13 m2 crab claw and a kite means one fast Tiki 21

Christian and I discussed and sketched out plans to combine a 5-12 square meter kite with a bigger main crab claw sail (the 13 square meter one proposed by James and Hanneke in the Crab Claw Rig for Tiki 21 plans). A 6-7m2 kite and the 13m2 main would yield about 20m2 of sail area — close to the original wingsail+jib combination of 208 ft2. We decided our optimal set up for this combination was hoisting the main on a mast centered on the center beam, moving the mainmast forestays back to the forward beam ends, and then flying the kite from the center of the forward beam. The kite pilot could sit or stand on the tramp, or maybe sit on the forward beam with feet dangling…

[nggtags album=20110308]

With the estimation that the kite lines are usually between 30 and 45 degrees off the bow of the board (or boat in this case), we’re hopeful that the forestays will not overly constrain for all points of sail. It may be trickiest going dead down wind (or preferably tacking downwind at least 30 degrees off dead-downwind) as the kite may de-power as the boat (pushed by the main) picks up speed. If the relative wind drops too far and the kite is up near neutral, it seems a worst case scenario would be a Hindenburg in which the kite drops behind the boat and the lines end up tangled in the rigging. We agreed to keep knives handy… Another worst-case scenario would be a broken forward beam or lashings, but we’re doubtful it will happen (kite lines are typically 600 lb test and the lashings are ~5 turns of 700lb test rope).

Christian helped pull down and peruse the 4 long (~7m) bamboo spars that Thomas found under the Ballard Bridge. We selected the straightest (or most uniformly curved) two. Later, I cleaned them up and marked mid-points, as well as the region on the upper spar that may need reinforcing (with extra bamboo or a 3m length of basalt sock?). Then I put beam cleats and hardware (main sheet lead/cleat, traveler blocks/prussick) back on — noticing a couple little spots where the black paint is thin, but gratefully realizing that more beam work can wait for next winter.

So it seems time to look for a dry place in which to stretch out the 24×30 white polytarp… All materials are ready for laying out, cutting, and at least taping up a new main!

Leave a Reply