Simplest Proa Rudders
I liked your build, Peter. Moving the pivot point forward for rudder balance means that the boards don’t have to tilt when they act like rudders. These rudders pivot through 60 degrees total.
In this model, the “board” has 2 degrees AoA to get the board working with less leeway.
Funny shaped slots, but very few parts. I might add a couple bungees to help keep rudders keep acting like rudders and boards keep acting like boards. They’d also help when you wanted to partially pull them up.
The usual side hung rudder problem of the hardware hitting waves, but i guess it could be worse.
chris
I’m loving the long flexible shaft to interlock the rudders. I’m thinking you could even play with the relative deflection by where you push/pull on the shaft. dead center for matching, push closer to one rudder to make it deflect more than the other. The flexibility of that shaft would have a lot to do with this possibility. A simple rod on a collar that can slide along the shaft as well as rotate around it would give multiple helm positions with wicked quick repositioning. Foot operation while using both hands for sheets would be easy as well.
I liked your build, Peter. Moving the pivot point forward for rudder balance means that the boards don’t have to tilt when they act like rudders. These rudders pivot through 60 degrees total.
I like this, a lot! Nice renderings, too. I envy your prowess with your CAD software. What are you using?
The usual side hung rudder problem of the hardware hitting waves, but i guess it could be worse.
chris
You could make the “hardware” thinner, to the point that it has negligible drag even when immersed. If the point loads on the boards become too much, you could consider 3rd “staple” between the top and bottom; also thin, but even further from the water.
Alternately, you could stick with two, very thin (1/8”?), then fashion thin “shoes” that actually bear on the boards. All truly skeletonized when viewed from forward, but plenty sturdy—and well-distributed pressure on the boards.
Just in passing, if I were tasked with creating a through-hull “trunk” for complex shapes like these, I think I might build a top and a bottom template, slap them onto a piece of styrofoam, and hot-wire a “core” for the trunk. Then fiberglass it. Next, either carve out—or dissolve in acetone—all of the foam, leaving the ‘glass shell. Now glass and/or finish sand the interior so it’s smooth and finally, glue and ‘glass the whole thing into the hull. The more I think about this, though, The better I like it as leeboards, like Chris shows. 😉
I’ve been locked in mental combat with proa rudders for a while now. I strive for discovering that perfect, elegant solution that my predecessors have missed and so far every time I “solve” one problem I conclude it makes worse many of the other competing criteria for rudder success.
We ask many things of proa rudders:
* Rotate one or more vertical (more or less) blade(s) on a yaw axis to enable directional change for the boat
* Lift on that same vertical axis to allow for adjustment of lateral area for helm balance, as well as anticipation of hitting things.
* Able to deal with unanticipated hitting of things without breaking anything. This usually means some way of rotating out of the way on a pitch axis - but only when the impact threatens damage.
* Able to functionally handle working in two opposite flow directions without increasing drag
* Hopefully not be too ugly and make our Industrial Design gene segments look like the double helix became a monkey’s fist knot
* Be very effective at turning a boat that we really want to be directionally stable 98% of the time. When we are inside that 2% window of needing them to work, failure to turn the boat means trouble.Sometimes complexity IS necessary, and that complexity is the result of evolution not the failure of evolution.
Just a different perspective.
Bill in Ottawa
I believe I understand your points, Bill. Exercises like the Simplest Proa Rudders aren’t offered as optimum be-all-to-end-all solutions. They are put forward to help us to think about design, about technology and about solutions to our own unique tolerance for compromise. It’s my personal belief, developed over 40 years designing, building and sailing inshore and offshore craft, that we ask too many things of most of the “stuff” we own, also that complex things break, and all the more so as we move farther from the repair shop.
I own a Prius. It is easily the most complex piece of machinery I have ever owned. 8 yrs old now and I have never so much as changed the oil—that’s what the dealer is for. He’s a mile and a half from my front door and, while the car’s been remarkably trouble free, he’s ready to fix whatever goes wrong, first thing tomorrow morning. Now, I submit I’d be foolish to the point of deathly to take such a car, for instance, into the African bush for an extended safari. I could beef up the shocks and add grippy tires, I mentioned that it has been remarkably trouble free, and the thing carries an amazing volume of my stuff—in addition to getting nearly 50 mpg, but I’d still be a damn fool to take it very far from that comforting dealer.
Sorry to ramble, but my point is this, sailing is simple (heck, windsurfers and kite surfers have exactly one moving part). Wherever possible sailing should be kept simple. Simple things do simple jobs. Well designed simple things do simple jobs well. Parts, gadgets and sub-systems left on the beach can never fail at sea.
Before I add any item to a “wanna do” list such as you show here, I carefully ask myself, is this really necessary to have on my boat? Is it strictly necessary that *this* gadget provide that functionality, or can something else—already in existence—do this job, too? Is it convenient and snag-proof? I also ask myself things like, is it easy to deploy? To recover? To repair? To repair at sea, with baling wire and chewing gum? (a far different question!)
Complexity is a fun hobby. You can do things with complexity that will wow both yourself and your neighbors. In the end though, how many of us have paddled dead skiboats across the lake—with the ski? Which device was the more dependable, optimized for transporting you home, when the gasoline was removed from the equation?
