Sail Balance - Position Relative to Mast

  • 09 Oct 2018 21:14
    Reply # 6715049 on 4793670
    Anonymous member (Administrator)

    Hi Christopher, welcome aboard!

    I see you have listed three questions. I agree with David ‘s answers to all of them.

    However, I have one more point:

    RUDDER
    I strongly recommend that you take contact with JRA-member Paul J Thompson, and let him advice you on how a proper rudder should be made (vertical, NACA 00xx section, 20% balance, endplates at both ends). Note: Don't fill the gap between the keel and the new rudder.

    Paul’s rudder (.. I hereby call it... The Thompson Rudder) is a break-through in heavy JR designs. Unfortunately, very few have grasped how good it is, just as it took a long time before the JR world (in the West) started to see the point in cambered sails.

    Good luck!
    Arne


    Last modified: 09 Oct 2018 21:16 | Anonymous member (Administrator)
  • 09 Oct 2018 19:43
    Reply # 6714919 on 4793670

    Hello Christopher, and welcome to the JRA. I see from your profile that you're not lacking in seafaring experience, to put it mildly! You'll probably have a lot of questions that are specific to your boat, so perhaps you could start a new topic with a title including the boat's name?

    1. 20% balance is getting towards the top end of the range, but shouldn't overbalance and snatch, I don't think.  I'd go for less if it were possible, but even if you went back to the larger main and smaller mizzen, it wouldn't shift the CE very much further forward.  However, sailing Tystie with ketch rig, I was very much aware that the mainsail was doing most of the driving, and the mizzen was there mostly to adjust the overall helm balance by reefing earlier than the main as the wind got up. You don't say what overall lead you designed, and I don't know what helm characteristics the Wylo II has, but I'd expect it to be similar to Tystie in developing substantial weather helm when heeled. Looking at the drawing of the junk rigged Wylo II in VOASI, I think I'd prefer to stick with that distribution of sail areas, correcting the design flaws in the sails themselves which you've identified. I hope that Annie will chime in on this, as she has sailed many ocean miles in a gaff rigged Wylo and also a rough passage in a junk rigged Wylo rigged to Nick's sailplan.

    2. Kurt's mehitabel is quite easily driven, which is why, I think, he can get away with flat sails; whereas the Wylo II is a much chunkier hull, and will need enough power in the sails to push through the seas. I'd have 8% or even 10% camber in the parallelogram panels, decreasing in the upper panels but never totally flat. Even if there's just a little rounding on the upper and lower edges, it helps to keep the luff and leech straight and the middle of the panel not starved.

    3. Roger Taylor's method of "hingeing' sail panels together is a good one, and there are some youtube videos in which he says he's very satisfied with performance. But I do think that Jami Jokinen's take on this method is further good step forward, with less potential for air leakage from windward to leeward side. It's a labour-intensive way of making the batten arrangements, but quite an effective one. Where it scores most, in my opinion, is on larger sails. Here, the sheer physical effort of shifting a near-complete sail around the loft floor and under the sewing machine would cause me to consider making it in two or three sections, joined by these hinges, but using one of the quicker methods elsewhere. On smaller sails, there's still a reason to use the method if the sail must be made in a confined space.

  • 09 Oct 2018 17:01
    Reply # 6714642 on 4793670

    Apologies for reviving an ageing topic, but it kind of fits my range of enquiries.  Feel free to redirect me to a different thread if you like.

    Whilst I have the attention of all the folk whose learned discourses I have been frantically reading, I'd like to ask a few queries related to rig design.

    I'm a (brand) new member, although I've been dipping in and out of the JRA site for a while, and trying to make sense of PJR (difficult in Kindle format - paper copy's in the post).  I'm in the process of acquiring a bare hull for a Wylo II which has been under construction since the 80s.  It has been configured as the junk-rigged version, which suits me perfectly as I've been converted to the benefits of the rig for single-handed cruising (as distinct from my current gaff ketch - a beauty, but can be hard work).  I always viewed Nick Skeates' original junk ketch design (and again, feel free to put me right) with a slightly raised eyebrow, as there are a few things which strike me as somewhat unusual - aft-raked masts, different sized lower parallelogram panels (a large lower panel getting progressively smaller further up), and very little clearance between the main and mizzen, which to my eye would dictate a double-sheeting system for the main.

