Rudder design/rebuild question

Sorry Petros, have to say it - this sounds pretty patronizing, and it is unnecessary. Tom Lathorp is not a beginner. He is not an expert in hydrodynamics, and he clearly stated it so many times, but he is not a beginner in anything that regards boats and their design.
Let's play nice people.

P.S.
Ok, I know - this post sounds patronizing too. Sorry for that. It's just a matter of respect towards Mr. Lathorp.

 

The comment was not meant to be put down. Many of Tom's contributions are reasoned and show excellent understanding and good experience, so it was with all due respect that I took the effort to explain it. What I meant by "beginner" was intended as a short hand way to say that many things in fluid mechanics on not obvious, and often terms get misused (even by some people that should know better, like those that publish technical reports). This only adds to the confusion.

Sorry Tom if I came across as patronizing, that was not my intent. I apologize, I have enormous respect for you, and your experience.

 

Apology accepted. Go and sin no more. I do think I have a decent amateur's working knowledge of the subject and was not as confused as you might have thought.

I learn from some of the discussions here although I depend on books and my experience for confirmation as a forum like this does not offer judgement as an option.

 

Couple of hours, yeah sure...

Well, here are my two cents worth - see the attached pdf:

1. The first solution is pretty simple. A kick-up rudder extension which can be lowered for low-speed maneuvering. Once lowered, its angle of deflection is the same as the tiller angle, acting as a rudder with a bigger chord. The extension in the drawing gives approx. 50% more area to the rudder.
2. The second solution is more complex but gives a higher lift. It is essentially a flap attached to the trailing edge of the rudder blade and connected to the transom with two wire ropes. The wire ropes are put in tension by the tiller rotation, as visible in the drawing.

Both solutions will increase the overall lift, though they are based on different hydrodynamic principles. I don't have much time to elaborate further on these drawings, but I believe they are pretty clear. In any case, don't hesitate to ask for more info if necessary.
As the others won't hesitate to make their considerations on this and to eventually propose better solutions.

Cheers

 

Tom you have considerably more then you think, certainly a lot more than an amateur.