Dave
“Simplicity is an acquired taste. Mankind, left free, instinctively complicates life.” Katherine F. Gerould
“Progress is man’s ability to complicate simplicity.” Thor-Heyerdahl
“Simplicity is the final achievement. After one has played a vast quantity of notes and more notes, it is simplicity that emerges as the crowning reward of art.” Frederic Chopin
“From naive simplicity we arrive at more profound simplicity.” Albert Schweitzer
“Have nothing in your house that you do not know to be useful or believe to be beautiful.” William Morris
“Simplicity is the ultimate sophistication” Leonardo da Vinci
I believe I understand your points, Bill. Exercises like the Simplest Proa Rudders aren’t offered as optimum be-all-to-end-all solutions. They are put forward to help us to think about design, about technology and about solutions to our own unique tolerance for compromise. It’s my personal belief, developed over 40 years designing, building and sailing inshore and offshore craft, that we ask too many things of most of the “stuff” we own, also that complex things break, and all the more so as we move farther from the repair shop.
I own a Prius. It is easily the most complex piece of machinery I have ever owned. 8 yrs old now and I have never so much as changed the oil—that’s what the dealer is for. He’s a mile and a half from my front door and, while the car’s been remarkably trouble free, he’s ready to fix whatever goes wrong, first thing tomorrow morning. Now, I submit I’d be foolish to the point of deathly to take such a car, for instance, into the African bush for an extended safari. I could beef up the shocks and add grippy tires, I mentioned that it has been remarkably trouble free, and the thing carries an amazing volume of my stuff—in addition to getting nearly 50 mpg, but I’d still be a damn fool to take it very far from that comforting dealer.
Sorry to ramble, but my point is this, sailing is simple (heck, windsurfers and kite surfers have exactly one moving part). Wherever possible sailing should be kept simple. Simple things do simple jobs. Well designed simple things do simple jobs well. Parts, gadgets and sub-systems left on the beach can never fail at sea.
Before I add any item to a “wanna do” list such as you show here, I carefully ask myself, is this really necessary to have on my boat? Is it strictly necessary that *this* gadget provide that functionality, or can something else—already in existence—do this job, too? Is it convenient and snag-proof? I also ask myself things like, is it easy to deploy? To recover? To repair? To repair at sea, with baling wire and chewing gum? (a far different question!)
Complexity is a fun hobby. You can do things with complexity that will wow both yourself and your neighbors. In the end though, how many of us have paddled dead skiboats across the lake—with the ski? Which device was the more dependable, optimized for transporting you home, when the gasoline was removed from the equation?
Dave
“Simplicity is an acquired taste. Mankind, left free, instinctively complicates life.” Katherine F. Gerould
“Progress is man’s ability to complicate simplicity.” Thor-Heyerdahl
“Simplicity is the final achievement. After one has played a vast quantity of notes and more notes, it is simplicity that emerges as the crowning reward of art.” Frederic Chopin
“From naive simplicity we arrive at more profound simplicity.” Albert Schweitzer
“Have nothing in your house that you do not know to be useful or believe to be beautiful.” William Morris
“Simplicity is the ultimate sophistication” Leonardo da Vinci
Dave:
I agree with your observations - I was waiting for someone to point out the obvious - the solution that most likely meets my complex criteria the best is a manual steering oar used only when necessary on a directionally stable boat. Have I decided to do the obvious? Not yet. I’m hoping I can come up with something better.
In my case I am hoping to improve other things (hull drag, seaworthiness, performance, trailer-ability, camp-capable, build ease, material costs) at the concession/degradation of others (aesthetics, appearance, tradition, non-functional considerations). I’m willing to ruthlessly pursue my objectives at the expense of things that may be important to other people. I’m willing to give up crowd appeal for the distinct pleasure of keeping up with someone else’s $35K-$50K purchase in a self-made boat that cost me time plus 5-10 thousand dollars.
A major criteria for me is range/speed - I live in a huge country and the speed benefit of a proa lets me see more of it in available time.
Your thoughts on complexity echo my observations developing and delivering products for thirty plus years. There is a vast difference between development engineering (meeting a clearly defined objective at all costs in the shortest time) versus production engineering (reducing process, parts, complexity and cost) to achieve the same functional result profitably. I think it is very difficult to combine development engineering and production engineering into one process (which seems to be the holy grail of Industrial Design folks). Simplifying stuff is only effective if you already know what actually works.
To a degree I see modern Westernized proas as one long development engineering exercise so far. This “Simplest Proa Rudders” discussion is evidence we are moving towards production engineering.
—
Bill in Ottawa
I’m working on speed and range, perhaps you’ll like it. How do you feel about inflatable bow sections? 😉
I’m working on speed and range, perhaps you’ll like it. How do you feel about inflatable bow sections? 😉
I have no preconceived notions and would gladly consider any thoughts!
—
Bill in Ottawa
I’m working on speed and range, perhaps you’ll like it. How do you feel about inflatable bow sections? 😉
If you diddle em a bit to steer, I’d be interested, possibly better than glassed over foam currently at top of list.
