Proa Shunting in Heavy Weather

[rob denney]

Hi, I am new here, have read nearly this entire thread.. I have been studying Proas and esp. HPs a while ago...I do like the spacy ufo looks of the Denny HPs.

Glad you like them.

Now i am once again looking for a world cruiser.. was delayed by C19 and other unforeseens...
I have put aside my reservation about bad resale value.. cause if I go for an HP .. i will keep it!
Now I have to figure out how it works for me.
Ive gone thru this looong thread and come to the conclusion that I like 90% of HPs characteristics ... but dont quite get my head around 2 points.
1. the rudder/leeboard issue.
A_ it can be raised in a steerable box and swiveled(kickup) away from bridgedeck. So impact safety only for one direction when sailing upwind with both down?

No. Kicking up, the rudder blades, the rudder mounts and the steering all work in both directions.
See Hydrofoils http://www.basiliscus.com/ProaSections/ProaIndex.html for the blade section shapes and performance.

Further if both can be used for steering they must have their rot. axis central which at speed may leed to flutter if not (as I read somewhere) they tilt back , rearwards of motion thru water? which would make them stable ...

Correct. The case is oversized so the top of the blades can rake/rotate forward to keep the steering axis ahead of the centre of pressure. This rotation is automatic and operated by the boom or main sheet when the boat shunts.

My Q: how do you control the steering input as the front blade will exert more steering force on hull than the rear? needing less input. When on the other tack (dir.) this balance must be inverted.

It is not a problem. If both blades are used, you steer until the boat is on the new course. It does not matter which rudder is doing the work.

Or is one forced to steer both rudders independent with different input?

This can be done with 2 wheels or tillers. It is more complicated to build the wheels, but not hard to do.

How would an autopilot cope?

The same as on a conventional boat, except for the tack/gybe function.

Maybe using hydraulic sys. with valveswitch for fwd/aft?

Could do, but it is more cost, weight and complexity.

2. where on a proa would you fit the 2 drives? I would go for serial hybrid in a proa with lots of PV on a large bimini.. maybe 15m²/ 3kW? assuming a 18m to 20m HP plus small 25_35kW rangextender (rotax/bombardier 35 to 55kg.) Powering 5 to 10kW pod motor on each rudder, one facing eithr way.. best with a symetrical bladeprofile, can also generate power and shld give app 8kt, or 1 to 2 azimuth drives motor in boat or pod. Regen option.

This is a cool approach. Maybe mount the motors on sleeves on the rudders so they can be lifted up clear of the water when not in use.
The current method is to lower the stern of the tender and use it's outboard. For boats where this is inadequate for maneuvering, a second, possibly smaller, probably electric motor can be deployed through the toybox. If this is on a rotating mount, it can be steered to push the boat in any direction. It would be lifted clear of the water when sailing but could be used for regen if it had a kick up fuse in case of a collision with a floating object.
Other options include:
Mounting the motors on tilting arms on the side of the hull(s), or the rudder sleeves so that they can be lifted clear of the water.
Placing them in boxes in the hulls so they can be lifted when not in use. The bottom of the drive unit has a plate on it to seal the hole.

I believe the rudder/leeward blade issue with differential steering , kickup /rake poss., lift up, is a complex issue.

You are not kidding. We have been refining it for 20+ years and there is probably further work to do.

If the trimming of both blades is done manually by helmsman.. he needs to know what hes doing or wont get best performance windward.... cant let a novice shunt?

Shunting a well set up proa is simple, anyone who can tell where the wind is coming from should have no problem. It is far easier to teach a novice to shunt than to tack. Most sailors are simply surprised at how simple it is.

There was the Q posed how to get best windward without too much drag, and if 2 or 1 ½ rudder immersed or 1 only...blade drag , as remarked, will be very much less (high aspect ratio) than hulldrag if latter shld create ww lift.

I think this refers to Rick Willoughby's posts on the harryproa chat group? Optimising the windward performance with blade immersed area and angle is a fun challenge, but the boats will sail well upwind without it.

I believe that it will show in the wake's angle to boat heading?

