6.5 to 7.5 metre performance/cruise multihulls

Discussion in 'Multihulls' started by Gary Baigent, Feb 27, 2015.

  1. Gary Baigent
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    Gary Baigent Senior Member

    I like that, Hielan, large tapered bearings.
     
  2. HASYB
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    HASYB Senior Member

    Yep….
     
  3. waynemarlow
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    waynemarlow Senior Member

    You will need to be a little careful on what tapers you use, get them not equal ( 1 degree wrong ) and they will either not seat squarely or will lock together.

    Have you considered the self aligning bearings you can get for conveyor belts and the likes, they have large Ali mouting flanges and are realtively cheap. Or perhaps the spherical bearings used in food applications with bronze inners and either Stainless or plastic outers. They can handle quite large stresses and are not that costly in reference the time it would take to make a set of tapers up.
     
  4. Marmoset
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    Marmoset Senior Member

    Just had another idea inspired by a little of everyone else's. I'm imagining a cast in star shape into top of boat with female matching form in beam section. Then just a simple spring loaded sleeve bearing that when loose lifts it off shape to turn and lock in desired position. Could even be just straight line webbing and slots for shape, doesn't have to be full or complex. Heck could even weld up a shaft on bottom of ball then press brass into beam for simple swiveling. Cheap light and over the counter as they say.


    Barry
     
  5. Gary Baigent
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    Gary Baigent Senior Member

    Yes, all god ideas and problems pointed out, thanks.
    Building a star shape or similar would also need to be very accurately done. And you're talking about castings and construction in metals.
    I'm a simple KISS Kiwi bloke. So I put it to you, team Turrent: use a childrens plastic bucket or similar for the mould and layup the first couple of layers of the bearing surface in glass/epoxy/glue filler mix (for hardness), then go to the carbon layers. Either way this can be male or female bearings - then when semi-cured, lap the two bearing surfaces together using an abrasive (like lapping in motor valves) until accurate. There you are. Very simple. Built in my back shed. Your thoughts?
     
  6. outside the box

    outside the box Previous Member

    Gary
    +1 on KISS and the valve lapping in idea.
    Just thoughts re building it, would female bearing (bucket) inverted into hull and male bearing (bucket) protrude from beam make for best scenario from strength bracing lack of hard spots point be simplest, you could have a central web down into the male from beam and incorporate female into bulkhead in hull?
    Would keep weight down to a minimum and be very simple without need for duplication of strengthening laminates and would keep the build harmonious without hard spots.
    Then the fastening could perhaps incorporate a soft connector/restraint to reduce loading points .something like the Dibley Tri
    We had looked at a very similar setup for the Ezifold Catamaran in the early days as per the attached cutout in testing we found for our needs with a bridge deck it proved complex needing a lift and turning element to it all so we moved on.
    Very much enjoying your build with this new boat, if you ever want any numbers crunched our guys would be happy to run them for you (no charge) they keep an eye on your work with interest.

    Cheers
    Craig and team Ezifold
     

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  7. Marmoset
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    Marmoset Senior Member

    Well lucky for you I'm legally simple! Lol but here's my simple version. X3 2"x6" pieces of 15mm ply rectangles. Cut them diagonally for 6 ramp wedges and align them fat end to center in star pattern. Glass them over nice maybe kev or carbon for wear. On beam side just the boxes for wedges built into beam section. Wax male and maybe even cast it on other part for perfect fit. Cheese but dead simple, and web shape would strengthen pivot point above deck. Once claimed it shouldn't see gobs of stress. Or if ya have access to welder same thing in steel or aluminum. If you can actually do 90 sweep you only need 4 or a plus sign.


    Barry
     
  8. Marmoset
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    Marmoset Senior Member

    Oh oh reading Craig's post again, lightbulb! Female receiver for sure, and why get tricky with fancy shapes! Just make the equivalent of a paddle wheel. Solid wood disk notched 4 times with fins glued in. Center drill for pass through or threaded into bulkhead as on long thread. Still brass center bearing in beam section but with an easy to match cupped disk shape with flap positions in it.

