How to Make Simple McRig Sails
Report Produced By Scott Wallis

The simple McRigs used for both my Razor 3 and Ranger footies, use a standard template, though of a slightly higher aspect ratio then commonly seen on McRigs.

The Z wire is from 2mm stainless steel wire – although piano wire is adequate it does suffer from rust unless dried and protected. The larger rigs for light winds would probably stand a stiffer 2.5mm wire.
How did the "Una" rig get it's name?

"The catboat is unquestionable an American craft. When one was sent to Cowes in 1852 by William Butler Duncan as a gift to the Marquis of Connyngham she was at once recognized as an American novelty; and her name, "Una" was adopted and is still in use in England to describe her type. "
William P. Stephens
published in Traditions and Memories of American Yachting part 37
The Z wire is bent to shape and the boom attached to the 3-5cm in front of the pivot (depending on rig size). Most of the rigs can use a straight section between the mast and pivot, but with later rigs (and in order to allow clearance over the box by raising the booms tail end (whilst not raising the whole rig)) the fore section has been ‘kinked’ to lower the mast position whilst clearing the bow.

The tip of the mast should lie approximately above the line of the mast step, as this seems to give a good all round performance. It is worthwhile mentioning that you should put something hard in the bottom of the mast tube to stop the wire mast drilling a hole in the bottom of the boat.
Mast and boom are of mainly linear wound 2mm ID 3mm OD carbon tube. The biggest rig is using a 4mm OD lower section for increased stiffness.
Measurement A (mm) B (deg) C (Deg) D (Deg) E (mm) F(mm) G (mm) H (mm)
Storm 40 100 170 75 160 85 300 80
C 40 95 175 75 170 85 500 45
B 40 96 174 80 205 120 500 75
A 40 95 180 70 260 135 550 125
A+ 40 98 162 90 270 140 800 100
The mast and boom geometry are created first, then they are laid out upon the sail material (big thin plastic bags). A luff seam is drawn on, at about 30-50mm in front of the mast position (which is subsequently marked). The foot is cut at the rear of the boom (allows the fitting to sit forward, creating camber). Depending on your choice of flat head, or rounded Leach, it is then drawn out. Quickly check the approximate Center of Effort (should sit about 40mm behind the mast step)
The sail is cut out, and then with the mast laid in position, the extent of the overlap is marked on the sail. A line of double sided tape is used to stick the luff seam back to the main sail, creating a smooth mast pocket. (Alternatively the pocket can be stuck using ordinary tape on the outside seam).





Duct tape is used to reinforce the corners of the tack and clew. (Using 3-5cm strips run along the key edges). Sail batons are added to the leech, made from clear plastic (pop bottles) attached with tape.