Flat, hinged or cambered?

  • 05 Jul 2021 11:29
    Reply # 10728865 on 461931
    Anonymous member (Administrator)

    How to keep the THP and YHP from fighting each others.

    One fault I made on Johanna, was to cut the mast too short. This, combined with the need to set the sail as far aft as possible, lead to very high tension on the THP and YHP. As soon as I could reef the sail, these problems disappeared.

    When rigging Ingeborg, I was more generous with the mast length, which let me move the halyard 5% aft of the middle of the yard, and the YHP 2/3 up. This reduced the tension in the YHP-THP quite a bit. However, the sail was still set with low balance. ‘Luckily’ this resulted in too much weather helm, so the sail was soon shifted forward, somewhere between 15 and 20cm. This again reduced the tension in these parrels. Now they are reduced to quite lightly loaded trimming lines.

    Then Ketil Greve took contact last autumn, in need for a sailplan for his new Kelt 8.50. The mast position dictated a sail with a high balance, around 21-23%. To achieve that, I had to remodel the top three panels of the AR=1.90 master sail so the yard ended at a 60° angle.
    As a result, Ketil, who made the sail himself, now sets it without needing a THP at all. I guess the upper batten parrel limits the forward movement. The halyard is next to vertical and the YHP is attached well aft of the middle. I sailed with Ketil after that little photo session. The sail went up and came down easily, and the lightly loaded Hong Kong parrels ensured each panel set well. A true Instamatic rig.

    My conclusion is that the finer the halyard angle is, and the closer the CG of the sail sits to the mast, the lower get the forces in the parrel pair; the THP and YHP.

    And yes, the top panels set just fine, both with 7-up and when 3-up...

    Arne


    F
    rom a little photo-session 18th June 2021


    Last modified: 05 Jul 2021 12:18 | Anonymous member (Administrator)
  • 05 Jul 2021 11:16
    Reply # 10728832 on 461931

    Arne,

    This is simple geometry and trigonometry, and I'm not going to insult your undoubted intelligence by giving lessons in it. However, you might well read chapter 2, page 6 of Slieve's writings, where he describes how he developed the SJR planform by getting his model to hang as naturally as possible:

    "One clear observation was that when the yard was correctly set up the sail and battens simply hung down like a curtain with no significant forces to worry about. 

    One clear feature was that the pressures on the battens were lower with the low angled yard and high sail balance rig compared with a high peaked Hasler-McLeod rig." 

    As well as the stresses in the rig, there are the mental and physical demands on the stamina of the crew to consider. By your own admission, your sailing mileage on each outing is trivial, and so the work involved in keeping your rig set well makes trivial demands on your stamina. I ask you to accept that sailing continuously, day after day, through squally and variable conditions, one seeks to reduce those demands.

    No, of course the rigs of Zebedee and Mingming II don't need to be reworked, so long as their skippers are content with them. Martin is not.

  • 05 Jul 2021 10:08
    Reply # 10728736 on 461931
    Anonymous member (Administrator)

    Paul and David.
    Could you elaborate a bit on where you have lowered the stress in the rigs with the profile (planform) you prefer, compared to the sails I design, with 60-70 degrees full-length yard (..basically the standard Hasler-McLeod sails with added camber...)? Should Zebedee and Mingming II have their rigs remade?

    Arne

    Last modified: 05 Jul 2021 10:13 | Anonymous member (Administrator)
  • 05 Jul 2021 08:17
    Reply # 10728460 on 10728437
    Paul wrote:
    LC's foresail is still the best setting sail I ever did and the variants that I've done based on it have been similarly successful. Low stress and sets well and possibly even more importantly, it was easy to get it set well.
    And that's the bit that I'm struggling to get Arne to understand and accept!
  • 05 Jul 2021 08:02
    Reply # 10728437 on 10728381
    Anonymous wrote:
    Paul wrote:
    David wrote:

    Here’s a rough and ready approximation of what I’d do for a new suit of sails for Taiko, starting with a clean sheet. The main yard is 4m instead of 5m, at an angle of 45˚ - 50˚ instead of 70˚. Similarly, the fore yard is 80% of the length of the old one. As you can see, this does not reduce the area. To keep the halyard close to the mast, the sail is rotated through 2˚ - 3˚ about the tack. This brings several more benefits with it, as the angles of THP and LHP are much improved, making them much more effective and less heavily loaded. The yard is lighter and under less bending load. Also, the centre of area moves forward, which helps with reducing the weather helm. I’ve put in two unsheeted battens so that the compression and bending load on each is reduced. These battens would probably not be hinged, but the lower ones would have hinges at their centre, at an angle of articulation of +/-12˚, with just a little barrel camber in the sail panels forward of the hinges, but not aft of them. 


    Those are of course pretty much LC's foresail.... I'd not put three upper panels in the foresail. Two panels is enough and it worked very well for LC.

    Indeed, that's true, Paul. I think it's because we were both designing a rig intended for extended passage making, with lower stresses on the rig and lower demands on the stamina of the crew in our minds. Things that I don't believe to be high on Arne's priority list.

    I agree, two head panels would probably have been enough for the foresail, except that aesthetically, I prefer both sails to look the same. Just possibly the three smaller head panels might be a reassurance when running under them in a F9, though.

    Agree, though I do think that two panels for the foresail is acceptable. Certainly the fact that the two sails are slightly different would not have perturbed the Chinese :-)


    LC's foresail is still the best setting sail I ever did and the variants that I've done based on it have been similarly successful. Low stress and sets well and possibly even more importantly, it was easy to get it set well.

