Generic "Fantail" sail planform drawing

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  • 27 Dec 2014 07:14
    Reply # 3177092 on 1060993
    Deleted user
    As I studied the photos of junks in Hong Kong, I noticed that they raked the mast forward to enable an almost vertical yard. This enable the soft wing sail to twist for power. I use the following AutoCAD command to find the CE of the sail: 1.trace the outline of the sail with polyline, 2.turn it into a "region",3.key in command "massprop" then select the region,4.the coordinate of the centroid will display on text. John Kwong
    Last modified: 27 Dec 2014 07:17 | Deleted user
  • 10 Dec 2014 00:04
    Reply # 3167142 on 1060993
    Deleted user

    By way of an introduction, here's my first bit of work towards re-rigging one of my small boats as a JR: Let the clew be located at (0,0), then the centroid of the generic Fantail sail plan-form is at (-0.4135,0.6253). When plotted this appears to tally perfectly with the gravity method by visual inspection. I determined the centroid coordinates by first constructing the fantail plan-form in an ancient CAD program, then analysing each panel as two triangles, calculating areas by Heron's formula and finding the centroids by bisector intersections, and finally reducing centroids for pairs of areas. Excel did the heavy lifting.

    I am deeply grateful for the existence of this Association and look forward to plumbing the depths of accumulated wisdom!

  • 15 Aug 2014 09:53
    Reply # 3075153 on 1060993

    In case it's useful to anyone, I determined the centroid of the generic fantail sail using the gravity method. You can see the result here. (I did the same for my existing HM sail here.)

    I worked this out because “Practical Junk Rig” says “The next stage is to draw the sail plan and work out the centre of effort (CE), which is defined as the geometrical centre (centroid) of the area of the sail(s)…”

  • 11 Aug 2014 09:17
    Reply # 3070370 on 1060993
    Tammy Norie's mast buries into a fibre glass box that's part of the seating, and is then bolted to a large and sturdy step (probably wood in fibre glass) by a bracket that could be moved.  It's 1185mm from the step to the partners, and there's room to move the mast foot aft by 95mm so I believe I can rake the mast forward an additional atan(95/1185) = 4.58 degrees without major modifications. Working from my overlay, I believe Fantail's mast is raked forward 4.3 degrees more than Tammy Norie's.  So I ought to be able to duplicate your angle.

    I think, with a bit of thought, I can even make it adjustable. I'll cut the hole in the box into a slot with a sliding cover stop cushions falling in, then remake the foot bracket with wide jaws and spacers.  With a bit of care I can have one spacer per degree of rake and try stuff out. I'll also take the opportunity to reinforce everything of course. Fun fun fun.

  • 11 Aug 2014 00:23
    Reply # 3070192 on 1060993
    Looks great, Richard.  Good luck with the new sail.  With luck, both the mast step and partners can be removed from their present position and replaced on a wedge-shaped base in order to put in the appropriate rake.  However, if the present rig is classic H/McL, the mast should be in the correct place anyway, and you will only want a couple of degrees of forward rake to reduce the chance of accidental gybing.
  • 01 Aug 2014 14:49
    Reply # 3061882 on 3053688
    Annie Hill wrote:Richard, if you look at this 'Fantail' (http://www.junkrigassociation.org/Sys/Profile/PhotoGallery/4772723/0/5015088?memberId=2781717&dh=54&cppr=0) (Sorry about the crude link, but the new WA platform doesn't work on my netbook screen), you will see the original Fantail rig: the mast is well into the boat.  Tystie used her existing mast; Fantail has her mast well aft, but raked forward to fit in with the accommodation.  I'm sure the Fantail sail would work well on your boat.  But if you have any doubts, using Arne's method of adding camber would make a big difference to your existing planform.
    Thank you Annie. Not just a Fantailed boat, but the Fantail too. I've done a similar waterline-matching exercise and it looks very promising. You can see the picture here. It could be tricky to adjust Tammy Norie's rake, but not nearly as tricky as moving the mast.

