the Revo Rudder

Discussion in 'General Paddling Discussions' started by mick_allen, Aug 24, 2016.

  1. mick_allen

    mick_allen Paddler & Moderator

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    Intro:

    I love rudders and skegs: the variable geometry they can provide: but I have always wondered if the ultimate of both those worlds was the unobtrusive ‘slotrudder’. So one of the early design exercises I spent much time on was exploring various approaches to these issues. As a designer, these explorations to me, were as dramatic, exciting, exasperating, and fascinating as any of the adventures that are written about in the trips forum. But rudders, skegs and suchlike do come with baggage: all the linkages, lines, fittings, retracting blades, housings, and turning assemblies that can tangle, rust, or jam. But if you like rudders and this kind of stuff, you accept it all and move on to what they can do . . .

    So the revo rudder is one of the slot-rudder approaches that I spent some extended time on and documented over a decade ago. But for a while recently, I have realized that I have more ideas on the go than will ever come to fruition and that maybe it’s time to let a few go. I’ve coveted this one for a good long time and I’ve had my secret pleasure - and now I think it needs to be brought out into the light to see if it will breathe.

    I expect this rudder and its several forms could be patented - but it would require a long expensive process that I would rather spend time on in other directions. A patent is no good without anticipating that it be turned into a business or licence reality or defended – and that’s more time that I don’t have free time for. But I would hope that anyone who successfully makes one of these will attribute it. I’m not in this for the cash, but the glory, the fame, and the fun.

    Performance Specification – Outline

    This rudder is a natural part of the ‘Let’s talk rudders’ thread in this same forum.
    In post http://www.westcoastpaddler.com/community/viewtopic.php?p=31420#p31420 , I listed some general performance specifications for slot rudders to which I’ll add specific checks and/or comments concerning the Allen Revo Rudder:

    - completely internal rudder assembly with only a slot in the bottom of the hull.
    Yes partly: more particularly in the understern part of the hull
    - absolutely no extra required hull or keel protruberances so hull can be as rockered or smooth or shaped as desired for any other reasons than the rudder.
    Yes to a degree, odd stern shapes might be difficult
    - absolutely no exposed lines or cables or rods or attachment points either below or on top of the yak to catch or cut or interfere or tangle.
    Yes to a degree: narrow sterns conflict with tiller width so small protective protruberunces may be required.
    - not necessary, but say can deploy to as much as 45deg ea side.
    No that’s way too much, a max 30deg would be the most widely applicable, but at first I’ll limit the throws to 20 deg – increasing this would be part of product development and more on the reasoning behind this choice later.
    - slim slot flush to bottom of hull, only as wide as the rudder blade (clearance added only if desired for anticipated sand/gravel jamming conditions – I would choose minimal clearance and possibly mount rudder 1- 2” off keelside- be interesting to test) .
    Maybe the slot opening would require some rounding as in all untested slot rudders. Offsetting is not possible with this approach.
    - an automatic self-aligning mechanism for the rudder blade to automatically and instantly insert into the slim hull slot. Will auto align and deflect if hit by moderate sea obstructions or by the user quickly panic ramming the rudder up with no thought to how the rudder is deployed when initiating. This is a complex mechanism and I would accept that big impacts or side impacts will cause the same damage as if a skeg.
    This one doesn’t quite work like that but it has elements of the above: some hunt and peck, some auto-aligning
    -as this alignment mechanism is so fundamental – say some redundancy to ensure realignment on retract.
    Not really available for this one except for hunt-and-peck being one type of minimal redundancy that would work here. But the auto-aligning is as robust as the rudder itself.
    - the internal rudder steering mechanism should be in constant engagement for minimized sideplay, minimized jamming, and minimized failure.
    Yes
    - an internal mechanism not much bulkier or heavier than a typical skegbox with an additional steering yoke and lines or cables or rods.
    It will have to be a little heavier as there are a few more pieces.
    - design refinements to minimize weed contamination of the rudder axis in the deployed mode. (but no protruberance on retract)
    one rendition can do this
    - options of typical fully articulated rudders or the more stronger true skeg rudders (where the trailing edge of the skeg articulates – like the rudder of an airplane). Both operate and retract similarly. (these are not necessarily interchangeable options)
    -Yes
    - options for high or low aspect depending on the duty expected. (these are not necessarily interchangeable options)
    Yes, but also might be interchangeable
    - apply to ‘most ‘ hulls by just cutting slot and gluing in the box.
    Too wide an application to say, but maybe yes with some minor complexity
    - allow typical skeg deploy knob with any type of rudder pedals or foot deploy, retract and steering - self adjust.
    Deploying will be atypical but steering typical
    -the potential for making very small, light (and likely fragile unless exotics mat’ls) for racing application.
    Yes

    So: No detail or product development has been done: at first one must assume good materials, effective fittings, tight tolerances, and small rudder throws.

