Heavy Steering

[smillinjack]

The Durbeck 46 ketch we are restoring has very heavy steering. It has a big prop and it takes a lot of right rudder under power. We have thought about making it Hydraulic steering,but we are not sure that would help. We have also thought about a mechanical advantage to the cable steering ,but not sure where to start there also. Any help would be greatly appreciated

[rmeador]

Have you looked into whether your prop is appropriate for your boat and engine?

[RichH]

Heavy rudder under power = prop blade tips too close to the hull. Consider a prop with less diameter and more pitch.

Suggest you consult with Michigan Wheel or other prop mfgrs. for a complete 'redesign' /evaluation of your prop (pitch/dia.), aperture size, tip clearance, etc. Youll need all the 'numbers' - boat speed vs. rpm, WOT values, tip clearance measurements to hull and/or aperture (with rudder full over and straight ahead etc.), engine power curve, present prop pitch/dia/mfrgr. etc. etc. to begin this 'journey'.

[Faster]

From photos found here: View Boat Photos - YachtWorld.com Photo #3

It looks like a rather large, completely unbalanced "barn door" rudder setup. This is likely the source of the weight of the helm. Difficult to deal with, nowadays most boats are designed with balanced or semi-balanced rudders to ease those kinds of loads.

Reducing propwash forces might help, but at what cost in speed/power??

A mechanical system with some advantage might well be the only way to deal with this.... there doesn't seem to be any opportunity or room to add any kind of balancing tab there....

[smillinjack]

The Durbech is a full keel and it is a heavy boat almost 40,000 lbs.ready to sail. The big prop is great when you are trying to get through the bridge finders and the tide is running 6 knots. I have learned to live with the rudder by using a line on the wheel as a helper. It,s tough on the varnish ,but that can be fixed. The autopilot will handle it under sail most of the time. Thanks for the good info.

[RichH]

Usually on a boat with a prop within an aperture the tip clearance to the aperture is 'vitally' important. If you have the extra rpm available (most boats are 'underpropped' anyway which causes the engine to 'lug' - never develops full hp because the prop limits max. rpm at 'full throttle'); then, usually a smaller prop will allow the engine to 'spin' for max. rpm/ max. hp output .... and by opening the tip clearance, you lose the 'heavy helm pressure'.
If you are also getting 'vibrations' as well as or along with the helm pressure - as felt on the steering wheel, then most probably the prop is TOO BIG for your aperture. Either remedy of opening the aperture space or smaller diameter prop. usually mitigates both - the vibration and the heavy helm.
The shape of the prop tip is also important vis a vis 'tip clearances' in an aperture, and thats why I recommended a 'consult' with a knowledgeable 'expert' AT a prop mfgr (application engineering section).

In my experience with a 'throbbing', heavy handed helm, going to a smaller diameter and change of tip profile shape (and also opening the aperture)... changed my boat to a non-vibratory and 'neutral' helm. I now have a 'short-hub' Max-Prop ... and after many pitch change adjustments have settled in with a good match for max. rpm, max HP output, and no heavy / throbbing helm.

I also changed the leading edge shape of the 'opened' aperture (to similar to a NACA '010' shape)... less rudder turbulence, better hydrodynamics and rudder efficiency.

The hogwash about a full keelers barn-door rudder is just simply that - hogwash, as if the boat is properly 'sail shaped for correct balance' the rudder will be no more than a few degrees (2-3°) off of the centerline ... and if thats the case then all the 'neck vein-popping arguments' about barn door rudders 'go out the window'. You're certainly not 'frantically racing around the buoys' in a heavy weight full keeler with a barn door rudder. ;-)