Colin Quilter's kayak sail

Colin's kayak sail


I built my first kayak sail in 2005, and immediately put it to the test by sailing 60km out to Great Barrier Island. Afterwards I wrote an enthusiastic article for the Auckland Canoe Club newsletter giving details of the sail in case others might be tempted to make one. For some reason, nobody did! I used the sail on solo trips along the coast during the next eight years, and in 2013 built a second version which was substantially the same, but had some small improvements. This article is a revised version of the one written in 2005 for the ACC newsletter, and incorporates changes made in the second sail.


If you want to see this sail in action, there's a short video on YouTube at Colin's kayak sail


On Auckland Harbour

The good points of the sail are:

1)  It works over a wide range of wind angles. I expected that it would work over an arc of 180°, from abeam (90°) on one tack to 90° on the other. However to my surprise I found that the sail assists progress even when the wind is from slightly ahead. In theory it shouldn’t be possible to sail against the wind in a shallow boat lacking a centreboard or keel; but to my surprise, this sail will do it. However when the wind is coming from ahead you must keep paddling (ie. motor-sailing); as soon as you stop paddling the bow drifts to leeward and no progress is made. If the wind is abeam or aft of the beam, you can paddle or not as you please.

2)  The sail works in as little as 5 knots of wind (reaching), and up to 25 knots when reefed.

3)  It is powerful. In winds of 15 knots or above it doubles my speed, (ie. from about 6km/hr to 10-12km/hr with the boat heavily loaded). The longest distance I have sailed in a single day is 93km coming north along the Wairarapa coast.

4)  It doesn't heel the boat much. It is easily reefed. It doesn't interfere with paddling. It stows neatly on the foredeck of the kayak.


Now for the bad points:

1)  It is intimidating because of its size, (see Figure 3).

2)  Despite my best efforts to simplify it, it is complicated. It violates the KISS principle (Keep It Simple, Stupid!). It takes about 5 minutes to hoist or stow.

3)  It cannot be tacked or gybed; (you have to lower the sail, turn the boat downwind, and re-hoist the sail on the other tack).

4)  It is sensitive to trim and sheeting; a prior knowledge of sailing would be a big help.

5)  You can't sail in company with other kayakers because you have little control over your speed. You will race ahead and the group will split. This sail is best suited to long solo trips.

6)  My kayak is a Sea Bear which has generous beam and stability. I doubt this sail would be feasible on a narrow, light boat.

7)  Finally, and perhaps most importantly: this sail will pull you into trouble very quickly. You can be 20km offshore after just 2 hours sailing. What happens when a front comes through or the wind changes direction? The sail tempts you to sail into a situation you can't paddle out of. I have given myself several frights in this manner.



Sea Bear with sail LS

The sail is shown in Figure 1, (but note that it never lies between the two legs of the bipod mast as in this drawing, it always lies across the boat, in front of the bipod, as in Fig. 3). The sail is a lateen, related to the ones used for centuries on Arab dhows. The sail hangs from a yard, and has a boom attached to its foot. The boom is shortened to avoid interfering with the paddle. One corner of the sail is held out by a middle spar which I'll call a sprit. The three spars are held together at the apex (tack) of the sail. The spars pivot at the tack; they all fold together like a fan to furl and stow the sail. The yard hangs from the mast at point A, and the boom is pulled downwards by a downhaul attached at point C. The sail is stretched flat between them. The downhaul runs through an eye on the deck, then back to a cleat near the cockpit. The sail rotates around the axis A-C, (not around the mast as a normal sail does). Figure 2 shows the arc over which the sail swings when the wind is from the left (port) side.




Sail arc diag.jpgIn a normal sail the angle of the sail to the wind would be controlled by a rope (sheet) attached to the rear end of the boom and running to a cleat or to the sailor's hand. However a sheet of that type would foul the paddle. This sail is controlled by a sheet which is attached instead to the tack of the sail. It runs forward to a pulley (block) at the bow, then back along the deck to a cleat near the cockpit. The sheet is also used to fasten the front end of the sail bundle down to the bow when it's rolled up and stowed.


Reefing the sail (reducing its area in strong winds) is simple. The yard is unhooked from the masthead, and the sail is hung from the sprit (at point B). The yard then folds down and lies on top of the sprit, so the top panel of the sail falls into folds and becomes inactive. The outer ends of the yard and sprit should then be tied together with a small line or Velcro, (or a heavy gust will spread the two spars apart and the sail un-reefs itself, to the consternation of the paddler).


The mast is a bipod, with two legs. The legs pivot where they are attached to the edges of the deck. The mast folds forwards to stow lying on the deck. It also folds backwards so the paddler can reach the masthead to attach or detach the sail. When sailing the mast is raked forward as shown, restrained against the pull of the downhaul by a backstay which is looped over a cleat near the cockpit. In an emergency a one-handed backward pull on the backstay loop will jerk it off the cleat, and the mast and sail will collapse onto the foredeck.





Dimensions (mm) are shown on Figure 3. They refer to the sail itself including the pockets which hold all three spars. It is important that the yard and sprit (which are the same length) are no longer than the distance from the front edge of the cockpit to the bow of the kayak, otherwise they will overhang the bow when the sail is stowed on deck. The only other important dimension is the position of the axis of rotation A - C, (I determined it by making a model sail out of paper and barbeque sticks). It runs at right angles to the boom, 750mm from the tack. If the axis of rotation is too close to the tack the sheet will carry a heavier load; if it is too far from the tack the sail will not weathercock into the wind and will become unmanageable.

Sea Bear with sail TS


The full sail area is 1.34 square metres; the reefed area is 0.77 square metres. The sail is made from light sailcloth. It has a circular window in the lower panel so the paddler can have some forward vision. The three spars and the masts are from aluminium tube. The yard and boom are from 22.23mm OD tube, the sprit and both legs of the bipod mast are from 19.05mm OD tube, (wall thickness 1.42mm in both cases).


Handling the sail

When stowed, the mast lies folded forward on the foredeck with the folded sail (in a sleeve-like sail cover) lying on top of it. Hoisting the sail takes about 5 minutes. The kayak is left to drift beam-on to the wind with rudder raised. The mast is hinged back towards the cockpit to attach the sail, then both are pulled up into the working position using the downhaul. With the sheet eased the sail weathercocks into the wind. It will hang quietly there even in a strong wind. Lower the rudder, pull the sheet in, and you're off!

Sail stowed