Succinct instructions on flat sail building

<< First  < Prev   1   2   3   Next >  Last >> 
  • 07 Aug 2019 10:58
    Reply # 7815720 on 7795562

    Hello Robert,

    A small voice of encouragement in case you decide to stay with flatness - a wise choice I think, for ocean sailing at the very least.

    'The Merits of Flat-Cut Junk Rig Sails' in JRA Newsletter #61 has all my thoughts, which haven't changed. I've sailed unimpressed on a couple of cambered-panel junks, and on our flat-sail 'mehitabel' quite a lot.

    Best of luck.

    Oh, one more thing. Two.

    Top Gun is an excellent and easily-worked material. Rolls compactly to pass through machine throat. 

    Having a canvas shop sew just the vertical seams saved us a lot of tedious labour.Vertical panel construction is robust (also ensures flatness...)

    Best of luck!

    Kurt

  • 28 Jul 2019 01:40
    Reply # 7799867 on 7799408
    Anonymous wrote:

    It seems that Paul and I came to the same main conclusion: By controlling the yard with a throat hauling parrel, THP, and a yard hauling parrel, YHP, the rest of the  (parallel-battened) sail will behave well.

    I still use Hong Kong parrels, but these now see very little load.

    It appears that I and the other junkies in Stavanger have tended to use stouter battens, and this has to some degree let us get away with the HK-parrels taking the whole load (before the THP was introduced...).

     

    Arne


    Since I started connecting the standing part of the halyard to a point between 5 and 10% of the chord aft of the sling point (which should be in the middle of the yard), I find I no longer need a THP.

    Apart from Aphrodite (my first cambered rig), I've never had any reason to use Hong Kong parrels. I do use one and sometimes two running luff parrels and on occasion I use a standing luff parrel. I like standing luff parrels but find they are only good for the lower part of the sail as the upper parrel almost invariably needs adjustment once a reef is put in.

  • 27 Jul 2019 14:58
    Reply # 7799408 on 7799153
    Anonymous member (Administrator)
    Paul Fay wrote:

     

    Update on Ti Gitu's sails.

    People have been quoting an article I wrote in 2011 about how Mo and I were not happy with our cambered panel sails and how at that time we thought that perhaps flat sails are better.

    We have totally changed our minds after sorting out all the original problems we found and have now rigged another yacht with cambered panels using current knowledge, which works well.

    When we made the cambered sails for Ti Gitu there was not a lot of knowledge about how to go about it and we found several problems.

    1/ When we designed Ti Gitu the rig exactly followed the Practical Junk Rig principles for flat sails, the only difference was that to gain sail area an extra panel was included. When we made the cambered panel sails we followed that sail plan which was a mistake. Because there is extra cloth in a cambered panel the battens need to be at a steeper angle to ensure that they stack properly pulling each batten aft as they stack which stops the sheets catching on the ends. David Tyler has produced a formula for batten angle for different cambers which works perfectly. If we had done that a lot of our problems would not have occurred.

    2/ We spent all the summer discussing camber and how to put it into the sail and eventually drew a camber using a radius from the leading edge to about 40% aft which then went flat to the aft edge. This gave a lot of round and fullness to the forward section which is good in light winds when a lot of camber is wanted but not so good when wanting to point up and in stronger wind. Chris Scanes, who makes excellent sails, uses a batten to go round a point at about the 40% aft point. This point represents the amount of camber required and the batten is simply bent from the front around the point to the back which gives a much flatter entry for the sail but works better in practice than the way we did it. We went for 8% camber in the lower panels and 6% towards the top but I would really like to hear what Chris and others think about that with their experience.

    3/ We had problems with the sail stacking properly due to the poor batten angle and in the end I fitted a parrell from the front of each batten round the mast and back to the front of the batten. As our masts are tapered this pulls the batten aft as it drops making the battens stack reasonably. I also reduced the length of the boom and the first batten to help with stopping the sheet fouling when gibing etc. which helps a lot.

