S2 6.7 Junk Rig Conversion

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  • 13 Nov 2018 01:46
    Reply # 6901837 on 6872873

    Thank you for the feedback, Arne.

    Truth be told I used an Excel spreadsheet to do all the scaled calculations. I found your advice sound. It was easier to print out and mark up your master sails than to try to get a precise drawing in QCAD.

    I am in need of some assistance. I have the parallelogram for Panel 7 (the one with the boom at the bottom) lofted full size on some red rosin paper. After using the baseline and rise method I ended up with one diagonal that is right on the expected length and the other being off about 3mm. Unless someone advises me otherwise I will assume that 3mm is OK that not spend time looking for what corner is not completely square. 

    I am now attempting to loft the round in this panel. The only other curve I have lofted was on my Puddle Duck. The rocker on that boat plan has 7 stations for an 8-ish foot long rocker. It was almost impossible to get the curve wrong.

    I have a nail at the tack, one at the max round point and one at the leech of the boom. I also see a note from Arne that the aft 40% of the round should be a straight line. I am really puzzled on how to draw the correct curve using only three points. It seems that the minimum I need is an additional point marked at the start of the 40% aft section that should be straight. That would allow me to clamp a bendy batten to 4 points and get a deterministic shape.

    I am also wondering if the 'batten' (the least expensive trim I could find at the home improvement store) might not be stiff enough for this task. I expect the stiffness will change the shape significantly.

    Is there something obvious that I have overlooked for this part of the full size paper lofting? I attached a few photos in case that is helpful. I expect I need something longer than the 8 foot trim I have now. I have put off buying a longer length of trim until I have some confidence that it is the right thing to use.

    Right now I am really happy that I did not go for a fan sail with many different panel shapes. Making 4 patterns is going to be plenty of work!

    Thank you in advance for any help.

    Arne, I saw in a different thread that you are back home after a hospital stay. I hope you are doing well and recovering.

    Scott.

    Last modified: 13 Nov 2018 01:54 | Anonymous member
  • 09 Nov 2018 11:46
    Reply # 6896213 on 6872873
    Anonymous member (Administrator)

    Scott, you seem to follow exactly the procedure I hoped that users of Chapter 3 and 4 of TCPJR would use (..note that i wrote users, and not readers…). In other words, print out the master sailplan you fancy, and then spend an hour with a calculator to scale up or down the sail. Maybe not as elegant as when using a CAD program, but you will soon be ready for lofting patterns, this way. That is what this is about.

    Arne

    Last modified: 09 Nov 2018 19:43 | Anonymous member (Administrator)
  • 08 Nov 2018 00:31
    Reply # 6893951 on 6872873
    I think I really made a decision this time. I have started following the process laid out in The Cambered Panel Junk Rig by Arne K. I am using Arne's suggested 2.05AR sail from his drawing earlier in this discussion.

    22 Sqm, 2.05AR and 8% 'barrel method' camber is the plan.

    Down stairs I have plywood on the floor as a work surface and I have Sheets 1 to 3 marked up with the sail plan details. Right now I am not completely sure how to draw the locations and size of the batten pockets for Sheet 4. I think this can wait until just before I start marking the canvas to cut.

    I hope to loft at least one or maybe two panels full size on paper this week. If anyone has time to look at my scribbling and inform me of any obvious errors I would appreciate it.

    I am also looking forward to getting my Odyssey color samples. On order from Sailrite!

    Scott.

    Last modified: 09 Nov 2018 14:20 | Anonymous member
  • 02 Nov 2018 00:33
    Reply # 6884971 on 6884907
    Scott wrote:

    I think I am on my own now. The Faintail sail, Arne's sail and the Weaverbird sail all seem to have different advantages. I find it harder to make a choice when all the options look good. 

    Somehow I will need to decide for myself what features are most important for the sailing I am likely to do. 

    Scott.

    Depends what you want, if you want ease of reefing coupled with known performance and handling, then Arne's sail which is standard HM is the way to go. Cambered or flat, it is now well understood and it works well. Any of the others is a bit of an adventure.

    However, I really see no point in a flat sail. Cambered sails work and work well, unless you are building a mizzen which will double as a riding sail, for that purpose, flat makes sense.


    Last modified: 02 Nov 2018 00:35 | Anonymous member
  • 01 Nov 2018 22:52
    Reply # 6884907 on 6884609
    Anonymous wrote:
    Scott wrote:

    The answer is going to be "Don't do that!" but ... Is there one of these two that will clearly work better than the other if the sail panels are cut completely flat?

    The answer is going to be "Do do that!", because although we've said that it doesn't make much sense to make a flat sail these days, knowing all that we know now; you still want to find out for yourself.

    But, do it with a polytarp sail, so that you make a minimal investment in finding out what works and what doesn't. Cut your shape out of one big tarp, add some pockets very quickly, made out of the offcuts, and make a rolled tabling around the edges, not webbing (to save money). This sail should last a summer or two. Put your initial permanent investment of work and money into getting a tabernacle and mast into the boat.

