Proa Circumnavigation?

Sure but in a kick up design the surface area can rip the rudder off the transom.

 

how do fences & pitching go together? (when the flow on the rudder/s is at an angle)

 

It will create a little bit of resistance, but i do not see it as a problem, a very low price for a good job, in short a minor detail, it is a simple solution for rudders that hang from the transom and go up turning, it is a different matter if the rudder blade goes up vertically, but it is better to turn in case of an impact.

 

Frank Bethwaite, High Performance Sailing

 

Depends on how large you make the fence. The transom, pintles, and gudgeons should be strong enough to withstand the rudder suddenly being turned 90 degrees at speed, so if your fences are small enough that the load is smaller than that when kicking up, isn't that good enough?

 

I am, I've been studying that design some. Actually I've got some questions for that guy...
Is he on here? One can no longer make an account on proa file or sailing anarchy.

 

He has answered some questions in this thread on Sailing Anarchy: Dear Mr. Sidecar https://forums.sailinganarchy.com/threads/dear-mr-sidecar.237849/

The Proa File discussion forum was closed years ago, but there is still a button for registering on Sailing Anarchy.

 

I'll try again later, their captcha isn't working so it wont let me in

 

In the various HP discussion sites the spade with rudder post in a tube gives the rotation without the pintle and gudgeons limitations.

 

Has anyone taken a page from outboards and done a rudder in a sled? There's a endplate.
I'm sure if he was still alive Phil Bolger would come up with a leeboard rudder. Traditional articulation and sideways safety.

 

That is not the direction we approached it from, but it is an excellent description. Thanks. I will use it when I describe the system to the Fijian traditional boat guys who I am advising on modern materials for their 30m/100' Drua (shunting canoe with same length, different shaped hulls). Might get me some brownie points. ;-). These guys have seriously 'up-sized" arms for a steering oar that takes 3 of them to lift.

Sensible and safe. Cavitation happens at over 50 knots, so a good problem to have. Ventilation when air is sucked down the the low pressure side of the foil. A really good visualisation of it. The 300mm/12" chord foil is lifting about 180 kgs/400 lbs. Other causes are rough surfaces and excessive angles of attack, both of which also apply to the foil in the video.
Fences work for fixed foils, no good for lifting ones unless the foil is attached to the case, not the board.
One of the enjoyable things about surface piercing large rudders is that you can get up close and personal with the flow. Watching the low pressure side water level drop as the breeze increases and seeing tell tales (aka thin bits of seaweed) flutter when the aoa gets too high teaches a lot about how they work.

The faster the boat, the more reinforcement of a non kick up board is required. My brother worked on SVR Lazartigue (maxi foiling tri) after it ripped a chunk out of the main hull when the fixed dagger hit something at 30 knots. The reinforcing to prevent this was huge, heavy and proved pointless. Making them kick up would seem to be a lighter, safer bet than more than half the fleet in that race suffering damage from having fixed foils.

Love to! Much more enjoyable than displaying my pissing prowess. ;-).

Starting point for the discussion: I found the biggest problem with beam mounts is getting enough steering leverage. Solutions were bigger separation of the beams, bigger rudders (ie, no separate daggers), the ability to lift them for balance and the ability to steer them individually, particularly so the aft one can be locked and the front one used for steerage upwind. The other problem is support, but that can be remedied with struts and more laminate. A cool solution is to mount them on the lee side, in the beams, which is one of the experiments I mentioned above. Initially, this was to reduce the visual impact, but it moves the board drag to leeward and vastly reduces the weight and complexity of the mounting, albeit with some handling issues.
I look forward to other solutions and ideas.

 

Thanks for the feedback Rob!
The leverage thing.... When he was explaining boat handling my Dad would always remind me a boat turns/ pivots from the center which is why the rudder was on a end.

Phil Bolger was great at doing what worked and tossing yachting ascetics out the window hence the lee board thought. A leeboard with tab is.... doing exactly what a Newick proa dagger rudder does. Moving the turning effort towards the stern the spade with rudder post can still do the same leeboard kick up thing and let a central board handle the leeway. And it can be romanticized with the steering oar ad copy.
All the same reasons the ancients did this apply today, save the hulls from damage, save complexity.

The sled on the other hand lets one use a beam mount with the arm length increasing leverage. Undoubtedly guys to the hulls would help with the side loads. The big sea issue of course means they would have to be pulled way up. For a proa these seem more work but make a lot of sense for a cat.

The leeboard spade oars could stay down with the front one free wheeling/turning so it wouldn't affect maneuvering. Great for faster shunts but I'd want to rotate it out for the long hauls to keep it safe. Yeah it kicks up but why hit both?

Lots of fun to contemplate and many angles, you are a good sport.

Cheers,
Cav

 

Re rudders: In the beginning of my journey down this this arcane path I used a steering oar on my first "real" proa P52. So simple, one oar sufficed for both directions a ball and socket joint allowed some steering with just a little twist of the shaft. You could maneuver the boat around oar wise docking. But at speed ( 8-9 mph) there was this little issue of the forces involved. My favorite video of P52 passing Chuck L. on it's maiden TX200 voyage has a 1.5 second segment where I waved as we went by. The other hand had a death grip on the oar and my feet were planted firmly on the lee side of the hull. Several people at camp that evening commented on the incongruous sight of such a strange craft flying up Baffin Bay with a 48 s.f. poly tarp sail with me holding a death grip on the oar that had a significant very visible bend in the shaft.

The next year we returned with quarter rudders on the weather side of the hull and a less effective but reefable sail plan. Rudders were retractable in pivoting cassetted open ended, bungee corded and swept forward to minimise ventilation. You could steer with thumb and forefinger and I learned a lot watching the flow of water around the bidirectional (Speer 30012 sections) rudders.

Since then I have gravitated to end mounted rudders in a spring loaded vertically pivoted cassette and haven't looked back. It took a few iterations to get it somewhat right but that is part of the joy of messing around with proas. One other comment. The original oar was also intended for propulsion but fell far short of being functional, I had a lot yet to learn. I've learned a little and a AD style sculling oar is now standard equipment and also serves for emergency steering.

I miss the ultimate simplicity of that original oar and reflect on it on occasion while in my little 12' double blade EasyB canoe which is the gold standard for elegant simplicity.

Cheers,
Skip

 

Yes, steering oar is a historical concept description, not a design suggestion ha ha. Balanced foils take much less effort. Sounds like you have done some good work.
In larger sizes control linkages to steer, disengage and retract start taking a fair amount of effort to finesse but that is part of the fun.