Maxi 77 junk rig conversion

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  • 15 Jun 2024 22:33
    Reply # 13370668 on 13370533
    Anonymous member (Administrator)
    Anonymous wrote:

    What would be Ilvy's junk rig without a JRA flag!? Therefore, I learned some basic embroidery skills, combined Ilvy's silhouette with the JRA logo and this little thing happened. Ready to be hoisted. 

    There are several different versions of the JRA logo available for members to use or adapt by clicking here

    They can be copied or many different services, including the Zazzle service which has some items pre-set-up, can print them on vinyl stickers, hats, clothing etc. 

    and don’t forget also that our treasurer can hook you up with a JRA burgee or colourful house flag 

    Last modified: 15 Jun 2024 22:41 | Anonymous member (Administrator)
  • 15 Jun 2024 13:38
    Reply # 13370571 on 13370559
    Anonymous member (Administrator)
    Paul wrote:

    Made a quick & dirty tiller brake. Arne, I hope you don't mind me abusing your clever and beautiful tiller break design :-D



    (..brake, break, brake break...)

  • 15 Jun 2024 12:31
    Reply # 13370559 on 13226713

    In between two squalls, I made a quick & dirty tiller brake break. Arne, I hope you don't mind me abusing your clever and beautiful tiller break design :-D

    1 file
    Last modified: 15 Jun 2024 17:36 | Anonymous member
  • 15 Jun 2024 07:38
    Reply # 13370533 on 13226713

    What would be Ilvy's junk rig without a JRA flag!? Therefore, I learned some basic embroidery skills, combined Ilvy's silhouette with the JRA logo and this little thing happened. Ready to be hoisted. 

    1 file
  • 09 Jun 2024 19:57
    Reply # 13367924 on 13226713

    Graham, I agree with you. In my opinion something else should happen or break, before the battens do. Howevery I guess everyone will need to find their own design philosophy, be it coastal or inshore cruising, racing or heavy weather offshore fun. Let's see if I - in the end - dimensioned my battens in accordance to my philosophy ...

    Eric, for sure. However, the Maxi 77 is not flat bottomed but rather round. It is not designed for planning, being also way too heavy. Also, the "hull speed" is not a wall which a displacement hull cannot pass. It is just that at Froude numbers around hull speed (Fr ~ 0.5-0.6) the wave resistance increases significantly more, relative to speed.

    Arne, my sailcatchers are derived from your design. As load carrying part I used the 50mm webbing still laying around from the sail sewing, sweetened up with the noce yellow sail cloth. However, it really does not appear to me that the line up to the mast carries any load from yard or battens leaning against it (compare the shadow in the attached fotos). It felt still quite slack, and also at that angle there couldn't be much load taken over by that line... However, I still see your other points.

    4 files
    Last modified: 09 Jun 2024 21:35 | Anonymous member
  • 05 Jun 2024 11:00
    Reply # 13366003 on 13226713

    It seems to me that the aim should be to have battens that are strong enough to allow the boat to be driven hard, and to survive squalls, no matter what type of hull you have.  Once you have achieved this, then it is just a matter of reducing sail area, whether on or off the wind, to keep control of the vessel, and this will indeed depend on hull type.

    They all have their advantages.  I've surfed downwind for long periods in light-displacement boats, which was huge fun.  They were easy to steer, but required constant attention to the helm. Displacement hulls obviously won't surf, and if you drive them too hard, are liable to broach, whereupon you may well start breaking things.

    The displacement hull is easier set up for self-steering in my opinion, but there are always exceptions to the rule.  People do use autopilots successfully when surfing downwind on light boats, but if the autopilot fails on the face of a large wave, chaos may ensue.  A few of the round-the-world racing yachts have capsized when their autopilots broke while surfing.  I would not choose a light-displacement flyer for solo ocean cruising, but others have.  John Guzzwell's Trekka was light, and he surfed at times.  More recently, Webb Chiles circumnavigated solo in his light-displacement Moore 24, Gannet, regularly replacing autopilots along the way, and says it is the best offshore yacht he has ever owned.

