Let's talk rudders

Discussion in 'General Paddling Discussions' started by RichardH, May 6, 2008.

  1. mick_allen

    mick_allen Paddler & Moderator

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    good point, though one could just do a complete thru mount and have the tiller mech exposed on top of the deck. About as much clutter as any rudder and one'd still have the retraction.

    Conjecture, but there probably is a bunch of waste space in that upper/over housing and just possibly with judicious use of a hack saw one could make it an inch or 2 lower.

    (edited to add: I might have missed something here: I wonder if difficulty sealing the retract rope aperature is why the skeg housing is kept so high? Will water infiltrate? Or if not, there might be an awkward hollow rudder shaft setup. This is all conjecture, as I'm not understanding a clean resolution with a 'rope' retract.)
     
  2. Mac50L

    Mac50L Paddler

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    I'd not noticed this thread before but mick_allen mentioned (13 March 2014) the P&H Skudder and the "patent applied for" at the bottom. Has anyone any idea when they designed or announced this? About 15 or more years ago we had Don Currie fitting such rudders to Skerries. Identical shaped blades. He wasn't all that happy with the results but at least some of his friends used them. He was also the person who designed the 90 degree retraction system that KajakSport "patented" after 2 companies had been producing that design in New Zealand for a decade. A decade later the American company said it was going to patent the same idea !!!

    Incidentally Don also came up with the auto-adjusting rudderlines too, going on 3 decades ago.

    Mention of the Prjion rudder that looks like a dagger and some saying it was a balanced rudder. It might be if it was in the water but Prjion always mount their rudders on a sticking up bit that makes sure the blade doesn't get wet when down. As the balance portion is at the top of the blade it isn't a balanced rudder when fitted to their kayaks. The wooden blade by Doug_Lloyd looks to be balanced and the balance part from about the middle and below. That's the way the rudders I produce are made.
     
  3. mick_allen

    mick_allen Paddler & Moderator

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    Looks like they announced it just prior to August 5/2013 at an outdoor show:

    It will be interesting to see if they get a patent for it as it is so similar to many of the other systems out there like you infer. Like what's to patent? They all have a fixed tiller to rudder post, some form of centralizing detent or balanced lines, a hinge axis at the bottom of the rudder post which often has a little bit of diameter and a retract (either by 2 lines or one line and spring or bungee sometimes inside the rudderpost). Like an 'artistic rendition' patent?

    My take is that 90 deg Rotating Sliding Pinheads have the further issue of introducing a loose slider adding one more dimension of slop into an already sloppy and weak (in concept) Pinhead Rudder approach. However I must admit that I have been surprised at the number of them that have been introduced. However, do you think there's any way that the blade could be designed to lay flat as it was pulled forward?
     
  4. Mac50L

    Mac50L Paddler

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    The Hobie one I presume you mean. Don also did a side mounted rudder and on retraction it lay flat on the deck. It only needed one extra piece of string, than the normal number needed, to make it work. I asked why it was mounted on the port side and not the steerboard (note the spelling) side. "Arrhhh," he said, "the water goes down the plughole in the opposite direction in the southern hemisphere." I promptly named it the "Southern Viking Rudder". A year or so later I found out there'd been research done near a decade earlier in Australia and they'd called theirs the "Viking Rudder". I have details somewhere on one of my computers.

    One other rudder type Don tried and used on his Nordkapp was a twin rudder arrangement, one blade each side and kept in the retracted position. If steerage was required the blade for the direction was dropped by the steering pedal and the blade being a bit off straight-ahead introduced the turning effect. The deeper the blade the more turning. Turn the other way and the other blade was dropped as much as necessary.
     
  5. mick_allen

    mick_allen Paddler & Moderator

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    Not that one: the Hobie rudder is actually a ‘Transom Hung Rudder’ . . . and with better materials, that just might be a rudder of choice. Conceptually, the ‘twist and stow’ could be robust because of the engaged rudder post, the low distance to the water, the low windage, and low obstruction when retracted.

