Primaat 24 conversion

<< First  < Prev   1   2   Next >  Last >> 
  • 04 Feb 2020 21:03
    Reply # 8726386 on 7891576

    I've started reinforcing the partners. It will be 60mm thick, plus the 30 mm  deck ring. I've doubled the thickness of the deck(2x10mm)  between the beams up to the sheer clamp.

    The mast step will be glued to the keel, to the hull and to the lower frame.

    The new rudder is 10cm deeper than the original, I hope it will be enough for good control.

    For the mast (9.5m high), I want to build it in epicea (spruce), hollow birdsmouth. Using Arnes method for calculating the diameter, I've found max diameter of 19,5cm, diameter at masthead  8cm.)

    For the battens (3.5m up to 4m), I've a seller near me who propose 35x2mm T6 alloy, 230€ the 7 battens. Do you think it's OK ?

    Slowly but surely, it's coming along !

    3 files
  • 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 ?

    1 file
  • 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.

    2 files
  • 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


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


    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!


    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 ?



    1 file
  • 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.

    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...


<< First  < Prev   1   2   Next >  Last >> 
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

                                                              Site contents © the Junk Rig Association and/or individual authors

Powered by Wild Apricot Membership Software