A new rig for Leeway

  • 27 Jul 2016 01:03
    Reply # 4157133 on 4138614

    I think I have my "working" sailplan for Leeway.  At 1068 sqft (99m2), it seems like a reasonable compromise between sail area and something that won't get tangled in itself (hopefully).  I could maybe decrease the sail area a bit more yet, but I have some time to think about that.  For now, I think it is close enough to workable to continue with the refit.  Soon we'll be insulating the aluminum hull and all the external welding for the rig must be done before that, including mast partners, sheeting points and the location for the rope clutches (more on that below).

    I settled on a rigid aluminum Bimini as the best way to keep the sheets clear of the wind vane and protect the crew.  It also offers shade, a place for solar panels, a horse for the mainsheet, a place to collect rainwater etc...  Although it might not be clear from the drawing, the sheets for the mainsail run forward along the top of the hard aluminum bimini, then down to the pilot house and finally aft to a winch.  It would have been nice to have them run under the bimini, but so far I haven't come up with a clever way to do that.  

    The Bimini decreases the Dmin to 1.25P.  Thus, I had to give up the transition panel at the top of the sail (the longer leach required too long a sheetlet) and it also forces a simple four part, with two point spans, sheeting arrangement for the mainsail.  Using split upper and lower sheets I need to store four sheets (two main plus two foresail) ranging in length from 65' to 121' (20 and 37 m) .  My plan is to store these four sheets, along with the two, three-part, halyards (120', 37m) on line reels.  A picture of my mock-up can be seen here.  The wheel in the picture is tied in place as I'm also considering moving our pedestal steering which fills the small aft deck and leaves little space to lean back when you want to heave on a halyard.  I think there should be space behind the wheel to put a few sheet bags for the shorter hauling parrels and downhauls.

    I'm a bit concerned about organising all the lines.  Our offset companionway forces me towards running all the lines to one station.  This seems a bit crowded, although you don't have to reach far for anything!  We only had one winch with the original Staysail Schooner rig, so I'm hoping we can make-do with one again (because, I'm not sure where we would put the second winch).  With only one winch, it seems I could splurge and upgrade to a self-tailing one.

    Any thoughts are appreciated.  The running rigging is different enough from my Bermudan experience to make me doubt myself and my sum total Junk time is two afternoons on Tystie and a couple of days on a Gazelle.

    For those that are interested in line-reels, I found a useful online calculator to figure out how much line a reel can store.  It is made for wire-rope, but yields results identical to PJR if you set the freeboard to 0.5 inch.  I built a test reel to confirm this.  It is useful if you want to vary the spindle height (drum width) a bit from the 3" recommended by PJR.  The results from the calculator are incremental as you increase the spool diameter, as it waits until you have increased the diameter by another full wrap before it shows  the increase in line that can be stored (I bet that is as clear as mud, just try it and see).


  • 25 Jul 2016 10:46
    Reply # 4154156 on 4154116
    Deleted user
    Arne Kverneland wrote:


    does that formula include the extra length of canvas along the diagonal, caused by the baggieness in the cambered panels? 


    Yes, it should work for cambered and flat panels provided the length L is the length of the cloth measured in a straight line between the lower corners of the luff and leech of the canvas. In other words, it's the length of the cloth laid flat, not the shorter length as seen perpendicular to the assembled sail. Another formula could be used in that case, if the foil section was a 'true arc plus tangent' type. I'm doing this on a phone so would like to double check with a laptop or calculator...
  • 25 Jul 2016 09:47
    Reply # 4154116 on 4138614
    Anonymous member (Administrator)


    does that formula include the extra length of canvas along the diagonal, caused by the baggieness in the cambered panels? 


  • 24 Jul 2016 22:31
    Reply # 4153646 on 4138614
    Deleted user
    Is it possible to generate an online calculator and plant it somewhere on this site? I certainly can't incorporate one in a post, but a quick scratch-of-the-chin formula for those interested would be: 

    Stagger (%) = {B/[Sq rt(P^2+L^2-2L*Cos(90+rise)])-1}*100

    where B is batten length measured from luff to sheetlet attachment point or leech, whichever is greater; P is length of luff of the panel; and L is the straight line length of the lower edge of the panel from luff to leech when the cloth is laid flat.

