Sailing with a light westerly to North Head at dawn.
With one eye on building a new single-masted sail this is a continuing experiment with the behaviour of a couple of different rig designs, as referred to in the previous post. A double-masted V-sail and a slightly weather-beaten single-masted Tasmanian rig are being used in the photo above.
Having sailed to the base of North Head we re-set our course 180 degrees and managed to pick up a breeze to take us southwards along the cliffs. Above are the V-sails on Tony and Derek's kayaks. Not withstanding the findings expressed below on the limitations of the V-sail, this rig works well in light breezes - picking up every breath.of air and giving the kayaker a free knot or so of momentum.
Breakfast of ocean trout at a favourite cliff spot - only accessible by nimble kayak in slight seas. And then, with our kayaks perched on the rock platform, we snorkelled amongst crayfish crevices and into deep blue drop-offs along the cliff's edge.
Just a limited observation on the historial precedents of sail design for modern sea kayaks ...
1. Observations of an Inuit's kayak sail:
- Single mast - Single sail batten - Single sail sheet - No mast stays - Sleeved / socketed mast housing - Fairly low sail area, say 0.6 to 0.75 sqm - Low centre of effort in the sail, say no higher than the paddler's eyeline - Mast housed off centre-line of the kayak - Mast step located well forward of typical paddle stroke - Limitations on engaging the sail at sea (or at least I'm uncertain how the sail is engaged at sea. Presumably by a paddling partner) - Sail and mast can be dis-engaged at sea by a deft flick of the paddle and retrieved by hauling in the sail sheet - Sail is stored off the foredeck (presumably on the rear deck or within the cockpit).
Above: Sailing by the Manitounuk Islands, 1927. (L.T. Burwash. Public Archives of Canada) Source - Inuit kayaks in Canada (1987) - E.Y. Arima
Above: Inuit sketch of kayak sail in elevation. (Same publication as above).
It is unclear whether this kayak sail has ancient origins or if it is a relatively late innovation based upon exposure to European and American sailing vessels.
The observations of this sail design include that the intent was to:
- keep the sail simple (one mast, one batten, one sheet), - minimise the risk of overturning (low overall sail area with low centre of effort, and - maintain a clear foredeck with the sail stored elsewhere when not operational.
The Inuit sail shown above is not too dis-similar in profile to many modern kayak sails.
However, unlike the Inuit kayak sail, modern kayak sails are typically stored in one of two ways: -
(i) folded down and lashed to the foredeck (where the sail is exposed to catching waves, accumulating water and impeding the paddler's performance); or (ii) housed within a sleeve on the foredeck.
2. Observations of a Maori canoe sail:
- Double mast (V-shape sail) - No sail battens - Multiple sail sheets. - Single forestay and twin side-stays - Large sail area, say greater than 1.5 sqm - High centre of effort in the sail, higher than the paddlers' eyeline - Mast housed on centre-line of the canoe, but able to be inclined to leeward to allow spill. - Mast step located forward of typical paddle strokes - With an open cockpit the sail is simply engaged at sea by the forward paddler - Sail can be disengaged by the forward paddler - Sail is stored within the canoe's cockpit.
Above: Nouvelle Zélande -Pirogue du canal de l'Astrolabe. Hand coloured engraving by De Sainson (1833)
The observations of this sail design include that the intent was to:
- maximise the opportunity to catch air movement above the paddlers' bodies (high centre of effort in sail) , and possibly - be able to trim the sail setting by adjusting the angle of the leading mast edge (as in a windsurfer's sail).
The above Maori canoe sail is also not too dis-similar to some modern sail designs that are marketed for kayaks.
Summary from the above observations ...
The Inuit kayak sail is well suited to the low moment-resisting profile of a kayak. Its sail area is relatively small and contributes to topping up the hull speed of the down-wind journey of the kayaker.
The Maori canoe sail - or V-sail - with its high centre of effort, is not as well-suited to the low moment-resisting profile of a kayak. In a canoe the combined weight of the mutiple paddlers leaning out to windward can compensate for the over-turning effect of the V-sail - this is difficult to compensate for in a kayak with a single paddler. The V-sail is also prone to a yawl-effect when travelling directly downwind. And when this type of V-sail is mounted onto the deck of a kayak it has a further disdvantage - the foot of the sail will generate a stalling effect on hull speed when the kayak's bow overtakes the wave infront and gets partially buried within the wave on its way through - which is often the case in steep seas. Obvious conclusion: The smaller profile of the simply rigged Inuit kayak sail rig holds multiple benefits for the sea kayaker as compared with the V-sail design of the Maori canoe.
Other thoughts:
In designing a modern version of a sea kayak sail rig the designer would do well to arrive at a solution that;
(i) limits the use of multiple mast stays (more lines on deck = additional risk of entanglement), (ii) has a rig (mast foot + mast + sail + sheet) that can be simply and quickly deployed and retrieved by the paddler, (iii) has the capacity to store the sail in such a way as to minimise the negative effects of catching seawater within the folds of the dis-engaged sail (i.e within a deck sleeve), and (iv) has its mast footing positioned well forward of the paddler's stroke.
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