It will, but it is difficult to get a precise reading. A better approach is to attach one end of a rope to the middle of the deck, high enough so that when the rope is in the water, it just clears the beam. Make a mark where the rope crosses the beam to indicate leeway angle, then play with the rudders and rigs until it is minimised. This provides hours of entertainment for those who like tweeking. ;-)

This Q to those of you with Proa experience:
> how do you best deal with steering the boat when beating upwind?

I find it is easiest to lock the aft rudder and steer with the front one, but have done the reverse, and steered with both, either together to speed up turns or in opposition to move the boat sideways.
Any other questions, please ask.

 

[rob denney]

"Pretty easy to test on 2 models tied together and pulled along the breaking wave front at the beach, if you think it is worth exploring. Even if it does, the wave needs to exceed the height of the beam to capsize the boat. In waves this big, you should be hove to or sailing carefully."

These studies have been done without the boards and suggested that wave induced capsized are possible at breaking wave heights of 30% of length, and likely at 50% (in catamarans). So, =to beam is a roughly equivalent, sure. Iirc the authors recommendations included a f/u looking at boards, although I doubt that I would be able to control the variables enough to have any statistical relevance if I perform them myself.

Try it and see. You are looking for reassurance, not "statistical relevance".

Since, 1 in 100 waves will be 150% of significant wave height though, and those are the most likely ones to be breaking, you're at risk even with a significant wave height of closer to 13'-15' waves on an average 40' boat (and yes, those are still very large). Heaving to/lying ahull doesn't protect against wave capsize, continuous skillful active sailing may protect some, but only preventing rotational energy really does fully, which would involve a sea anchor/drogue or theoretically having minimal lateral resistance in the leeward hull in multis, and shallow draft/high topsides in monos for skidding purposes.

It is pretty obvious while sailing when it is time to consider your options from easing sheets, weathercocking the rig, reefing, heaving to, running off, drogues and sea anchors. I sat out a Force 8 gale in the Bay of Biscay in my 3.9m/13' wide Iroquois cat. Dropped the sails, pulled up the rudders and the boards. The boat sat at an angle to the waves that was broad enough for breakers to crash over the boat from the side (about 2m/7' high). Scary, but never felt like tipping over. A 12m/40' Harryproa is almost twice as wide.

"Pretty close. Let me know if you want a set of plans. ;-)"
That would depend on if you're flexible with appendages. I don't see why the rudders shouldn't be able to be reduced and provision made for a leeboard. If the drum interfaces are made to the original plan, the customer would bear the cost of reverting to the plan, but it would be simple enough to to - and then you'd have empirical evidence for your preference. That is not to say n any way that there is any onus on you to do so, or that choosing to maintain your design as is implies anything with regards to your character.

I have no control over what you build so don't see a problem. I help anyone who wants to try something different, and provide free advice and (often endless) discussion in the thinking about it stage and during the build. However, we are not going to redraw the plans for something we don't think will work as well as the standard unless we are paid to cover the time to do so.

Alternatively, if you actually showed your system in an open format so that it could be assessed and if you discussed the compromises needed objectively, I might then be persuaded.

By open format do you mean post the plans publicly? Or is the attached sufficient? I love discussing the compromises, especially objectively. Let me know what you don't understand or what compromises I have missed.

I don't mean the following as an insult so please don't infer that tone). Cult leaders have demonstrated repeatedly that if you cut people off from discussion with others, have a strongman personality at the top, and repeat the same thing over and over, then people will believe just about anything. I'm open to be persuaded, but it would only be by open discussion, which I personally don't count the harryproa forums as due to the structure following aforementioned patterns that are known to be subversable. The problem is not that there is not some very interesting discussion happening amongst intelligent people there, but rather that it is happening only within a narrative (the same problem is seen with polarization in politics).

"Insulted"? Not at all. "Cult leader" may be overdoing it though. ;-) I seldom post during the discussions in the HP chat group for this very reason. When I do, it tends to curtail the discussion. I don't know how to make it more open than it is, but if you want a whole lot of mostly objectionable rather than objective about me and Harryproas, visit Sailing Anarchy's Multihull forum. I do think you might be better off focussing on the boat design aspects than the philosophical ones.

I raised some concerns about the generalized inherent obstacles to what diagrams of your rudders would face, and while I have been enlightened on a few points, most are unanswered (and some now reasked by another member's post).

