Junk rig on modern hulls

Discussion in 'Sailboats' started by BATAAN, Sep 2, 2011.

  1. pdwiley
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    pdwiley Senior Member

    Joss, welcome. It's good to hear from another junk rig person with hands-on experience.

    I'm building a stretched Witch at the moment, just under 12m LOD. I thought about a Gazelle but wanted to stay under 12m for various reasons. Tom has done me a new sail plan for the hull, as much sail as one can get on her. Total of 840 sq ft including the topsail.

    If you've any photos to post of either of your boats, please do so. Other than GINGER you're the first person I've read about with a small Witch so I'd be interested in your comments on how a 26' steel boat worked in practice.

    PDW
     
  2. joss
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    joss New Member

    reply

    Being small and Corten steel JULIA seemed to have the scantlings of a miniature ship. A South Africaner who sailed over on a 1906 pilot cutter called her "a f..... hurricane hunting ice breaker." Seaworthy, seakindly design. Have been pooped such that the mast and rig is all you see and the design just sheds it off as it keeps on trucking. Sailed as well and frequently better than other 26' cohorts when I lived on the Chesapeake. Gaff rig can be (gaff) vanged and crew set in the chains forward to achieve incredible windward performance - the Hunter always complained he had a dirty bottom; the old wood Alden was not surprised. Anything off the wind and Tom's habit of hanging all working sail on the boat pays off. The junk rig lets one carry it longer and makes it infinitely easier to reef. The design is very easily driven. It is easy to over sail it for the thrill, but she doesn't like it. The design like any good one has "grooves" she loves to sail in. It will sail to windward of its own accord far better than I could ever helm it. Could be balanced dead downwind using appropriate main area and jib sheeted flat as steering sail. Because of her small size, she was tender to me moving about so I installed a Ratcliff auxillary rudder powerd by a push-pull autopilot for motoring and allowing me more freedom to move about and stay settled without having to trim the rig each time. Mizzen and jib made for comfortable sailing when it blew hard and the mizzen would keep her pointed up to heave too or make coffee. Small but always dry. Can't imagine you being disappointed. That said, it is a boat and it is a compromise. They have a saying in Antarctica: Murphy was born there, but he travels by boat.
     
  3. peterchech
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    peterchech Senior Member

    Forgive my ignorance, but can you explain the auxiliary rudder, exactly what it is and how it helps you not have to trim the rig as much?

    Also, are junk rigs as sensitive to oversheeting as a bermuda?

    I've played around a bit with balanced lugs, and like them (except in the complication of setup) is the junk easier to hoist/trim than the lug? (lug needs a killer downhaul to go upwind effectively, and I have had issues getting lugs to set properly, requiring different trim every time I go out to get it to set...)

    I often consider somehow putting a square sail on my keelboat, mainly because I do alot of downwind work in the Hudson river and there isn't enough sea room with all the ferries/etc. for me to feel comfortable hoisting the kite. Not to mention what a PITA it can be when short crew especially...
     
  4. joss
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    joss New Member

    Mr. Ratcliff built a SS frame and small 2 sq.ft. balanced SS rudder that bolted to the transom and instead of a wind vane (because of the mizzen) driving the rudder linkage it was linked to a tillermaster drive that drew less than 1/4 Ah. JULIA was 5280 lb. displacement and with a full keel was sensitive to me moving fore/aft/laterally and could head up, gybe or do other "interesting" things that boats do when they get a mind of there own.
    Tom Colvin has a saying regarding the junk rig: when in doubt sheet it out. With no telltale like luffing it is different, but not difficult to adapt.
    If the thin foil aerodynammics theroy is working, then yes they are sensitive to oversheeting because the principle forces are coming off the front and back edges of the sail in opposition to lift in addition to lift from the minimal and relatively constant curve/camber of each panel and not the whole stifly battened sail. I think it might be managing turbulent flow to advantage, but always on the fringe of chaos where it breaks down easily. It makes you pay attention to many more aspects of boat performance and comfort. I don't have permanent downhauls rigged on JOSS but can in minutes with multipurpose lines always available for such 'tuneing' and vanging when conditions allow wing and wing. Yes, a square certainly still has it's place if we could do something with the spar. I guess it's no worse than poles and paraphanalia the downwind sails of a modern boat require. The Witch hull liked dead downwind with a gaff main and club footed jib sheeted flat. If your using Tom's double sheet system of your junk trimming can be absolutely minimal. Or, if you want to play with the euphroes, snotters and blocks you can trim the sail flat at the top and full at the bottom, vis versa or middle or whatever suits fancy. Tom's lazy jack system allows the bottom bits to be replaced easily as they see the wear under the lowest boomlet. Yeah, single-handing leaves no one to blame, but time to spare to plan (and have the big anchor ready).
     
  5. BATAAN
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    BATAAN Senior Member

  6. pdwiley
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    pdwiley Senior Member

    I've thought of doing something similar and welded a set of 12mm threaded s/steel acorn nuts into the transom when I built it. I may never use them, but they're there. The other thing I considered was putting a pipe vertically through the hull just fwd of frame 17 (aft of the rudder) for a balanced steering vane setup - lock the main rudder and drive the small one via wind vane or autopilot. I didn't do that in the end and I can't be bothered cutting the holes now. The junk rig has the boom/bottom batten overhanging the stern so same issues WRT any wind vane steering gear. Tom claims they're unnecessary on this hull so I guess I'll find out in due course.

    I had to make my Edson type steering gear as the price these days is totally ridiculous. I did make provision on it to add an autopilot later by providing the stub shaft to attach a sprocket or similar. Has to be a wheel type autopilot not a tillerpilot though. We'll see what happens to the boat budget.