    I'm several hundred miles from my copy of PJR and can't remember if P refers to vertical length or a length perpendicular to the batten - the formula above uses the vertical length (i.e. the luff length between battens).

    I've given this a quick revision but it might pay for some fellow engineers could give this a glance.

    Last modified: 25 Jul 2016 07:29 | Deleted user
  • 24 Jul 2016 05:07
    Reply # 4152787 on 4152606
    Bryan Tuffnell wrote:If I may jump in...

    Darren, your post looks like it is, or could be with contributions from others, a complete synopsis of the post PJR state of the art. I think there's real merit in keeping that post as a resource, or developing it further for those contemplating a sail design.

    Unfortunately I don't have excel!

    If others want to add comments, I'd be more than happy to continue to update and edit the document and make it available to everyone.  I haven't built a single Junk rig yet, so others more competent than I would have to contribute to make it something useful.  If there is interest we should probably move the post to a new thread.

    Annie is right about Libre Office and Calc.  My OS is Ubuntu and I have used Calc in place of excel for years.  The compatibility is very good and the functionality very similar to Excel.

  • 24 Jul 2016 01:48
    Reply # 4152658 on 4152606
    Bryan Tuffnell wrote:If I may jump in...Unfortunately I don't have excel!
    May I suggest you go here and download Calc from Libre Office?  It's Open Source, free and compatible with Excel.  With such a good idea, it would be a shame not to carry it though :-P
  • 23 Jul 2016 22:46
    Reply # 4152606 on 4138614
    Deleted user
    If I may jump in...

    Darren, your post looks like it is, or could be with contributions from others, a complete synopsis of the post PJR state of the art. I think there's real merit in keeping that post as a resource, or developing it further for those contemplating a sail design.

    Two further comments: batten stagger on cambered panels must still follow the ratio of batten length to panel diagonals measured along the cloth, and this is calculable with trigonometry from a few parameters. An excel spreadsheet could be developed where one puts in their batten length, camber, point of maximum draft, batten rise, panel height... and the program spits out stagger. Unfortunately I don't have excel!

    Fantail has a short yard, high yard angle and low aspect ratio, and in her case shifting the yard sling point aft on the yard dramatically changed the ease of setting the sail. The yard hauling parrel now has no load on it when the sail is fully hoisted in a calm sea (it does prevent the yard from swaying across the mast on a seaway). However, once the sail is reefed it is of course the lazyjacks that determine boom rise, and the geometry of the sail changes.

  • 23 Jul 2016 20:02
    Reply # 4152456 on 4138614

    Arne and David,

    Thanks for contributing, one of the hardest parts I've found about figuring out cambered sails is making the jump between PJR and the current best practice (even with the excellent written work of Arne and Slieve and some personal tutorial from David Tyler).  One problem is that although everything is in the forum archives and old magazines, it is difficult to sort through what ideas have been tried and subsequently been discarded or modified.  Hong Kong Parrels are an example.  They seem to have been widely used, often despised, and then partly replaced.  But, I haven't found a clear explanation of the current recommended use of Hong Kong Parrels.

    This post started out just about Hong Kong Parrels, but morphed into everything I think is not covered in PJR and must be found spread elsewhere here on the JRA.  It is mostly my notes for my own benefit, but perhaps someone else would find it useful.  If anyone has the time to read through it and find my errors, that would be appreciated.  I should explicitly state that I am not complaining about the fact that info is spread throughout the JRA, things are still much easier for someone now than it was when all of this was being figured out originally and I'm grateful to all that have shared their work.

