Beam Design.... Again!

Discussion in 'Multihulls' started by cookiesa, Jun 29, 2015.

  1. redreuben
    Joined: Jan 2009
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    Location: Beaconsfield Western Australia

    redreuben redreuben

    So why the secrecy, what design is it ? Would be kinda helpful don't you think ?

    Some of Roger Simpsons plans have Alternative ply beams for the aluminium he specifies. (from memory)
     
  2. cookiesa
    Joined: Mar 2007
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    Location: Launceston, Tasmania

    cookiesa Senior Member

    Just for the groups benefit, the design has been modified so I am not going to publicly name the design out of respect.

    Thanks for your suggestion today Redreuben, as I said problem is now solved.
     
  3. outside the box

    outside the box Previous Member

    Cookiesa
    Hi there
    We have been quietly reading where you are at with what to us seemed a simple request in the OP.
    If you have no luck and would like to run some figures for yourself you are welcome to email me at admin@ezifoldyachts.com and I will have one of our Engineers scan a page of calculations and load paths for a similar sized Catamaran that you can apply once you have worked out the needed parameters for your own boat and it's intended use.

    The guys were talking today about this as there are many outcomes possible, simple small craft beam design or a very simple boat design for that matter is not some dark science. Working out the load paths, cycle loads and other elements combined etc can seem that way.

    Look forward to seeing your project turn out a roaring success.

    Brooke and Team Ezifold

     
  4. cookiesa
    Joined: Mar 2007
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    Location: Launceston, Tasmania

    cookiesa Senior Member

    Thanks to everyone the beam is now complete and looking pretty good, much better I feel than an alloy one would have!

    Now on to rudder tubes :)
     
  5. aussiebushman
    Joined: Oct 2009
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    Location: Taralga NSW

    aussiebushman Innovator

    Rudder tubes

    Hi Cookie

    Glad you sorted the beams. Re Simpson, he advocated rudder tubes made from glassed-over pipe (can't remember what the recommended material was).

    I had mine mad e out of 316 stainless steel with tangs welded to the full width at each point of the aft curve. Then WRC was bonded over this structure and faired - never regretted the expense especially when the building cradle collapsed and the boat landed on the rudder on one side - didn't even look like bending or breaking!

    Regards

    Alan
     

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  6. redreuben
    Joined: Jan 2009
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    Location: Beaconsfield Western Australia

    redreuben redreuben

    Cookie, show us a photo ! So I'm assuming you are doing spade rudders and not the transom hung ? Well you've done a beam so why not do carbon stocks into glass tubes ?
     
  7. cookiesa
    Joined: Mar 2007
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    Location: Launceston, Tasmania

    cookiesa Senior Member

    I like the look of that rudder shaft, I was thinking of going stainless only because I haven't played with carbon and not sure I want to experiment with such a critical, and often loaded part.

    I'm not 100% committed either way yet, I may just use the transom hung rudders for now and revisit this down the track.

    I do like the idea of nice clean transom steps..... Hmmmmmmm

    I can't seem to upload multiple images from the IPAD so the one attached also shows laying up the mount sleeves
     

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  8. cookiesa
    Joined: Mar 2007
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    Location: Launceston, Tasmania

    cookiesa Senior Member

    Beam image
     

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  9. cookiesa
    Joined: Mar 2007
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    Location: Launceston, Tasmania

    cookiesa Senior Member

    What else to do when you're not at 100% other than mull over the next stages...

    The image shows the area I have to work with, it isn't the easiest to see but down the bottom (top of hull) where it slopes down to the stern there is a bulkhead, and then around 500mm towards the bow is the next one. Where the slope down toward the stern is, I believe will be about the waterline, so thinking perhaps bringing it half way between the two bulkheads for efficiency.

    This is also a watertight compartment that has nothing else in it, so uses otherwise wasted space. (My thinking is if I went ahead with spade rudders, this could end up with a false floor to maintain the water tightness (I have already increased the water tight compartments so there is no compromise to floatation anyway).

    Above the new false floor is where I could mount tillers and run the link bar just under the rear of the bridge deck, making it accessible if required. Due to family compromises wheel steering was on the agenda anyway

    The image shows a beam across the bottom of the keel, assuming this position I have a height of 430mm between the hull and "baseline"

    This would also leave the sterns clean for sugar scoops.......

    Current rudders are approximately 630mm deep and taper to the narrowest point from 350mm down to 220mm (including balance portion) (pictured, these remain the property of the designer, here for reference only)

    So on a roughly 430mm X 350mm I end up a similar overall size, in a more efficient mounting position, but with a wider blade.

    Now to look at some rudder designs and see if it could work......
     

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