These designs are clever.
However, I learned a couple of principles from Rob:
1. make no holes in the hull
2. ground strikes will happen

And even though some HP boats make exception to this, beam mounted is required. With beams high above water surface this poses a challenge with the high moment forces. But this is structurally simple to solve. No moving parts.

On to the moving parts. Sometimes I wonder it is way less complicated to have a set of fore and aft rudder boards for each shunt direction. This means four rudder boards. This eliminates the need for a rudder being able to fully swap direction. One could also put the boards at the right angle down for each of the directions to have the force vectors in a better balance with those of the sail(s). If one takes along 1 rudder board as spare anyway, this costs only one other rudder board and all four are operational instead of taking cargo hull space. This also simplifies and makes steering mechanics up to the wheel more robust. And maneuvering slowly in close quarters is helped with all the rudder boards down. So, all in all, I would think that the cost of one extra board is compensated by the other gains. 

What do you think?  

--- In harryproa@yahoogroups.com.au, "Dennis"  wrote:

I agree that having the structure inside the hull would be stronger, but I made this model to demonstrate the features that I (we all) wanted.  I hadn't see a way to make the inside the hull "fool proof" and the external method is.  the big difference is that it's not a working example yet!  and there's plenty of details to sort out.  Still it's just a model and that sure helps out the thinking process, that is when I can finally get back to this.  I got other irons in the fire right now.  I'd not mind if someone else too this and ran with it though, and posted their results!  

--- In harryproa@yahoogroups.com.au, "Peter Evans"  wrote:

Hi Dennis

Your idea looks cool, certainly will work.

My thoughts (rightly or wrongly), that having the board inside the hull provides structural benefits (better distrubution of loads), and also there is no external structure that can cause drag should there be a high seastate


--- In harryproa@yahoogroups.com.au, "Dennis"  wrote:

http://youtu.be/6LvxzIp9XHI
here is my concept example of a fully rotating kickup drum cassette rudder
never mind the hull it's on, that one end wasn't finished, it's not a tacking proa.
I have other videos of my proa model on my youtube channel.

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