    Specific Specification – Outline:

    This rudder is not universal, it will require a different form for each kayak form. One form does not fit all.

    -firstly, the rudder is situated inside the end of the kayak.
    -secondly, it is similar to a normal rudder in that upon impact it can rotate backward out of the way.
    -thirdly, it is related to a slot-rudder in that its mechanical arrangement is such that it can be rotated forward and will auto-align into a forward hull-slot.
    -fourthly, if desired, this forward hull slot can also penetrate the deck, so that the forward rudder rotation can then continue around to the rear and stop anywhere along a 360 degree continuous rotation.
    - fifthly, this rotation can be either be forwards and/or backwards using the deployed rudder as the starting point. If the rotation is forwards, it auto aligns into the slot. If the rotation is backwards, hunt and peck is required to enter the deck slot.

    Note in the above descriptions that the slot is not required to be both in the deck and through the hull, it can be either. As implied above, if the slot is only in the deck, hunt and peck is required. If in the hull only, auto-align works, but of course no 360 deg rotation is possible.

    -sixth with a simple [conceptually at this stage] change of blade assembly, it can change from a full blade rudder to a skeg-hung rudder. [not to be confused with the possibly misnomered ‘skeg-rudder’] If the slots are there, the skeg-hung rudder can auto-align and retract in either direction as in the other cases. The skeg could also only be partial so that partial blade balancing could be provided – that possibly also auto-aligns in either retraction direction.

    Use Specification – Outline

    The revo rudder is mainly aimed at the pointed and gently upswept sterns of kayaks – although it can be designed for more vertically stemmed ends. Other than the blade, all other parts of the rudder are intended to be hidden within the hull form although there will be a conflict between a narrow hull and a wide tiller at the rudder location. The rudder is intended to be simplicity at it’s almost extreme within the complexity restraints of rudders. The simplicity is extended as: all adjustments, mounting, or knockdown is external to the hull.

    The intention is that the rudder is robust, tight, and strong – for this reason, the specification is that the mounting location in a slanted stern is required to be at least 3” deep. To a large degree these aspects depend on the unknowable structure of the particular hull at this location.

    So: robust, simple, applies to many hulls, rotates each direction – implies hard use in either direction. Those are big shoes to fill, but it’s fun to attempt.

    Synopsis:

    This rudder is not like any underhull slot rudder as there is no rear slot for it to auto-retract into, but as the blade can freely rotate rearwards anyway it does not matter - and in most orientations it has all of the slotrudder hallmarks. Its negatives are:
    -the conflict between rigidity and the 3" stern size mentioned: bigger size will be better if configuration allows.
    -the rudder is at the extreme rear of the kayak where there is no blade end plate effect as as would be farther forward in a typical slotrudder or underhull rudder. ie there will be pressure losses at the surface.
    -the rudder is at the extreme rear of the kayak where ocean wave action will continuously vary the depth and therefore effectiveness of the rudder.
    -it's new and different and has not been detail developed.

    [Next will be a few diagrams for parts naming, and an explanation of 2 simple but fundamental concepts that this rudder combines.]
    [Looking over this, I still have to edit some of the previous wording]
     
  2. JohnAbercrombie

    JohnAbercrombie Paddler

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    Interesting!
    Have you built a mock-up or prototype?
    :big_thumb
    :popcorn:
     
  3. mick_allen

    mick_allen Paddler & Moderator

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    Because of an unrelated matter that just came up in the last few minutes, this topic will be put on hold for a week or two.
     
