Halyard Angle

  • 25 Jun 2022 19:53
    Reply # 12828820 on 12828422
    Anonymous member (Administrator)

    I’ve found it to be unwise to make too firm rules around the JR. I have made many ‘rules of thumb’ in my time, but these rules must sometimes be stretched. I have yet to make the perfect JR, and I don’t stress too much to reach perfection either, because then every sail would have to be designed from scratch, and after a first test sail has been constructed, test-sailed and assessed (..and then scrapped...), a second sail must be made to make it perfect. Luckily, I am quite good at accepting the good enough result.

    About that halyard angle: In my head that angle was between the halyard and a vertical line, simply because I just about only draw vertical masts. But OK, I may spell it out from time to time; halyard('s) angle from vertical.

    There are many noise factors around the choice of halyard angle, such as the length and angle of the yard, and also the chosen position of the halyard’s slingpoint on the yard.

    When I draw a new sloop JR for a boat I have not sailed, I often aim for a halyard angle of 15° if I am free to choose (..which I rarely am...). This angle lets the skipper shift the finished sail forward or aft until the helm’s balance is right. If it results in a 30° halyard angle, that is less than perfect, but it may be possible to live with it. The more I am unsure of the position of the sail centre, the longer I make the halyard’s drift between mast crane and slingpoint, to make room for a wider adjustment and still staying within the 5-30° halyard angle sector.

    With more experience with a boat, I can decide for a lower halyard angle and be safe that there is little need for adjustments.

    This happened after I had rigged my Ingeborg. She turned out to have too much weather helm, so the sail was shifted forward as much as I could without recutting the sail. Actually, the sail could well be shifted another bit forward, so when JRA-member Frederik Elslo asked me to design a rig for his sister-boat of Ingeborg, I drew up a new sail with a shorter chord.

    David’s idea of aiming for 10-20° halyard angle, makes sense to me from another reason. When the sail is fully up, it helps the YHP to peak up the sail. Remember, the sheet is doing its best to ‘un-peak’ the sail, in particular when close-hauled.

    This thread almost forces me to generate another one: Mast Rake. I have some opinions on that. Must see...

    Arne


    Last modified: 26 Jun 2022 10:47 | Anonymous member (Administrator)
  • 25 Jun 2022 05:00
    Message # 12828422
    Anonymous member (Administrator)

    Halyard Angle

    There appears to be no mention of this in PJR  (Practical Junk Rig by Hasler & McLeod) and I think it is a recent term coined by Arne but not clearly defined. It is a very useful concept in that it covers a number of aspects of junk rig geometry all at once. But the experts continue to use the term in the context of a “special case” and leave it undefined in the proper manner (not allowing for the “general case”).

    Sooner or later a DIY junk sail designer might make a calculation based on a misunderstanding, under-estimate the halyard angle, and the result might be less than ideal.

    Not the end of the world, but I am raising it as a minor issue because I have had the experience of dealing with a sail with a halyard angle which was too great, and I think it is important for future readers of the forum posts to be made clear as to exactly what this critter actually is, and why it is important. It should probably be defined unambiguously and added to the list of technical terms in the JRA “Vocabulary”, since it does not appear in PJR.

    Here are some examples of slightly loose use of the concept:

    In the “Are two masts too much on a Cape Dory 28” thread, David recently recommended:

    “•           Mast in a position that gives a halyard/mast angle around 10˚ - 20˚, so that the halyard is lightly pulling the sail forward against the LHP which opposes it (which  a vertical halyard doesn't, resulting in to-and-fro movement in a seaway, and possible chafe)”

    In an excellent little thread “Mast height above yard” Arne wrote: “If the yard is set with a very low angle (peaking angle), there must be enough drift to prevent the angle between the mast and the halyard from becoming too wide…”  Quite right, as I have found, but…

    Leading to Darren, in the “Flat, Hinged or Cambered” thread  coming to the slightly erroneous conclusion: “2)  The halyard should be as close as practical to being in line with the mast when the sail is at full hoist.  I think David Tyler and Arne use a guide that the halyard should be less than 30o to the mast centre-line, but less is better.  The lower this angle the lower the forces for getting the sail to set nicely, you've been an advocate of this approach Paul.”

