junk lateen yawl ?

Discussion in 'Sailboats' started by Timothy, Apr 22, 2008.

  1. Timothy
    Joined: Oct 2004
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    Timothy Senior Member

    I have been following the threads aft mast rigs and cat boat across the Atlantic and in a flight of fantasy I stole every idea I have read about and came up with this rig for my boat. I suspect its an engineers nightmare. Tensioned battens,a sail with a clean leading edge that reefs as the mast telescopes ,all accomplished with only a single halyard and down haul. Balanced on all points of sail even when reefed and demountable to boot.As I said a complete flight of fantasy. never the less I made a computer model of the rig on my boat and I kind of liked the way it worked out. Any way here are two renderings I took. Any chance it might actually work?
     

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  2. Gilbert
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    Gilbert Senior Member

    The sails look cool. I have no idea about the technical problems involved.
    But your boat looks to have a classic schooner underwater profile so I'm thinking the main mast should be aft, not forward.
     
  3. Nordic Cat
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    Nordic Cat Senior Member

  4. Doug Lord

    Doug Lord Guest

    Wow! I was doing some research and went to Garry's site then posted his patent and decided to check out this thread. Your rig appears to incorporate
    some ideas he talks about and it would definitely work. Its a small world...
     
  5. Timothy
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    Timothy Senior Member

    I can say that Mr. Hoyt's rig was definitely one of the concepts I stole from. I must admit that given the offset necessary to provide clearance for a sail of ,lets say, a draft of ten percent of the cord ,I find it difficult to see how a mast can be made stiff enough to maintain luff tension without bending like a bow . If this is indeed a problem I thought it might be better to use a short elliptical mast with a long flexible yard to provide gust response .The sail has a luff pocket on the yard so that the yard ,virtualy a mast extension ,maintains a clean leading edge. The whole rig rotates and maybe the mast itself could provide some lift or help keep the laminar flow attached to the sail or though I think it more likely that it would create detrimental turbulence on the bad tack. But who knows? As for the telescoping reefing system well don't laugh but attached is an animation of a cutaway view of how it works in fantasy land.By the way the Idea for the yawl was to free up my cockpit so that I can build a Bimini from solar panels that is not shaded by my masts and sails. the idea behind the raked masts is that as the main is reefed its center of effort moves forward by an amount sufficient to keep the center of effort of the whole rig constant. I can dream.
     

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  6. Nordic Cat
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    Nordic Cat Senior Member

    Have you considered going with a Ballestron type rig instead? There was an Australian built cat that had a "gaff boom" at the top of the mast to increase sail area, that also rotated. Probably simpler to engineer and build.

    Rearding the telescoping mast concept - it looks good - keeping the weight down and retaining the functionality might be tricky - but I'm sure it can be done.

    May I suggest that you speak to Rob Denney of Harryproa, I know he is working on a telescoping mast concept for his boats. www.harryproa.com


    Regards

    Alan
     
  7. Timothy
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    Timothy Senior Member

    I confess the idea for the mast was stolen from a concept that Mr. Denny proposed for one of his proas. I should also say that Mr Denny's assertion that unstayed carbon fiber masts can be made as cheaply as aluminum extrusions at half the weight is the basis for what little faith I have that the rig can be engineered and built. I shall definitely get in touch with Mr. Denny if I actually pursue the Idea. Re the ballestron rig . I have read that they work very well ,but this is flight of fancy and what started me off was the design of Nigel Irons of Romily, beautiful, and a old photo I saw of Nat Herreshofs own boat the fully battened cat yawl Clara. I figured if he could build a cat yawl with free standing masts and full battens in 1898 ,than given the materials around today then who knows whats possible? Remember that this rig is for my boat which was built for free standing masts and so when I was trying to work things out I had to design the rig so that the center of effort would remain where it was in the original rig and not have the masts intrude into the accommodations. I wanted a higher aspect ratio and more sail area for pointing in light winds and yet keep the center off effort down as much as possible.Even with the mast rake the lead is slightly larger and the center of effort slightly higher than it is with the original cat ketch {schooner} rig. I think I can get by with this as I have read that a swept foil must have more twist to maintain elliptical loading and I expect limiting twist with this rig might pose problems .
     
