at. They are quite at home in sloppy conditions with a seasoned paddler and generally maintain the best speed into headwinds and current.

Every kayak you buy will be a compromise of places you want to fish and gear you want to carry so it is probably best to buy a boat to match where you want to be fishing 90% of the time and you can’t go too far wrong! I was once told that 95% of the time, the kayak is more capable than the user, which is probably very true, so irrespective of what you end up buying it is a case of trying to up-skill to help put you in the 5%.

Thanks for reading & tight lines!

Sea Sherpa