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third rail


third rail

Some days ago you ran an article about a boat with Three rudders.
By coincidence, we have just finished the successful testing of just such an arrangement on our I550, we found it to be the most successful way of harnessing the tremendous power of this vessel. Photos are attached wit rudder linkages removed for clarity.

We initially started with the Two rudder setup in an effort to keep the boat under control with maximum sized flat top main and asymmetric. We found that the vessel became decidedly unstable with spinnaker set in true windspeeds over 35 knots.

The solution was to add a tapered Third rudder which has made the steering behaviour relatively docile downwind under kite in windspeeds up to 45 knots and boat speeds approaching 25 knots.

Upwind speed seems unaffected due to the tight taper of the centre rudder. An additional benefit is that the "barn door effect" of having Three rudders hard to port or starboard on the starting lin holds the boat almost perfectly still close to the pin until it’s time to unleash this monster.

The only downside so far is that we lose a little speed when there are swarms of jellyfish around. The "thump" when they hit the rudders is considerable.

Regards,

Walrus
Melbourne,
Australia.