Maxi 77 junk rig conversion

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  • 14 Jul 2023 13:06
    Reply # 13227751 on 13226713

    Hi Arne,

    wow, what a reply! Thanks for your effort and the sketch, this was really quick. I like the look of the junk rig on the Maxi 77. It really suits her :)

    I agree with you about the hull shape being a good candidate. The rudder is quite large, but if necessary, the lateral area of the rudder could easily be increased.

    Now that you already drew a sketch, I should mention some further design constraints and ideas: As both my girlfriend and me have to fit into the V-berth, I can't take away more space there to put in the mast. It would not be to much an issue for daysailing, but we want to sail around Sweden from April to Oktober next year, so would need any space under deck which is available...

    The mast will be in a tabernacle, to quickly lower it. For this tabernacle, I am thinking of something special (but probably ugly...): It should be totally above deck, with no party protruding through the deck. This means, that one able transversal girder needs to be located above deck, which supports the bottom of the tabernacle. The top of the tabernacle needs then to be stiffened sideways, by diagonal beams. The whole thing would be mounted to the hull by only four screw, located at the toe rail (which of course will have to be stiffened from inside).  I try to sketch some details next week or so.

    By this rather radical design, there will be no space lost at all under deck. Of course this will increase windage on the bow as well as probably be not looking too yacht-like. However, I regard my boat as a work boat rather then a yacht.

    Also, I want the front hatch to be usable.

    For the mast position, this would allow the mast to be placed backwards up to the front hatch, so about 300-400 mm further aft.


    About the sailing area: With the bermudan rig, the main sail has 10 m², the fock has 7.5 m², the genua I has 24 m² and the spinnacker has 50 m². This makes for a total SA of 34 m² with main and genua.

    With the junk rig, I would like to increase the SA to about 35-40 m². She is not heeling that much due to the balast located in the bulb keel. Also I prefer to just be reefing earlier, and have a lot of sail in ligth winds. Also, according to your sketch this could be achieved by extending the sail more to the front, with the positive side effect of more mast balance.

    Any thoughts on this preliminary ideas?

    By now, it is all just ideas and sketches in my head. I will need to actually calculate the stiffness of this special tabernacle, and maybe readjust. However, my gut tells me the loads will be manageable.


    Cheers,

    Paul


  • 13 Jul 2023 12:43
    Reply # 13227232 on 13226713
    Anonymous member (Administrator)

    Paul,

    thanks to the rainy weather the last couple of days, I have recently done some in-door playing with junkrigs.
    I find the Maxi 77 to be a good candidate for JR conversion, with her good-transom-hung rudder.
    I started with looking for a place to fit the mast. To avoid colliding with the WC, I moved it 30cm forward of that bulkhead. This gives enough room for building a strong maststep. However, this mast position calls for a fairly (not extremely) broad sail with moderate mast balance (i.e. sail in front of the mast). The CE of the resulting sail sits about where the Bermudan mast sits now. The way it has been rigged will let you shift the sail a bit forward or aft to hopefully get the helm balance perfect.

    Have a look.

    Arne

    (Full size diagram on Arne's sketches, Section 7-22)


    Last modified: 15 Jul 2023 15:30 | Anonymous member (Administrator)
  • 13 Jul 2023 09:45
    Reply # 13227182 on 13226713

    Hi Frank,

    thanks for the hints, I'm going to get in touch!

    Cheers, Paul

  • 12 Jul 2023 10:55
    Reply # 13226718 on 13226713

    Hello and welcome Paul,

    Tony and Kay are both located near Lübeck. My boat will hopefully be ready to sail next spring/summer and I'm located near Stralsund, but which is probably to far for a day trip.

    Frank

  • 12 Jul 2023 10:27
    Message # 13226713

    Hi everyone,

    after beeing fascinated by the junk rig for a couple of years now, I finally acquired a boat which is small enough for me to start junk rig experiments: a Maxi 77. Being subscribed to the JRA for a year or two now, it feels like the right time to really start that project.

    I've been looking to a lot of files in the archives, and it is absolutely stunning! There is so much information, a really lot of interesting stuff. I already want to say a huge thank you to everyone contributing. With those information at hand, it should really be doable.

    To me: I am a shipbuilding engineer at just about 30, located in Kiel, Northern Germany (please excuse my english...). A few years ago, me and my girlfriend took our ancient two-masted Beneteau Evasion 32 for a year to discover the french canals and sail through Denmark. Having worked a lot in fluid dynamics and some basic yacht design, I now kind of get the point why this moving air around me is drawing my boat forward...

    Saying that, I absolutely feel drawn to the split junk. It just makes sense from an aerodynamic view. Probably best being combined with camber. However, I feel a bit reluctant to start my "junk rig career" with one of the most modern, high-tech designs. Maybe start with a simple junk first, there will be still enough to learn on the way. Cambered panels might be a good compromise... don't know yet, still have to decide which way to go.

    Though I am fully convinced of the junk, it will be a good idea to actually having sailed a junk rig befor digging into such a huge project. Therefore, I am hoping to get to know junk rig enthusiasts around the german northern coasts. Maybe there will be an option to join on an evening sail or something. An hour or so would be absolutely enough, just to get a feeling :) I am in good contact with Ingo with his "Atropos" in Kiel, but he is quite busy right now. Same for "Vertue 2" of Lübeck... Some five years ago there was an aluminium Reinke called "Fledermaus", two-masted junk rig, located in Flensburg, but she was sold (to whom?).


    When my junk project proceeds, I am pretty sure that more questions will arise. Also, I am trying to give some update now and then. But for now, I would be really happy if someone could help me out with a sailing contact around here.


    So long,

    Paul


    Last modified: 12 Jul 2023 10:27 | Anonymous member
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