    4/ The panels had a dreadful crease across them which people on the Yahoo Junk rig forum told us of ways to solve. I later found that many of these people had little or no experience of sailing let alone sailing a junk and all the ideas they suggested were rubbish especially the Hong Kong parrels which I still believe are an abortion that should never be tried. It was these Hong Kong parrels that bent our battens. Setting the sail properly came after a friend took photos of Ti Gitu sailing and I realised that if the top of the sail is set properly the rest simply hangs correctly. ( I think Arnie actually wrote about this at the same time ) To achieve this I simply added a yard throat hauling parrel to pull the forward end of the yard down and back, topping up the upper panels and allowing the sail to hang correctly.

    I did cover this in a later article in the JRA magazine here

    https://junkrigassociation.org/Resources/Documents/
    Ti%20Gitu's%20New%20Sails%20%20-%20Making%20a%20Cambered%20Panel%20
    Junk%20Sail%20Work%20-low%20res.pdf

    This is written about on my website at

    http://www.faymarine.com/Pauls%20Information%20Site/
    Junk_Rig.htm

    5/ With a flat sail the load is fed into the yard and battens along their length. With a camber panel sail the weight and loads are all at each end and the Practical Junk Rig sizes for the yard are not enough. We made aluminium yards with a bracing section above which solved that problem.

    Our sails are now almost as easy to handle as the original flat sails. We hoist the amount of sail we need. Haul in the yard parrel so that the halyard is vertical alongside the mast. Finally we haul in the yard throat parrel until the diagonal creases disappear from each panel. Haul in the sheet and off we go.

    We have no other control ropes except a downhaul which we use when dropping the sail and can't reduce the pressure of wind in it.

    The battens we have are 50mm dia. for the top three and the original 35mm dia. for all the others. Since removing the Hong Kong parrels we have had no further problems with any bending.

    The sheets are still extremely upright, at the maximum quoted in Practical junk rig. This would appear to oppose what the throat parrel is doing but in practice if the wind is strong we just haul the throat parrel a little extra to counter this.

    It may be better if we were to fit a track to enable hauling the sheet to windward but we won't bother. We were in Holland waiting to cross the IJsselmeer once a gale had passed. When we left it was to windward with probably 50 or 60 other yachts all pointing as high as possible. Ti Gitu didn't point as high as the very latest plastic blobs but did point higher than the traditional yachts, roughly in the middle of the fleet. That's good enough for us although if we get around to new sails we will probably go for a little less overall camber and have camber formed by the batten method which will probably improve things.

    Downwind the camber seems to help the sail set on the side we set it. The flat sails would jibe at the slightest rocking of the boat.

    So the question was would we have flat sails again and the answer is a definite no. The camber helps with power, pointing, keeping her 'in the groove', and even down wind. Now that the construction and setting have been learnt the only down side is that they are initially more complicated and therefore more expensive to make but we think that the advantages outweigh that.


    It seems that Paul and I came to the same main conclusion: By controlling the yard with a throat hauling parrel, THP, and a yard hauling parrel, YHP, the rest of the  (parallel-battened) sail will behave well.

    I still use Hong Kong parrels, but these now see very little load.

    It appears that I and the other junkies in Stavanger have tended to use stouter battens, and this has to some degree let us get away with the HK-parrels taking the whole load (before the THP was introduced...).

     

    Arne


    Last modified: 27 Jul 2019 15:02 | Anonymous member (Administrator)
  • 27 Jul 2019 10:07
    Reply # 7799153 on 7795562

    Update on Ti Gitu's sails.

    People have been quoting an article I wrote in 2011 about how Mo and I were not happy with our cambered panel sails and how at that time we thought that perhaps flat sails are better.

    We have totally changed our minds after sorting out all the original problems we found and have now rigged another yacht with cambered panels using current knowledge, which works well.

    When we made the cambered sails for Ti Gitu there was not a lot of knowledge about how to go about it and we found several problems.

    1/ When we designed Ti Gitu the rig exactly followed the Practical Junk Rig principles for flat sails, the only difference was that to gain sail area an extra panel was included. When we made the cambered panel sails we followed that sail plan which was a mistake. Because there is extra cloth in a cambered panel the battens need to be at a steeper angle to ensure that they stack properly pulling each batten aft as they stack which stops the sheets catching on the ends. David Tyler has produced a formula for batten angle for different cambers which works perfectly. If we had done that a lot of our problems would not have occurred.

