The Why & Wherefore Of A New Design
About five years ago I bought a second-hand sea kayak. It was an apple-green Arctic Raider; apart from the colour, it was just the kind of sea kayak I was looking for. When I went to see the kayak, I found it in excellent condition, with the added bonus of a sail rig. I bought the lot, on the spot.
The first few months that I had the kayak, I found it quite unstable. This was partly me – I had previously been paddling a very stable but high-performance skin-on-frame kayak – and partly the way the kayak was fitted out. Over a period of a few months, I gradually refined the fit-out until the Raider and I were one. During this time, I didn’t dare play with the sail.
The sail was a spinnaker, a commercially-available sea kayak sail, on a telescopic mast. The Raider’s foredeck had a mast step, reinforced with a fibreglass knee-tube. On the first few attempts to use the sail on a local estuary, I found the rig very difficult to use. I was able to improve stability by jamming bottles of lead shot under the seat (up to 11 kg of shot!), but not enough to relax and enjoy the ride. On open ocean, it was nearly impossible to even step the mast (ie: put the sail up) without capsize. I would capsize almost immediately on two out of three attempts. This is a nuisance, as you can imagine, and doesn’t make sailing a pleasant experience. I never got a good run with the spinnaker.
The ability to roll is a reasonable pre-requisite for kayak sailing. It helps to have a certain level of comfort under water too, as it is often necessary to pull the sail down and dismast, preferably also to bundle up the sail and stow it, before rolling up again.
A spinnaker may well be a good downwind sail on a purpose-built sailing boat, but it’s not much good on a sea kayak. A spinnaker is a loose-footed sail, therefore tends to flog around in any sort of wind, decreasing stability. At the same time, it needs both hands for control, so you can’t paddle or brace.
For a short while I experimented with parafoil kites. Many people are enthusiastic about kites as sails. All three parafoils that I tried took a lot of mucking about to get them flying and when wet they were next to useless. I wasn’t encouraged to continue trying.
About a year later, I had the opportunity to try a Tasmanian pattern sprit sail – very popular down south, but not as common in NSW. Unfortunately, it was blowing a gale and I had no idea how to use it – oops, wet again! Despite this, it looked like a good idea, so I made one – a friend had some aluminium tubing for the mast and boom, the local archery shop had a suitable arrow shaft for the sprit and the local sail maker sold me some 30 gsm polyester sail cloth. This turned out to be a good sail. I have several good memories of long runs downwind or on various reaches, outrunning my paddling companions without a single paddle stroke (as long as you don’t count lots of bracing and turning strokes). The rudder that came with the Raider was a boon.
The disadvantages of the Tasmanian pattern sprit sail are twofold:
- the mast step must be within reach of the paddler in order to step the mast and set sail – this means that the sail, especially the boom, is in the way of a normal paddling stroke, restricting forwards paddling, turning and often bracing;
- the sail is quite high above the deck, increasing the tendency to capsize in a gust of wind.
Throughout this time, Norm Sanders and others were developing various features of the folding sprit sail (see The Old Sea Dog’s Gear Locker in Issue 36 of NSW Sea Kayaker). Bruce Wingrove used a separate folding step with his rig and Mark Pearson and Mik Snoad used different sail shapes and sizes.
Two clear advantages of the ‘Norms’l’ are that:
- the sail, when raised, is outside the paddler’s reach and therefore doesn’t affect paddle strokes;
- the sail can be close to the deck, minimising the tendency for a gust to capsize the kayak.
A further advantage, not so clear at first glance, is that the sail can be positioned well forward, so that when under way the kayak, paddler and sail are more-or-less neutral in the wind, and the kayak will go where you want, without a desperate need for a rudder. The Tassie pattern sail needs a rudder – the sail has to be in reach of the paddler, so it is almost always too far back on the kayak (it has a strong ‘weather helm’). Without a rudder the kayak will always tend to turn up into the wind. This effect is even more exaggerated in those Tassie rigs with a second mast and sail behind the cockpit.
In contrast, the Norms’l works on a rudderless kayak!
Rob Mercer’s “Norms’l” in action
So, I reasoned, there may be a way to have some, or all, of these advantages without butchering my Raider to remove its fixed mast step. I scoured sailing books and other resources, looking for a sail pattern which might give me a better rig.
I also developed a simple mathematical model for testing the various sail types for the tendency to capsize, based on the distribution of sail area with height. Out of about fifteen different sail rigs, a few really stood out:
- the V-sail, a commercial North American sail rig, is atrocious – a very high capsize potential more or less guarantees that you’ll get wet often;
- the Norms’l is good – its stability characteristics are very hard to beat, certainly not beatable with a Tassie rig;
- the 2,500 year old Mediterranean sail pattern called a lateen, which is still in use in some types of dinghy and in the traditional Arab dhow – with this sail pattern (and a little tinkering) it was possible to equal the Norms’l’s stability and have the mast in reach and have the sail out of the way of normal paddling strokes, all at once!
Several modifications to the lateen are necessary:
- the aft edge of the sail would be in the way of normal paddle strokes unless it was cut away – so, I cut it away;
- a cut-away would leave the aft edge of the sail unsupported – so I supported it with a sprit placed in between the boom and the luff spar (the spar at the leading edge of the sail);
- instead of raising the sail by sliding it up the mast on a parrel – the traditional way – the mast, sail and various spars have to be permanently attached to each other; this makes a different sort of assembly necessary.
The modified lateen sail in action, photo from leeward. Note the very short boom, only 20 cm behind the mast
The mathematical model says that a 0.75 square metre cutaway lateen would have about the same capsize potential as a Norms’l of the same size and about half the capsize potential of a Tassie rig of the same size. Good!
Disadvantages? Hmm. A few:
- the cutaway lateen is more complex to make and has more parts;
- it is not as simple as a Tassie sprits’l to rig on the water – it takes an extra three to five seconds to set the sail or to stow it away after a capsize – this is time when you don’t have your hands on the paddle shaft;
- the sail must be set on the correct side of the mast for the apparent wind, in order to maintain aerodynamic efficiency, then swapped if you change direction;
- it fills the field of view and is hard to see past.
- the cutaway lateen is a high aspect ratio sail, like the wing of a glider, so you can expect higher efficiency, especially on a reach (with the wind coming from one side);
- because of its reduced tendency to capsize, it is stable on a reach;
- it is completely out of the way of paddle strokes – you can go tearing down or across the wind under full sail power and full paddle power simultaneously;
- some of the sail area is forward of the mast, so the balance of wind on the Raider required less rudder;
- it keeps its shape in all winds (where a Tassie rig or a Norms’l will tend to billow out and lose even more efficiency as the wind freshens.
All in all, it looked as if it would be the perfect sail for my new Baidarka. Well, after a few good sailing days, including a wild downwind run sailing and towing on the Rock ‘n’ Roll weekend, I’m certain of it. The Baidarka is very strongly swede-form and the sail sits so far back on the kayak that the Baidarka shows a strong weather helm and more steering strokes are necessary than expected.
This is manageable. Naturally, the sail and kayak look good together, too.
In future, kayak sailing experimenters might try to combine:
- the Norms’l – for its forward position on the kayak;
- the Wingrove hinged, socketed step – for convenience stepping the mast while on the water;
- the cutaway lateen, for its high aspect ratio, low capsize potential and cool looks.
Anyone is welcome to measure and copy this sail rig. Just get in touch.