    And Paul letting it pass: “Yes, you have got it…

    Well, in my opinion, not quite.

    I notice the fore mast on Darren’s proposed rig has a forward rake. That can alter the picture.

    The halyard angle should be defined as the angle between the halyard and a vertical line thought the masthead halyard block(s), when the sail is at its maximum hoist.  Referring to the mast or the mast centre line is loose use of the concept, which muddies an understanding of what is actually at play here.

    The forces applied by the halyard are best resolved in two directions: a vertical component which balances the vertical force of gravity (the primary function of the halyard) and a residual horizontal component (which is useless for hoisting the sail, should be kept to a minimum, but in some instances might still have a useful other role to play if it is not too great). The mast or mast centre line have nothing to do it. Sometimes the mast itself is designed to be vertical – that is merely a happy coincidence: the special case.

    This is not arguing about semantics. If Joe Bloggs has a foremast with a forward rake of 6 degrees, and designs a sail plan with a “mast/halyard” angle of 20 degrees on the assumption that he is within David T’s guidelines, then unfortunately his actual halyard angle will be 26 degrees and he might encounter some problems with the rig. From my experience with a low yard-angle rig, I think a halyard angle of 26 degrees is probably starting to get a little too high. The lower the better, and I think David’s 20 degrees is a better rule of thumb for maximum (true) halyard angle. I seem to recall somewhere Arne referring to 18 degrees.

    The major problem occurs before the question of “getting the sail to set nicely” even arises.

    This point has not been adequately emphasised.

    If the halyard angle is too great, the last few feet of hoisting the sail becomes intolerably difficult. Not only is the halyard now coping with the full weight of the bundle, but it’s angle to the vertical is progressively increasing towards its maximum – the “halyard angle” – and in turn, the effort being applied to the halyard is progressively contributing less towards hoisting the sail, and progressively more towards forcing the yard to move forward. It’s not a problem when hoisting just up to the first reef (at that point the halyard drift is still great and the halyard angle is still small) – it’s getting that last panel up which becomes a battle, and then undue effort is also required to force the yard back to its proper position.

    In short, it’s a rig with an un-harmonious relationship between masthead height, halyard drift, and yard-angle/sail-balance - which is summed up very neatly by the single elegant concept: “halyard angle too great”. It has nothing to do with the mast centre line. It may be understood directly as the result of the vertical component of halyard force diminishing and the horizontal component of the halyard force increasing, near the last part of the hoist.

    One cure is to increase the height of the mast and hence lengthen the halyard drift (as I did, and it fixed it), but this is not easy to do retrospectively, in most cases. I think I am not the only one to have encountered this problem. In a more harmonious combination of the above variables (masthead height, halyard drift, and yard-angle/sail-balance), the sail is easier to hoist, and the forward seeking tendency of the yard is gentle. In some rigs (including now my inshore, sheltered-waters rig) no special parrel is needed to tame the yard,  it sits nicely with just the restraint of the other running rigging. Paul sums it up like this: “…you want the sail to "hang" from the halyard attachment point in a manner that has it nearly where you'd want it to be. The closer you can get the sail to just naturally position it's self in the needed position, the easier it will be to get the sail to set well…” and adds that his sail too, needs no special parrel on the yard to achieve this happy state. Though I note with interest what might be wise advice from David in that first quote at the beginning of this, in which I think he is saying that a gentle forward seeking tendency of the yard may not be such a bad thing, as it can be countered by a lightly loaded parrel, thus locking the yard somewhat and helping to prevent chafe in an off-shore heavy-duty rig.

    May I request that the experts adhere a little more rigorously to what appears to be the more general geometric concept of “halyard angle”, thus emphasising and clarifying its true importance, and as an aid to better understanding?


    Last modified: 25 Jun 2022 11:23 | Anonymous member (Administrator)
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