    The first item has already been rectified, as the original builder of the hull has already altered the positions of the mast steps to make the masts vertical (with Nick's approval, I noted when looking through old correspondence, and his admission that junk rig is not his area of expertise - an admission which he repeated to me when I met him recently).  The second is no big issue to solve by building a sail with equal sized panels.  The third has caused me to experiment with a different combination of the two sails' relative areas and positions whilst not moving the mast positions (which although at the current stage of build would not be impossible to change, I'd rather not start cutting out perfectly good steel if I can avoid it.

    I have come up with a rig using the standard H&M planform, making the mizzen slightly larger and the main slightly smaller, both at an AR of 2.2, but in order to gain the separation between the sails (using Arne's recommended 1m, which ties in fairly well with the H&M formular), I have had to give the main a balance of 20% chord, which makes for about 17% area.  The mizzen has a slightly less extreme balance of 15% chord.  As such the CE is virtually coincident with Nick's original on the F&A plane, but a little higher.  This is still lower than the gaff cutter's CE but I have to bear in mind the extra weight of two masts, battens etc.  I don't want the CE (or C of G ) to be too high as it is the centreboard version, therefore more susceptible to weight aloft, which I intend to mitigate by using hollow masts.

    Sorry for the lengthy preamble: my questions are as follows...

    1.  Would the balance as stated above be considered acceptable in the normal run of JR design?

    2.  I would like to camber the sails to improve light wind windward performance (having ruled out the split cambered rig as I don't think it would work without moving the masts), although have read Kurt Jon Ulmer's article on his set-up on Mehitabel and am encouraged by his thoughts on flat-cut sails, so am considering a compromise of a fairly light camber (say 6% on the main and 4% on the mizzen) on the parallelogram panels, and flat-cut top panels.  What are the readers' thoughts?  My ultimate aspirations are towards long-distance cruising, although I'm likely to spend a few years around NW Scotland, my current cruising ground, until I thoroughly prove the boat.

    3.  What thoughts do people have on the sail on Roger Taylors' Mingming 2, and how it is put together (seperate, cambered, lower panels, each with a loose foot held to the batten with webbing loops?  Has anyone heard any reports of how it performs?

    As a newby keen to get the best out of his new boat, I'd be glad for any input, without starting a new war of words...

  • 15 Sep 2017 21:59
    Reply # 5262879 on 5262717
    Anonymous
    Richard Brooksby wrote:
    Michael Moore wrote:

    So, rather than go off on a series of modifications, having of course determined that the Junk sails have the same lead as the original Bermudan ones, we should ask if excessive weather helm is due to a hull form that is not designed to sail on its ear?

    For what it's worth the Coromandel has the same hull as the Corribee, and was surely designed to sail on the heel, given its shaped keels.

    So far I have found that the advice to let the sail out then pull it in just a little does not apply. That just causes me to go very slowly. Tammy goes fastest when properly close hauled, on her ear. But then you get the weather helm.

    To me weather helm means it’s time to reef. How about you.

    I can reduce weather helm by reefing in the conditions I mentioned, but also speed. I have found no really good combination of reefing, sheeting, and weather helm. I conclude that I have a moderate rig problem. Does that seem valid?

    I think we have a 'not enough draft in the sail' problem! For sure if you pull a flat sail in tight it will be sailing stalled, giving a lot of heel and with it weather-helm. Do this with a pointy sail and you get the same result. In that case however some of the force (drive) is forward. The angle of attack with a flat sail is about 3 degrees, any more and it will stall. If we are running it does not matter if the sail is stalled. If we are reaching it matters less. To windward, 3 degrees attack or it is as you say! 
  • 15 Sep 2017 20:02
    Reply # 5262717 on 5260832
    Michael Moore wrote:

    So, rather than go off on a series of modifications, having of course determined that the Junk sails have the same lead as the original Bermudan ones, we should ask if excessive weather helm is due to a hull form that is not designed to sail on its ear?

    For what it's worth the Coromandel has the same hull as the Corribee, and was surely designed to sail on the heel, given its shaped keels.

    So far I have found that the advice to let the sail out then pull it in just a little does not apply. That just causes me to go very slowly. Tammy goes fastest when properly close hauled, on her ear. But then you get the weather helm.

