Freedom 40 Cat Ketch Junk Rig Conversion

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  • 20 Feb 2017 01:03
    Reply # 4618324 on 4617035
    Annie Hill wrote: I found a good fix to this problem was simply to fit two boom parrels - one that went aft around the mast and one that went forward around it.  With the boom more or less fixed, the rest to the sail didn't appear to be able to lurch around much, either.  And, of course, it doesn't add any friction when raising the sail.
    I've done the same on LC, it has worked well.
  • 19 Feb 2017 06:01
    Reply # 4617329 on 4617035
    Annie Hill wrote:
    David Tyler wrote:

    I use them, as they also damp down excessive fore and aft movement of the sail in a seaway, and they permit me to get away without a LHP.

    I found a good fix to this problem was simply to fit two boom parrels - one that went aft around the mast and one that went forward around it.  With the boom more or less fixed, the rest to the sail didn't appear to be able to lurch around much, either.  And, of course, it doesn't add any friction when raising the sail.
    Barry and Ann - thanks for the input.  As is, I've got the boom shorter than the battens by 5% which may help me make the Dmin of the lower sheet span fit.  As to stagger - I am hoping to be able to work with the batten parallels and possibly the THP or LHP to help with the reefing.  

    We are getting through some serious rain here.  Good time to keep working on all this stuff.

    Erik

  • 18 Feb 2017 23:19
    Reply # 4617035 on 4613081
    David Tyler wrote:

    I use them, as they also damp down excessive fore and aft movement of the sail in a seaway, and they permit me to get away without a LHP.

    I found a good fix to this problem was simply to fit two boom parrels - one that went aft around the mast and one that went forward around it.  With the boom more or less fixed, the rest to the sail didn't appear to be able to lurch around much, either.  And, of course, it doesn't add any friction when raising the sail.
  • 18 Feb 2017 21:25
    Reply # 4616971 on 4613440
    Erik and Evi Menzel Ivey wrote:I do think a batten angle greater than 10-11 degrees looks odd.  I would love to do less of an angle, but I need the rise to get the Dmin to work.

    I'm thinking that one way to "fix" that problem of two steep a batten angle looking odd would be to design the bottom panel different and having the remainder of the parallelogram panels normal with the batten angle a bit steeper.

    Arne does something like this by shortening the boom. You could also make the bottom panel wedge shaped so the next batten up has a steeper angle, or perhaps do both. The geometry is very solvable one way or the other.

    Now I'm starting to think...I just remembered that when I reef my sails, the sail bundle doesn't end up parallel with the battens above it anyways. These junk sails just seem to find their own set, despite my efforts to keep everything orderly!

  • 17 Feb 2017 02:20
    Reply # 4613440 on 1424184

    I better write something since I was the one to start this thread.  I've been thinking that David's guide on % camber/batten angle/P would only work for my planform if I do hinges. Else I will need to make batten and other parallels work since I do think a batten angle greater than 10-11 degrees looks odd.  I would love to do less of an angle, but I need the rise to get the Dmin to work. 

    I've been playing with the shelf-foot method of creating camber and spending too much time in front of the computer...


    Erik

  • 16 Feb 2017 22:05
    Reply # 4613160 on 4613081
    Anonymous member (Administrator)
    David Tyler wrote:

    ...

    But why build a problem into a sail, so that a fix has to be employed? Why not design the sail correctly in the first place? We aren't talking rocket science here, just recognising that a cambered panel should have a little bit shorter diagonal than a flat panel.


    My main reason to do it my way is that I never build less than 8% camber into any of the parallellogram panels, and I don't want the prescribed 14 degrees rise at the boom. On none of my sails, so far, have i needed to  add downhauls to get the sails down, not even on Johanna (48sqm)  and Ingeborg (35sqm), with their 5-part halyard. I therefore reckon that I don't have a friction problem with my half-long batten parrels, described below.

    And, as said; I don't bother with inventing problems. There are enough of them on other fronts in life.

