Most sailors are familiar with the crab claw rig, common on the proas and sailing canoes of the South Pacific. In his seminal book on sailing aerodynamics C. A. Marhaj concludes that is is one of the most efficient rigs over a broad spectrum of conditions. Small wonder that an iceboater should be inspired to give it a go. A report by Peter Adrian from Sweden on his crab claw rigged iceboat:
Am sailing my second season with my modified iceboat: an Isabella Classic with 5m2 (54 sq. ft.) crab claw sail. Just a win-win over all compared against the same boats with conventional Bermuda rig. Just one thing I’ve noticed is she no longer lifts the windward runner at over 60km/h (37 mph).
The yard is made fast to the apex of a bipod mast and fixed to the hull at the bow, so it cannot move. Like the traditional oceanic rig, only the boom is free to sheet in and out. Iceboats are sailed close-hauled at all times, and tack downwind, so the narrow sheeting range between the bipod is no problem.
The sail is cut dead flat, so it is the simplest of rigs for the home builder. Another advantage is the iceboat can be parked in its box more or less completely rigged. Pull the sack off the spars/sail, lift the yard and clip it to the bipod mast. Install the runners and the boat is ready to go in 5-6 minutes, while the Bermudas are still still fighting to get their stuff ready in 20-30 minutes, and even longer if minus 5C!
It might appear at first glance to be a lateen Cheapskate rig, but look closer and you’ll see major differences. All you’d need is two of old windsurfer masts and some bent aluminum tubing for the bi-pod mast. Any new Cheapskates out there who haven’t built their rig yet? This could be interesting…