Cyberspeed in Catsailor says a SC21 is very difficult to tack
Posted: August 29th, 2015, 9:07 pm
How about that havliii? Is your boat hard to tack? What about this cyberspeed guy? Well, he doesn't understand "shared lift" or what makes a beach cat tack well/quickly. On the SC21 the daggerboard is moved forward of the main beam. It is about three ft forward of the normal position. In this location it carries or is exposed to less that 100% of the sideforce from the sails. To bring the boat back in balance an oversize rudder is used. The rudder is installed in a balanced condition so it can carry the balance of the sail side force without creating a heavy, hard pulling tiller.
What makes a boat tack? Now, when a centerboard boat tacks it tends to pivot about the CB. The rudder, located several feet aft on the transom, generates a side force and the aft end of the boat responds and moves in a circle around the pivot point, the CB. Torque created by the rudder makes the boat tack. Now in the case of the 21 with the forward located CB , the lever arm between the CB and rudder is increased relative to a boat with the CB located near the shroud chainplate and this longer lever arm makes more torque to tack the boat. Also the 22 has an oversize rudder which generates more side force and this increases the tacking torque also. So the unique geometry of the SC21 with shared lift makes the boat tack quicker not slower. Mr Cyberspeed doesn't understand. A SC 21 8.5ft wide will tack quicker than a SC20 12ft wide.
The thing that bums me is that this error comment was published in Catsailor and now many readers will think it is true. They do not know that a dummy said it.
What makes a boat tack? Now, when a centerboard boat tacks it tends to pivot about the CB. The rudder, located several feet aft on the transom, generates a side force and the aft end of the boat responds and moves in a circle around the pivot point, the CB. Torque created by the rudder makes the boat tack. Now in the case of the 21 with the forward located CB , the lever arm between the CB and rudder is increased relative to a boat with the CB located near the shroud chainplate and this longer lever arm makes more torque to tack the boat. Also the 22 has an oversize rudder which generates more side force and this increases the tacking torque also. So the unique geometry of the SC21 with shared lift makes the boat tack quicker not slower. Mr Cyberspeed doesn't understand. A SC 21 8.5ft wide will tack quicker than a SC20 12ft wide.
The thing that bums me is that this error comment was published in Catsailor and now many readers will think it is true. They do not know that a dummy said it.