S2 6.7 Junk Rig Conversion

  • 20 Nov 2018 16:15
    Reply # 6915943 on 6872873
    This POLYESTER RIPSTOP (DWR) - 2.6 OZ is the closest thing I have been able to find to the ' 92 gm/sq m/2.7 oz sq yd textured ripstop polyester from Pennine Outdoor' (broken link now) that David T. first mentioned and that Jami J. decided to use.

    I think Jami's boat and type of sailing are very similar to my own. I would like to find a fabric similar to what Jami used.

    Last modified: 20 Nov 2018 21:46 | Anonymous member
  • 19 Nov 2018 21:10
    Reply # 6914741 on 6872873

    I just now found the lengthy discussion from when Jami was deciding on a fabric. I will be sure to read through this thread.

  • 19 Nov 2018 08:39
    Reply # 6913627 on 6913221
    Scott wrote:

    David, 

    Thank you for the suggestion to use load-spreading patches with the Odyssey material. If I understood correctly this would mean only two triangular patches. One in the upper most panel all the way aft (peak) and one in the upper most panel all the way forward (throat). Is my understanding of the throat and peak correct? I have to say that describing the material as having a 'high proportion of filler' is making me rethink using this as sail cloth. I am interested to know what cloth you personally recommend for a 22 sq ft sail.

    Your understanding is correct. But use more than one patch in each place - two or three is usual at points of high stress, smaller patch first, then larger on top.

    The conventional choice will always be polyester sailcloth, which after all's said and done is made for the job in hand. 4 -5 oz would be right for your boat. Most of them only come in 36in width, which is inconvenient if you want to get a whole panel out of one cloth. Boring white is available in 58in width. 4 oz in sailmaker's measure = 5 oz/sq yd. Sailmaker's measure means one yard of length at 28.5in wide - don't ask why, the reason is lost in the mists of time.

    But we're not conventional, and there's a point in making junk sails from soft UV resistant cloth. These are heavier than 4 oz, but I don't have any problem with that - I'm using 9 oz/sq yd cloth on Weaverbird. Weathermax 80 is still a front runner, if you can work around its tendency to pucker when sewn along its length. That's easy if cutting a barrel-cut 2D panel lengthwise from one cloth, as the only sewing is along the batten seam, and puckering is actually good, as it gathers up some unwanted excess of length in the edge. 

  • 19 Nov 2018 00:32
    Reply # 6913221 on 6872873

    David, 

    Thank you for the suggestion to use load-spreading patches with the Odyssey material. If I understood correctly this would mean only two triangular patches. One in the upper most panel all the way aft (peak) and one in the upper most panel all the way forward (throat). Is my understanding of the throat and peak correct? I have to say that describing the material as having a 'high proportion of filler' is making me rethink using this as sail cloth. I am interested to know what cloth you personally recommend for a 22 sq ft sail.

    Arne,

    From what I gather you have ripstop nylon in mind. I like the idea of avoiding UV damage issues by making the sail out of a protective cover like Odyssey. On the other hand this might not be such an important feature when I am only sailing a short part of the year. I have not been able to find the specific weight of the cloth that you have used. On sailrite I see 0.5 oz and 0.75 oz and 1.5 oz ripstop nylon. Just to keep it interesting these weights are 'per sailmakers yard'. I guess this is one yard of the 60" wide material? I am interested to know what your choice would be for a 22 sq ft sail as well.

    It is hard for me to know when it is time to stop and think before moving forward with this project and when it is best to make a decision and keep going. I would like to make this the best sail I can make and feel good about the results so I do not want to rush too much. On the other hand it seems like I could spend years just thinking about what cloth to use.

    Edit: This Silpoly fabric looks very interesting to me. It is polyester. It has a ripstop weave. The specs claim lower water absorption and increased UV resistance compared to ripstop nylon. It is lighter than Odyssey and it is coated on both sides. Does anyone have experience with this fabric?

    Last modified: 19 Nov 2018 02:19 | Anonymous member
  • 18 Nov 2018 08:55
    Reply # 6912440 on 6872873

    Scott,

    Keep in mind the bad experience that some of us have had with Odyssey, due to its high proportion of filler to woven cloth, I think. It doesn't seem to enjoy the cyclical diagonal loadings which happen in the throat area. This is not to say it can't be used, but to advocate load-spreading patches at throat and peak, just as you'll see in the corners of any bermudan sail.

