Primaat 24 conversion

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  • 02 Dec 2019 09:21
    Reply # 8153083 on 7891576

    With this kind of planform, I believe that you can keep considerable camber all the way to the top -- maybe 4% in the top panel, then 6%, and the rest of the lower panels 8%.

  • 30 Nov 2019 14:59
    Reply # 8146743 on 7891576

    I made a crude paper model of the sail, using Slieve's spreadsheet for calculating the camber in each panel.

    The sailcloth I'll use is 90cm wide, the broadseams are split 2/5 on the first and second seams, 1/5 on the third and none on the 4th.

    I used 8% camber on the 5 lower panels and 6% on the 2 upper panels, but perhaps I should reduce more : 6-4-2 on the 3 upper panels ?

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  • 19 Nov 2019 08:00
    Reply # 8128714 on 7891576

    I continue working on the sail plan.

    Do you see something wrong with this version ? Mast moved forward, rudder 10% bigger.

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  • 04 Nov 2019 13:53
    Reply # 8090544 on 7891576

    Don't worry, the sail will have some camber ! I'm interested in junk rig since I've discovered that junk rig goes well to windward thanks to camber.

    Anyway, I have to make a new rudder (the old one is broken, rotten plywood), I can make it bigger or with an endplate.

    I'l see if I can move forward the mast, or put more rake.

    Thank you for your help

    Thomas




  • 04 Nov 2019 09:57
    Reply # 8090335 on 7891576
    Anonymous member (Administrator)

    Thomas,

    I think the ideal would be to have the CE 10-20cm further forward. That said, if the boat were mine, and the mast had to sit where you have put it, I would give it a try as it is. A finkeel plus separate rudder design needs less lead than a full keel and integral rudder design.
    I would have a plan B ready: In case the boat turns out to have an annoying weather helm, I would start with fitting a big endplate to the existing rudder. I am pretty confident that this will help, but there is also a possible plan C: Make a new rudder and fit it to the transom.

    Good luck!

    Arne

    PS: I hope you make the sail with some camber in it.


  • 04 Nov 2019 08:45
    Reply # 8090309 on 7891576

    I'm struggling to find the right lead for my sail.

    If I follow the PJR rules, the 9% of WL forward the LCR including rudder, or the 6% abaft the BM CE, I find exactly the same place. I like it because it's the same place for the mast.

    But I read in the forum that we can go to 12, 15% of lead in order to prevent too heavy weatherhelm.

    Do you think I'm right with this sailplan ?

    Thanks

    Thomas


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  • 11 Oct 2019 15:19
    Reply # 7928244 on 7891576

    Thank you for your reply, Arne and David.


    For the camber,  I think I prefer broadseam, for the simplicity of the batten.

  • 11 Oct 2019 14:28
    Reply # 7928188 on 7891576

    172 gsm is 5 oz/sq yd which is plenty strong enough. Are you proposing to use hinges, like Weaverbird? 

  • 11 Oct 2019 13:32
    Reply # 7928133 on 7891576
    Anonymous member (Administrator)

    Thomas, pardon for butting in here.
    Both proposed sailcloths will work, I but I would no doubt choose the lighter one at 172g/m2. This will inflate and set better in very light winds.

    Camber.
    More important is that you make the sail with camber in the panels. A sail with camber in it will perform a lot better than a flat one.

    I suggest you let David specify the construction of the cambered panels. The challenge is to make the sailmaker follow David’s instructions...


    Arne


  • 11 Oct 2019 12:59
    Reply # 7928070 on 7891576

    Weaverbird's sailplan with a seventh panel, 24m2. AR 2.26

    The mast is the same height as the original woodenmast, the weight should'nt be a problem.

    I've asked an estimate from a sailmaker, he propose Contender Sailcloth,  « Supercruise Coloured »  4,00 oz,  172 g/m2 or « Fibercon AP Coloured »  5.38 oz , 231 g/m² . 

    Do you think 172g/m2 will be enough for this sail ?

    Thanks !

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