Sailboard rig

Discussion in 'Sailboats' started by AleX`G, Aug 10, 2006.

  1. Paul B

    Paul B Previous Member

    The Designer of the Wyliecat boats is not JIM Wylie. If you're going to continue to drop names you should at least try to get them right.


    -
    There is no such thing as as aeroskiff 14.
     
  2. Doug Lord

    Doug Lord Guest

    Wyliecat

    My apologies to Tom!


     
  3. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Question;

    I have been persuaded that wing sails have a very narrow range of ideal trim. An experienced sailor could deal with this on a full sized (people) boat. A model is a whole other deal. The skipper can not feel the gusts or shifts that the boat feels because it is out there somewhere. That means that the skipper will always be behind the curve. One of the things that makes models interesting and/or frustrating perhaps. My limited experience is with an EC12 and a bunch of experimental RC boats of my own devising. Also RC land yachts which are a hoot but very difficult to drive competantly as acceleration is eye popping and trim response time is very short. Wing sails on a land yacht are probably the only way to go because the vehicle is so fast. Not necessarily so with a boat. Can superior RC sailors deal with the wing sail well enough to make it a good choice ?
     
  4. Doug Lord

    Doug Lord Guest

    wing sails on rc models

    Messabout, my view is that a wing sail would be very ,very difficult for an rc sailor to trim no matter how good he or she is. I think significant improvements in rc sailpower can be had with things like a square top rig with upper and lower out haul. The gust response and planform contribute to noticeble improvements.
    I have very little confidence in significant improvements being made on miniature boats with solid wind sails...
     
  5. AleX`G
    Joined: Jun 2006
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    Location: Scotland

    AleX`G Junior Member

    We shall see in due course. If it does fail I could alwasy make a computer controlled system. And use a conventional sail.
    I see no reason why it should fail. Surely the wing would maintain the correct angle of attack itself and you adjust the flap to change lift/drag ratio.


    Alex
     
  6. AleX`G
    Joined: Jun 2006
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    Location: Scotland

    AleX`G Junior Member

    Hey guys hat to bring up this question again but i am getting to the point were i am actually making the sails.
    The wing sail turned out to be just too heavy and i dont think i could get the weight down enough. So now i would like to concentrate on a square top main and a jib probably running to the top of the mast.

    I have one question though im hoping you guys can help with. For the gaff extension doesnt it need to be able to rotate with the boom when adjusting the main sheet. If this is so it will not automatically return to its neutral position so to say so how do you adjust the tension in the gaff and the top of the sail. Can you use leech tension to work this or would a seperate control line be required.

    I will be making the mast out of aluminium. I thought about using a spring attatched to the gaff so the head of the sail could let air out in large gusts. Would this work?

    What ratio of main to jib for sail area would you guys recomend assuming max mast height 90cm.

    The image below represents kind of what i am thinking of but i am unsure about battons and exactly how the gaff works. To i need something that will tension the boom?

    Alex
     

    Attached Files:

  7. b_rodwell
    Joined: Apr 2002
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    Location: Sydney, Australia

    b_rodwell Junior Member

    Making it work

    Hi

    I am very close to launching my 4.7m x 1.5m dinghy with a sailboard rig. The rig is a second hand ($600) 10.4sqm formula windsurfer sailboard rig. It is stayed to the point where the wishbone boom clamps on the mast. The mainsheet is off the end of the wishbone.

    I bought this rig aware that it would not have the optimal drive characteristics for my application. This has been confirmed when trying out the rig on dry land. It is very flat at the top.

    I now want to add more shape. My inclination is to do this by stiffening the top mast half with carbon tows. I would be interested in your views on this approach. And is there any science to work out the amount of carbon tows that would do the job?

    Brian Rodwell
     
  8. Hansen Aerosprt
    Joined: Mar 2007
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    Location: SF Bay

    Hansen Aerosprt Junior Member

    Brian:
    As you have surmised, Formula windsurfing rigs are highly refined for a particular set of dynamic problems rarely encountered by small boats and not the best choice. Not knowing which sail and mast combination you have, it is a little hard to give specific advice but in general, Formula sails have rather stiff battens and flat twisty sections in the top of the sail.

    There are a few things you can do to add shape: less downhaul (which may cause problems,) softer upper battens, stiffer mast or re-cut the head of the sail. If you have access to a local sail repair station or are handy with it yourself, the best way to add shape is to peel up the top 2-3 batten pockets and take a 2-3cm wedge out of the leech running forward to the 1/4 chord point under each pocket. Then replace the pocket and soften the battens in the front half before replacing them. This will tighten up the leech and add shape using the same mast. If you wish to stiffen the mast, it will be 'trial and error' but you can set up a spread sheet to predict the added material needed by using the inverse of the fourth power of the outside diameter minus the fourth power of the inside diameter to predict the deflection change. That is, for a given diameter, wall thickness and material, increasing the wall thickness will stiffen the mast accordingly and the deflection will be less. Even with a stiffer mast, you should more than likely do the sail re-cut as well. Otherwise you will probably never get the desired shape.
    Good Luck!
    Bill Hansen
    Hansen Design
    Hansen Sails, LLc
    Current 'chop top' boat projects
    Hoot Dinghy
    Laser Turbo
    Antrim Wing Dinghy
    Cal-20+ Uni-rig
    Wyliecat 17
    Wyliecat 30
    Commodore Tompkins Wylie yacht tender
     
  9. b_rodwell
    Joined: Apr 2002
    Posts: 60
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    Location: Sydney, Australia

    b_rodwell Junior Member

    Making it work

    Hi,

    Thanks for your detailed information.

    The sail is a Sailworks NX2 10.4. The mast is a Fibrespar Reflex 4600 QT 520/26/32.

    Does that change any of your recommendations?

    I would like to use a sailmaker to make the changes to the sail. Who in Sydney OZ would be the best to do this sort of work?

    Brian Rodwell
     
  10. Hansen Aerosprt
    Joined: Mar 2007
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    Location: SF Bay

    Hansen Aerosprt Junior Member

    Brian:
    That sail doesn't have many battens in the top third so my recommendations won't help as much as you will probably want. The top batten is too high to do much but should be done anyway to tighten the leech. Another method would be to remove the upper sleeve and 'luff adjust' it by adding luff curve in the top 1/3 of the sail. All-in-all, you won't get far towards an effective dinghy sail with the kit you have. I can't help with sail repair in Sydney, sorry.
     
  11. CT 249
    Joined: Dec 2004
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    Location: Sydney Australia

    CT 249 Senior Member

    Bill, can you tell me the relevance of the number of top battens? Are they relevant simply because they are a convenient seam to use when introducing the seam taper?

    I'm thinking of modifying older FW sails for use on a Lechner and IMCO, and the un-modified FW sails don't seem to be all that good on a longboard, in terms of speed for size.
     

  12. Hansen Aerosprt
    Joined: Mar 2007
    Posts: 62
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    Location: SF Bay

    Hansen Aerosprt Junior Member

    CT:
    Yes.
    In my experience, adding built-in shape works best at the battens. If you are just trying to tighten the leech, you can take a straight wedge all the way to the sleeve 1/2 way between battens. This is effectively an increase in luff curve and easier than removing the sleeve. You may have some slight distortion at the sleeve if the wedge is large. If you do this, you will need to reinforce the area along the luff to prevent it from pulling apart under downhaul. The other option is a stiffer mast. A combination of all three should get you there, i.e., batten re-cut, leech tightening and mast selection.
     
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