    Barry
     
  9. outside the box

    outside the box Previous Member

    Barry
    Gary I think has it nailed with his valve lapped perfect matching surface idea. With this you could run something as simple as lanolin (sheep wool grease, yup a kiwi thing) between the highly finished surfaces as lubricant, that stuff simply laughs at salt water, we have used it as a general purpose marine lubricant for years mast pivot balls etc works a treat.
    Cheers
    Craig and team Ezifold

     
  10. HASYB
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    HASYB Senior Member

    Regarding your aproach to the children's bucket.
    Why not press the first, cured, form, wrapped in plastic, into the second form, still wet and in bucket.
    Actually, you don't really need a perfect 360 degrees fit. only the position when sailing is crucial. So you might even want to ellipse the bucket just a bit for aligning.
    When there's no pressure, lock up, the light, I presume, beam wing will turn easy enough.
    Don't use grease because you only want it to turn when not being loaded.

    But being pedantically big & KISS headed the following perhaps just for fun.

    having looked again at the pictures of your subordinate small arthropod animal with six legs and generally one or two pairs of wings I would build a large tapered bearing. Lets say the width of this flying beast's main hull.
    Make a simple enough mold with the hight a bit more than the hight of your beam.
    Push the layers of thin ply for the first tub in the mold, plastic, then layers for the second tub, plastic. Next take the tube of a lorry and inflate till satisfying pressure. aline with stick in the middle and rope. Again, only the position when sailing is crucial and the beam wing is light.
    I would instal the constructed bearing with the largest diameter up so it would be naturally pressed and locked when under load.
    Rest my case with proverbial Bobs being uncle's.

    Cheers,
     
  11. HASYB
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    HASYB Senior Member

    Forgot to ask if you happened to know where those beautiful ring frame construction idea's originate from or did you think them out yourself?
     
  12. Gary Baigent
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    Gary Baigent Senior Member

    You creative outside-the-box thinkers are overloadng me - will give serious contemplation. Thanks.
    Didn't realize it, Hielan, but actually don't know if I've seen double ring frame as one unit before - but someone must have done it.
    The bearing only has to work over 90 degrees - but for ease of fairing/polishing, might as well do the complete 360.
    The plastic wrapping thing; I've done this a number of times before for various boat parts but still end up fairing - because of slight wrinkles.
     
  13. redreuben
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    redreuben redreuben

    Everyone else is having a go so I may as well have a go. Sorry can't draw so will attempt to describe.
    I'm thinking two matching circles, from the side the join is like a long waveform (think corrugated iron but longer) with one at 0 and one at 90 so to swivel you rotate so the top (crossbeam) lifts out of one trough and rotates 90 to next trough. Clamped down that should be firm.
     
  14. Gary Baigent
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    Gary Baigent Senior Member

    Yes, Red, that is the same principle design of a number of suggestions here ... but, I don't want to have to lift the beam to move it, then drop it into place. As I see it, locking the beam further out with bolts and cleats on the flared hull will do the locking job fine, the central bearing is really just a swivelling point. Sure, it must not slop around, nor jump out, has to be a neat fit - but that can be built, even by an average non-perfectionist back shed-der.
    The bearing diameter has to be large, yes, but not as wide as the waterline beam of the hull, no?
     

  15. HASYB
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    HASYB Senior Member

    OK, I thought you might have come across the method when researching one or two light brigade's or perhaps even airplane constructions . Would be nice to see it in other application just to understand it a little more.
    Yeah, although often annoying sanding is, I try to think, one of the meditating, seamingly eternal returning pursuits of boatbuilding.
    For the rest I was only trying to emphasize that for me a 100% accuracy approach wasn't needed to make it work, just trying to trace back the real essentials of the construction.

    And on the very chance of being a real bore and pain in the arse, but again, for the last time I promise, because still don't know if you understood me correctly.
    Why not make the bearing at least as wide as and on the level of the deck from the main hull and also use it to strengthen/be part of the construction of the main hull and the swiveling beam?


    Maybe you think it's ludicrous but at least now it's clear, no?
    Hight of tapered bearing can be hight of beam.
    Before answering you might want take an intensive bath contemplation think tank moment or two.
     

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    Last edited: Apr 27, 2015
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