    Arne

    Last modified: 16 Feb 2017 22:06 | Anonymous member (Administrator)
  • 16 Feb 2017 21:11
    Reply # 4613081 on 1424184

    I agree, Arne, that short, or semi-short batten parrels are a great way of making any sail, however designed, reef and furl satisfactorily. I use them, as they also damp down excessive fore and aft movement of the sail in a seaway, and they permit me to get away without a LHP. The downside is extra friction - acceptable in a small sail, not so much in a large sail.

    But why build a problem into a sail, so that a fix has to be employed? Why not design the sail correctly in the first place? We aren't talking rocket science here, just recognising that a cambered panel should have a little bit shorter diagonal than a flat panel.

  • 16 Feb 2017 20:38
    Reply # 4613043 on 4612071
    Arne Kverneland wrote:

    Another way of dealing with batten stagger

    Folks,

    frankly, I think you are about to invent a problem, or at least, turning a tiny problem into a big one. Having seen how easy it is to scare new or wannabe junkies, the matter of batten stagger can easily grow into a showstopper to them.

    KISS :-D
  • 16 Feb 2017 11:17
    Reply # 4612071 on 1424184
    Anonymous member (Administrator)

    Another way of dealing with batten stagger

    Folks,

    frankly, I think you are about to invent a problem, or at least, turning a tiny problem into a big one. Having seen how easy it is to scare new or wannabe junkies, the matter of batten stagger can easily grow into a showstopper to them.

    The only sails I can think of which need these careful calculations to avoid negative batten stagger, are wide-chord sloop junkrigs, fitted to boats with inefficient rudders. These will benefit from sliding the sails forward, increasing the balance to ease the helm when reaching and running. To achieve this, these sails need to be fitted with very long batten parrels.

    For all the sloop junkrigs I have had, I have chosen boats with efficient rudders, so not even on Johanna, with the sail’s chord being 83% of the waterline, did I feel the need for altering the balance of the sail under way. On schooners, of course, altering the balance in any of the sails, is out of the question.

    My advise to those who want to set the sail with a fixed balance (after initial trials and adjustments), is to rely on semi-short batten parrels. They should be long enough for easy hoisting and lowering the sail, but short enough to keep the sail from moving more and more forward (=negative stagger) as one reefs or furls the sail.

    My compromise method has proven to work well: I cut the boom and lowest panel about 4% shorter at the clew (see JRA Magazine 42 p.19 about this). What happens when I drop the first panel is that the sail moves about 3-4% forward, but thanks to the shortened boom, the first batten will land flush with it. On later reefs, or when furling the whole sail, the short batten parrels (and the now almost vertical halyard) keep the sail from moving further forward. There is also room for cheating a bit, in particular if reefing with the sail pulling: By hauling on the throat hauling parrel, THP, as the halyard is eased, one can control the forward position easily. The result is a furled sail bundle with just about no stagger at the leech, and thus no sheet tangle when re-hoisting the sail  -  which, Btw. this exercise is all about.

    Cheers, Arne

     


    Last modified: 17 Feb 2017 12:26 | Anonymous member (Administrator)
  • 15 Feb 2017 23:21
    Reply # 4611342 on 1424184


     Camber  Growth of diagonal, when measured along the cloth as opposed to the straight line distance, corner to corner
     4%  0.45%
     6%  1.0%
     8%  1.8%
     10%  2.7%

     Camber;     P/B  Rise of batten above horizontal, to give 1% positive stagger
     4%;     0.2  9.6 degrees
     4%;      0.35  12.3 degrees
     6%;     0.2  11.5 degrees
     6%;     0.35  13.4 degrees
     8%;     0.2  13.8 degrees
     8%;     0.35  14.7 degrees
     10%;    0.2  16.0 degrees
     10%;    0.35  16.3 degrees

    So as the camber increases, so does the need for a shorter diagonal, but so also does the differential between the diagonals needed for narrow and wide panels diminish.

    For comparison, the rise of the sheeted battens in the fantail sail is  8.2, 11.5, 15.6, 19.6, 26.8 degrees. The geometry of the panels is very different, of course, from that of a HM sail.

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