    The thread should be V69 bonded polyester. Using the same colour disguises crooked stitching, using a contrasting colour highlights it, but helps later in the sail's life, when broken stitches need to be re-done. Perhaps a compromise is to choose a thread colour just a little darker than the cloth colour. 

  • 17 Nov 2018 23:47
    Reply # 6912245 on 6872873
    Anonymous member (Administrator)

    Scott,

    my uninformed guess is that you now, after having made those patterns, have risen to be the local authority in the field.

    It is correct that the Odyssey III is now called just Odyssey.

    As for thread, use what the experts at Sailrite recommend.

    I used Odyssey III on the 20sqm sail for my Frøken Sørensen. It worked, but on a sail this small, a lighter cloth would be preferable, if available.

    Anyway, good luck,
    Arne


  • 17 Nov 2018 23:30
    Reply # 6912210 on 6872873

    Hi Arne,

    Thank you for the help and support. I have two of the four paper patterns drawn. I would not say that I am now 'good' at making patterns, but I am probably about as good as I will ever be. The maximum rounding points are where they should be at 0.35B and there is a straight taper to the leech. 

    It would be really great if there was someone anywhere near me that could take at look at these big paper drawings and tell me if they look approximately correct. I have not had much luck capturing the pencil lines using my cell phone camera. All the pictures look like big pieces of paper taped together, the lines are not clear. Since it seems like I am the only would-be junkie in the region I guess checking all my numbers three or four times through the whole process will have to be enough.

    I hope you or someone else can check a few assumptions I am making. I have seen 'Odyssey III' mentioned here on the JRA forums. The only product I find with that name is called simply 'Odyssey' without the 'III" at the end. I assume that this is the same material. Will the material currently made by Marlen Textiles called 'Odyssey' be acceptable for sail cloth? I like the way it looks and feels on the sample card. As long as I am careful to keep the shiny (coated?) side of each panel on the mast side I think it will look really nice.

    As far as thread goes I have been assuming that I can just get a spool of whatever sailrite.com suggests as the best match for the Odyssey color I order. Does this sound like a good plan or do I need to make sure I get something with specific material properties such as strength and size? Would a contrasting thread color be better than a matching color for some reason?

    I am slowly making progress ... I think.

    Scott.


    Last modified: 17 Nov 2018 23:32 | Anonymous member
  • 13 Nov 2018 19:54
    Reply # 6903085 on 6872873
    Anonymous member (Administrator)

    Scott,

    if that (lengthened) spline is curved as it looks (and to the calculated max round), you will be all right. Personally I add another nail or two closer to the luff to increase the curve of the spline there, but I don't torture the spline in any way, and I make sure that i don't move the max. camber point forward of the planned 35% from luff.

    Arne

    Last modified: 13 Nov 2018 19:57 | Anonymous member (Administrator)
  • 13 Nov 2018 18:57
    Reply # 6902933 on 6872873

    Arne,

    I will double check the length along the battens, and the luff and the leech for accuracy.

    Will something the size of the trim in my pictures, but longer, make an appropriate rounding shape?

    Scott.

  • 13 Nov 2018 10:16
    Reply # 6902214 on 6872873
    Anonymous member (Administrator)

    Scott

    I guess I would give highest priority on getting the length along the battens the same, and then the length of luff and leech. If they are ok, a diagonal a bit off can only mean that the rise angle is not exactly right. That is not such a big deal. Weather the rise angle is 9.7°, 10.0° or 10.3°, is hardly noticeable (but it shows on the diagonals). This practice will ensure that the luffs of the four lower panels are straight, and that the panels fit together along the battens.

    When bending that spline to get the right round, I place a nail at that 40% point. The idea is that the spline should not need to be forced into position at the aft end, but ‘find’ its position, thanks to the ‘40% nail’.

    Accuracy:
    Remember that this is not rocket science. We should be very satisfied with approaching 3-diget accuracy, and in most cases two digits is the best we can do. I mostly make my drawings with millimetre resolution, but am more than happy if I get close to the nearest centimetre during lofting and sewing.

    The problem with getting the patterns perfect, only shows that practical construction of stuff is very different from producing accurate (computer) drawings. When I developed my ‘chain calculator’ method for finding the needed round and camber, others soon developed computer programs to do the job better. They surely produced results with impressing numbers of digits, but my guess is that the needed fudge-factors built into their algorithms did not produce more accurate camber than my primitive chain method does.

    Finally, this shows the superiority of using paper patterns  -  much cheaper to do errors on paper than on the canvas ...

    Arne


       " ...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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