My bad and not at all intentional. Anything that is not clear, or unanswered, please say so.

Sidestepping (such as me discussing the reduced reliability from complexity resulting in changing the narrative to crash resilience, which is admittedly the trim tabs worst feature and brought up ad nauseum),

The HP rudders are as reliable and simple as we can make them after 20+ years of development. What else do you want to know?
"Ad nauseum" beats the hell out of a hole in the boat, bent shaft and no steering after a collision. Unless you understand this, you are deluding yourself about trim tab steerings' usefulness on a proa.

misdirecting (such as discussing the drum in the hull solely as the attachement point and ignoring the pivot),

Unintentional. Sorry.
The drum pivots to kick up and has a larger contact area with the hull than a daggerboard. It is also better reinforced and has no holes below the water.
The blades pivot to steer on large diameter stainless steel pintles attached to the drums with far more carbon tow than is required to resist the loads.
The blades rake for balance pivoting against the lower edge of the case/sleeve. This also has more carbon around it than is required.
Any pivots I have missed, let me know.

and applying 'just engineer it to withstand,' to your preference but denying that same argument for alternatives that you've decided not to use won't win me over either (but that is a preference, it may be enough for others).

Engineering a daggerboard or trim tab rudder and their cases to withstand impact at 20 knots is not the problem. Nor is the added weight and cost. If the board/trim tab can withstand that impact, think what will happen to anyone not wearing a seatbelt on the boat. Something like this, but without the crumple zone.

1:15

So, Rob, I am sincerely open to being informed, please show us your rudder system

Kleen Breeze rudder drum pic attached. The latest editions are cleaner and simpler but essentially the same principle. Let me know which parts you don't understand.

and explain how it has overcome the issues involved with being placed ahead of the CLR,

What issues? There are none that I am aware of. The rudder is part of the CLR, it cannot be placed "ahead" of it.

how you maintain control over the CLR while still allowing for kicking up

When the rudder(s) kicks up, the recommendation is to dump the sheets, stop and pull the rudders back down, not keep sailing and expect to "maintain control over the CLR"

and the variable drag of steering,

Not an issue. Please explain what you mean.

how the well documented issues of a centrepivot foil design are addressed,

I have done so several times, sorry it is not clear. see attached quick sketch

and why you wouldn't choose a lower stress option, even if you can engineer for something more critical

It is not about "stress options", it is about what happens when you are sailing.

etc. Etc.

What etc, Etc have I not explained?

 

[Dejay]

Huh, that is a surprising and awesome solution!

 

[NewSalt]

Thank you for what you have provided Rob; no, full plans are not required.

My question wrt to controlling CLR with variable drag etc. is wrt to the automatic raking nature of the rudder foils. If they are free to adjust themselves, do they not rock back and forth in a sloppy sea state? I only see control lines leading in one direction, is there a bungee on the other? If so, wouldn't varying speeds vary the CLR?

Is the oversized sleeve rectangular or trapezoidal? If the former, does not that create two point loads (upper forward, and lower aft) and since the foil draft is infinitely adjustable, then the location of the point loads is infinitely adjustable resulting in the need to reinforce the entire foil on both edges?
If the latter, then depending on the orientation of the trapezoid, then there is a point load on one side, but the other side is fully supported. Of course, since the foil is reversible, both sides would still need to be reinforced.

The rudder before the CLR has a greater effect on steering (this can be a positive or negative). The concern would be when combining this with an overbalanced rudder that tends to over correct. I do see how this is less of a concern with the raking of the rudder relative to the pivot (I could not appreciate this from previous descriptions and previous diagrams that I have seen show them being fixed in relation - as the first attached does).

Re: the crash test, I'd like to point out again that this is oversimplification from previously built boats. If I were going the route of trim tabs, I did specify that I would have a rockered hull that would gradually absorb the energy of any collision prior to impact with the rudder, and I specified a spade (therefore no daggerboard skeg) with a shear off tip to address these things specifically. Others have suggested quadrantboards to address this, although I am not aware of anybody building them and that doesn't address the damage that kicking up would do to the actual rudder.