    On the list of things that seem different or not explicit from PJR are: 

    Hong Kong parrels:  reading through the forum, it looks like these are a necessary evil to avoid creases in cambered sails.  Arne's earlier sails had many, and progressively over time folks have managed to find way to eliminate all or many of them, mostly through modifications around the throat hauling parrel.  The problem with Hong Kong parrels is that the provide yet another line for things to get hung-up on.  Also, if adjusted too tight it looks like Hong Kong Parrels can bend or break battens.  It looks like the correct adjustment for Hong Kong parrels is normally slack, and only going taut when sailing close-hauled.  Arne has suggested that thin bungee could be added to them to keep them out of the way when reefed, but let them stretch easily when the sail is lifted.

    Throat/Luff Hauling Parrel: most cambered sails seem to combine these for one less line.  It is now usually run from the yard to the first few battens below.  Once adjusted the fully hauled sail should lie pretty close to the right position with no other standing or running lines adjusted other than the halyard and Throat/Luff Hauling Parrel.

    Yard hauling Parrel:  The yard hauling parrel can be moved higher (30-40cm) than the halyard to help peak up the yard.

    Paul Fay Yard Hauling Parrel:  Getting the yard to peak properly and the rest of the sail to hang naturally below seems to be the key to getting a low stress sail.  Paul Fay redesigned the yard hauling parrel so that the free end is run to, and pulls down from, the forward end of the yard.  This helps, rather than fights the luff hauling parrel in peaking up the yard.  Peaking up the yard can further be assisted by moving the halyard sling point slightly aft of the middle of the yard.

    Yard and Battens:  The yard and battens of a cambered sail have to be heavier than the recommendations in PJR, this is because in a flat sail the loads are spread evenly across the battens and yard.  However, in a cambered sail the loads are spread to the luff and leach.  This requires stronger battens and yard to resist bending and breakage.  However, I haven't found a recommendation on how to scale-up PJR battens for cambered panel rig.  The batten spec database can give some guidance.


    Batten rise angle:  The PJR suggestions for batten rise to create positive stagger don't work with a cambered sail.  Instead 10 degrees seems to be the replacement that is broadly used now.  This is roughly double what PJR recommends.  Even this amount alone won't create the desirable positive batten stagger.  

    Batten Stagger:  The unusual stagger behaviour of the cambered panel sail can be tamed by using shorter batten parrels.  I think Arne uses half-length ones.  Paul Fay has used his version of standing luff parrels (connects both ends to the luff end of one batten), that get progressively shorter up the mast and thus induce positive stagger.  Apparently, the PJR version of standing luff parrels can also be used (fixed line from one battens luff to the luff of the batten above it).  These would have the advantage of remaining slack until the sail is hoisted.  Either of the standing luff parrels are of more use on a schooner where you are unlikely to want to change the balance of the sails.  I haven't figured out how Slieve's combined downhaul/batten parrels would work in this framework.  The best material for these fixed parrels is not bare line (which tends to grab the mast or other lines), but either webbing (Arne), or line inside a semi-rigid plastic sleeve (Paul Fay).

    Boom batten:  The lowermost batten on cambered panel sail should be shortened by 4-5%.  This is because cambered sails don't follow the stagger rules for flat sails and the resulting negative batten stagger can cause fouling of the sheets.  Arne cured this by cutting 5% off the length of the bottom-most batten.

    Halyard:  The halyard drift in PJR is generous and David, Arne and others have cheated it and been OK.  Arne's rule for this is that the angle between the halyard and the mast should not exceed 30 degrees, rather than specifying a ratio to the sail as PJR does.  The minimum drift recommended is 60 to 70cm, but more is better.  When using less drift than PJR recommends, you should probably use a halyard with less than three parts(Arne uses three part, David uses two part) to lower the wringing load on the mast when the sail is let out for running.  This has the advantage of making the sail easier to reef (there is less overhaul resistance and the sail drops easier), but in increases the compression load on the mast and means you will have to use a winch for raising larger sails.

    Schooners/Ketches:  With cambered panel sails you are likely to need to sheet the mainsail to windward in order to point high.  This can be accomplished by a horsed sheet (traveller) or with double sheets (port and starboard).

    High aspect ratio sails:  split sheets (upper and lower) or double sheets (port and starboard) are strongly recommended for a high AR sail.  The steep sheeting angles present in a high AR sail mean that a single sheet system is unlikely to be able to control sail twist.

