Maxi 77 junk rig conversion

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  • 10 Feb 2025 09:46
    Reply # 13461104 on 13226713
    Anonymous member (Administrator)

    Tacking angle versus wind speed.

    Another big factor affecting the closest sailing angle to the true wind, is simply the wind strength.
    On the diagram below I have played around with wind speed and boat speed vectors for my own Ingeborg..

    This is the constant factor: Ingeborg points about 32-33° from the apparent wind, as indicated on the wind indicator. She does so in any wind speed on flat water. I have added a couple of degrees leeway in the diagram, so the apparent wind is set to just below 35°.

    In 7 knots true wind, she may touch 4.0kts.

    In 14kts true wind, she may touch 5.0kts.

    These are not accurate numbers, but they are still realistic.

    As can be seen on the diagram, where the wind strength (wind from north) is 7 and 14 kts, is that Ingeborg sails a lot closer to the true wind in stronger winds, but still outside 45°.

    My guess is therefore that it will take perfect conditions and an America's Cup helmsman to consistently tack Ingeborg inside 90°

    Arne

    (Get better resolution in Arne's sketches section 8 diagram 32)


    Edit:
    At 7kts wind , the tacking angle is thus 108 degrees and the VMG only 2.35kts.

    At 14kts wind, the tacking angle shrinks to 93 degrees and the VMG climbs to 3.44kts.

    Last modified: 11 Feb 2025 11:46 | Anonymous member (Administrator)
  • 10 Feb 2025 08:19
    Reply # 13461089 on 13226713

    Graeme, you are right. I forgot to mention that the baltic sea is mostly tide-free. There are currents in denmark due to wind-driven water movements, and during that gps track in the Schlei we had about 0.5 kn against us. However, in the skerries of the Swedish east coast, there are no currents.

  • 10 Feb 2025 07:29
    Reply # 13461086 on 13226713
    Anonymous member (Administrator)

    The angles on the GPS chart track are hugely affected by tide, of course, depending on whether the tide is favourable or unfavourable. I suppose the angles only have meaning, in an absolute sense, if there is no tidal flow. Would not mean much on our coast. But I forgot - there is little or no tidal flow in the fiords??


    Last modified: 10 Feb 2025 07:32 | Anonymous member (Administrator)
  • 09 Feb 2025 22:39
    Reply # 13461010 on 13226713
    Anonymous member (Administrator)

    Paul had been kind enough to let us use his upwind tacking video on the JRA YouTube site:

    https://youtu.be/Qh1Qx-rhfZ8?feature=shared

    many thanks, Paul

  • 09 Feb 2025 16:26
    Reply # 13460904 on 13457288
    Asmat, that's a very impressive track of Branwen in that Loch! I get the feeling that not only does a junk rig can be very able upwind, but also a junk rig gets sailed upwind - where normally one would be too lazy to bother and use the engine. 

    Arne, definitely there is some considerable deviation between heading and course. It's always worth asking for what is actually talked about :) Thanks for measuring the angles in Asmat's and my chart.

    However, I do not quite agree with just simple averaging. The amount of bad angles is considerable, as one does not always steer focused etc - those angles don't tell us anything about what the boat could do. How about using only the best 3 % (P03)? Didn't Alan Boswell in JRA issue #85 take a similar approach?

    By the way, Ilvy was reefed two panels down when recording that track in the Schlei fjord. There was even a foto taken:

    We managed to tack almost inside 90° (on gps track), when conditions where close to perfect. Have a look at those in the Kalmarsund, entering Paskallavik:


    It's just so much fun to tack upwind in those confined spaces :-)


    Cheers,

    Paul

  • 31 Jan 2025 16:34
    Reply # 13457423 on 13226713
    Anonymous member (Administrator)

    Ilvy’s and Branwen’s tacking angles look good to me. Remember, leeway is included in these figures, so Ilvy’s found average tacking angle of 97.5° and Branwen’s of 107° are in my view very good  for these boat types.
    I surely cannot tack my Ingeborg inside 90°, but she still points and tracks at least as well as the boats around us.

