S2 6.7 Junk Rig Conversion

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  • 06 Dec 2018 16:08
    Reply # 6948424 on 6872873

    At the moment I only need a close guess for the diameter of the battens so I can build the sail properly.

    This is my rough plan:

    1. Laminate together two 2 x 6 x 14' stock boards. One 2 x 6 = 1.5" x 5.5" = 38mm x 140mm

    2. Cut two square sections from this laminated stock to create two 51mm x 51mm square section battens. My intention is to end up with something close to battens with quarter-sawn grain. I tried to show this in the attached photo.

    3. Round the batten edges

    4. Seal with epoxy or paint or both.

    Are there any big problems with this?

    Last modified: 07 Dec 2018 21:55 | Anonymous member
  • 04 Dec 2018 15:57
    Reply # 6945050 on 6944889
    Scott wrote:

    I am seriously thinking about using spruce for the yard, the boom and the battens. I am sure that this will make for a heavier rig, and more weight aloft.

    Is there any other reason why I should not use epoxy laminated spars made from the stuff that is labeled 'Pine / Spruce / Fir' at the home improvement store?


    Scott,

    If you select stock with only small knots, and laminate battens from two pieces such that the run of the grain in each piece is a mirror image of the other (if you see what I mean), then you can get very stiff strong spars. Sure, a tube is the best for strength /weight ratio, putting all the material in exactly the right place, but apart from that, wooden battens will work fine for you. The same with the yard, but laminated from three or more pieces of small stock, so that any inadequacies in each piece are compensated by sounder material in the others. Given that, you needn't pay extra for prime, clear, straight grained boatbuilding timber.


  • 04 Dec 2018 14:11
    Reply # 6944904 on 6872873
    Anonymous member (Administrator)

    Scott, I like your attitude!
    Although aluminium tubes are my favourite these days, for battens, you could well try wooden battens, boom and yard.
    I made the yard for my Malena from spruce, in 1990, following PJR recipe, and it held for 21 years with minimal care or maintenance. Your boat is after all not meant to criss-cross the big oceans, so a broken batten is no disaster.
    If I were to do it, I would choose the lightest wood (spruce, not balsa or cedar) from the store and just make them a bit thicker to compensate for lost strength. Remember that strength grows with the cube of the dimensions (sides or diameter) while the weight only varies with the square of the size.

    Arne


  • 04 Dec 2018 13:53
    Reply # 6944889 on 6934708
    Anonymous wrote:

    Scott,
    there is a trap which is easy to fall in  -  the paralysing fear of making something which isn’t perfect.

    Relax, most cloths that are rot-proof and wind-tight will do. If Odyssey can be had at a reasonable price, then go for it. The sail will come out at about 7kg. It is on the stout side, but on the other hand, it will stand quite brutal handling and resist some chafe. Besides, it sews very well without pucking (at least on my machine).

    Arne

    (.. playing in the cheap, available and good enough league...)


    I am OK with making something that is not perfect. I really enjoyed making my Puddle Duck out of only things that could be purchased at the local home improvement store and at the fabric and craft store here. I am honestly really impressed with how well some decorative polyester ribbon seems to work as a webbing bolt rope on that sail. It is fairly low stretch and strong enough to be to be 'good enough'.

    What can be paralyzing on the S2 conversion is that I only have the budget to do everything once. If I purchase something that I think is good enough, and it is not, the whole project will need to be put on hold for maybe a year or so until I can purchase the right material.

    I am absolutely looking for cheap, available and good enough. Just in case it is not totally obvious yet -- I am trying to find something less expensive than Odyssey that will do the job. I am waiting on a different 1-yard fabric piece to be delivered. I plan to pull on it, look at the fabric through a bright light, and guess at if it can be used as sail cloth.

    While I am waiting I am also thinking about spars. I found a lamp post that seems to be strong enough and priced so that it will not eat up my entire boat budget for the year. But I am having a hard time with the pricing of aluminum alloy tube!

    I am seriously thinking about using spruce for the yard, the boom and the battens. I am sure that this will make for a heavier rig, and more weight aloft.

    Is there any other reason why I should not use epoxy laminated spars made from the stuff that is labeled 'Pine / Spruce / Fir' at the home improvement store?

    Last modified: 04 Dec 2018 16:34 | Anonymous member
  • 29 Nov 2018 23:44
    Reply # 6938689 on 6872873
    Anonymous member (Administrator)

    Odyssey for sails.

    I may have expressed myself in such a way that it looks as if I am selling Odyssey canvas. I am not, and after reading about the problems the Kiwis have had with sunrot with the material, I would of course not recommend it to sailors on lower latitudes. However, since I live on the rainy coast of western Norway, at 59°N, I have other concerns than sunrot  -  mildew for instance. I now use to cover Ingeborg's furled sail bundle  -  for one or  for both reasons...

    Arne

     


    Last modified: 30 Nov 2018 08:58 | Anonymous member (Administrator)
  • 29 Nov 2018 08:10
    Reply # 6937640 on 6937060
    Scott wrote:

    I appreciate the spirited discussion on materials and sail construction. There is much to think about.

    I got my order of POLYESTER RIPSTOP (DWR) - 2.6 OZ. I like the way it feels (for what that is worth) and it definitely sheds water very well. It seems less stretchy and stronger than other materials. I would say it is much less stretch than any nylon I have looked at and slightly less stretch than Odyssey.

