Rig moving laterally !

Discussion in 'Sailboats' started by xarax, Jan 9, 2007.

  1. xarax

    xarax Previous Member

    An interesting new idea : A rig that can be shifted laterally (GRL : gréement réglable latéralement) to improve stability and righting moment.
    Aster Wind : http://www.asterwind.com/
     
  2. Vega
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    Vega Senior Member

    I have seen that boat at the Paris boat show. It looked very well made and it is a very nice boat. It is probably a good idea, but the application of that principle to a bigger boat seems complicated to me. Kind of scary, a big rig moving from one side of the boat to the other side.
     
  3. Chris Ostlind

    Chris Ostlind Previous Member

    So, let's look at this in a pragmatic fashion...

    You have what very simply amounts to a catamaran with matching hulls. You have eliminated the business of needing to have a super strong and non-bending forward beam to resist the compression forces of the mast. The mast cmopression is now being pushed through a hull form and all its structure. The parts removed were stationary, fixed elements with reltively littel maintenance associated. You have eliminated a good deal of weight in the process and have helped the multihull form to enhance its potential performance as a result.

    In exchange for the above, you have added a moving mechanical system with a track and a set of support beams for the shrouds. You have added back to the boat some of the weight taken away and made the boat much more complex in the trade. The parts added will require a good deal of maintenance and will be subject to failure through wear and tear to the system.

    The sliding mast system reminds more than a little of the goofy idea currently being put forth about having a track mounted sliding ballast system above the deck of a boat, simply to enhance righting moment. In both ideas, adding complexity to a boat for a questionable benefit is not my idea of the direction for good design. There's just too much stuff to go wrong and when there is... the ocean will find a way to make sure it happens.

    Many folks would look at the form and suggest that it has the same advantages as a proa, so why not build a proa and be done with it? A proa has no sliding track for the mast structure, the compression loads are localized through the hull structure and it has an equally small wetted surface (or better)

    I don't read French, so my short synopsis is simply by eyeing the boat and speculating. If there's something I missed about the design, I'd love to hear about it so I can more fully understand the process.

    Otherwise, it seems rather inconvenient to have to remove anything that I would like to have on the deck in order to get the rig across to the other hull in a tack or gybe.
     
  4. Doug Lord

    Doug Lord Guest

    Sliding rig

    Ostlind it's your appraisal of sliding on-deck ballast that's goofy! One of the Herreshoffs used just such a system in the 1800's on his favorite boat and Julian Bethwaite has proposed such a system on a 60' Maxi Skiff.
    The sliding rig is interesting but wouldn't the righting moment be reduced by the weight of the rig? At least in the center of a cat at relatively low heeling angles it contributes to RM.....
    ---The pix I saw showed the boats with the rig to leeward; I imagine the rig could be moved to windward and increase RM due to rig weight as well..
     
    Last edited by a moderator: Jan 9, 2007
  5. Chris Ostlind

    Chris Ostlind Previous Member

    So, Doug... if the concept is so powerful and it was first done back in the 1800's; why, pray tell, has it not found wide acceptance in the sailing world as a viable technology?

    Second... you have not addressd the business of undue complexity to an ocean level sailing craft. There are huge issues with corrosion, leading to excess maintenance and inevitable breakage of what you deem critical equipment. Is it those issues which have caused prudent sailors and designers to leave the so-called brilliance of the form far behind?

    Third... if Bethwaite's proposed design (mind you, it's only a concept machine at this point with absolutely no movement in the direction of actually building one) is so credible, why haven't the design icons of the industry seen the light, as it were, and included the stuff in their no-holds-barred design proposals?

    The answers are there, Doug, just simplify and add lightness.. Therein lies the secret to all fast racing machines. The complicated versions eventually all die-off from their own limitations and they always take the class with them. Can't buck history on that front.