  4. Mac50L

    Mac50L Paddler

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    It sounds a lot like the drop-down extension added to some Mirage or other manufacturer's rudders.

    http://www.users.on.net/~pcarter/rudders3.html
     
  5. Doug_Lloyd

    Doug_Lloyd Paddler

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    Waiting with baited breath...

    BTW, I don't do scramble rescues and the like, just the reenter and roll. Rudders on the stern don't bother me. They do for BCU paddlers and similar dogma driven derivatives. Nevertheless, a workable Revo Rudder cries out for realization...

    Doug
     
  6. mick_allen

    mick_allen Paddler & Moderator

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    So I’m taking this potential website data loss opportunity in the next few weeks to give out a big mea culpa to everyone following that I haven’t put anything into this thread for a year now.

    For me, rudder ideas have been an escape subject for years and last year at this time I was in a fairly mellow place where I thought it would be enjoyable to begin to put together a bunch of posts that would explain and illustrate a group of thoughts that I have had on a specific family of slot type rudders. In fact, I was mulling over possible routes that I would take to go over the majority of what I think I know about other families as well – they just seemed to naturally fall in step with the overall picture.

    But then my personal life was hit by the double whammy where I got a phone call and all of sudden became the primary care giver for two people – and while this state has been a roller coaster over the last year, the basic situation is still similar. The point of this explanation is that some of the fun and joy has been tempered to the point that this thread has not been something that I had or have been looking forward to doing more on. Plus I have a whole bunch of kayak-related and other avenues on my plate in addition anyway.

    There have been no protoypes built as the majority of the types have been drawn to schematic and sketch level resolution - although one group has been draw to full scale working drawings. But of course, with any of them there’d be a whole design development and engineering process where all kinds of issues would develop that would have to be resolved in some manner. But this has been a natural situation for my whole family [both parents were design professionals] and professional life - which started in the theatre with professional lighting and stage design and then switched to a slightly more regular design life in architecture. I’m aware of the process and although known materials and procedures are used in any of them, the approach and concept is of a one-off and often has to be rapidly performed. So no naivety here, but no surety either: any of them would require a process and some would be much better in aspects than others.

    So that’s the situation now. And I’m sorry for the delay but I’ll pick this up sometime in the near future - because I think it could be fun.

    But I’ll leave this thought for anyone who is interested:

    think of a flag pole in a varying breeze and think of the flag . . . what does the flag follow?
     
  7. Yeti

    Yeti Paddler

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    for Mick: "A unique feature of this kayak is a rudder that folds down into the deck"
    The new SKUK Quantum
     
  8. mick_allen

    mick_allen Paddler & Moderator

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    I can’t recall seeing a complete deck retraction, but the VCP trim rudder mentioned in the ‘talk rudders’ thread was halfway there.
    VCP-C-Trim.jpg
    and here's some SKUK quantum rudders images:
    cutout:
    SKUK-Quantum-1a.jpg


    housing:
    SKUK-Quantum-1b.jpg

    All rudders have compromises - mine probably more than most - but it any case, here’s a few issues with the quantum rudder:
    • - firstly, it has none of the conceptual elegance that an auto-aligning blade has on retract – this is purely another hunt-and-peck rudder except it now originates far away from the water from the deck rather than directly from the hull.
    • - It essentially is a pin-head rudder in that all the workings could be exposed to damage from external impact while retracted. The housing is however, streamlined to the hull shape so these possibilities are extremely minimized. I like how it would be out of the way for tows and scrambles, etc.
    • - A natural blade profile is compromised by the rudder post location on retraction, so the rudder shape [side profile] will have to be very thin and therefore possibly long to be effective. [long thin [high aspect] blades are flexible, weak, and most importantly stall easily].
    • - With the above compromise as well as having hidden lines, rudder torque will be very low – or conversely the rudder will be very twitchy and hard to set as it would be very responsive to small line movements.
    • - And because of the line concealment and possible line interference near the very ends of the kayak, rudder deployment angles will have to be kept low
    Issues.jpg
    But like stated, all rudders and skegs have compromises . . . but this one misses it on the first step of reasoning elegance.

    Mind you, for very small deployment angles, there juuuuust might be a way to make it auto-align a little bit - let's see if they do it.
     
    Last edited: Jul 24, 2017
  9. Mac50L

    Mac50L Paddler

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    Basically it looks like you are making the hull higher / deeper so that the blade can be hidden when retracted. But you also have the difficulty of retracting easily when using the 270 degree method.