    I remember that quarter rudder! It might clutter up the rear deck, however. It is still shown on Pete Carter’s website:
    http://www.users.on.net/~pcarter/rudders3.html


    Further on the subject of steerboards & portboards: here’s an early example of a port mounted steerboard, 500BC : Odysseus’ ship:


    Quarter ( ie side mounted) rudders are really interesting in that they were used way, way back. In ancient Egypt they often had several quarter rudders on each side; into Medieval times, some of these rudders would get up to 40 feet long and weigh in at 5 to 10 tons: (look at the size of the people in the graphic!)

    Those behemoths could only be turned on their axis like rudders today. [edited to add: also note that they all (even the ancient ones) are balanced]


    Pinhead Rudder terminology:

    However, I call the usual 270 degree rotating rudders that we use ‘Pinhead Rudders’: because the entire structure of the rudder (the ‘Head’) is connected to the uppermost top of the rudder post (ie the ‘Pin’).. .The heads of these pins typically are on the highest and most rearward point of the stern in order to facilitate the rudder blade rotating or sliding back over to rest on top of this high rear deck surface. Unfortunately, the distance from the post top to the centre of effectiveness of the rudder blade is the longest for all rudders, meaning that greater torque (and therefore wear or play) can be applied to the pin.
    [don’t get me wrong, I’m not necessarily being critical, just pointing out issues – I find them all interesting – and there are good reasons why they’re popular]
    Examples of ‘Pinhead Rudders’:
    you can see everything happens on the top of the pin.

    ‘Pinhead Rudders’ have 2 rotating axes that introduce play. Firstly the rudder post as mentioned and secondly the rotating axis for blade retraction. For this second factor, the housing itself needs to be absolutely robust so play is minimized between it and the pin head and additionally the blade has to be held within that housing so that minimal blade sideplay takes place between the housing and the blade.

    Sliding Pinhead Rudder terminology:

    The ‘Sliding Pinhead Rudders’ that I was referring to, unfortunately have a further feature that adds to potential slacker tolerances: the sliding blade apparatus. In order for something to slide, there has to be some sort of latitude and in order for something to slide really well in our environment, there likely has to be a little more slack as well. The other unfortunate aspect with these rudders, is that often the retracting rotation axes is performed with a slightly lower quality hinging method than that same axis is with traditional pinheads, thereby introducing more chances of play – especially over time and usage. Not necessarily bad rudders, but more issues to design and engineer.

    Examples of ‘ Sliding Pinhead Rudders’:
    again, everything happens on the head of the pin

    ***

    The twin skeg ideas sounds great. Another idea is to shape the blade cross sections to a lifting airfoil section so that more lift occurs as the individual skeg is further deployed than if just a symmetrical cross section is utilized. Or maybe same thing with twist.
    I remember years ago, when designing my first surfkayaks (for my own amusement only), playing with the notion of ‘Slam Rudders’ which are one way operating side rudders (at the typical dual fixed fin locations) that both deploy at the same rate but opposite and both operate together but with only one full width pedal (ie the ‘Slam’ bar): when deployed on the level, slows the drop; release for speed; when deployed on a turn only one side is immersed so slam direction is always correct. So you have speed, slowing, and turning options. ‘Slam Rudders’, heh heh heh.
     
  6. Mac50L

    Mac50L Paddler

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    Peter Carter's pages, yes, that's the one I was referring to.

    I knew KajakSport and Sealect had done the 90 degree but not Nortik and Eddyline though that latter one looks very much like KajakSport's Navigator rudder.

    The Siren vase looks very much like a rudder on each side of the ship - enough to make any Odysseus passing the Sirens get tied to a mast. Note the siren is that bird in a vertical dive. Is that the origin of the reference to women as being "birds"?

    "slightly lower quality hinging method than that same axis is with traditional pinheads, thereby introducing more chances of play – especially over time and usage. Not necessarily bad rudders, but more issues to design and engineer."