    First, though, you'll have to decide on what kind of sailplan, in order to know where and how long the mast has to be.


    David,

    Thank you for the very well reasoned advice regarding a polytarp sail. I agree it makes sense for me to learn about flat sail performance at a lower cost and then later build the final sail with a quality long lasting material.

    I think I am on my own now. The Faintail sail, Arne's sail and the Weaverbird sail all seem to have different advantages. I find it harder to make a choice when all the options look good. 

    Somehow I will need to decide for myself what features are most important for the sailing I am likely to do. 

    Scott.

  • 01 Nov 2018 19:17
    Reply # 6884609 on 6883177
    Scott wrote:

    I will try to put the "tall tabernacle" out of my mind. Thank you for the response.

    Seems I am back to not knowing what to do, so I put the Fantail sail and the Weaverbird sail on top of the line drawing of the original rig. Maybe I should rig it so I can swap back and forth between the two? (A joke, of course).

    I think the answer is going to be "Don't do that!" but ... Is there one of these two that will clearly work better than the other if the sail panels are cut completely flat?

    Scott.


    The answer is going to be "Do do that!", because although we've said that it doesn't make much sense to make a flat sail these days, knowing all that we know now; you still want to find out for yourself.

    But, do it with a polytarp sail, so that you make a minimal investment in finding out what works and what doesn't. Cut your shape out of one big tarp, add some pockets very quickly, made out of the offcuts, and make a rolled tabling around the edges, not webbing (to save money). This sail should last a summer or two. Put your initial permanent investment of work and money into getting a tabernacle and mast into the boat.

    First, though, you'll have to decide on what kind of sailplan, in order to know where and how long the mast has to be. The Fantail planform will work better than others, as it adds some camber by the fiendishly cunning chinese method of allowing the upper, fanned panels to twist a little. These panels can be flat, even if, later, you come to realise that the lower panels can have and should have had some shape sewn into them. 

    Having said all that, later on when you've experienced a flat sail and got bored with sailing to windward slowly, you could do as I've one, and add camber by putting double cone hinges into the lower battens of a flat or near-flat sail. This way, you retain the one good thing that a flat sail has going for it: its docility.

  • 31 Oct 2018 22:08
    Reply # 6883208 on 6883186
    Anonymous member (Administrator)
    Annie Hill wrote
    I didn't have any more than the usual problems of the sheet fouling the leech of the sail.  I don't think there would be any advantage to lengthening to top sheeted batten.  

    Annie,

    it appears that your and my view on what is usual, is not the same. On the early sails I had, with a forward-leaning leech, sheet tangle was quite frequent when making long gybes. On the last three boats, i have kept the leech vertical or even leaning a bit aft, and on these there has been very few snags. In fact, for some reason I cannot explain, on my present Ingeborg I seem to get away with any sort of gybe without any sheet tangle. I do make batten 2 from top longer than the others since the leech of panel 3 leans forward.

    Arne


  • 31 Oct 2018 21:37
    Reply # 6883195 on 6872873
    Anonymous member (Administrator)

    Scott,

    sorry, but I couldn't resist the temptation, so I imported the Sailboatdata.com's sailplan and plonked one of my junkrigs on it. I ended up with a moderately tall sail with hopefully a not too tall mast (8.07m above wl.). See for yourself (batten length 3700mm).

    Arne

    PS: If you drop me a line, I'll mail you the .dxf file.


    Last modified: 31 Oct 2018 22:18 | Anonymous member (Administrator)
  • 31 Oct 2018 21:22
    Reply # 6883186 on 6882147
    Arne wrote:Scott,

    The fantail sail has proven that it works. Just take care and terminate the battens flush with the leech. This will minimise the sheet tangle. Would it be an idea to lengthen the top sheeted batten? Annie should be the right one to answer on this.

    Arne


    I didn't have any more than the usual problems of the sheet fouling the leech of the sail.  I don't think there would be any advantage to lengthening to top sheeted batten.  One thing, however, is worth noting with the fantail sail: the battens don't lie neatly along each other when it is reefed, unless you slack off the YHP.  Deeply reefed, the top batten tries to dive its forward end under the sail bundle.  I never felt too happy about not snugging up the YHP, but I'm not sure if this caution was justified.  Those more technically competent than I might like to comment on this.
  • 31 Oct 2018 20:59
    Reply # 6883177 on 6882763
    Anonymous wrote:
    Scott wrote:

    How tall can I make a tabernacle? 

    The top of the tabernacle should be just below the foot of the sail, so that the sail doesn't have to pass over the extra width as it is reefed and furled.

    I will try to put the "tall tabernacle" out of my mind. Thank you for the response.

    Seems I am back to not knowing what to do, so I put the Fantail sail and the Weaverbird sail on top of the line drawing of the original rig. Maybe I should rig it so I can swap back and forth between the two? (A joke, of course).

    I think the answer is going to be "Don't do that!" but ... Is there one of these two that will clearly work better than the other if the sail panels are cut completely flat?

    Scott.


    Last modified: 31 Oct 2018 21:04 | Anonymous member
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