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  • 05 Jul 2021 07:37
    Reply # 10728381 on 10727295
    Paul wrote:
    David wrote:

    Here’s a rough and ready approximation of what I’d do for a new suit of sails for Taiko, starting with a clean sheet. The main yard is 4m instead of 5m, at an angle of 45˚ - 50˚ instead of 70˚. Similarly, the fore yard is 80% of the length of the old one. As you can see, this does not reduce the area. To keep the halyard close to the mast, the sail is rotated through 2˚ - 3˚ about the tack. This brings several more benefits with it, as the angles of THP and LHP are much improved, making them much more effective and less heavily loaded. The yard is lighter and under less bending load. Also, the centre of area moves forward, which helps with reducing the weather helm. I’ve put in two unsheeted battens so that the compression and bending load on each is reduced. These battens would probably not be hinged, but the lower ones would have hinges at their centre, at an angle of articulation of +/-12˚, with just a little barrel camber in the sail panels forward of the hinges, but not aft of them. 


    Those are of course pretty much LC's foresail.... I'd not put three upper panels in the foresail. Two panels is enough and it worked very well for LC.

    Indeed, that's true, Paul. I think it's because we were both designing a rig intended for extended passage making, with lower stresses on the rig and lower demands on the stamina of the crew in our minds. Things that I don't believe to be high on Arne's priority list.

    I agree, two head panels would probably have been enough for the foresail, except that aesthetically, I prefer both sails to look the same. Just possibly the three smaller head panels might be a reassurance when running under them in a F9, though.

  • 05 Jul 2021 01:07
    Reply # 10727295 on 10725161
    Anonymous wrote:

    Here’s a rough and ready approximation of what I’d do for a new suit of sails for Taiko, starting with a clean sheet. The main yard is 4m instead of 5m, at an angle of 45˚ - 50˚ instead of 70˚. Similarly, the fore yard is 80% of the length of the old one. As you can see, this does not reduce the area. To keep the halyard close to the mast, the sail is rotated through 2˚ - 3˚ about the tack. This brings several more benefits with it, as the angles of THP and LHP are much improved, making them much more effective and less heavily loaded. The yard is lighter and under less bending load. Also, the centre of area moves forward, which helps with reducing the weather helm. I’ve put in two unsheeted battens so that the compression and bending load on each is reduced. These battens would probably not be hinged, but the lower ones would have hinges at their centre, at an angle of articulation of +/-12˚, with just a little barrel camber in the sail panels forward of the hinges, but not aft of them. 


    Those are of course pretty much LC's foresail.... I'd not put three upper panels in the foresail. Two panels is enough and it worked very well for LC.

    1 file
  • 04 Jul 2021 20:42
    Reply # 10726351 on 10712425
    Anonymous member (Administrator)
    Martin Simmons wrote:

    Arne,

    Presently I am seeking advice as to what may be alternatives for Taiko. No decision will be made until we get back to NZ where the availability of materials will be better than in French Polynesia .

    Certainly the wooden yards and battens need to be replaced and, if we are to retain cambered panels, some reworking of the rig will need to be made at this juncture. We liked the way Tystie’s  articulated battens popped backwards and forwards with each tack. I am uncertain if our masts are tall enough to use such system without the loss of sail area, which cannot be afforded. We will have to wait and see what those of greater knowledge consider best suited to our mast configuration.

    One thing is certain; we must have camber to sail well.

    Martin

    Martin.
    I wonder if you would let us know more details about your problems with the present sail? The couple of photos of your boat seem to indicate that the rig is not far for OK. However I am unsure of how you have rigged the YHP and LHP (THP?), how the sheets are configured and if you have now fitted Hong Kong parrels.
    It would be most useful if you also could show us the sailplan.

    I think the choice of using wood for boom, battens and yards is an unlucky one, so when you get access to aluminium, I suggest you switch to that material. Wood is too heavy, stiff and brittle for battens (..which I’m sure you have found out by now...).

    Btw, what sort of keel and rudder has your boat?

    Arne


  • 04 Jul 2021 13:22
    Reply # 10725161 on 461931

    Here’s a rough and ready approximation of what I’d do for a new suit of sails for Taiko, starting with a clean sheet. The main yard is 4m instead of 5m, at an angle of 45˚ - 50˚ instead of 70˚. Similarly, the fore yard is 80% of the length of the old one. As you can see, this does not reduce the area. To keep the halyard close to the mast, the sail is rotated through 2˚ - 3˚ about the tack. This brings several more benefits with it, as the angles of THP and LHP are much improved, making them much more effective and less heavily loaded. The yard is lighter and under less bending load. Also, the centre of area moves forward, which helps with reducing the weather helm. I’ve put in two unsheeted battens so that the compression and bending load on each is reduced. These battens would probably not be hinged, but the lower ones would have hinges at their centre, at an angle of articulation of +/-12˚, with just a little barrel camber in the sail panels forward of the hinges, but not aft of them. 


    1 file
  • 30 Jun 2021 01:24
    Reply # 10712425 on 461931

    Arne,

    Presently I am seeking advice as to what may be alternatives for Taiko. No decision will be made until we get back to NZ where the availability of materials will be better than in French Polynesia .

    Certainly the wooden yards and battens need to be replaced and, if we are to retain cambered panels, some reworking of the rig will need to be made at this juncture. We liked the way Tystie’s  articulated battens popped backwards and forwards with each tack. I am uncertain if our masts are tall enough to use such system without the loss of sail area, which cannot be afforded. We will have to wait and see what those of greater knowledge consider best suited to our mast configuration.

    One thing is certain; we must have camber to sail well.

    Martin

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

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