Skip
Dave,
I like your “Simplest Proa Rudders” a lot. 😊 Tangential thinking!
“You could make the “hardware” thinner, to the point that it has negligible drag even when immersed. If the point loads on the boards become too much, you could consider 3rd “staple” between the top and bottom; also thin, but even further from the water.”
If you have a third ‘staple’ midway between the other two then it doesn’t have to have the allowance for f&a movement (or very little anyway) as the other two ‘staples’ do as it becomes the pivot point around which the board will pivot upon shunting. It also stops the board from moving f&a as a whole when not under load.
f you have a third ‘staple’ midway between the other two then it doesn’t have to have the allowance for f&a movement (or very little anyway) as the other two ‘staples’ do as it becomes the pivot point around which the board will pivot upon shunting. It also stops the board from moving f&a as a whole when not under load.
Perfect. Thanks! I was concerned with just how sloppily they’re restrained, overall. What keeps the rudders from just floating out and drifting away, perhaps in the middle of a shunt? If in a fancy morphing-shaped trunk, the functionality you point out is gonna be there, but not with just two “staples.” Third staple nails it down. Thanks!
Dave
You’re welcome, Dave! I guess you could weight the bottom of the boards or use bungies to hold them down. Or perhaps the tillers could be used somehow to do the same.
I modeled up “simple rudders” for Herbie. This is a take on Chris’ rudders, being non-linked, steer only with aft rudder. Herbie’s hull extensions naturally function as “rudder holders”, and I love the idea of using negative space as the cam, talk about less is more! There is a high density plastic top and bottom cam, the top cam has a “keeper slot” to hold the rudder in place as the “forward” rudder. The white disc on the rudder keeps the thing from falling through the slot. I would use bungees and small control lines to make sure the rudder stays firmly in/out of the keeper slot.
You’re welcome, Dave! I guess you could weight the bottom of the boards or use bungies to hold them down. Or perhaps the tillers could be used somehow to do the same.
Given that the rudders are a loose fit in their restraints, why not just make them buoyant (hollow ?) and secure and adjust them with a downhaul ?
I’m not so sure about the third ‘staple’ - I’d be concerned about misalignment and binding. Why not use the locking slot in only one of the staples - the other would be simply a butterfly slot for steering which would locate the rudder fore-and-aft. When the boat is shunted the was-rear rudder would pivot aft in the non-locking staple and lock in the other one. No alignment needed…
I guess from a ‘wetted-area’ perspective you’d want the ‘locking-staple’ on deck and the ‘pivot-staple’ underwater.
I really like the one piece bendy tiller idea. It might be a good thing to use with ‘properly’ hinged (centre hinged) side hung rudders, because the return spring effect would help to counter the overbalancing tendency, so there may be no need to move the rudder fore and aft on each shunt.
On a slightly different tack, I had an idea recently for what may be the most complicated proa rudder. The idea comes from the wingsail thread. I’ll try to explain it:
Imagine a rudder with a tail fin, like say the sail from Saildrone scaled down, turned upside down and hung under the boat. There would be two of them, one forward and one aft. Each rudder is steered by its tail fin and the tail fin linkages are connected so that they act in opposite directions. These rudders will only be able to produce a turning moment, they will not (as a pair) be able to resist leeway, so their sole function is to steer the boat. Leeway would have to be prevented by some other means. The advantages of this rudder setup are:
1) You never have to worry about shunting them because they will always naturally tend the align with the local water flow.
2) Very little input is required to turn the rudders, so good for self steering systems.
The disadvantage is fairly obvious, lots of moving parts.
pr1066 wrote - Given that the rudders are a loose fit in their restraints, why not just make them buoyant (hollow ?) and secure and adjust them with a downhaul ?
Yep, sounds like a good idea to me. 😊
I’m not so sure about the third ‘staple’ - I’d be concerned about misalignment and binding. Why not use the locking slot in only one of the staples - the other would be simply a butterfly slot for steering which would locate the rudder fore-and-aft. When the boat is shunted the was-rear rudder would pivot aft in the non-locking staple and lock in the other one. No alignment needed…
You’re right, Peter. Aligning three of them calls for accuracy. But there are ways to jig them together and bond them to the hull as unit. More fiddly, for sure, but quite doable.
I see what you mean by removing the bottom staple and moving the proposed middle one down. You still have most of the advantages of the three staples set-up without the extra work of keeping them aligned while installing them. But you don’t get the full benefit of the locking slot in the bottom staple, though it may not matter. The board may set up a flutter or oscilation under some circumstances or it may not.
One thing that will change is that the head of the rudder-board will have to move f&a considerably more as the board pitches from one shunt to the other. The movement that was spread between two staples now has to be accomodated by one staple meaning it will need to allow twice the movement. This will call for more complexity in how you design and attach the tillers, I think.
That’s an interesting thought about moving the lower staple to below the water surface. It involves a little more drag but could also limit cavitation. But I’d be guessing about that. Of course, the further away from the top staple you move the bottom one, the more the rudder head (and tiller) has to move f&a.