Thoughts on rudders, tillers, wheels,etc.

[Owly055]

    The boat I've more or less settled on for my purposes, the Searunner 31, leaves a number of things to be desired.........but doesn't any boat?   They are center cockpit with the aft cabin being the primary living area for all intents and purposes.   It's the most useable space in the boat.   The distance from the rudder to the cockpit is quite large, about 10 and a half feet to the forward edge of the cockpit.  That pretty much precludes using a direct tiller, as with the North Sea 27, across the top of the aft cabin.  A feature I like about that boat.
     The options thus are a wheel, or a remote tiller, both of which have been used.     The original drawings show a skeg rudder mounted beneath the hull, but in fact virtually every one built has a transom mounted rudder.  Cables pass through the hull typically to a wheel in the cockpit.  The rudder of course is a typical barn door rudder, an in my opinion essentially crude and inefficient drag device, though they have worked for thousands of years. 

     Rudders work by creating a side force.  In the case of the barn door rudder, a lot of drag as it directs water away to one side.   Modern racing boats typically use a rudder that is a hydrofoil (airfoil designed to work in water).  The foil creates lift, just as a wing does, but of course it's lateral lift instead of vertical lift.  The lift drag ratio is many times higher than the than the lift drag ratio if you could call it that, of a barn door rudder.    There is a reason we don't put engines on barn doors and try to fly them ;-)
   
     I propose replacing the barn door rudder with a hydrofoil rudder, hinged about 25-30% aft of it's leading edge, with supports extending back from the  transom  into reliefs in the rudder blade itself where bearings (probably made from UHMW) on a stainless steel rudder stock would allow it to rotate freely.  Properly selecting the pivot axis, should give some centering moment, but still keep "tiller loads" extremely light.   The rudder assembly would be mounted to a frame, hinged to the top of the transom with a break away, and the rudder would have a tip plate to improve it's efficiency.   

     With the extremely light loading, the actual tiller or wheel up in the cockpit would have little to do, and thus could be pretty compact.  Rather than a tiller sweeping the cockpit, or a wheel taking up a lot of space, I can see the possibility of having several steering stations with a sort of stick like a whipstaff that you might drop into a socket, to be retained by a pin or a ball lock assembly, etc.   You could sit on a cockpit seat.........windward side, and steer with a stick that would be like resting your hand on the gearshift of a manual transmission, and there could be a third location up under the dodger.   Below are photos of Roger Taylor with his whipstaff on Ming Ming, you can see the ropes at the top that come through the back of the cabin to it, and photo of a man using a classic Viking type rudder & tiller, which is like a great oar, and is in fact an airfoil type shape, inherently balanced, and fairly long.  It moves fore and aft, and the tiller arm is quite short.    Also a photo of a Nor'Sea 27 aft cabin with the tiller sweeping across the cabin, and a sail plan for the Searunner 31 showing how far the cockpit is from the tiller.

                                                                                   H.W.

      Light tiller loads