Dejay, I'm not sure how much of proa community history you are aware of. I have followed for a very long time, but not contributed due to the animosity and due to not being in the position to actually need discussion as I was not yet looking to build. Rob has a direct, at times argumentative approach. I have the same, and view debates as a positive thing so long as everyone respects each other.

I only bring this up because Rob has been accused in the past of having dummy accounts used to support his position. In this thread, you've claimed multiple times to be inexperienced on the topic, but then acted acted as a moderator with some bias, (by censoring me for being direct about specifics that are universal and not dependent of Rob's solutions, but did not challenge when Rob speaks similarly in generalities), and have chimed in more than once about the "elegance" of Rob's solutions whilst also chiding me (I believe wrongly) because you don't think I should make statements based on "aesthetic preference."

I feel that this approach might do more harm to Rob's position than the good you intend.

 

[Dejay]

Sorry NewSalt, I didn't mean to be adversarial towards you. I probably should keep my mouth shut more often. But I thought I could help steer the thread in a bit more productive direction. My apologies.

Yes I am a novice and a fan of Rob's work because the HPs seem to innovate on a lot of things and he shares a lot of info openly. I suggest we let old shitstorms and suspicions rest.

Funny enough I did to edit myself about those wibbly-wobbly rudder leeboards, wondering how those were invented... "Oh no the rudder wobbles in the casing! Wait that gives me an idea" haha

 

[NewSalt]

Dejay,
No worries, and there is no reason to apologize to me. Don't feel that you need to keep quiet either.
It's clear that you're a fan of Rob's, and that's a good thing. I was just being mindful of the optics.
The basis of good discourse is applying the same 'rules' to yourself as to your opponent in thought. Just as I feel it fair to call out what I feel are logic errors (and have gotten more satisfying answers as a result), I feel it fair for you to call me out on mine (and I reconsidered and ammended my approach as a result). We'll all come with different styles and approaches, so long as whatever standard we are applying to others we also apply to ourselves and those who agree with us, we can have a positive and constructive debate.

We likely won't agree on everything at the end, but I've evolved my thoughts significantly during this process.

 

[Robert Biegler]

Is the oversized sleeve rectangular or trapezoidal? If the former, does not that create two point loads (upper forward, and lower aft) and since the foil draft is infinitely adjustable, then the location of the point loads is infinitely adjustable resulting in the need to reinforce the entire foil on both edges?
If the latter, then depending on the orientation of the trapezoid, then there is a point load on one side, but the other side is fully supported. Of course, since the foil is reversible, both sides would still need to be reinforced.

Another option is an X-shape. Then you always have the upper half on the forward side and the lower half on the aft side providing contact area. You would still have a point load when the rudder reverses rake, but that might be dealt with by making that part out of rubber, if point load is a concern.

 

[NewSalt]

That would do it

 

[rob denney]

Thank you for what you have provided Rob; no, full plans are not required.

My question wrt to controlling CLR with variable drag etc. is wrt to the automatic raking nature of the rudder foils. If they are free to adjust themselves, do they not rock back and forth in a sloppy sea state? I only see control lines leading in one direction, is there a bungee on the other? If so, wouldn't varying speeds vary the CLR?

The drawing is to show how it works, not to build from. There is a lot more detail in the plans. The blades stay in place once the boat is moving due to side force and drag.

Is the oversized sleeve rectangular or trapezoidal? If the former, does not that create two point loads (upper forward, and lower aft) and since the foil draft is infinitely adjustable, then the location of the point loads is infinitely adjustable resulting in the need to reinforce the entire foil on both edges?
If the latter, then depending on the orientation of the trapezoid, then there is a point load on one side, but the other side is fully supported. Of course, since the foil is reversible, both sides would still need to be reinforced.

Trapezoidal, narrow at the bottom. The leading and trailling edges take the fore and aft loads, the sheer web/spar down the blade transmit the side loads. Everything is built accordingly.

The rudder before the CLR has a greater effect on steering (this can be a positive or negative). The concern would be when combining this with an overbalanced rudder that tends to over correct. I do see how this is less of a concern with the raking of the rudder relative to the pivot (I could not appreciate this from previous descriptions and previous diagrams that I have seen show them being fixed in relation - as the first attached does).

