CNC Plans not Included

Discussion in 'Multihulls' started by jorgepease, Sep 19, 2016.

  1. UpOnStands
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    UpOnStands Senior Member

    Attached Files:

    Last edited: Jun 23, 2017
  2. jorgepease
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    jorgepease Senior Member

    In your system, if the rudder is turned anyway but straight, something is going to snap. Also the pivot needs to be forward or the rotation of travel is going to drive the rudder down instead of back and up.

    In mine that won't happen and it's much stronger, I don't understand your comments at all. Plus with a sacrificial nylon bushing you would have extra clearance for easy release at any angle.

    Additional benefit is the drive wheel reduces the load on the entire system. For now I have it running on top of my deck as I have to make that deck thicker anyway. In which case I would leave access panels and a way to extract the shaft. Alternatively I could just put it under the deck and cover it with a cowling of sorts.

    RNDR65.jpg RNDR66.jpg RNDR67.jpg
     
  3. UpOnStands
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    UpOnStands Senior Member

    This wheel is far more stable but, binding. Turn your rudder 40 degrees and the drive wheel to match. Then look at the forces on the sides of the slot - they seem to be extremely small as regards turning the rudder back to center. But move your model and see what you come up with.
    Yeah, cassette pivot on mine should be fwd of the rudder stock. But what I wanted to show was an alternative to the system shown in daycharter thread where the tiller is simply pivoted on a bolt that passes through the rudder stock. Very simple, but wear and tear would make the steering very sloppy.
    Have to look at how to accommodate kickup with appreciable rudder angle but for 99% of the time the kickup would used for beaching/drying out. Rudders can be centered.
     
    Last edited: Jun 24, 2017
  4. groper
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    groper Senior Member

    Your mad to consider anything but hydraulic. Its a 60ft, 12 tonne crusing boat. Why feel the need for "direct feel" - the boat spends 99.9% of the time on autopilot!
     
  5. UpOnStands
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    UpOnStands Senior Member

    Putting the hydraulic actuators in the cassette so they pivot with the rudder stock and use flexible hydraulic lines to allow kickup?
    But if mechanical drive was needed, any good designs?
     
  6. groper
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    groper Senior Member

    Yes- like i showed many pages back... its the way its been done many times without complaints by the owners... so simple and it "feels" just fine.
     
  7. Manfred.pech
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    Manfred.pech Senior Member

    Hi Jorge, I am a bit confused about this. They add tubercles to a clear wing and have a "reduction in induced drag" and an " 17.6% increase in lift to drag ratio" at an 10° angle of attack. I`ve read a lot of publications about the humpback flukes since 2003 but most of the "tests" reported of an increase of drag at 10 deg. A better result was referred to about 20°.
    For instance: A dissertation at technical University Aachen/Germany of B. Kerschgens. Result (CFD), the foil with tubercles had a nearly 30% worse lift to drag ratio than the profile without bumps which delivered more lift and less drag.
    A remarkable better ratio is reported for 20°: 24% increase in lift to drag ratio. I think the hype about the humpback whales fluke needs more scientific research and less enthusiasm.



    [​IMG][​IMG]
     
    Last edited: Jun 25, 2017
  8. jorgepease
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    jorgepease Senior Member

    That's interesting. Maybe that is why they have only licensed it for use in fans and wind vanes, they can optimize and fix the angle of attack.
     
  9. jorgepease
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    jorgepease Senior Member

    Wish I knew how to do keyframe animation on Rhino. I will try to do it so you can see.
     
  10. jorgepease
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    jorgepease Senior Member

    Hydraulic would be the easiest way to do it, no doubt and I personally am fine with hydraulic but there seems to be a lot of people that frown on it. There are a couple of threads out there discussing it. I think I have to see what the price difference is to make up my mind.

    Apparently though, there are some big production boats using this system.
     
  11. groper
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    groper Senior Member

    Are the people that frown on it using a better system on 60ft catamarans? This isnt a 16ft hobie cat, nor a 40ft performance cruiser.... its a big boat and once the plotter has been set and the autopilot engaged, thats likely the last time youll think about it whilst you pour yourself a martini and go rub some sunscreen on your ladies skin as you enjoy the scenery go by :)
     
  12. groper
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    groper Senior Member

    Oh and when you need to dodge traffic or similar- you reach for your wireless remote in your pocket and turn the boat by pushing a button. So it doesn't interupt the attention your lady deserves up on the front trampoline by needing to go back to the helm :)

    I made one of these for my last boat for about $100- the remote looks like a garage door opener and it hooks into the hydraulic autopilot pump motor...
     
  13. jorgepease
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    jorgepease Senior Member

    I think most people had 40-45 foot cruisers in the one big thread on the cruiser forums. Though, I am hoping my boat comes in under 10 tons and is exciting to sail, the truth is I don't really care about feedback steering. I can get feedback in many other ways. Surely hydraulic is cheaper too? I should inquire from Jefa.

    UOS is right about the binding when rudder is all the way over and kicks out. I think a push pull system is the better way to do it so the slot stays parallel to the exit path.
     
  14. jorgepease
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    jorgepease Senior Member

    Okay here is the revised steering ... if it's even worth it ... It really would be on auto pilot 99% of the time and when I am motoring in the shallows or marina, the rudders would be up or locked straight.

    The corrected drawing keeps the slot parallel and allows enough extra space to accommodate the pivot ark at any angle. The nylon bushing makes it an easy slip without binding. I think the push and pull can be gotten direct from the bevel box using their drag arms.

    Some considerations
    - Price??

    - Nobody is going to complain about not having hydraulic but can't say the same the other way around.

    -Reduced maintenance. No hydraulic hose, seals etc... to worry about. The transmission components will long outlive the boat.

    -If I can keep the boat light, (say under 9 tons) then even though it's not a racer, it should still be exciting to sail ... which, for enthusiasts, I can understand that direct drive would be appealing. I personally don't like the hydraulics on my power boat.

    So far, I get the feeling this boat is going to be around 9 tons, even with a ton of batteries. Watertight compartments are next and then I will get the area and estimate the weight better.

    I am going to ask the engineer about designing special space frames constructed like a box truss. The strength would be immense and it would be incredibly light. I am curious to see how far I could take this approach. When I am not building boats I could be fabricating components. It would make assembling a beam extremely easy to have end fittings which are just glued together!!

    6 Pounds LOL!!
    PS - Innovations - Carbon Fiber Trusses & Beams http://element6composites.com/applications-trusses-beams.asp
    Weighing in at only 6 pounds, this carbon fiber truss comprised of ¾” x ¾” tubes and gussets was subjected to a cantilever test with 800 pounds placed at the end without breaking.

    RNDR68.jpg boxtruss.jpg
    RNDR69.jpg RNDR70.jpg RNDR71.jpg RNDR68.jpg boxtruss.jpg
     
    Last edited: Jun 25, 2017

  15. jorgepease
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    jorgepease Senior Member

    Think I have all the bulkheads and watertight compartments accounted for. Decks are complete except for stiffners and upper bridgedeck (if I go that route). I think it's enough to start the weight estimate, so tomorrow I will start that.

    RNDR72.jpg
     
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