JRA NL 20, Bunny Smith.

  • 16 Mar 2011 16:40
    Reply # 547036 on 484001
    Anonymous member (Administrator)

    Stavanger, Wed

                       The scalloping mentioned in PJR p. 16-17


    Before designing my first flat junk sail for Malena late in 1989, I did not pay any attention to the "scalloping bit" in PJR. My only ambition was to make a flat sail in the Hasler-McLeod style. I guess I wanted to learn to walk before trying to run.

    Only after the first 1990-season did I contact Robin Blain to become a member of the JRA and buy all the back issues. The process from flat sail to the today’s cambered panels (NL 24, 26 and 30) was full of cutting and trying, including the hinged battens. This was inspired by Paul McKay’s writing about his wishbone junk and a simple sketch he made of a hinged batten (which he never made). The idea about adding fullness in each panel was inspired by Vincent Reddish’s article in NL 22. I didn’t receive that issue, but luckily I read the story in the PBO-magazine. I don’t remember where I got the idea about using that barrel cut method (NL30) to get better control of the position of the max camber point, but I guess it was a logical step from the quick and dirty "tuck" or "fold" method in NL26.


  • 15 Mar 2011 16:04
    Reply # 546316 on 484001
    Deleted user
    It is amazing the "new" ideas that we find in "old" places.

    I was reading up on batten design in PJR, and ended up in a discussion of how the sail scallops a bit in the breeze and what effects it has.  Then I read this sentence: (pages 16-17)

    "It would be possible to cut a sail with this fullness built into each panel, thus achieving more arching in ghosting weather without requiring the battens to bend at all, but the implications of this would have to be studied empirically on a full-sized boat."

    Arne, I don't know if you noticed this before you started making your sails like this--it is easy to miss or forget about one sentence like that.  In any case, thank you for doing the empirical studies on a full-sized boat!

    Once again, I'm very impressed with how much the Hasler & McLeod would write about what they had decided to do and why....but left in little mentions like this more-or-less saying "We haven't tried this, but it could be worth looking at" sprinkled throughout.

    And I wonder what other gems well worth trying are hidden away!

  • 13 Jan 2011 23:36
    Reply # 495420 on 484001

    "– ouch, that would be bad!"

    Don't worry, Arne, despite your good ideas we can still get it wrong.


  • 13 Jan 2011 15:33
    Reply # 494977 on 484001
    Anonymous member (Administrator)

    Stavanger, Thursday

                  .. the slow rate of newsletters..

    I wonder for how long that Insect Flight Theory would have lasted if today’s internet had been around in the early nineties. The flow of information through the newsletters was appallingly slow, so a meaningful debate was not really possible. Just look at the numbers below.

    I received...

    .. NL30 in September1995 containing info as old as from Oct. 1994...

    .. NL31 in July 1996 containing info as old as from Mars 1995...

    .. NL32 in December 1996 containing info as old as from Jan. 1995...

    ... etc, etc...

    In practice this meant that when I sent in a reader’s letter about Malena in Dec. 1994, I would not be able to read any comment about it until July 1996 – 1½ year later! Now, there were never any comments, but I got many encouraging letters directly to my home address. Guess why.

    I remember I had two ideas about this:

    With this slow updating rate of the newsletters, I could actually have had a faster letter-debate with a person in Australia a hundred years ago when the mail went by sail!

    I was pretty content that I had no JRA expert hanging over my shoulders so I could do my cutting and trying without being pushed in any direction.

    So this forum is definitely a big step of progress – it lets ideas fly faster...

    Cheers, Arne

    PS: Maybe this internet forum is too fast and that the noise from all my writing hinders others from working out new ideas – ouch, that would be bad!

    Last modified: 13 Jan 2011 15:33 | Anonymous member (Administrator)
  • 11 Jan 2011 20:21
    Reply # 493629 on 484001
    Yo, but wouldn't the world be a sadder and duller place without the existence of people whose motto is 'my mind's made up - don't confuse me with facts'.  Impossible as they are to live with.  Bunny may have been wrong about bumble bees, but it was all great fun and made for highly entertaining discussions

    Probably Bunny's greatest bequest was to get so many clever people thinking more laterally about junk rig, so that we (tentative) 'Baggy Sailers' can benefit from their ideas. 
  • 11 Jan 2011 06:30
    Reply # 493295 on 492779
    Kurt Jon Ulmer wrote: Thanks to Ketil, David & Arne, Bunny and Vincent.
    I'm motivated to spend some hours perusing JR Newsletters. I have a few on paper, and borrowed a set once while contemplating the rig. Now there's a thick stack of .pdf ones available to me, and I'm grateful!

