Junk Rigging, a question on suitability

Discussion in 'Sailboats' started by Jislizard, Jan 27, 2010.

  1. Jislizard
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    Jislizard Junior Member

    Hello, I have no previous sailing experience but I have always (since the early 80s anyway) wanted a Chinese Junk. It is the look and elegance of the hull and the sails that I am interested in. Sailing abilities are at this moment a secondary consideration but should probably be taken into consideration before buying any plans.

    I have joined a boat club to get some practice in but there are no junk rigs and no one yet will admit to having sailed in one.

    A few of the sailors I talked to mentioned that junk rigs were only good for catching the trade winds and are terrible at going into the wind. they also mentioned how unsafe they were and that wooden boats were a liability.

    All-in-all not very positive. They showed me the wood on a few boats and I agree that the Australian sun is pretty harsh, they are all faded or blistered and look pretty tatty after apparently only 3 months or so in the sun. Can you get a canopy to cover them as you can with cars?

    For sailing into the wind they recommended buying a really big engine. How bad are they at sailing into the wind?

    It was just the safety issue that is the concern at the moment. Are they really that unsafe? Any vessel in my hands at the moment would be but are these even more dangerous?

    Does anyone on the forums have any up-to-date experience on Junk rigs? The boaties in the club were talking about the ones back in the 60s/early 70s though with the design I was looking at http://www.jonquedeplaisance.net/index2.html there doesn't seem to be much in the way of changes in shape.

    I have read a few forums from people who have junks but they are in the minority so there must be a reason for it. they also only mentioned the pleasures of junk sailing and not any of the drawbacks.

    Thanks in advance

    MArk
     
  2. ancient kayaker
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    ancient kayaker aka Terry Haines

    There are some discussions of junks and junk rigs on this forum and elsewhere, do the searches and see what has already been written. If I had to summarize, the general feeling seems to be that they are ho-hum compared to modern designs of both rigs and hulls.

    The junk concept was an ingenious response to a lack of suitable boat building materials and and a requirement for short-handed sailing of big heavy boats. Within those restraints they are remarkably good at what they do, but you can do a lot better with the materials available today in most places. Most modern "junks" feature only the rig and don't have a real junk hull.

    However they are singular, iconic and eye-catching. Nothing wrong with that. A guy like me who is building a square rig for a very small sailing dinghy and several other thoroughly weird things certainly has no cause to criticise out-of-the-way ideas!

    A neglected glass-fiber or Ally boat will easily outlast a neglected wood boat, but well-built and well-maintained wooden boats have lasted several lifetimes.
     
  3. Jislizard
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    Jislizard Junior Member

    Thanks, I have read a few of the threads, I tried to post in one of those instead of starting a new thread but it was too old and wouldn't let me reply. Wish they had mentioned that before I wrote it all out.

    Ho Hum I can put up with, I am not planning on round the world trips or racing. The look is right and if it isn't any more dangerous than any other I don't mind the loss of a bit of function.

    Cheers

    MArk
     
  4. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    http://groups.yahoo.com/group/junkrig/

    There is a very active junk rig group at http://groups.yahoo.com/group/junkrig. So-called 'flat' junk sails don't work very well to windward. Significant improvements have been made with cambered-panel rigs (also called quilted junk rigs), and split-panel junk rigs. Arne Kverneland has a good description of making and using the cambered-panel rigs in the junkrig Yahoo group at Files > Arne Kverneland's files > Technical files > The Cambered junk sail. You will have to join the group to access the Files, though all the messages are public.

    Have fun,
    John
     
  5. gonzo
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    gonzo Senior Member

    The original junk rigs were designed for materials that stretched a lot and were weak compared to modern ones. A full battened sail that looks like a junk rig can be aestetically pleasing and have some benefits. With modern fabrics, the need for control lines is very reduced, which simplifies the system.
     
  6. sharpii2
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    sharpii2 Senior Member

    Flat sails CAN go to windward

    I once had a Super Snark(r) with a boomed lateen sail.

    The cloth was cut absolutely flat with a sleeve for the boom and the yard.

