Hello from Iowa! Junk equivalent of a Sunfish rig?

  • 10 Jun 2022 15:05
    Reply # 12812254 on 12806132

    Seems someone has already fitted a junk rig to your dinghy.

    https://ginzorama.blogspot.com/2010/08/launch-day-woohoo.html?m=1

  • 10 Jun 2022 09:58
    Reply # 12812036 on 12806132

    Hi, Neil.


    I adapted the "Ah-Sup" sheeting method for use on my Wayfarer dinghy, which I unfortunately have used very little since building it.


    How mine is configured is that the helm's sheet goes through a block on the transom and is tied off to a triple block.


    A separate single continuous line runs from the sheetspans blocks on the leech run through this triple block to perform the same functions as would obtain on the mainsheet running to the transom on a larger boat.


    Twist control and control of reefed battens.


    In Ahsup's case, he seems to have simply tied away excess sheet at the leech of the sail at each batten as he reefed.


    I went one step further and brought the line going through the triple block further forward along the bottom of the boom to a turning block at the mast and down to a jammer cleat on the Tabernacle.

    So when I reef, at the mast, I drop the required number of battens and haul in and cleat this control line to bring the leech back to it's proper amount of twist and put the excess line in a bag.


    So there are 2 sheets in action. 


    A single sheet ( the "active" sheet) with only one turning block from helm's hand to triple block. This controls the sheeting in or out of the whole sail.


    This means friction is much reduced compared to the standard PJR layout with lines running through multiple blocks.

    Important for maximum responsiveness in an unballasted dinghy when big gusts come. It seemed to work well.


    The 2nd sheet ( the "passive" sheet) is only operated when reefing or increasing sail. Hauled in to provide the right twist and then cleated off. Or released to allow putting up more sail and then adjusted to give the proper twist to the leech.


    Unfortunately, this system still leaves a lot of line in the water in the event of a capsize, ( lots of line just can't be avoided with the Junk rig) but I personally believe it does improve sheeting response in a gust which is important in a small dinghy.


    So I suppose for a cruising dinghy, as for a cruising yacht, the importance of reefing early is the key to avoiding capsizes or broaches.


    It's just made a bit easier in the dinghy with one sail and no need to be fiddling with tying in reef knots on a flailing boom. All reefing work can be done at the mast, which in an open dinghy leaves you sitting safely amidships.


    My sail is a Split rig which pushes the leech further forward and creates more space aft for creating better sheeting angles per PJR.


    Split rig is not that much extra work to make.


    Alternatively, I believe some users of one-piece PJR style rigs have pushed the sail area forward of the mast to close to 30% and suffered no problems with lack of sail responsiveness in gusts. So that might help create more space aft for sheeting also.


    Also sailmaking might be a little less time consuming.


    So you need to decide which type of rig you might use, sort out the mast position with regards to CE and go from there.


    If yours is a fully open boat, perhaps you might consider building some sort of longitudinal box with multiple positions to install the mast, so you could experiment. :-)


    I just haven't had time to do more with mine, but if I get it up this year, I will take photos of sheeting arrangement and send on 


    Good luck with your project.


    Dave D.




    Last modified: 10 Jun 2022 10:06 | Anonymous member
  • 10 Jun 2022 04:02
    Reply # 12811906 on 12811848
    Neil wrote:

    Thanks Graeme, the dinghy issue was wonderful to read. There's so much cruising-oriented content on the JRA site, it was fun to see the smaller, simpler boats get featured.

    Well, Neil, insofar as the magazine is concerned, we can only work with the material that we are given.  And of course the same applies to the fora.  I should love to see more articles about open-boat cruising with JR, so I hope that you wil be sending the magazine editors some good pieces, once your boat is completed!
  • 10 Jun 2022 02:19
    Reply # 12811848 on 12806132

    Thanks Graeme, the dinghy issue was wonderful to read. There's so much cruising-oriented content on the JRA site, it was fun to see the smaller, simpler boats get featured.

    That is the boat that I'm building. There was at least a little bit of work to locate the mast step for the conversion from Bolger's sloop to Carnell's lateen. The stayed sloop rig steps directly on the floor, away from any frames, while Carnell puts the lateen step and partner up forward against the frame at station 6. It doesn't seem like a coincidence that the CE of the lateen rig falls directly over the leading edge of the leeboard (which is where Jim Michalak and others suggest putting for a flat little boat like this).

    I will try some of Arne's sketching to see what I can come up with for a sail plan. One of my concerns is getting the PJR 10 degree angle between the top sheetlet and the leech with only 16 feet to work in.

    My other concern is the complexity of a 3, 4, or 5 part sheet in a small boat where there might be an awful lot of tail lying around when sheeted in. Froken Sorensen is about a third longer and has twice the sail area. The simplified sheeting arrangement on Ah-Sup looks interesting where a single-part sheet is used for sailing and the sheetlets are adjusted on their own standalone set of spans. I wasn't able to figure out how it's rigged from issue 73 where it is described first, but maybe someone else here has done it successfully and could share a picture or diagram.