    Sail Camber:  This is a bit of a horses for courses kind of a thing.  Generally, it looks like folks going offshore have been happiest with something under 9% in the lowest panel, and then gradually decreasing to little or no camber by the time you get to the triangular top panels.  Even a bermudan storm trysail has some camber so it may not be necessary to have perfectly flat top panels.  There is of course a group who supports flat sails for offshore work that only have induced camber from sail-set.  You can also find examples of folks who would like more camber if they regularly find themselves wanting to sail to windward in light airs.  Hull shape also seems to play into this.  Heavier hulls that require more drive should consider a bit more camber.  The disadvantage of more camber offshore seems primarily to be increased slatting of the sails when the boat rolls in light winds, increased chafe due to extra fabric in the reefed sail fluttering and a sail bundle that doesn't reef as neatly.

    How to sew camber:  The primary method seems to be Arne's well instructed method just using rounding to add camber.  However, if I've read Slieves work correctly, it looks like there is not much more work to use a Round and Broadseam method.  If you are using a fabric with some stretch it looks like just rounding will do well at the expense of some wrinkles that likely have little effect other than appearance.  If you just use rounding the fabric should be left a bit slack along the batten.  If you are using stiffer sail fabric, such as regular dacron sail material, then Round and Broadseam should result in fewer wrinkles and the sail can be stretched taut along the batten.  The point of max camber should be around 35 to 40% of the sails chord.  If you use the Round and Broadseam method of sewing, you can make the entry angle of the sail steeper for better performance (although there aren't really any tests of how much this benefits).

  • 23 Jul 2016 16:58
    Reply # 4152276 on 4138614

    Erik and Barry,

    Those, who've sailed a lot offshore and those who were a bit too greedy in choosing sail area all seem to agree that smaller is better.  I've hear the message, although I admit that everytime I sit down to draw sails it takes real discipline to not try and sneak in a few extra square meters here and there :-)

    I wish I had sailed Leeway harder and had a better feel for the amount of Lead.  However, I went through every design book I had or could find online and the original 16% lead was a bit extreme (although it gets better if you don't include the rudder as some do).  Fortunately, a full keel boat is less sensitive to lead than other keel types, and a Schooner offers lots of sail balance options, so I should be OK between 8 and 12%.

    I agree with those that say that yard angle is largely controlled by the sail balance on the mast.  So, with an equal-area schooner I think the other restraints force you to a high-angle yard.  The only thing that makes me wonder is that Van Loan uses halyard angles that are way outside what PJR would say is OK.  I wonder if the low halyard angles of Van Loan, and a slightly aft sheeting point wouldn't help to peak up the yard.  Although, this might come at the expense of stressing the mast.

    I used 10 degree batten angle just because Arne, David and others do.  I took 10 degres as the replacement for the previous PJR calculations around batten slope and reefed-stagger of the sailed.  As Arne and David have pointed out, there are other good reasons for the stagger.

    You can decrease the height of the panels (P) to give yourself a lower Dmin for the sheeting.  The problem is that it comes at the expense of more battens.  If you have a high AR sail, then you already have extra battens.  This means more sheets, more complicated sheeting arrangements and more overhaul resistance from the sheets when you go to raise the sail.

    I got lucky on material and was able to buy the last of the clearance tan Haywards Clipper Canvas that David and others have been using lately.  I've have a real weakness for tanbark sails.

  • 23 Jul 2016 09:01
    Reply # 4151906 on 4151904
    Arne Kverneland wrote:

    Boom rise

    I have been using 10° rise as a standard, after the first sail on Malena came with 5° rise.  The increased rise ensures better view to leeward when beam-reaching in some wind. It does not take that much heel of the boat to make the boom appear to be drooping, so to me 10° rise makes sense. The extra rise also adds quite a bit to the sheeting clearance (Dmin), which is critical on many rigs.

    Cheers, Arne

    Yes, I would use at least 10 degrees for these reasons alone.
       " ...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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