    At the JRSRC rally last weekend someone commented that Tammy Norie had an absolute textbook example of the HR rig. She ought to, since she was mothballed for so long. Tim McCloy (China Blue) also saw it recently and noted the same thing. Partly for that reason I won't modify what I have, but preserve it as is and build a new one. Camber is part of the plan, of course!


  • 24 Jul 2014 23:00
    Reply # 3053688 on 1060993
    Richard, if you look at this 'Fantail' (http://www.junkrigassociation.org/Sys/Profile/PhotoGallery/4772723/0/5015088?memberId=2781717&dh=54&cppr=0) (Sorry about the crude link, but the new WA platform doesn't work on my netbook screen), you will see the original Fantail rig: the mast is well into the boat.  Tystie used her existing mast; Fantail has her mast well aft, but raked forward to fit in with the accommodation.  I'm sure the Fantail sail would work well on your boat.  But if you have any doubts, using Arne's method of adding camber would make a big difference to your existing planform.
  • 24 Jul 2014 16:10
    Reply # 3053290 on 1060993
    I'm inexperienced with junk rig but (I hope) learning fast. So far I find the flat-sailed HR rig on Tammy Norie lacking drive below F4 and unable to make progress to windward in light airs in a chop. This may just be poor technique on my part, but when I bought her I was definitely thinking about making a more up-to-date sail. I have offshore ambitions. The fantail rig just looks right.

    I admit that I have not done any homework yet, but I made this crude overlay by matching the waterlines of Tammy Norie and this fantail, just to get an idea if it's at all feasible.

    It quickly raises one question: does the mast position of the Coromandel rule out the fantail (at least, the standard one). If so, what can be done? But also, what homework should I be doing?


    Last modified: 24 Jul 2014 16:11 | Anonymous member
  • 17 Jul 2014 23:49
    Reply # 3047890 on 1060993
    Deleted user

    Thanks for the advice, i'll take it and not learn the hard and expensive way why it isn't suitable for multi masted rigs. It does make for a nicer looking sail than a parallelogram though, so I spent the last couple of days designing a new sailplan with some slight irregular fanning, nearly straight and vertical leeches, all the battens have positive stagger, and it does look a little better than the original plan.

  • 14 Jul 2014 20:48
    Reply # 3045305 on 3044523
    Robert Leask wrote:

    It will be a few more months before I'm reunited with my boat, but I can at least do some planning. I took Davids generic fantail plan and made a model of it in Rhinoceros, and tried scaling it to my planned 3 masted rig. It sure looks pretty, compared with the parallel batten plan I had before.

    Several questions come to mind: is there any reason this planform would not work out on a multimasted rig? Also, my foremast will be canted forward about 15 degrees - would it still work with that much angle? Lastly, if I were to change the aspect ratio by scaling it a bit on the horizontal axis would that be a bad idea?

    Having never sailed a junk rig before I expect a rather steep learning curve when I first set sail. I'm thinking I could make my mainsail out of the real stuff, that's the most straightforward. Perhaps I should make my foresail/mizzen out of cheap polytarp, just to be sure the sailplan works before making permanent ones?

    Sorry, this shape is not suitable for a multimasted rig. I've tried to design a fanned shape for a two masted rig, and have failed. The only thing that works, in practical terms, is the usual parallelogram panels, with maybe fanned top panels. The Fantail sail battens stagger back wards at their forward ends, and this means that the sail needs to move forwards on the mast as it it furls. either that, or the mast needs to be forward-raked. Fantail worked out OK with 6 degrees of forward rake, but beyond that, nothing is known, though Yeong had a foremast raked at 10 degrees. 15 degrees is too much for any type of sail, I'd have thought. On no account vary any of the proportions of this sail - if you do, the ratio of panel width to diagonals will alter, with adverse effects.  
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