    To me weather helm means it’s time to reef. How about you.

    I can reduce weather helm by reefing in the conditions I mentioned, but also speed. I have found no really good combination of reefing, sheeting, and weather helm. I conclude that I have a moderate rig problem. Does that seem valid?

    Last modified: 15 Sep 2017 20:09 | Anonymous member
  • 14 Sep 2017 23:28
    Reply # 5261325 on 4793670

    Arne and Chris, thanks for writing such good recommendations for the Split Junk Rig.

    Regards from (biased) Slieve.


  • 14 Sep 2017 19:38
    Reply # 5261022 on 4793670
    Anonymous member (Administrator)

    Michael

    your reasoning sounds ok, apart from  two points:

    ·         If you are to sail more than a mile from shore, you are no longer free to decide the sea-state. If the boat is rolled about more than just a bit, an unbalanced hull with a small rudder will be hard to steer with any rig.

    ·         One may position the CE of the sail perfectly for close-hauled sailing, only to find that the weather helm increases as one bears away on a reach. This can be felt with the BR, but to a much stronger degree with a sloop JR. This is because much of the sail moves outside the boat. My guess is that Slieve’s Split JR is the best in keeping the boat in balance on a reach and run. On a Coromandel, with the mast in the original position, I would have gone for the SJR.

    Arne


  • 14 Sep 2017 19:32
    Reply # 5260999 on 5260832
    Michael Moore wrote:

    I have been thinking about the ideas and opinions expressed on this thread and it seems that we may be guilty of a category mistake.

    Some boats are designed to sail on their ear. The Folkboat and its derivatives such as the Twister, which I have owned, for example. Other well known designs which I had the misfortune to sail when I was a delivery skipper are reluctant to do this and require continuous attention to reefing.

    So, rather than go off on a series of modifications, having of course determined that the Junk sails have the same lead as the original Bermudan ones, we should ask if excessive weather helm is due to a hull form that is not designed to sail on its ear? 

    To me weather helm means it’s time to reef. How about you.

    Michael


    I think you have a point. So many other considerations also, which may impact on sailing performance. I was very reluctant to place my mast any further forward on my Red Fox Vision. The lines for'd were just too fine and no forefoot to speak of - It just did not look/feel right. The Solent chop can induce mind numbing piledriving ( I'm thinking of my Freedom 30) with speed falling to almost nothing. Drag caused by slight weather helm - starting at an appreciable angle of heel - may be the lesser of two evils?
  • 14 Sep 2017 18:30
    Reply # 5260832 on 4793670
    Anonymous

    I have been thinking about the ideas and opinions expressed on this thread and it seems that we may be guilty of a category mistake.

    Some boats are designed to sail on their ear. The Folkboat and its derivatives such as the Twister, which I have owned, for example. Other well known designs which I had the misfortune to sail when I was a delivery skipper are reluctant to do this and require continuous attention to reefing.

    So, rather than go off on a series of modifications, having of course determined that the Junk sails have the same lead as the original Bermudan ones, we should ask if excessive weather helm is due to a hull form that is not designed to sail on its ear? 

    To me weather helm means it’s time to reef. How about you.

    Michael


  • 11 Sep 2017 21:24
    Reply # 5075010 on 4793670
    Anonymous member (Administrator)

    After following some of these topics, it seems to me that several models of both the Newbridges and the Kingfishers need new rudders. This they do no matter what rig one fits onto them. If a deep, large swing-up rudder is out of the question, I suggest one fits twin, balanced rudders (with endplates, of course) on the transom. This will also let one mount the outboard engine on the centreline, between the rudders.

    Outboard engines, trapped in a well, live miserable lives, and do their best to slow down any boat under sail. Do you remember how Gary King struggled with his Ashiki, until he learned to raise the outboard?

    There is another British class in this size range which I rather recommend - the Hunter 19 Europa. That boat is sweet as apple pie and sails and balances very well on any leg.  I loved crewing on that boat ( fin version).

    Arne

    Hunter 19, Europa. To me, this is a great design.


    Last modified: 12 Sep 2017 10:56 | Anonymous member (Administrator)
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

                                                              Site contents © the Junk Rig Association and/or individual authors

Powered by Wild Apricot Membership Software