    Why not the 90 degree retraction, similar to KayakSports' Navigator and SeaLect, which are actually the Daggerboard rudder which went into production a decade before those companies started their production. Using this design the blade can retract straight into the slot in the hull and is totally hidden, goes in straight and appears to be what you are trying to achieve but with a difficult solution.

    See -
    http://www.kask.org.nz/rudders/
     
  10. mick_allen

    mick_allen Paddler & Moderator

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    “looks like you . . .”
    - the sketch is not of mine but of the SKUK Quantum issues that I see.

    **

    The problem with the one you mention is that the lines and tiller are still always exposed to damage and tanglement – the main issues that a slotrudder attempts to solve. And to a lesser degree, but still an issue, self alignment would have to be a little bit of the hunt and peck. [The line will pull it in, but there’d still be colliding functions to some kind of a degree.

    In any case, here’s a possible sketch. The sliding housing would have to be more substantial than shown [unfortunately] for blade stability. And the T tiller/hinge would be expensive to make to keep the low profile.

    HiddenT-Head.jpg

    And as it’s transom hung, one has to have a deep [for a slot AND a hinge] vertical stern close to the waterline which negates a majority of elegant kayak shapes. That’s probably the main killer as it has to use double the hull depth, right at the very back, than any of the others do . . . although the quantum is no better for depth - but could be under cut [ie sloped] a tiny bit as the rudder post is inset about 2 inches.
     
  11. mick_allen

    mick_allen Paddler & Moderator

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    So there's nothing intrinsically wrong with that rudder, it just has a specific set of constraints - and all rudders have those. If one was to explore it a little further, I could see playing around with shaping the blade, maybe minimizing the kayak housing . . .
    HiddenT-Head2.jpg

    and adding slam stops combined tiller damage deflectors.
    And who knows, it might surf one heck of a lot better! The lines might be a little low to the water, but can't have everything . . . with work, could be a keeper for the situation.

    But one issue is the depth . . . . because of the rudder post . . . so what if there was NO rudder post?
     
  12. AM

    AM Paddler

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    I don't know about the "majority of elegant kayak shapes". The Delphin, for example, which broke the mold for ocean playboats has a vertical stern. And the designer of the Chatham 16 has said that he only added the pointy ends for marketing purposes. You could chop the stern off a C16 to fit your rudder. As long as you aren't planning on surfing backwards...
     
  13. mick_allen

    mick_allen Paddler & Moderator

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    Yes, of course you’re right: there’s no reason for any layout to be more elegant than any other – the rudder drawn just has those certain limitations in that it doesn’t fit the conceptual profile of pointed end kayaks . . . and in complete agreement with your point, what normal rudder does? So this is no different: you could chop the stern off or add a drooping angle at the back to take the hinge as the others do or just put it on a more appropriately shaped one. . . . or maybe there’s some other possible approaches that play with the pointy end geometry of those type of kayaks, that I’ll touch in the next post or maybe the one after.

    However for this one and continuing from the last, it is fun to contemplate alternate scenarios to see what comes from other approaches.

    With the NZ/Chinese type mentioned in the previous post I wondered if there was a way to actually eliminate the rudder post and thereby get a slightly shallower side profile. All that would be left would be the tiller and sliding housing, but if the tiller was restrained by helicopter swash-plate analogs, as well as by the overdeploy restraints, it could be held in place by the slidehousing or if necessary grooved protrusion in the swash plates.
    HiddenT-Head3.jpg

    That way the complete lower part of the hull could be cut away to match those other or some other appropriate situations.

    And if a long slide was used, maybe another modification could be made. . . .
     
  14. Mac50L

    Mac50L Paddler

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    Not sure what the Chinese have to do with it.

    The part in mine that the blade is held and slides in, what is its front edge becomes horizontal when the blade i stowed. This makes a good carrying handle, saving lifting by a toggle which is forward of the stowed blade. Yes, the whole assembly is strong though not heavy as it has plenty of lightening holes (they let the lightening out....:)).

    As for height of aft deck, no higher and actually lower than most. Those fancy up-sweeping sterns are just for show and windage. They were originally there because the craft were skinned. No skin, no limitations.