    2/ We spent all the summer discussing camber and how to put it into the sail and eventually drew a camber using a radius from the leading edge to about 40% aft which then went flat to the aft edge. This gave a lot of round and fullness to the forward section which is good in light winds when a lot of camber is wanted but not so good when wanting to point up and in stronger wind. Chris Scanes, who makes excellent sails, uses a batten to go round a point at about the 40% aft point. This point represents the amount of camber required and the batten is simply bent from the front around the point to the back which gives a much flatter entry for the sail but works better in practice than the way we did it. We went for 8% camber in the lower panels and 6% towards the top but I would really like to hear what Chris and others think about that with their experience.

    3/ We had problems with the sail stacking properly due to the poor batten angle and in the end I fitted a parrell from the front of each batten round the mast and back to the front of the batten. As our masts are tapered this pulls the batten aft as it drops making the battens stack reasonably. I also reduced the length of the boom and the first batten to help with stopping the sheet fouling when gibing etc. which helps a lot.

    4/ The panels had a dreadful crease across them which people on the Yahoo Junk rig forum told us of ways to solve. I later found that many of these people had little or no experience of sailing let alone sailing a junk and all the ideas they suggested were rubbish especially the Hong Kong parrels which I still believe are an abortion that should never be tried. It was these Hong Kong parrels that bent our battens. Setting the sail properly came after a friend took photos of Ti Gitu sailing and I realised that if the top of the sail is set properly the rest simply hangs correctly. ( I think Arnie actually wrote about this at the same time ) To achieve this I simply added a yard throat hauling parrel to pull the forward end of the yard down and back, topping up the upper panels and allowing the sail to hang correctly.

    I did cover this in a later article in the JRA magazine here https://junkrigassociation.org/Resources/Documents/Ti%20Gitu's%20New%20Sails%20%20-%20Making%20a%20Cambered%20Panel%20Junk%20Sail%20Work%20-low%20res.pdf

    This is written about on my website at http://www.faymarine.com/Pauls%20Information%20Site/Junk_Rig.htm

    5/ With a flat sail the load is fed into the yard and battens along their length. With a camber panel sail the weight and loads are all at each end and the Practical Junk Rig sizes for the yard are not enough. We made aluminium yards with a bracing section above which solved that problem.

    Our sails are now almost as easy to handle as the original flat sails. We hoist the amount of sail we need. Haul in the yard parrel so that the halyard is vertical alongside the mast. Finally we haul in the yard throat parrel until the diagonal creases disappear from each panel. Haul in the sheet and off we go.

    We have no other control ropes except a downhaul which we use when dropping the sail and can't reduce the pressure of wind in it.

    The battens we have are 50mm dia. for the top three and the original 35mm dia. for all the others. Since removing the Hong Kong parrels we have had no further problems with any bending.

    The sheets are still extremely upright, at the maximum quoted in Practical junk rig. This would appear to oppose what the throat parrel is doing but in practice if the wind is strong we just haul the throat parrel a little extra to counter this.

    It may be better if we were to fit a track to enable hauling the sheet to windward but we won't bother. We were in Holland waiting to cross the IJsselmeer once a gale had passed. When we left it was to windward with probably 50 or 60 other yachts all pointing as high as possible. Ti Gitu didn't point as high as the very latest plastic blobs but did point higher than the traditional yachts, roughly in the middle of the fleet. That's good enough for us although if we get around to new sails we will probably go for a little less overall camber and have camber formed by the batten method which will probably improve things.

    Downwind the camber seems to help the sail set on the side we set it. The flat sails would jibe at the slightest rocking of the boat.

    So the question was would we have flat sails again and the answer is a definite no. The camber helps with power, pointing, keeping her 'in the groove', and even down wind. Now that the construction and setting have been learnt the only down side is that they are initially more complicated and therefore more expensive to make but we think that the advantages outweigh that.