    Thanks for the welcome,

    -Neil in Iowa

  • 07 Jun 2022 00:29
    Reply # 12807997 on 12806132
    Anonymous member (Administrator)

    Welcome to the JRA Neil, it will be great to hear more about your boat building project and your cruising on the backwaters of the Mississippi. I think there is a growing interest in small boat cruising in sheltered waters.

    Is this the design you are building? About 16'?



    It rather looks as though the substitution of the sunfish rig was done in a very simple manner (as befits a small boat) with no change to the mast position and without too much worry about the so-called centre of effort (CE). To get something resemblng helm balance it looks as though the crew has simply shifted their weight aft a little (and possibly moved the lee board back a bit too). While the trim does not look perfect, it demonstrates that these things are not too critical on a skiff, and within reason, you can be fairly relaxed about mast placement on your little boat. If it were a junk rig I suspect shifting everything forward a little would be better, but I leave that to others to comment on.

    You are right, the lateen rig is very simple - and for an hour or two of knocking about on a sunny afternoon, about as good and simple as it gets. On the other hand, if you plan to go cruising and exploring, perhaps for a few days at a time, the junk rig will be far superior for a small boat such as this. The extra time setting up a rig which does look a little complicated at first, is well worth the effort. When it comes to actually sailing in a variety of conditions, the junk rig is by far the simplest to manage.

    Is there an existing design for a junk sail that could “drop in” for the Sunfish lateen?   Not as such, but if you go to the "MEMBERS' AREA" of the website and look in "Documents" then "Technical Articles" you will be able to find "Arne's Files" which is an excellent starting point, because Arne has provided some stock sail plans which can be scaled up or down to any size you want - and also an excellent introduction on how to make your own sail and rig your boat.

    (Arne has also invented a simple dinghy junk sail he calls the "Halibut Special" which might substitute directly for your sunfish sail, and match your shortish mast,

      though I suspect for a 16-footer he might prefer to see a scaled down version of one of his full junk rigs.) You might ask him about these things, on this forum.

    I am guessing you will want to use the existing mast, and if it proves to be a little too short, there are ways its length can be extended.

    If you want to follow a conversation on open cruising dinghies and junk rigs, here is a forum thread that might help you to bounce some ideas. The Junk Rig Association - Junket Boat.

    Good luck with your project. Your proposed cruising ground is of great interest.


    PS I just remembered, there is JRA Magazine Issue 79, if you are logged in you can download it from the JRA MAGAZINES section of the website (see menu up to the left)

    I have just found you can't. The system is not working properly for some reason, and Issue 79 does not seem to be available. I will email it to you. This issue has a selection of little boats with their various junk rigs featured, including Freebie which is my inspiration.


    (have a look at Freebie here).

    Also in the magazine, have a look at Dave D's split-junk rigged Wayfarer. This sail is slightly more complicated to make, but easy to use and suits the mast position a little further aft.

    Happy reading.

    Last modified: 07 Jun 2022 08:36 | Anonymous member (Administrator)
  • 05 Jun 2022 03:24
    Message # 12806132
    Greetings JRA, I am a new boat builder and sailor living in Iowa, USA. I am building a small, simple plywood skiff to try my hand at sailing on the large dammed backwaters of the Mississippi River. The boat design is Dave Carnell’s Nutmeg (e.g. https://www.duckworksmagazine.com/01/articles/featherwind/index.htm) based on Phil Bolger’s Featherwind, but simplified and designed to directly drop in a Sunfish lateen rig.

    Using a commercial rig that has been mass-produced for many years has lots of advantages for a low cost boat project. (Carnell’s plans refer to it as the “$200 sailboat”.) In fact, I got the spars for free from a neighbor who had one behind their barn and a used sail online for $40.

    But, the Sunfish rig has some limitations, perhaps the biggest one is that it can’t be reefed. In my reading, it seems like most sail-and-oar dinghy cruising types are choosing balanced lugs with two or three reefs sewn in, but those sails are either quite expensive on my budget or demand sailmaking skills that I am not confident I can learn.

    The new cambered junk designs appeal to me because they are very easily reefed and accessible to beginner construction. (They do lose out on rigging complexity against the sheet-and-halyard Sunfish rig.)

    Is there an existing design for a junk sail that could “drop in” for the Sunfish lateen? Can any of the rigging that PJR describes be simplified for a small 6.9m2 dinghy sail? The CE on the lateen is quite far back from the mast, and my calculations suggest either a very short aspect ratio (AR =1.2?) or needing to move back the mast step which would not be too terribly difficult on an open skiff like this.

    Greetings from the Midwest and thanks in advance for any suggestions you might have for a deeply intrigued rank beginner.

    -Neil

       " ...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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