Re: the crash test, I'd like to point out again that this is oversimplification from previously built boats. If I were going the route of trim tabs, I did specify that I would have a rockered hull that would gradually absorb the energy of any collision prior to impact with the rudder, and I specified a spade (therefore no daggerboard skeg) with a shear off tip to address these things specifically. Others have suggested quadrantboards to address this, although I am not aware of anybody building them and that doesn't address the damage that kicking up would do to the actual rudder.

It is not an oversimplification. You are reading what you want to see, not what I wrote.
No amount of rocker in the hull will absorb enough impact not to damage in hull rudders or daggerboards in a collision with a floating object. A shear off tip is insurance against going aground, but no help with a floating log. Quadrant boards that kick up in both directions would be a tricky build. At cruising proa speeds and weights, an impact is likely to look like the video above.

Dejay, I'm not sure how much of proa community history you are aware of. I have followed for a very long time, but not contributed due to the animosity and due to not being in the position to actually need discussion as I was not yet looking to build. Rob has a direct, at times argumentative approach. I have the same, and view debates as a positive thing so long as everyone respects each other.
I only bring this up because Rob has been accused in the past of having dummy accounts used to support his position. In this thread, you've claimed multiple times to be inexperienced on the topic, but then acted acted as a moderator with some bias, (by censoring me for being direct about specifics that are universal and not dependent of Rob's solutions, but did not challenge when Rob speaks similarly in generalities), and have chimed in more than once about the "elegance" of Rob's solutions whilst also chiding me (I believe wrongly) because you don't think I should make statements based on "aesthetic preference."

History is better than philosophy but still unrelated. Could we please stick to boat discussions? I would add the following to your remarks. Threads on Harryproas usually have 3 things:
1) The haters never concede that there are problems with Pacific proas or that there are benefits to the Harryproa solution.
2) When these problems and solutions are pointed out, instead of discussion, they resort to personal attacks.
3) Anybody who stands up for Harryproas is accused of being a dummy account and/or have their knowledge and opinions disparaged.

I feel that this approach might do more harm to Rob's position than the good you intend.

********. I think it is great. Please carry on Dejay.

 

[NewSalt]

I'd agree, haters are not going to change their minds; neither are 'true believers.'
It is only the reasonable middle ground who are going to grow from debates like these.
Interesting thing is that the perception of who is the hater, and who is the believer flips depending on which side of the discussion one is on when it comes to the proa world (tragically).

I have changed my opinions significantly due to specifics we've discussed that haven't been brought up in other threads, so I know that I am in neither camp.

In case it wasn't clear, I have no problem with your directness, despite the grief it has attracted to you. I have a similar approach to discussions. I WAS talking boats when Dejay decided that my describing fundamentals that applied to all foils not just Harryproas' was not showing you enough reverence. I don't kiss rings; neither do you and that is a good thing because if you did, we would not have Harry-styled proas in the numbers that we do.

I hope that you misunderstood my objection - which is that Dejay censors others for doing exactly what they themselves are doing. This is not the basis for a respectful discussion or debate. If you understood that and are encouraging it, I am frankly disappointed and might have been wrong to dismiss the complaints of your detractors. It's not okay to savage opponents with directness but then expect them to approach Harryproa advocates as supplicants.

Wrt to boats: have you thought of using x shaped (I interpreted this as hourglassed) rudder sleeves to maximize support as was suggested by R. Biegler? If so, what are the challenges that have prevented them from being implemented this way?

 

[NewSalt]

It is not an oversimplification. You are reading what you want to see, not what I wrote.
No amount of rocker in the hull will absorb enough impact not to damage in hull rudders or daggerboards in a collision with a floating object. A shear off tip is insurance against going aground, but no help with a floating log. Quadrant boards that kick up in both directions would be a tricky build. At cruising proa speeds and weights, an impact is likely to look like the video above.

Crash tests for vehicles represent what used to be considered worst case: hitting an immovable object, which is the equivalent of hitting an equally massed object moving at exactly the same speed. This is because you go from full speed to dead stop immediately (if you're smart car head on collisions a Mack truck, then you accelerate backwards though). It is the rate of deceleration that matters. Of course, cars don't travel as slow as proas, but crash tests are often performed in the range of the fastest proa speeds. This one being conducted at 21.7 knots is a bit of a stretch.

