converting to junk rig

  • 20 Jan 2019 22:57
    Reply # 7011960 on 6996033

    Iain,

    Do you have, or can you locate, an original sailplan for your boat?  They often have the CE marked on the drawing.  If you have this, you can scale one of Arne's drawings to give you 10% more sail area than the bermudian working rig, then superimpose this over the original drawing so that the two CEs are in the same place.  I like the junk rig's mast to be about 10% of the chord (horizontal distance between luff and leach) back from the luff.  Voila!  You have your mast position.  If you don't have a drawing and are uncertain of the design even, you could be a bit cavalier.  Assume the CE of the original rig to be about 200mm aft of the bermudian rig's mast position.  Locate your new junk sailplan's CE there and go for it!  I am not much of a maths wizz either, and sympathise with your inability to get into PJR.  I converted my boat, Arion, this way, and the balance is fine.  I call myself an empirical engineer.  I don't calculate things, I just copy them! 

  • 17 Jan 2019 09:29
    Reply # 7006178 on 6996033

    Iain,

    Like ueli, I have to recommend Arne's chapter 3 as being a good description of the rig design process for someone who has hands-on skills, like yourself, to follow. He has master plans of his sail shapes, that you only have to scale to the area that you need, so the only major design task is to put it onto the boat in the right place.

    If you cannot get your head around this (it isn't rocket science, and taking it slowly and step by step will get you there, do persevere), then you'll have to get professional help for some of it. Alan Boswell's contact details are on the back page of the JRA magazine.

    Looking at the photo of your boat, it doesn't seem to be a Russell Marine Islander 23, but I don't recognise it.

  • 16 Jan 2019 23:37
    Reply # 7005620 on 6996033
    Anonymous member (Administrator)

    Ueli,

    You may be right that my way of finding the CLR is out-dated. However, it depends.

    If one does not already master a CAD program, it is a lot faster to do the drawing work manually, with a good calculator at hand. It is simply waste of time to learn CAD if you only plan to make a sail every five or ten years. Moreover, the manual process of drawing up the sailplan is similar to lofting the sail in full size, so it is almost like a training exercise before lofting.

    Remember, I am writing for the doers, not for skilled keyboard jockeys with no actual intentions of cutting in canvas. That’s why I choose to show them the manual, analogue way of doing things.   

    Cheers, Arne


  • 16 Jan 2019 15:07
    Reply # 7004439 on 6996033

    hi iain

    take a look at arne kvernelands files – to find a possible sailplan (and mast position/s) specially at the third chapter of his book.
    the 'cut out and balance' method to find the center of lateral resistance might be a bit outdated in times of free software (i.e. inkscape) which spits out the geometrical center of an irregular shape in seconds. but it still works, and everything else is great!

    ueli lüthi

  • 16 Jan 2019 14:11
    Reply # 7004328 on 6996033

    HI David the books I've got are 1/ Practical junk rig & 2 Design and build your own junk rig now I've gone through both books and I cannot make head nor tail of how to place a mast in the right place reading these books to me you need a degree to work this out not a DIY skill its like being put on a boat without a compass and told to find your way home math's are not my strong point but i can get by .. I may sound a bit thick but I'm not I can rebuild engines without a manual build bikes and cars and i cannot work this system out ......iain


  • 13 Jan 2019 00:40
    Reply # 6997564 on 6996033

    Essentially, you need to draw a junk sail with at least the same sail area as the working rig of the original sailplan, preferably about 10% more.  The centre of effort of the junk sail needs to be in the same place as the original, though some say a bit further forward.  This means your new mast will have to shift forward as well.  It will be keel stepped, and well braced where it comes through the deck. 

    Basically it is simply a lugsail.  It has a halyard that attaches to the centre of the yard.  The halyard is slightly offset at the masthead, on the side the sail sits.  The multiple part sheet attaches to the aft end of the boom and battens.  There are a few other control lines, such as a parrel that holds the yard to the mast and  another than tensions the luff.  Details of these are illustrated in the literature.

    However, it is impossible in a single post to give you anything other than a brief outline like this.  You could get a professional to design the rig, and even build it, though the cost will be hard to justify.  I think David Tyler's suggestion of initially reading Arne's pages is a good place to start, plus Practical Junk Rig of course.  If you are an experienced sailor, you should be able to translate your knowledge easily enough, paying attention to the different ways of sheeting the sail, rigging the halyard, etc.  If there are JRA members near you (look up the members list), an examination of their boats would be invaluable. 

    Good luck!

  • 12 Jan 2019 08:17
    Reply # 6996693 on 6996033

    Hello Iain,

    Could you say more, please? What books have you got, and what in particular don't you understand?

    Have you checked out Arne's writings at the top of this page, which are a good guide for newcomers to the rig on how to make his version of it?

    Last modified: 12 Jan 2019 08:18 | Anonymous member
  • 11 Jan 2019 20:12
    Message # 6996033

    Hi to you all, My name is Iain now I have just got hold of an Islander 23 and would like to convert it to a junk can anyone help with this as i've got some books on the subject but I cannot figure it out need help please.....

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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