    When I read that someone are tacking inside 90°, I generally lean back and think “yeah, right”. What you see on the compass is not quite the same as what a GPS-tracker will show you, in slack waters.

    Arne


    (..see Arne's sketches, section 8-24...)

  • 31 Jan 2025 10:28
    Reply # 13457288 on 13226713

    That's an impressive tacking angle, Paul. 

    As an experiment, I recorded Branwen's GPS track while beating against a SW4 breeze the length of Loch Lochy, an enclosed freshwater loch, part of the Caledonian Canal. 

    I was pleased with this heavy centreboarder's performance under her home made sails and it goes without saying that none of the other 3 yachts that exited the lock with me at the NE end of the Loch bothered to put their sails up.

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  • 30 Jan 2025 17:36
    Reply # 13457011 on 13456808
    Anonymous wrote:

    Thank you, Mauro and Patrick!

    Yesterday, we've been invited to slide in a short presentation in an online seminar. It was the Trans-Ocean e.V. Micro-Seminar series, dealing about 2 h with sails and sail repairs when cruising. We were allowed to present three slides with less than 5 min of talk duration. Though not that much of a talk, however, the audience was huge counting about 350. We presented in short the - for us - major advantages of the junk rig: reefing fast and on any course, easy tacking, noiseless, relaxed downwind courses, ease of maintenance. In addition, we showed the drone shot (appended) of Ilvy going upwind in combination with one of her gps tracks.

    One sailor we met in Sweden while sailing was sitting in the audience, and he happily confirmed our great tacking angles, live, during the talk. His third-party description, together with the drone shot and the gps track, didn't let any doubts about the junk rigs upwind capabilities surface :-)

    Our impression from our talks at the Düsseldorf boat show was, that mostly only sailors joined that talks which were already kind of interested in the junk rig. But how to reach others, which never heard of the junk rig before? I think, yesterday was such a chance, as the junk rig was implemented into a seminar about bermudan rigs. We hope to have risen at least a bit of interest!


    Cheers,

    Paul


    PS: It was very nice to have another junk rigged crew within the audience: Taiko.

    Congratulations again Paul!

    Your drone footage and tracks are the best way to show how a junk rigged boat with cambered sail can work upwind.

    On the start line of the first GGR there was a junk rigged boat,  what a dream to see a second one  in the next edition of this race!!!

    She would for sure get a massive amount of attention…and perform good as well! 

    Cheers

    Mauro

  • 30 Jan 2025 12:22
    Reply # 13456841 on 13226713

    An impressive display of the effectiveness of combining a cambered junk sail with a hull design that is very efficient to windward.  Interesting drone footage. 

  • 30 Jan 2025 09:06
    Reply # 13456808 on 13226713

    Thank you, Mauro and Patrick!

    Yesterday, we've been invited to slide in a short presentation in an online seminar. It was the Trans-Ocean e.V. Micro-Seminar series, dealing about 2 h with sails and sail repairs when cruising. We were allowed to present three slides with less than 5 min of talk duration. Though not that much of a talk, however, the audience was huge counting about 350. We presented in short the - for us - major advantages of the junk rig: reefing fast and on any course, easy tacking, noiseless, relaxed downwind courses, ease of maintenance. In addition, we showed the drone shot (appended) of Ilvy going upwind in combination with one of her gps tracks.

    One sailor we met in Sweden while sailing was sitting in the audience, and he happily confirmed our great tacking angles, live, during the talk. His third-party description, together with the drone shot and the gps track, didn't let any doubts about the junk rigs upwind capabilities surface :-)

    Our impression from our talks at the Düsseldorf boat show was, that mostly only sailors joined that talks which were already kind of interested in the junk rig. But how to reach others, which never heard of the junk rig before? I think, yesterday was such a chance, as the junk rig was implemented into a seminar about bermudan rigs. We hope to have risen at least a bit of interest!


    Cheers,

    Paul


    PS: It was very nice to have another junk rigged crew within the audience: Taiko.

    1 file
    Last modified: 30 Jan 2025 09:09 | Anonymous member
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