    Last modified: 29 Jul 2019 22:12 | Anonymous member (Administrator)
  • 26 Jul 2019 15:57
    Reply # 7798207 on 7795562

    Bagginess.  Styles change.



  • 26 Jul 2019 11:34
    Reply # 7797856 on 7795562

    Yes Sir. That is what i meant. 

  • 26 Jul 2019 11:07
    Reply # 7797806 on 7797754
    David Tyler wrote:
    Robert wrote:

    Each of my sails sre about 370 sq ft. Do i need false seams in the panels.  Thanks

    By false seams, do you mean the way they used to do it with cotton sails, making a kind of Z shape down the centre of a cloth? This was done because cotton cloth was nowhere near as stable as all the synthetic materials that we use now. We can use cloths up to 150cm wide without worrying about whether it's too weak or too stretchy.

    There is one school of though that says vertical seams in junk sails limit the damage if you get a hole or tear in the sail.  Some people have discussed making each panel out of one piece of material, but putting in false vertical seams to mimic this effect.  Perhaps this is what Robert means.  If you do get a big tear in a panel though, you can just tie two battens together and take that panel out of contention.
  • 26 Jul 2019 10:01
    Reply # 7797796 on 7795562
    Anonymous member (Administrator)

    Controlling batten stagger in a cambered panel sail.

    I feel I am about to commit some topic drifting here, so I move this to this topic.
    Arne

    Last modified: 26 Jul 2019 10:40 | Anonymous member (Administrator)
  • 26 Jul 2019 08:27
    Reply # 7797754 on 7797114
    Robert wrote:

    Each of my sails sre about 370 sq ft. Do i need false seams in the panels.  Thanks

    By false seams, do you mean the way they used to do it with cotton sails, making a kind of Z shape down the centre of a cloth? This was done because cotton cloth was nowhere near as stable as all the synthetic materials that we use now. We can use cloths up to 150cm wide without worrying about whether it's too weak or too stretchy.

  • 26 Jul 2019 00:29
    Reply # 7797435 on 7795562

    I sailed with both a cambered and a flat-cut sail on Arion (recently sold and sorely missed).  The first sail was cambered and I initially had a lot of issues with it, but eventually tamed the sail using the same methods Paul Fay used.  Once I had done that the sail worked brilliantly for several thousand miles of ocean sailing, but unfortunately it fell apart after 4 years due to the use of inferior material (Odyssey 111).  I replaced it with a flat-cut Dacron sail, only because I could not find a local sailmaker who would attempt a cambered sail.  I did persuade him to put a little round in the top three fanned panels though and found that worked really well.  The fanned head of the sail worked like having a topsail set on a gaff rig. But some camber in the lower panels could only have improved performance to windward.

    Windward performance with the flat sail was ok in smooth water but the most noticeable difference was that the boat took a lot longer to accelerate out of a tack.  And I missed the telltale signs of the luff lifting slightly on the cambered sail (it just sort of panted) when I was getting too close to the wind.  It was very easy to keep the cambered sail in the groove when going to windward.  However, Arion was at best a stately performer to windward, with its heavy, beamy hull, and once the wind freed to about 60-70 degrees, there was no real difference in performance between the two sails.  I would say that if you have a boat with good windward potential, then a cambered sail makes a great deal of sense. 

    But it also depends, to some extent, on what sort of sailing you intend to do.  Shirley Carter has a small, heavy boat that does not have much potential for making passages hard on the wind in the open sea, and she is a committed deep sea voyager who mostly sails with the seasons and prevailing winds.  I can see that for her a cambered sail holds little advantage, and that she found the extra loading on the sail and battens not worth the bother, as well as not liking the look of the sail (that is a personal, not a technical issue, however).  So, if you are going to spend most of your time sailing down the trades across oceans on a small, heavy boat, a flat-cut sail might make sense, but if you have a boat with some windward sailing potential and spend more time coastal cruising, then a cambered sail is worthwhile.  And it can be engineered so as to be perfectly reliable.  I will certainly choose a cambered sail of some sort if I build another sail.

    Last modified: 26 Jul 2019 00:34 | Anonymous member
<< First  < Prev   1   2   3   Next >  Last >> 
       " ...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