Heeling..

  • 11 Apr 2021 12:12
    Reply # 10298565 on 10291718
    Anonymous member (Administrator)
    Paul wrote:

    Thanks guys.

    This concurs with my own experience - on a reach to a run.
    Close hauled I’m heeling just as much as the pointy rig, though maybe only because I was holding onto full sail longer - as Slieve has said SJR tends to bring out the hooligan in you.

    Incidentally, I thought that these results did seem to suggest that SJR sailed a LITTLE closer to the wind than some other Junk Rigs ?


    Paul,

    frankly, I think those numbers are of little value since the tests have been conducted on different boats.
    Alan Boswell wrote 8. Oct. 2020:
    «You could conclude from this that in normal sailing conditions, and taking account of both tacks, most of the junks make ground to windward at between 75% and 80% of the speed of the bermudan rig.»

    What is for sure is that if my junkrigs had been 20-25% slower to windward than the Bermudan rigs, then I would have dropped the JR a long time ago. My observations indicate that my junkrigged boats perform  only 0-5% worse than those with pointy rigs.
    This little test race is a good indicator, me thinks.

    Arne

    (PS: To improve Ingeborg after that race, I slackened the sail along the battens, so now I measure 8% camber. More important; I made a wind indicator which makes it much easier to hit and maintain the best tacking angle)

    Last modified: 11 Apr 2021 12:25 | Anonymous member (Administrator)
  • 10 Apr 2021 21:25
    Reply # 10295808 on 10290459

    Arne I am not sure why PJR’ warns against squaring away beyond 90 degrees but I don't think, with SJR at least, that this puts any compression in the battens. (Note the SJR normally has a quite different batten parrel and sail-setting arrangement from the other rigs - perhaps this has something to do with it).

    My SJR rig was set up (without intention) with an extra long mainsheet (two mainsheets, actually) and by accident after a gybe the sheets were let fly and the sail swung until facing in completely the wrong direction, which caused some consternation for moment, and a bit of a tangle up trying to sort things out again. But no harm done and no forces on the battens. Alan (Zebedee) will remember - he was on the helm at the time!) We all agreed that a knot must be tied in the mainsheet to make sure that never happens again - I still haven't got around to it.

    I can't make the same claims as Slieve regarding windward performance, with my home-made sail, and have no way of knowing, all I know is it goes well enough. I matched myself recently against a fleet of Farr 6000s, bigger and much more powerful boats than mine - and I felt they were a bit faster than me to windward - not by much. Downwind I walked past them with ease, and even one which was carrying a spinnaker made some ground on me but after a couple of hours had still not overtaken.

    The windward roll is real, not theoretical. I knew about it from reading Slieve's notes, but did not take it very seriously until a situation one day,  on a broad reach, running down a narrow channel and into a protected anchorage - I was sitting to windward, and as the channel forced me to head more and more to leeward, paying out the sail as I turned, I realised that I was almost there and rather than gybe, which was becoming inevitable, I let the sail go out further than 90 degrees, rather abruptly - and the result was an instant, quite vicious  roll to windward - and sitting on the windward side I was unbalanced and could not scramble back into the cockpit, got a good close look at water running over the windward deck, while holding on as best I could to avoid going over the side. In a small boat you need to be a bit careful about that situation.





    Last modified: 10 Apr 2021 21:30 | Anonymous member
  • 10 Apr 2021 13:57
    Reply # 10294596 on 10290459

    Oh dear! OK Arne, here I pop. This could be a long winded answer.

    Early western junk rigs were reported to heel less, even when they had more sail area than their Bermudan cousins. This is not surprising as the flat airfoil produces very little lift at the low angle of attack before knife edge separation produced a separation bubble behind the luff . That is, assuming the luff was tight and straight, which it often wasn't. From what I observed I believe that flat sails were routinely oversheeted to get high pressure on the windward side and therefore stalling and not generating the much greater low pressure force on the lee side. The resultant lift/ drag ratio would be very low so downwind performance would be good, but upwind poor, as we all know.