    PDW
     
  7. BATAAN
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    BATAAN Senior Member

  8. DennisRB
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    DennisRB Senior Member

    Here is a website which tells the story of a young Aussie couple sailing there 29 foot junk rigged boat from Canada to Australia via the northwest passage. Click on "the boat" to read about their boat and rig.

    http://www.yachtteleport.com/
     
  9. sharpii2
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    sharpii2 Senior Member

    I've thought of a different approach to a Chinese lug. One that sacrifices some of its virtue to gain a little bit better performance.

    I call it a 'gilled stack sail'.

    The bit in front of the mast is attached to the 'boomlets' only. It is supposed to act as a leading edge flap for the sail behind the mast, which is laced to the mast.

    There are only two 'boomlets' and a yard, so the number of reef positions is reduced to just two. But these two reefs should be just as easy to execute as reefs on a more typical Chinese Lug.

    Another advantage is there will be no more worrying about the sail chafing against the mast.
     

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  10. BATAAN
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    BATAAN Senior Member

    Was invented long ago but without the battens. It's referred to as a 'split lug' and was used some on naval boats, then abandoned.
     

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  11. Doug Lord
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    Doug Lord Flight Ready

    =======================
    Thanks for the picture, Bataan. Excellent historical reference to a square top jib!
     
  12. sharpii2
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    sharpii2 Senior Member

    I can see why it was abandoned.

    I imagine such boats never suffered for want of crew.

    The old fashioned dipping lug would definitely be superior in that case. It's all one sail and it's always on the lee side of the mast. Phil Bolger claimed it was the most weatherly of the 'traditional' rigs (he didn't like my idea at all).

    The situation I'm thinking of is a single handed boat. Not having to dip the lug would be advantageous, even if it came with extra sheet lines and, perhaps, lower performance.

    In any case, what I am suggesting is similar to that, but different for two reasons:

    1.) there is no second set of sheet lines to control the forward portion of the sail. It is held above and below by a boom, yard, or 'boomlet', and

    2.) the pitch of the bit of sail before the mast, relative to that behind it, stays fixed.

    I made a sail very different from the one shown, but designed to work on the same principle, when I was a teenager.

    It was made of 4 mil polyethylene and duct tape and was jib headed. It was mounted on a four man vinyl raft, using a framework I designed.

    It went to windward in a surprising fashion, once beating a boat nearly the same size, with and nearly the same sail area and load, up wind.

    The real problem I saw with this system was with reefing.

    When tying a reef, one has to be very careful to make sure the 'gill' keeps its pitch in relation to the sail behind the mast. Such can be fussy business at a time when getting things done quickly is of prime importance. Hence, I came up with the idea of 'boomlets' which take care of that for me.

    In earlier drawings, I had the yard nearly parallel to the boom with two battens at each reef point, one for the 'gill' and one for the sail behind the mast. This was to simplify things a bit.

    After more reading about traditional rigs, I became convinced the forward sloping yard was the way to go (to increase tension on the luff and to shorten its length, making it less likely to sag). Reading about the virtues of the Chinese lug pretty much sealed the deal, especially for the boat I was attempting to design. It is very narrow, making working on deck a much more hazardous occupation. Having a sail that comes close to reefing itself would be of great value in this situation.
     
  13. Schoonertack
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    Schoonertack Junior Member

    BATAAN; Good to see you posting; Ye old Scallywag. I went threw this thread quickly, didn't see what i have been wondering about for a few days. That would be the small matter of Lightning Strikes.Surely not a problem on your boat with your boat with wire shrouds and a length of chain over the gunnel,but what about the unstayed rigs?
     
  14. pcfithian
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    pcfithian Junior Member

    I've been looking at junk rigs for some time, for me the merits of easier sail handling, unstayed mast, and simplicity outweigh the slight drawback of not pointing so high. I don't plan on racing, and am old enough not care about it.

    I really like the layout of the Didi 34, why would this concept not work? A robust hull I can build, proven by several builders, and a single sail junk rig.
     

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  15. BATAAN
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    BATAAN Senior Member

    Before you venture into designing a junk rig, sail on several boats with one and under various conditions. What you have drawn, while it looks straightforward to the layman, would not set well at all due to the overly square shape of the sail. Remember the sheets pull down hard. There are good reasons the Chinese settled on the various sizes and shapes of batten lug they use and to be successful one should start there. Read the literature like Junks and Sampans of the Yangtze and the Hasler-McLeod book before you jump head first into an empty pool. While seemingly simple, the rig is very subtle at times and redesigning it without deep understanding courts failure. Unstayed masts with Chinese rigs are fine on boats with little stability and not overly large sails but I watched one break off at the deck on a boat that was suddenly pressed with a hard gust going downwind in a narrow channel with nowhere to head up to ease the pressure and insufficient time to ease the halyard. The unstayed mast with a rather heavy Chinese lug on it is subject to whip when pitching and the inertia load alone can break it. Typical Chinese unstayed masts are very large at the deck in proportion to mast length and are extremely strongly stepped. Also a fin keel design can give problems with weather helm as you have drawn it. Battens are always a problem. I use 2" aluminum 6061t6 aircraft tubing for my 1000 square foot sail and have broken several and the boom in a bad knockdown. Wood or bamboo would have died long ago and I am still using the same battens I originally rigged in 1985 with basically zero maintenance. Here is a pic of our main being bent on and the Big Eye Chicken junk sail it is derived from. This points as well as a gaff sail and it wonderful in light airs, reefs in seconds and is very controllable as to shape with the luff parrals.
     

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