    To conclude... it must have touched a nerve for you when I indicated that nobody in particular was touting a foolish enterprise with their own moveable thing-a-ma-jig. It was nice of you to provide the connection to the proper individual for me. Doug, you can write me off-list with regards to these non-rhetorical questions. It's only fair that you not further hi-jack the conversation with your own brand of techno-wizardry.

    And now, I apologize, forthwith, for possibly encouraging Doug to poach this thread when we were nicely engaged in a conversation about the moveable rig craft as provided by Xarax.

    Now, back to that interesting French boat.

    Has anyone managed a readable translation of the supplied URL? I've used Babelfish on it and its worse than reading a Mongolian instruction booklet in English.
     
  6. Vega
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    Vega Senior Member

    Back on the cat.

    The site is very bad. I have found some papers about that cat that I had pick on the Stand.

    That system is not only for improving speed in light airs, but also to give more seaworthiness to the boat.

    They say about it:

    The LCR challenges: Safety and Performance

    The Lateral Control Rigging (LCR) is a system which allows to move the rigging from one hull to the other. The LCR prevents the boat from capsizing and it improves the performances whatever the weather is.

    When it is not windy, the leewarded LCR relieves the windwarded hull. When it is windy, the windwarded LCR maintains the stability of the boat.


    About the 28ft cat:

    The multi-hull dayboat, interchangeable deck (regata, leisure, cruise) retractable roof, and automatisation of the LCR adjustment.

    Aster 28 has been designed to be the lightest, classiest and most performing boat of his category.


    The 18ft cat holds the Crossing Chanell record for cats with less than 20ft.

    It seems interesting to me;)
     
  7. rayk
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    rayk Senior Member

    aaaaaaarrrrrrggghhhhhh....
     
  8. xarax

    xarax Previous Member

    "When it is not windy, the leewarded LCR relieves the windwarded hull. When it is windy, the windwarded LCR maintains the stability of the boat."
    As far as I can tell, it seems that it is like having an atlantic and/or a pacific proa, depending upon the weather conditions. You choose to enhance the righting moment in favour of more sail area OR reduce the righting moment in favour of safety. I would be glad if somebody could explain the whole thing, because there are many gray areas in the concept...
     
  9. yipster
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    yipster designer

    interesting and makes me think of a proa
     
  10. Vega
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    Vega Senior Member

    Yes, I agree. It has the advantages of a Proa without the inconvenients. It seems a smart concept to me.
     
  11. rob denney
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    rob denney Senior Member

    G'day,

    What inconveniences?

    regards,

    Rob
    www.harryproa.com
     
  12. Vega
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    Vega Senior Member

    Hello Rob,

    The boat can be tacked normally, instead of "shunting".

    When I was talking of advantages, I was referring to these small sporty boats. On cruising boats (bigger) I have said that the system seems impractical to me.

    Regards
     
  13. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Doug, We have all pretty much trashed water ballast in this forum for a long time - with reason. Adding ballast to the deck (high up) that cannot be removed (as water ballast can) and may be subject to breaking free (harder with water) seems counter-productive.
    Thoughts?
    Steve
     
  14. Doug Lord

    Doug Lord Guest

    To avoid contributing any further to a change of subject in Xarax's thread I've moved a copy of Steves post and my answer to it to this thread:
    X18-T ---Experimental 18'/Movable Ballast/Foiler - Boat Design Forums
    Address:http://www.boatdesign.net/forums/showthread.php?t=14107
    --------------
     

  15. rob denney
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    rob denney Senior Member

    G'day,

    Shunting may be a trifle slower, but it is far more convenient. No changing sides, no flogging sails and no chance of being caught in irons. It is also completely reversible at all times and allows for all the weight to be kept to windward without needing to haul it across each tack. The ability to sail in either direction is also very handy especially in man overboard situations.

    Shunting and tacking are similar to the situation of everyone sailing multihulls and someone suggested replacing one of the hulls with a lump of lead so the boat was slower and fell over all the time. If everyone shunted and someone suggested tacking, they would be laughed out of town.

    regards,

    Rob

     
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