    Arne demonstrated that putting camber in the sail would increase the L/D ratio and give greater drive on all point of sail. The SJR was my attempt to analyse and improve the windward performance, and to simplify the ever increasing spaghetti controls apparently required to set the rig and to shift it fore and aft on various points of sail. I was looking for a low stress KISS rig.

    When I owned Poppy I did not meet a junk rigged boat that I could not beat, except when Bertrand's small cat was on the reach as by being unballasted was not restricted to waveform speeds so could reach at over 10 knots. I always matched similar cruising rigged Bermudan boats to windward and even when they flew chutes off the wind, but of course could not beat the expensively prepared racing brigade who have had years of development under their belts. I'm not sure what is happening in the performance tests, but probably due to my early training in experimental work I hold little reliance on tests in uncontrolled conditions and which have the results 'factored'. That is why I elected to use the Island Race to compare rigs, and am happy with the performance when sailing alongside comparable Bermudan boats. Overall position in the Island races requires tidal knowledge beyond my experience. (I approached one potential winning helmsman in an effort to get good junk publicity, but he wanted a £1,000 fee for his services!)

    Going back to heeling, the SJR does heel less than Bermudan, but only in certain situations. To windward there should be no difference, and that is borne out in practice. As the sheets are eased the L/D of the Bermudan rig starts to fall off, and the ratio of forward drive to leeward heeling force will impair the performance. As the SJR sheeting is fixed as the rig rotates the L/D does not increase so the boat accelerates when the total force moves forward as it bares away and does not heel as much as the Bermudan boat. This is good up to squared off and the wind about 135° from the bow, at which point it becomes clear that the total thrust force it forward of 90° to the rig and to windward, and which can only be explained by the inbuilt jib sheeting angle which proves the efficiency and importance of the cambered jibs. Arne has correctly identified this situation, and is right in saying that I would not set the rig greater than squared off. Even then in gusty conditions it was advisable to sheet in a little to stop the windward total forces. The best performance is obviously with the total thrust is straight ahead.

    It is a major regret that Arne did not get to sail Poppy with me as I believe we would have gained from the resultant analysis (and possibly arguments). I have been lucky enough to sail Johanna on two occasions with him, and both were great educational experiences for me.

    I agree that the 'lesser heeling' on the reach was probably what brought out the hooligan in me. Lets face it, if the boat doesn't heel too much, why reef? Just let the forward drive make the boat go faster. The rig allows for smaller area for equivalent performance, so why reef, unless you want to slow down.

    'nuff said.

    Cheers, Slieve.


    Last modified: 10 Apr 2021 19:20 | Anonymous member
  • 09 Apr 2021 20:45
    Reply # 10292370 on 10291897
    Anonymous member (Administrator)
    Nils Myklebust wrote:


    Could it be such sheeting far out that Poppy experienced when it heeled to windward?   


    I hope Slieve will pop up here soon. However, I very much doubt that he used to square out Poppy’s sail “past square”. I guess the sail would then run out of sheet very soon, and a stop-knot would be there to prevent that from happening.

    PJR’ warns against it because it would result in too much compression in the battens.

    Arne
  • 09 Apr 2021 18:46
    Reply # 10291897 on 10290459

    Regarding heeling to windward:  In an old Newsletter (which I can't find now) I "doodled" a sketch showing showing wind from (say) 45° behind and the sail sheeted out considerably more than 90°.  Then the resultant force on the sail will have a component to windward..!

    The purpose was to reduce the heel, and at the same time have a high lift factor on the sail giving a maximum force forward, but afterwards I realized what a bad idea it is.  It gives such an unstable condition, where only a small yaw makes the boat roll and the pressure on the sail will come on and off.  Totally unmanageable, and maybe this is the reason why PJR does not recommend to sheet out more than 90°.

    Could it be such sheeting far out that Poppy experienced when it heeled to windward?   


  • 09 Apr 2021 17:36
    Reply # 10291718 on 10290459

    Thanks guys.

    This concurs with my own experience - on a reach to a run.
    Close hauled I’m heeling just as much as the pointy rig, though maybe only because I was holding onto full sail longer - as Slieve has said SJR tends to bring out the hooligan in you.