    I could tell because it lay absolutely flat on the floor. No sail I have ever had did that because they were cut with a built in curve, fore and aft.

    Once the sail was rigged it actually ended up with a negative camber, meaning one with the curved side facing the wind, like an upside down airplane wing. This was because the boom and the yard were held apart by the mast in the middle with the aft ends of the boom and yard able to bend. This loosened the materiel aft and, to some degree forward, but held the material in in the middle drum tight.

    I had no trouble going were I wanted with that rig. I just didn't go to windward as fast as I would of with a more conventional rig.

    There are probably thousands of people who learned to sail on boats like that.

    Far from aerodynamically perfect, but serviceable, none the less.

    The flat sail had another advantage. It could be feathered into the wind without fluttering severely. This is why I was able to sail up wind in a twenty five knot wind without reefing. I didn't get home fast, but I did get home.

    A typical traditional Junk does not have a keel.

    Instead, it has a huge, balanced rudder which retracts into a trunk when the boat is beached. The rudder not only steers the boat but provides almost of the leeway prevention as well. There are western boats that work this way too. The Yorkshire Coble is one.

    The problem with this system is that all the steering and leeway loads are put on the rudder shaft, so it must be quite strong. I have read several accounts where the rudder shafts failed.

    A long, shallow keel with an attached rudder could be put on a junk hull which would eliminate that problem, but eliminate beach ability as well.
     
  7. ancient kayaker
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    ancient kayaker aka Terry Haines

    Bob: that sounds like a crab-claw sail. The lateen sail and sprit sails can be cut flat which makes them attractive to amateur sail makers.

    Mark: there is a thread on the Maltese Falcon square rigger at http://www.boatdesign.net/forums/sailboats/maltese-falcon-hit-miss-12459.html which uses the Dynarig square rig concept and an interesting version of the Dynarig at http://www.boatdesign.net/forums/sailboats/square-rig-variation-30031.html which has an idea posted by me at post #14.

    I hope to build something along those lines. The original Dynarig does not allow the sail to be twisted so that the lower parts of the sail make better use of the reduced wind speed near the surface, not as much of a problem in a vessel as large as the MF. I hope to try out a scheme of sail twisting in my version if I am able to complete it; it will be a bit more important on a 10 ft boat!

    These are all somewhat similar to the junk rig in that they have the sail divided into sections, with each section connected between a pair of spars that control the sail's shape. The main difference is, the spars are curved not straight as in the junk, which should give a more efficient sail shape, and they do not need all of the control lines. Eliminating some of those is a good idea as Gonzo pointed out.

    The main problem with a single-sided sail with a permanent curve built in becomes apparent when changing tack. It is necessary either to wear ship, or to momentarily back the sail which causes the vessel to lose way. For this reason I am trying to adapt the concept to a double-sided sail which will, of course, be a wing-sail, but unlike the Dynarig, that does not lend itself readily to reefing or furling. Haven't figured that challenge out yet.

    Perhaps these will give you some more ideas.
     
  8. Jislizard
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    Jislizard Junior Member

    Thanks for the replies, I have joined the Junkrig Yahoo group so I will explore that more thoroughly. I will buy a book on sailing, it should have a gloassary and some pictures of all the different rigs so I will have a better understanding of the differences. For everything else I will Google.

    I will look at the Junk Rig Association as well, although you have to pay to join it might be worth it.

    Thanks for the pointers, I have plenty of time before I even start looking at building the boat so by then I should have a better grasp of the basics.

    Mark
     
  9. souljour2000
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    souljour2000 Senior Member

    Good luck..welcome to the forum...there are many smart people in here who know much,much more than I do about all kinds of boats...hang around here awhile and you will learn alot...feel free to post any tidbits of interest you find concerning junk-rigs...history etc..I dont know much about them at all but it seems they would have been good coastal traders...since they would have been well-suited to coastal wind systems...which are typified by an "off-shore" or breeze from the land in the mornings and "onshore"- or from the sea in the afternoons and early evening...lateen and junk rigs both were easy for a small crew to handle ...as earlier stated...and with coastal winds there was always wind coming from one side or the other...at night there is often wind too and in the summers this was a great time to sail without the harsh,burning orb beating down ...without much light at night to tie lines by and so forth...a simple rig was also good for this reason...
     