    Something I keep going on about, good engineering. And that doesn't mean complicated either. The Navigator is flimsy and the one I did is solid, the blade holder coming down and can lock against the vertical pin, everything being mounted on a T bar, 8 mm SS rod for singles, 10 mm for doubles. As the blade holder's top is level with the top of the T when the blade is down, this puts the bottom of the blade holder just about touching the water, as low as it is possible to go unless of course you go and mount the whole asembly on a Prion Seayak which to my mind has the stupidest stern design possible.

    Mine is a bit like the Nortik but not in plastic, not 2 pieces and the blade just about hard against the vertical pin.

    https://sites.google.com/site/kayakamf/kayaks

    If you click on the pictures of the Mac50L "has been launched" and "on the Avon River" you will see the rudder up and down and on the double, down.
     
  7. kayakwriter

    kayakwriter Paddler

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    Wow. Thanks, Mick Allen et al. This is like taking an on-line tutorial on rudders at the WCP College of Kayak Knowledge.
     
  8. Mac50L

    Mac50L Paddler

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    Then there's the foot pedals and good and bad design. Try this -

    http://kask.org.nz/wp-content/uploads/R ... ls40V2.pdf

    Note that the crucial part of the design of auto-adjust rudder lines is having the line go round the hinge pin or its geometric/position-line.

    The absolutely worst design are the sliding pedals, a 3 decade old design and still fitted to some kayaks. Nothing to brace against and can get grit in the slides. Had one like that a year or so back in north Queensland, Australia and it was the guide's kayak too.
     
  9. mick_allen

    mick_allen Paddler & Moderator

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    In relooking around I notice some more photos and information on the P&H Venture Skudder:

    In Richard Wilcox's blog: http://seakayakphoto.blogspot.ca/2015/10/p-skudder-long-term-test-of-sea-kayak.html there's some additional photos and info:

    sideview:

    and the following comments:
    "Unlike the more expensive Kar-itek skeg/rudder (which I have used over many years) it does not self centre as you lift it. This means you need to centre it with your feet first."
    which is as suspected in other post mounted blade systems:
    From Richard Wilcox's comments, it seems as though it doesn't have the detent or bungee centering that Thomasson has considered with his almost identical approach. The advantage of the Thomasson approach is the large post has wider support to keep the blade from wobbling or getting post wear - as you can easily see happening in the P&H Venture at 0:59 of https://www.youtube.com/watch?v=mQSQPBddbiI. [The Thomasson disadvantage is, when deployed, that large post's geometry intrudes into the slipstream.]
    also there was an earlier surmise:
    which is borne out by that last video:


    Which all sorta brings me back to Mac50's comment a few posts back:
    because this approach is so extremely basic and has been used by so many [as one can see from all the examples in this thread - Lightspeed, Lettman, Fibreline, Thomasson, Currie, etc] that you have to wonder how it is to be patentable at all. What's to patent: tiller?, post?, blade?, retract? - maybe the shape of the 'slot'?? [if it was me, I'd patent a deployable detent - or cam the post top]

    So far, the only sophisticated system that has been available [now not, I think - [pun: it's been retracted]] is the Karitek SkegRudder. Sophisticated in that if the blade is hit from below, its mechanical design requires it to automatically centre and then retract into an actual slot in the hull of the boat. It was too big, expensive, and clumsy, but the design was the most sophisticated.

