PROJECT WINDRIGGER - Dec 2003 installment

As a result of trialling Windriggercat MK 2 earlier this year I decided to try and improve its sailrig. Ultimately I settled on an option illustrated in photos 1, 2 and drg 1, which illustrates its concept.

Photo 1 - Mast-aft-of-the-cabin option.

Drg 1 - Masts-aft-of-cabin for biplane rig. Note centrehull for crew comfort - details of it are the following pages.

Photo 2 Mast-aft-of-cabin sailrig mounted on Windriggertri

My thoughts and reasoning leading to adopting the new sailrig:

1. My existing biplane/unstayed mast rig satisfied nearly all my requirements and its only short-comings are difficulty in rigging and inability to reef. Also the sailboard sailrigs are designed to de-power in high wind-strengths by flexing to leeward - which is not necessary when the sailrig is mounted on a catamaran. These deficiencies could be fixed by using a stiffer mast and a sail without battens which would allow reefing by furling around the mast.
2. I considered using a conventional Bermudian sailrig but found it would have had to be at least 7.5metres in height to provide the 14 sqm of my existing biplane rig. To me, this means a much higher Centre-of-Effort and consequently greater pitch-poling probability. So I decided to impliment what sailboarders have been doing for the last 25 years - incline the sailrig aft so that it produces lift and to leeward so that the sail drive-force acts along the fore-and-aft centreline of the hull as in a balanced sailrig.
3. Mounting the sail forward of its mast provides the following advantages - the sail is free to rotate 360 degrees and feather the wind - which I have found makes for safer sailing; it eliminates interference between mast stays and sails; allows the two masts to be cross-braced as shown in Drg 1 resulting in much lower mast-compression loads than that of Bermudian sailrigs. Also because the luff spar carries the loads induced by the fore-and-aft sail forces, there is not a need for fore and back stays.
4. This sailrig provides options for making it a balanced sailrig by its facility to be able to move the fore-foot of the sail across the deck and the peak of the sail across the upper mast spar, so that its Centre of Effort acts along the fore-and-aft centre line of the hull containing the mast.
5. The sailrig is not limited to sailboard sailrigs - for example it should be possible to use a conventional jib-sail or genoa mounted on a luff spar designed to minimise deflection induced by the sail forces and its jib sheet. A luffspar in the shape of a wingspar of a wingsmast/softsail combination could provide a very efficient sailrig. With these options it would be possible to reef the sail by furling it around the luffspar.
6. Fittings are included to allow the peak and fore-foot of the sail to be moved to vary the fore-and-aft inclination of the sail so that the inclination can be adjusted to suit wind strength.

Photo 3 - Windriggertri - I used my F2 Strato sailboard hull to save making another plywood outrigger hull.

Photo 5 - Windriggertri rigger for trailering

Photo 6 - Windrigger MK 5 - the sailrig is reversed by sliding the fore-foot along a track on the deck.

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