  10. sharpii2
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    sharpii2 Senior Member

    Nope.

    It was definitely a Boomed Lateen.

    The difference from that and a Crab Claw are two fold.

    One, With the Boomed Lateen the boom runs more or less parallel to the waterline. With the Crab Claw, the boom is cocked up to a pretty extreme angle, say, 30 to 45 deg. from horizontal.

    Two, the angle between the boom and the yard is usually quite acute, as little as 30 deg. on a Crab Claw. On a Boomed Lateen the angle is usually from 45 to 75 deg.

    Also, a flat cut sprit sail will work, just as any sail flat cut will work. But nowhere near as well as one cut to a proper three dimensional shape. Perhaps a flat cut sprit sail will work better than say a flat cut jib header, because, being loose footed, it is allowed to curve horizontally and it is roughly rectangular in shape, so the curved sections go all the way up to the top of the leech. Still, the air on the high pressure side will freely leak around the open head and foot of the sail. With a three dimensional cut, those ends will be more or less sealed to the thickness of the curve.

    It is my guess that a Low aspect ratio sail will work better when flat cut than a high aspect ratio one. Perhaps I'll throw that idea out on the 'sail aero dynamics' thread and see what they say.
     
  11. ancient kayaker
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    ancient kayaker aka Terry Haines

    I've not heard of a sprit sail cut anything else but flat but I am always willing to learn new stuff. However, what happens when the sprit is to leeward?
     
  12. sharpii2
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    sharpii2 Senior Member

    Hi, AK.

    The sprit bisects the sail diagonally, creating two bulges on the leeward side. Even these bulges may work better than a flat plane. But even if they don't, the sail shape is far superior on the other tack.

    It is my impression that sails, except for those designed exclusively for down wind sailing, were originally cut flat until the airplane was invented and airfoils were better understood.

    This hardly mattered in real world terms because just about all the material used stretched to some degree, both permanently and temporarily. This often, by default, created the fore and aft curved shape. Often, the curve was greater than desired and it got deeper as the wind grew stronger, just when you wanted it flatter. It was a real materials science race to find the fabric that stretched the least. Hence the journey from wool, to flax, to Egyptian cotton, to Dacron(r),to Kevlar(r), and now, on very high performance sails where cost is less an issue, Mylar(r).

    The last three materials mentioned stretch so little that the curved shape has to be built into the sail. This is good because now the sail maker can have more precise control of the airfoil shape. With bendy spars the sail can even be designed to automatically flatten as the wind rises. This is because the spars bend at the ends and stay where they are in the middle, held there by the halyard at the top and the vang and/or sheet at the bottom. Since the deepest part of the curve is near the middle, this tends to pull the sail flat as more load is put on the halyard, sheet, and vang as the wind rises. I briefly owned a boat with bendy spars. It was a revelation in performance! It moved at the mere rumor of a breeze!

    BTW- Shape can be built into each sail panel of a Chinese Lug. Doing this will probably restore the performance to the level of one made with more traditional, stretchy, fabric, where the curve occurs naturally. Doing that and placing the boomlets ('battons') further apart, perhaps at just three or four reef points, could go even further toward improving performance, while maintaining the rig's main advantage-quick and easy reefing.
     
  13. gonzo
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    gonzo Senior Member

    Sprits have a good and a bad tack, the same as lateens.
     
  14. ancient kayaker
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    ancient kayaker aka Terry Haines

    Good info Sharpii2, thanks! BTW, back when the first America's cup race was run Brit sailors firmly believed the more belly in a sail the better. That race proved how wrong they were, and there were several other lessons they had to learn from America as well.

    Gonzo: I am making a small lateen rig for one of my kayaks. Since it can only carry a small sail, I am mounting the yard on a short bowsprit rather than on a stubby mast. Thus it will not have a bad tack. I believe the sail on a lateen rig is usually used on the lee side of the mast, like a dipping lug.
     

  15. gonzo
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    gonzo Senior Member

    If you mount the lateen on a bow sprit, how do you hold the upper yard?
     
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