    But I'll comment for a bit about the 'skudder' and the 'skeg-rudder' naming and design approach:
    Possibly the most important advance in boat rudder design is the stem-mounted rudder blade. This was a major advance because all of a sudden the relatively fragile blade and rudder assembly was very well protected and extremely well supported by hull shape and framing. We typically hear of the importance of this central rudder placement advancement - but it wasn't the central placement that was the advance - that has/had been done for thousands of years: ancient egyptians [we're learning], the chinese, etc - it was the strong, protected location in a vessel whose waterlines necked down at the stern [ie skegged] so that the rudderblade did not have to be exposed below the hull to be effective. All of a sudden permanent mounting was possible whereas before huge, huge dismountable rudders were necessary [some shown previously in this thread] that dipped deep into the water outside the parameters of the hull.
    And now with the presence of deep shortened keels such as in many sailboats, rudders have often been separated from those keels in order to achieve the best turning moment, but with this approach there has always been concern about the now newly exposed rudder. This exposed rudder is often called a 'spade rudder', but because of that possible damage exposure, a slightly different approach is used with small strong skegs built right in front of the blade that take some of the hydrodynamic loading, but much more importantly protect the fragile blade and change the structural concept of the blade from one of a cantilever to that of being fully supported along its length - huge changes of duty.

    So same thing . . . . . why the &^%$ don't we have deployable skegs that have those fragile blades mounted behind them so they can take a little abuse? That's what a 'skeg rudder' should be. That's what a skeg mounted rudder is anywhere else but our funny little kayak world. Would operate the same, would perform essentially the same, but would be as strong as that big skeg hinge. comment over. TMI probably
     
  10. Mac50L

    Mac50L Paddler

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    I think it is the Edison approach as in the light bulb that Swan had patented before Edison. It didn't stop Edison taking out patents on it and eventually they were revoked and the lawyers made a lot of money.

    KajakSport did tell me it would be OK for me to carry on production - as if they could have stopped it, which they couldn't, and I presume they knew they legally couldn't.

    The KASK website has most of the storyline on the production history of the daggerboard rudder.
    http://www.kask.org.nz/rudders/#more-333
    Maybe a few notes about who has taken out patents and how it is unlikely they would stand up might need to be added.
     
  11. mick_allen

    mick_allen Paddler & Moderator

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    They also might need to subtract the image shown of the ‘daggerboard’ rudder. When expanding a version of those images, one can plainly see text of a Kajaksport Navigator rudder. . . .

    click on this image above to read the text on the rudder

    But it really would be helpful if KASK showed a good picture of an actual Currie rudder of the day. There’s got to be some, any picture if all those boats had them. If nothing else, send 3 good pics of your version as even that would be helpful. Do you have any better photos of your version than this lousy zoom attempt of mine?:


    Anyway, back to the Navigator:

    I note that Seadog has been given patents for engineering improvements over and above that system as they mention the Navigator rudder right up front in their application
    http://www.google.com/patents/US8210114
    So one has to again wonder about the whole point: essentially the patent can’t be for the basics, but just the technical detail of their particular approach: retracting coil springs, ‘adjustable’ depth [really?] blade tip attachment and a few others. And looking at just one of the parts blow-ups:


    the parts count is getting up to 68 and higher with some duplication! Amazing ‘design development’: refined and nice drawings but I sure wouldn’t want to be one of the end of the line suppliers having to have parts on hand.
     
  12. Mac50L

    Mac50L Paddler

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    A sort-of they stole our idea, we'll "steal" their pictures. I thought that was the irony of it all.

    A drawing of the set-up and a couple of pictures. The first picture, the blue line is the pull-down line. The pull-up is of course tied to the top of the blade. The red plastic bits are the hinge blocks. The aft slide plastic is now usually replaced by a sheave at the top and a short bit of "V" at the bottom. The bit of yellow flattened tubing acts as a compression spring to keep the pull-up line taut when in its locking block beside the cockpit.

    The "T" bar is retained with a split ring so is field serviceable, not like some (early?) Navigators which had a screw which fell out. Note the nuts are all Nyloc nuts.

    The short bits of nylon line at the ends of the blue Spectra rudder lines are there as sacrificial bits and should be changed every year or every decade, which ever springs to mind.

    The white on the keel is carborundum epoxy so the kayak can be dragged up a rocky shore, leaving grooves in the rocks.