    I drove my 24' (7.3m), 5-ton, junk sloop, Arion, very hard downwind.  We were never likely to surf, but surged on the crests of waves for long periods at times.  That boat never showed any sign of broaching, even under its previous bermudan rig.  With the junk rig, I eased the sheet right out until the upper sheeted batten was athwartships, and the unsheeted batten above it, plus the yard, were beyond athwartships.

    How you sail your boat will depend on many factors, including design and personal preferences, but the yard and battens should be stout enough not to break except under exceptional circumstances.  It should not be determined by the amount of sail you carry.  The only consideration for reducing sail should be the control of the vessel.  It will also depend on the sort of cruising you do.  For inshore or coastal cruising, I'm quite happy to drive the boat hard, but for offshore passages I subscribe to Roger Taylor's philosophy of easing along.

  • 04 Jun 2024 15:45
    Reply # 13365624 on 13364747
    Anonymous member (Administrator)
    Anonymous wrote:

    Arne, thanks for clearification, I understand your reasonable points. Sadly this means that I will have to lower the fun while flying...


    To simplify, there are two different type of hull:

    - The heavy long-kell hull (like Arne Folkboat) that will not overpass the hull length speed limit. For those to overcanevas the hull will only create a big bow wave without almost any effect on the boat speed.

    - The light flat-bottomed hull with fin-keels (like the Maxi 77) that may override the bow wave and start surfing. When the boat starts to surf, the drag of the hull decrease and the boat may accelerate. For those, to overcanevas (in a reasonable way) will allow to have great surfing experiences. Rather than reducing the sail area while broaching or down wind keep as much as possible sail area and if a batten is bent just change it for a stiffer one ! (Eric Tabarly used to say when something broke :" ce n'était pas assez solide!")


  • 03 Jun 2024 08:46
    Reply # 13364966 on 13363985
    Anonymous member (Administrator)
    Paul S wrote at 31th May:
    As for tacking angle in light winds, there are two possible reasons for that:
    • Tacking angle on the chart will always be worse in light winds than in strong winds, since the headwind (boat speed) component is relatively stronger than in stronger winds. We don't sail twice as fast in 12kts winds as in 6kts.
    • Some fine keels may lose grip in lighter winds. My former boat, Johanna was not so good in that respect.


     Ah, this is not what I meant. I mean sailing with too less sail area for a given wind, i.e. reefeing too much and thus being "too" slow.

    This is after all not rocket science.

    As you reef the sail, the mast and the boat’s superstructure will still be there in full size to produce parasitic wind drag. Thus, the speed to windward will drop, and the pointing angle will be wider and wider the smaller sail you set.

    To give an idea of how much wind drag there is in the boat and rig, drop the whole sail in a good breeze, and then measure your downwind speed. You will be surprised...


    Last modified: 03 Jun 2024 08:48 | Anonymous member (Administrator)
  • 02 Jun 2024 14:48
    Reply # 13364747 on 13226713

    Arne, thanks for clearification, I understand your reasonable points. Sadly this means that I will have to lower the fun while flying...

  • 02 Jun 2024 10:35
    Reply # 13364719 on 13364716
    Anonymous member (Administrator)
    Paul wrote:

    I have been warned, that one shall reef early when running, as there would be a danger of "batten breaking". However, I don't quite understand, if for example I lower two panels, why the battens of the upper panels should then have less load... Sure, with two panels down the boom and lower two battens have way less load. But this does not affect the upper ones, does it?

    Your logical thinking about this is good, but there is another factor (or two). When I deep-reef my sails, the lee topping lift appears to support the yard and the remaining battens at work. Therefore, it appears to me that these see little load, even in a strong blow (photo). Of course, it depends on how the lazyjacks are arranged. I use a pair of stout, nearly straight topping lifts and then just add (non-structural) sail catcher to these.


    PS: another reason for warning against driving hard with the sail squared out, is that the battens see increased compression load in this position. This may make wooden battens snap almost without warning. Aluminium battens bend more under load, and give you a discrete hint...

    PPS: yes, and the two top battens are stouter than the others...

    (see my member's album, photo section 8, photo 20)

    Last modified: 02 Jun 2024 10:38 | Anonymous member (Administrator)
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