  8. brian eiland
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    brian eiland Senior Member

    Interesting concept....nice presentation.

    I'll just make this posting so I can be notified of new discussions...limited time at the moment
     
  9. Guillermo
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    Guillermo Ingeniero Naval

    Yeap. I'll follow up too.

    Cheers.
     
  10. safewalrus
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    safewalrus Ancient Marriner

    Now that is a nice looking boat!! I shall follow this with interest! Can't see why it won't work, but somebody will come up with a reason why not (usually me!!) You may not be too popular with the 'sailing set' for pinching ideas but hell, most ideas these days are rehashes of older ideas - in new clothes!! As they say there's nothing new under the sun - no but you can rethink the old ones, and this looks like a damn good rethink!! And to hell with patents etc if it works - use it!!
     
  11. yipster
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    yipster designer

    months back i've done deep searches on the net on masts, telescopic too
    sounds good but could not think of or find any satisfying looking systems
    multi stayed and shrouded perhaps but freestanding is i think a tall order
    and the hoyt sail has some lateen sail handicaps like tacking i belive
    let me be not to grumpy as i like the thinking, keep me posted too :)
     
  12. Timothy
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    Timothy Senior Member

    While rigging my windsurfer here in Thailand I got to thinking about my concept for the junk lateen rig and I thought why not put the telescoping sections in a luff pocket and essentially slide a fully rigged 12 meter windsurf rig up the mast. The problem would be to somehow lock in the sail shape using luff pocket and batten tension and to still allow the sail to be reefed. I went home later and turned on my fantasy machine and came up with this. The mast sections are elliptical D shapes and the battens are on cars that allow the battens to slide from one side of the mast to the other, and the cars themselves slide up the mast sections on tracks that angle out from the mast section before they terminate causing the battens to tension the sail. The mast is kinked and rotates and because the yard is fixed to the mast on its own car and the boom is not, as the sail twists (limited by the travel of the boom ), the rig should cant to windward and the luff pocket ( perhaps 20% of the cord) tensioned by the battens and shaped by the mast should provide for attached laminar flow. Not clear? Or just not possible? Even if it is possible would it be better to have the thicker wing shaped foil or stay with the thin sectioned foil of the junk lateen rig and live with the drag and engineering problems of the offset mast? Any way attached is a short animation as how I think the thing may work. Chuckles.
     

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  13. timothy22
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    timothy22 Junior Member

    Very nice concept. Phil Bolger is a fan of big mains and small mizzens way aft, so you are within the range of doable there. The rig looks very much like the old sliding gunter rig, so again, doable. The knock on the sliding gunter was that above dinghy size the gunter was a beast with all that weight up high waving back and forth, especially when gybing or reefing in a breeze when the halyard was eased. I do have some reservatons with all those parts flying in loose formation. That is a lot of stuff that has to slide and not bind when wet and stressed. I know for a fact that a sail with a luff pocket for the mast will bind when wet. A somewhat simpler solution might be a rotating wingmast of say 10% of chord length with luff track, full battens and the gunter mounted on 2 cars spaced apart to tame the beast a little. I know someone has worked out a system for overrotating the mast on each tack so the lee side of the mast lines up with the battens. Or you could stick with what you have, use standard cars in pairs, one on each track each with its own batten. And a yard for each side as well. Now you can have two sails side by side forming a true wingshaped airfoil that can be opened out to double its size downwind. And that idea is stolen, too, so you would be consistent.
     
  14. Cutta
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    Cutta Junior Member

    Wondering how this is going - any developments - would certainly like to see this or similar built
     

  15. sean9c
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    sean9c Senior Member

    Looks like a Nigel Irens hull
     
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