    No fancy glossy bits, just rugged components, plus a bit of mud on the bottom of the blade.
     
  13. mick_allen

    mick_allen Paddler & Moderator

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    heh, heh, heh, heh: good one!! Still chuckling.
     
  14. Mac50L

    Mac50L Paddler

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    The Sea-Lect rudder patent, parts 52,54,56 are I suspect, a spring to hold the rudder unit down. This idea was done on the TopSport version, about 1995.

    Mick, I think you read my bit as I was doing lots of edits (drawing didn't go in first time).
     
  15. mick_allen

    mick_allen Paddler & Moderator

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    you`re right, I was in the middle of your post and now you got me twice, heh heh.

    anyway, thanks for the photos: I completely mis-categorized and misunderstood your rudder to be a `sliding pinhead`as are all the others. It looks the same, but its T-bar rotating and carriage mounting system makes one heck of a strong and stable assembly surpassing the `pinhead`approach by a mile.

    Although I`m not a slider fan, and regardless of the wear and tear, your rudder and its approach looks absolutely beautiful to me.
     
  16. Mac50L

    Mac50L Paddler

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    Odd? interesting? bit of patenting. Not actually sure what is covered and they admit to the Navigator rudder as being prior. Basically neither Sea-Lect or KaJakSport could legally stop mine or Challenge Plastics versions from continuing to be produced.

    I'd be interested to see how the Sea-Lect one would work in one of our National parks, lots of course sand just waiting to jam it.
     
  17. JohnAbercrombie

    JohnAbercrombie Paddler

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    With your rudder design, is it just the weight of the blade that keeps it in the water? Without a spring mechanism, the blade is free to 'kick up' to clear kelp, logs, etc. ?
     
  18. Mac50L

    Mac50L Paddler

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    Yes. Never found it necessary to add a hold-down line, just the weight does it.
     
  19. mick_allen

    mick_allen Paddler & Moderator

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    Anyway for others, the requirement for structural pinhead thickness for plastic or stiffness for thin metal housings:

    is what Alex has eliminated with the ‘T-bar’ structure that he uses. This makes for a much stiffer upper structure, but he also mentions a few posts back [but needs to add in the next ‘improvement’ heh, heh]:

    "the blade holder coming down and can lock against the vertical pin"

    which would add even more stability to the whole system. The tabs would have to be refined so that they do not impede rudder throw:



    Because ‘Rotating Pinheads’ only rotate the rudderblade back down, their only recourse to effect blade stability down lower is to resort to a permanent extended rotator housing possibly drag adding like this misapplication [it’s slightly unfair to show it as a pinhead as this is typically transom mounted in a much more stable manner –but to make the point]:


    It's a tough design problem if you are predisposed to a pinhead type application where the housing is desired to be above the deckline of the boat and have no permanent transom or transom-type rudder housing left hanging down - how can one engage the pin for that extra bit of stability?? Although not really a pinhead, Alex's T-bar is the only one that has done it. [Note: transom mounts almost inherently engage the pin down lower, we're talking here about all pinheads]

    I am not sure if anyone is really getting all this about 'pinheads' and structure and stability and distance to the water, but if you are, you just gotta find the following photo a little humourous:



    **

    But returning to the hunt and peck Slot Rudders like the P&H Venture Skudder patent process mentioned above, I just was just looking at the old Lettman approach:

    http://www.lettmann.de/technik/boote-technik/steueranlagen
    and the newer one:

    http://helmi-sport.eshop.t-online.de/Lettmann-Biskaya-HV-Expedition-mit-integriertem-Steuer

    and wonder again what was left to patent. That earlier cutaway has got to be almost identical.
     
  20. Mac50L

    Mac50L Paddler

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    This is something that can be done but with the strength of the T as used, something that I have never found needed to be done.

    If stress is placed on the rudder such that something will break, what part do you want to break? Rudder unit?
    Stern off the kayak?
    Having a weak link somewhere is sometimes a good idea.