    Incidentally, I thought that these results did seem to suggest that SJR sailed a LITTLE closer to the wind than some other Junk Rigs ?

  • 09 Apr 2021 14:36
    Reply # 10291115 on 10290459
    Anonymous member (Administrator)

    Yes, this sounds odd, Scott, but I don’t think it is, after all.

    Remember, on an ordinary, cambered junk sail (or Bermuda mainsail without a jib), the sail is sheeted to the centreline  -  of the boom or battens. The resulting force on that sail points somewhere around 90 degrees to the boom and battens. For this reason, a standard junk sail  (or that single Bermuda sail) must not be sheeted too closely to the boat’s CL. On my Ingeborg, which is a reasonably weatherly vessel, the clew of the boom rides just inside the gunwale when close-hauled.

    The jiblets of a SJR or the jibs of an Aero Rig (or on Paul McKay’s Aerojunk) are sheeted to a fixed angle to the boom (12°?). The force-vector from the jib will thus point several degrees forward of 90 to the boom. The combined force vector from jiblets and main section of the SJR will therefore also point more forward than on the plain junksail.

    Then, if you square out the boom and battens to 90°, you should expect the boat to heel ‘to windward’ when running straight downwind.

    This may lead one to think that the SJR is more close-winded than a standard, cambered JR. I am not so sure about that. The SJR has by now been tested quite thoroughly against other boats. It has not shown any significant improvement in windward performance. I haven’t sailed with a SJR, but I guess these sails will be sheeted closer (more closely???) to the boat’s CL. than standard junks, when close-hauled.

    My armchair guess is therefore that the SJR-s main advantage is an increased resistance to stalling which possibly could result in better drive on a reach.

    Arne

    PS  -  update, 10th April:
    I forgot to mention two or three more advantages with the SJR.

    • 1.      The sheet forces will be considerably lower with a sail with 33-35% balance than with one with a balance of 12-17%. On small sails, up to twenty-some square metres, this is not so important, but if the sail area approaches  forty, fifty or sixty square metres, a SJR will be much easier to sheet, with less use of winches, and lower sheet purchase (..say 3:1 instead of 5:1...)
    • 2.      The much higher balance ratio of the SJR will also ensure easier steering downwind, so one may get away without fitting a bigger rudder when converting to (S)JR. The SJR will simply be closer to a squaresail  -  and that can bring out the Hooligan (or Viking) in the helmsman.
    • 3. The loads on the battens may even be lighter on a SJR (right, Slieve?).

    A.


    Last modified: 10 Apr 2021 17:31 | Anonymous member (Administrator)
  • 09 Apr 2021 13:46
    Reply # 10290921 on 10290459

    That makes sense to me, Arne.  I'm also thinking of the description Slieve wrote up about Poppy, with the Split Rig, actually heeling to windward in puffs while the Bermudians around him did the normal heel to leeward.  That's an odd phenomenon. 

  • 09 Apr 2021 11:12
    Reply # 10290520 on 10290459
    Anonymous member (Administrator)

    Paul,
    I’ve heard that too. It was said mostly in the days of flat junk sails. With a flat sail, one would ease the sheet a little in a blow, and thus depower the sail, without anyone seeing any difference in the sail. The downside was that you would then go nowhere slowly. Doing the same on a cambered junk sail, will give the same de-powering effect, but now with a visibly ‘deflated sail’.

    When I set my first cambered junk sail (hinged battens  in 1991), the power of the rig rose a lot. When close-hauled this meant more heeling, just about the same as with the original Bermuda rig. The reward was close-hauled performance, about in the Bermuda class.

    On a close, beam or broad reach I still sail more upright than with a Bermuda rig. The reason is that I can let out the sail better while keeping the same camber. If you let out the sheet of a Genoa, it only gets baggier and baggier, and thus heels the boat more. My guess is that a Bermuda rig with the staysail on a boom would sail more upright on a reach, more like the JR.

    Clear as fog, right?
    Arne


  • 09 Apr 2021 10:27
    Message # 10290459

    Hi Everyone,

    I’ve often heard the assertion that Junk Rig heels less than Bermudan, can anyone please explain why this is so..

    ta

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
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