    Bunny Smith most certainly achieved a lot. His big mistake was he changed to many things at once, so he could never really tell which item he changed was actually the beneficial one. His other great mistake was that he was to busy trying to make the facts fit his theory and this blinded him to the many hints to where he should have been looking. None the less by shear bloody mindedness he got to where he was trying to go, even if he never really understood how he got there.
  • 10 Jan 2011 18:55
    Reply # 492779 on 484001
    Thanks to Ketil, David & Arne, Bunny and Vincent.
    I'm motivated to spend some hours perusing JR Newsletters. I have a few on paper, and borrowed a set once while contemplating the rig. Now there's a thick stack of .pdf ones available to me, and I'm grateful!
  • 25 Dec 2010 12:59
    Reply # 485424 on 484001
    Anonymous member (Administrator)

    Stavanger, Christmas day, before going to another Christmas dinner party...

    I think Ketil is right here. During Bunny Smith’s experiments he changed 2 parameters; fitting both "turbulating " keep battens and bendy battens. Credit for the improved performance seems to have been given mostly to the Insect Flight Theory. Alan Boswell had an article about this in NL 25, p.39.

    Bunny then did another thing that I think was very clever: He fitted a leech line between the tip of the yard and the tip of the upper batten and thus introduced camber in the top panel (see NL23 p27). The effects of twist in the fanned sail were mainly discussed by Vincent Reddish (NL 22), I think.

    Like David, I too think that the top section of a fanned sail produces a lot of drive. I have tested Johanna’s sail in a god Force 7 (inshore) with only the 3 top panels up, and the boat went like a witch, tacking and manoeuvring just like in a breeze with full sail set. During the rally in August I surprised both the crew and myself by demonstrating the power of these 3 panels in a medium F4. Johanna remained quite close-winded, maybe 5° worse than with full sail up. On a beam reach we were only a decimal from touching 5kts with those 21sqm on a 3 ton boat. On sails like these, with tall yards, the top panel represents about half of the total luff length so if one puts just a bit camber in the top panel, very much can be won.



  • 25 Dec 2010 08:52
    Reply # 485414 on 484001
    Ketil Greve wrote:

    Getting tempted with "Ideas we would not agree with today" 

    Gp.Capt. Bunny Smith's boat "Fenix" had a sail in which the yard and the top batten were steeply angled, much more so than on most junk rigs. I have said from time to time that this factor itself is capable of allowing a sail to take a cambered shape in its upper part, without needing bendy battens or cambered panels. I can't remember reading in Bunny Smith's writings that he ever measured or tried to evaluate this camber, and I don't think that he fully appreciated its effect. 
    I've just made a paper model of a fully fanned sail for my tender, that will use this effect to the maximum. I've put a photo into my personal photo albums. To get the fullest camber, only the bottom 3 battens would be sheeted, allowing the top 2 battens to fall away. The sail drawing is in the Box files.
    This fully-fanned sail type is only suitable for a small open boat. However the fanned sails that I made for Tystie and Malliemac exhibit the effect as much as is practicable, in a cruising boat's sail. I always felt with Tystie's single sail that it was the top part of the sail, up where the air is moving faster, that was producing most of the drive, and that when I reefed, I was withdrawing that part of the sail from the fast-moving air, just as much as I was reducing the sail area.
  • 21 Dec 2010 21:36
    Message # 484001

    Getting tempted with "Ideas we would not agree with today" I had a very intreresting look into the thinking of the Honorable mr. Smith. Reading it with novel eyes, it seems to me that the old master stumbled over the culprit without recognizing the real deal: Camber in the sail. Being too concentrated on turbulent/ linear airflow, he seems to have introduced camber in the sail, (bending battens) and experienced a great improvement in performance. Being concentrated on turbulence, the camber factor seems to be forgotten. Please reread and comment. Personally I intend to add a sort of slot in front of the sail to see if I can move the pulling forces of the sail a bit more forward to increase the sails performance close to the wind.


    Ketil Greve

       " ...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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