    Unfortunately, if I give it a little effort, I can blow air though it. It seems that a coating of Polyurethane or Acrylic or something to make the fabric air tight is a necessary feature. This fabric does not have a coating.

    I will probably use this to make some bags. I can't imagine it is good to have air blowing through a sail.

    It seems the supplier used straight scissors or a razor to cut the fabric. A hot knife or pinking shears would have been considerate. When I unfolded the fabric large parts of the weave came apart in a long thread.

    It's not a lack of coating that should cause you to avoid this cloth. Try holding it up to a strong light - can you see pinhole-size leakage of light through it? If not, it's tightly woven enough. If it can be used for kites and tents, as the supplier claims, then it's airtight enough for a lightweight sail. It's similar to the cloth I used for my windvane, which is still strong (but faded, as it's red) after two full seasons of exposure to UV. 

    Yes, you'd need a hot knife to work with it. Also, V69 thread will be too heavy. Use a 100% polyester thread intended for outdoor clothing and equipment, metric size 75, Tex size T-35.  On the construction, it's up to you whether you listen to Arne or to me; I'm just going to repeat that good construction methods are going to be essential to making a successful sail in a cloth this light. I would recommend a sailplan with a low yard angle  to decrease stresses around the peak and throat, too. Amiina's very lightweight split junk sail has a low yard angle. Weaverbird's sail, yard angle ~ 45˚, though made from heavy cloth, is designed to minimise the loadings on the parrels, and therefore also the loadings on the cloth will be lower than with  ~ 70˚ yard angle.

  • 29 Nov 2018 00:25
    Reply # 6937311 on 6933427
    Anonymous wrote:
    Anonymous wrote:
    Anonymous wrote:

    I ordered small sample swatches for several different fabrics and also two yards of the POLYESTER RIPSTOP (DWR) - 2.6 OZ. I am not totally sure what I am going to do other than pull on them to see how they 'feel' and then maybe check that my sewing machine can stitch through several layers.

    Here are my findings for lightweight cloth...think parachute, kites, hot air ballons:

    A, B, C

    Turns out your linked source above beats them all.

    rself

    Thank you for the reply and the links to lightweight fabric. In your profile I see that you are using Odyssey III for your sail. Do you have any experience using lighter cloth for a junk rig sail? It seems like everyone is using Odyssey or an even heavier fabric.

    Scott--I have considered making, say the lower 3 panels of 2-3 oz. But no, too much work sewing up 3 new panels then seam stripping to remove the current 3 panels then re-sewing the new set of 3 in place. Is there a benefit? The 6 oz material begins to inflate top of F1 (3 knts) and fully inflates by top of F2 (6 knts) so, really, maybe a detectable benefit on an upwind course, maybe.

    But for your intended light-wind summer sailing should be fine.

    I believe the split junk rig Amiina's newest sail is 2-3 oz. It's about the same size as your S2. Search this JRA site for info.

    If you haven't seen it here is a good article comparing Amiina with the bermuda equivalent. And here is a video showing 3 small junkrigs, including Amiina, in light air.

    rself

    Last modified: 29 Nov 2018 00:59 | Anonymous member
  • 28 Nov 2018 23:15
    Reply # 6937235 on 6936581
    Anonymous member (Administrator)

    David wrote

    No, one should not un-learn western sailmaking. Sailmaking is sailmaking, whatever the kind of sail. Bad practice is bad practice, whatever the kind of sail.


    Okey, so the millions of Chinese got it all wrong during all those centuries  -  too bad for them.
    Only problem; I think their sails made a lot of sense…


    Last modified: 28 Nov 2018 23:16 | Anonymous member (Administrator)
  • 28 Nov 2018 22:50
    Reply # 6937223 on 6872873
    Anonymous member (Administrator)

    Scott,

    I’m on thin ice when it comes to deciding if a cloth is air-tight enough or not for using as a sail, so take this with a large pinch of salt. I read somewhere, some time, that there was a sort of standardised way og measuring this sort of airtightness, but I have forgotten where I read it.

    Just remember, the average differential pressure in a sail is mostly well less than a MilliBar (hekto Pascal, hPa, these days), which is only 1.0cm water column. Only on small spots of the sail will the pressure ever reach 2-3 hPa. In a sail, 1.0 hPa would mean about 10kp/sqm sail area so a 20sqm sail would produce 200kp force with that little pressure. It takes some wind to achieve that, somwhere around 30kts (again, double check it).

    My point is that we can easily blow a pressure that is 50 times higher than that wind pressure .

    Therefore, if you need to use some force to blow through the cloth, and you are unable to just breath through it, it may well be useful as a sail. If it is cheap and easy to work with, it may be worth a try. Make a couple of bags of it first to see if it sews well with your machine.

    Good luck,
    Arne


    Last modified: 29 Nov 2018 08:39 | Anonymous member (Administrator)
  • 28 Nov 2018 22:21
    Reply # 6937199 on 6936719
    Anonymous wrote:
    David wrote

    Arne,
    I can only answer your questions with more questions: how many sea miles, how many hours of sailing? What matters is not the number of years your sails have existed, it's the hours of seatime they've had.

    Ah, the sea miles question, I waited for that. Not much to brag about there, I am afraid. However, I guess that Johanna's sail in 2014 had seen as much sailing time as Asmat's blue sail of that Kingfisher 26(?).

    Or am I wrong there, as well?

    Arne

    More, Arne. I sold Antares in May 2011. 

    Asmat

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