rudder placement

Hello all,
What is the most efficent position for the rudder.? On the stern as in photo (not my boat but similar) or underneath foreward of the aft waterline?
Peter

 

Gooday Peter - Gawd - you in the 'great south land' - (we just a stone's throw north of you - inland from Cairns - ha ha).

Gad - zooks - such a big 'agruement' so early in the morning & so early in the week ! !

Wow - this will sure - put the 'cat in the middle'

1000 different answers - some very fine yachts - cruising, racing - big, meduim & large - have used many different positions & designs. There's about 4 big books - in just this 1 little subject.

Personal choice has a lot to do with anyone's decision - I M H O

Very important is the selection of the size - profile - section - foil profile & whether you choose to move the max thickness aft as you go deeper. Many a 'Master yacht designer' has labored long & hard to get all this as close to correct - as they thought was posible.

I've some personal beliefs & pref's but - the arguements that will follow are more than I wish to get into.

Great fortune in arriving at a suitable answer - that you can be personally happy with - OH & that does the job well (or better than well) Ciao, james

 

even though i have a skeg hung rudder i would rather a transom hung rudder for cruising. no through hull fitting to leak and can be removed for repair or replacement easily. like james says, everyone probably has a their own preference, this is mine.

 

Peter

If by efficiency you mean lift to drag ratio then you should use the hull as a reflective plane which effectively doubles the aspect ratio. That means immersing it somewhere fwd of the operational waterline.

But the most suitable design depends on several factors. Also if this is a retractable keel trailer sailor then you want a rudder to match.

 

NO, it is a Sonata Keelboat similar to the one in the photo.
The keel is already modified with a bulb.
I am interested in steering performance of one verses the other.
The stern hung rudder is not at its best broad reaching or beating when there is a bit of a sea running.
Peter

 

Mike has it right from an efficiency point of view, but as he also eludes to, there are several considerations in regard to rudder types and placement. What are your goals with the new rudder?

 

Make the steering more predictable. Hopefully keep the rudder in the water and the boat under control

 

can you make a retractable or swing rudder. that way you can run a deeper blade to compensate for the stern lift on waves. might be an easy way to fix the problem.

 

Anythings possible, BUT, the gudgeons are 9" apart and the load on them is considerable. They wear out quickly and are a weak point.
I wouldn't want a swing or retractable rudder, don't think I could make then strong enough. I have already broken 2 blades and know of another one.
These boats were designed as a trailer sailer but at some stage some were given a keel. No one thought that some of these boats would end up in places where no ts. would venture.

 

It sounds like you have multiple issues to contend with. My first thought is a better rudder. Better placement, plan and section forms as well.

It appears you have enough room to get her "tucked under" the stern, while still permitting the shaft to come up aft of the cockpit (tiller sweep). You could try an end plate, placed at the LWL of you current blade, which would make the rudder work better at modest angles of heel. Can you post a picture or two of the full rudder? Also make, model and year of your boat?