Let's explore whether this would happen in the case described...

Hitting a log or container would not equal impacting a wall. They are solid objects, and certainly of concern, but, when stuck, they absorb energy themselves by rolling and accelerating in the direction that you are moving. If the concern with floating object being worse due to lifting after the max depression of the hull, that effect also would increase the hull's transfer of energy as described later.

So worst case scenario is likely hitting a large boulder sitting just under the water. On a dead flat proa bottom with dagger boards, yes the boards accept the full brunt. On a rockered hull with rudders no deeper than the hull as described, the hull would impact first. The shape of the hull would result in deceleration directly through friction and upward pitching (and hopefully not in fracturing of fibreglass).

If the full amount of the energy is not stopped at that point, then yes, the rudder boards would then impact, but now from a slower velocity. [I never claimed that the hull would absorb enough energy to prevent damage to the rudders, in fact I was clearly stating the opposite by arranging for shearing tips - so I guess if you're correct, we're both guilty of reading into the posts]. Hitting the hull first IS the equivalent of a crumple zone.

The maximum further energy that can be lost to the obstruction is equal to the strength of the rudder (because now the hull has shallower draft) and shearing absorbs some of that energy in a fashion that does not contribute to rapid deceleration, and potentially also result in clearing the obstruction so as to not transfer any more energy.

Overall, the rock robbing the proa of energy happens over a much more spread out period of time, even if only a few seconds, which results in less peak deceleration.

This is why I say that the crash test is an oversimplification. That is not to say that the deceleration is of no concern, only that the graphical portrayal above is not representative; it is hyperbole.[/QUOTE]

 

[Dejay]

NewSalt, I already apologized to you and suggested we move on. Repeating old accusations, suspicions and talking points is "rubbing new salt into old wounds". It's neither productive nor respectful.

 

[rob denney]

NewSalt, I already apologized to you and suggested we move on. Repeating old accusations, suspicions and talking points is "rubbing new salt into old wounds". It's neither productive nor respectful.

Well said. And funny. By the way, the asterisks in my previous post replaced what i actually said, which was male bovine digestive waste.

New Salt,
Think of the cases we use as half X's. The problems and solutions are the same, but the loads are lower due to the rudder bearing on the bottom of the case rather than half way up it.
It doesn't really matter if the video is representative or only partly so. Any benefits (the only one I can see is aesthetics, offset by the internal space they take up) of in hull rudders are so strongly outweighed by the safety benefits of kick up rudders that it is no contest as far as I am concerned, both as a user and a responsible designer.

 

[NewSalt]

NewSalt, I already apologized to you and suggested we move on. Repeating old accusations, suspicions and talking points is "rubbing new salt into old wounds". It's neither productive nor respectful.

You're directing this at the wrong person. Rob brought this back up; I only responded to his position. (You can scroll up on this same page to confirm). But this is an example of what I objected to, so I will restate that I don't accept that only one voice be allowed to speak (even if it was mine) and others be censured for speaking in kind/in turn.

I have not repeated old 'accusation, suspicions, talking points' except in one instance to warn that you might lose the reasonable middle/undecided that we later talked about if you didn't allow for even ground in this debate, thus 'I was thinking of the optics;' I know it was that that turned me off in the past, not wtww arguments themselves.

It doesn't really matter if the video is representative or only partly so. Any benefits (the only one I can see is aesthetics, offset by the internal space they take up) of in hull rudders are so strongly outweighed by the safety benefits of kick up rudders that it is no contest as far as I am concerned, both as a user and a responsible designer.

I'd agree. And from the start of this discussion I indicated that dagger rudders were a concern to me and I was ready for an alternative. For me personally, your solution as presented here finally represents one that satisfies my requirements and I moved off the dagger boards a while back, which also allowed me to move off of the rocker.

But, that doesn't mean that I should let illegitimate argument/straw man fallacy stand.

 

[rob denney]

I'd agree. And from the start of this discussion I indicated that dagger rudders were a concern to me and I was ready for an alternative. For me personally, your solution as presented here finally represents one that satisfies my requirements and I moved off the dagger boards a while back, which also allowed me to move off of the rocker.

Marvellous.