Chinese Lugsail - A copy of Victor Winterthun's Chinese Lugsail page
 

The Chinese Fully Battened Lugsail.

If you do not participate in regattas, but want an easy handled rig for safe cruising, you should value the Chinese Lug rig. Also called Junk Rig. The main advantages are: 1. Easy reefing. 2. Low Tech. 3. Cheap to build. 4. May be entirely home built. 5. Easy to repair everywhere. As it is so easy to reef, you may have a great working sail area. The rig may be made with stayed masts, or with unstayed masts. The latter being the most usual. The sail were used in many different designs in old China. The types that are adopted here in the west are represented mainly by 4 types.

Type 1, represented by Tom Colvin:


Type 2, represented by Hasler/Mc Leod. See the book "Practical Junk Rig":


Type 3, represented by Derek Van Loan. See the book "The Chinese sailing Rig":


Type 4, represented by Professor Vincent Reddish:

The sails with fanned battens were usual in the South China Sea, in the Macao/Hong Kong area, but also as far west as Thailand. I think that fanned battens are the most logical choice for a sail with very low AR. It also looks best to my opinion. Sails, with a low Aspect Ratio of 1.5 like this, is ideal for reaching and running, and therefore for working with the monsoons. Used only for reaching and running it is not necessary with camber in the sail. For working upwind, it is better to use greater Aspect ratio, and some camber. Aspect ratio is defined as height of the sail^2/Area of the sail. Here in the West people, for a long time, believed that all Chinese sails should be flat, and that they generated lift in another mysterious way than other sails. I don’t understand why, because I have seen old pictures of Chinese sails that are obviously not flat. Vincent Reddish was the first person I know of, that was talking about camber in the panels. That inspired others to experiment further.
Portuguese Lorcas with cambered panels.
Vietnamese sampan with sail made of palm leaves.

Here the problem is not too little, rather too much camber. The Hasler/Mc Leod rig, as described in their book, is flat. The flat sails gave the Chinese Lug an unfair reputation of being slow to windward. However, all other recommendations in the book are sound, and probably the best place to seek basic knowledge about the modern Chinese Lug. After too many years of guessing, dominated by people who believed that some sort of turbulence produced lift in the Chinese lug, Junk Rig Association decided to pay for some research at the Exeter University. The result proved that there was no mystery about the Chinese lug. It had to have camber to be effective upwind, just like other sails. It is not important how the camber is created, as long as it is practical, safe and don’t make it more difficult to reef. Two methods have shown good results, and have been well tested. 1. Camber built in the sail by means of hinges in the battens.

The camber will develop in the lightest of wind, but will not increase in stronger wind if the battens are stiff enough. My boat has one hinge in the middle of the battens, which gives ca. 6.5% camber. With this sail I can tack trough 90 deg. With flat sail, the tacking angle was 110 deg. If you have a heavy boat, and need more camber to get maximum power, you should use two hinges in each batten, but not to near the mast. If they are to near the mast, they will have a tendency to flip the wrong way. This is dependent of how much sail you have in front of the mast. With the use of hinged battens, the sail can be made flat. Only some curvature along the boom is necessary. This means that the method may also be used to build camber into existing flat sails. That was what I did. In China it was usual to have bundles of bamboo aboard as spare parts, and for using as additional stiffening of the sail in stronger wind.

Malena with hinged battens.
My boat Iris with hinged battens.


Here with one hinge in the middle of each batten, with about 6.5% camber. Earlier I had two hinges. One at 30% from the luff, and one at 50% from the luff. That worked OK for all but the upper batten. The upper batten had a tendency to get an S-form around the mast when the wind came from the port side. However, with only one hinge at 50% from the luff, it is no problem.



Beatrice, a heavy Swedish motor sailor with hinged battens. She has one hinge in the upper battens, and two in the lower battens. Camber is about 8%.

Camber sewn into each panel, combined with stiff battens, is the other well tested method. In the olden days, the canvas was stretchy, so it was hardly necessary to sew in camber in the panels! However the Chinese prestretched it by means of sand before it was hoisted. Modern canvas is a lot less stretchy, and we have to sew in camber. With this method, you may choose more freely the point of maximum camber, and it is probably the best method to choose, when starting from scratch.

Malena with cambered panels.
Johanna with cambered panels.

Regarding the tacking angle, it is important to remember that it is not dependent only of the sail, but just as much of the design of the boat and the keel. My boat has a rather blunt bow and a keel on the smaller side. Her tacking angle wasn’t any better with the original Bermuda rig.

Camber in panels for Junk Rig Sails.

 

L = Length of batten.
D = Height of panel.
f = Additional canvas for creating camber.
c = Camber in % of L.

Control lines used in the modern Chinese lug.

Comments:

  1. Sheet.
    • On bigger boats it may be best to have an upper, and a lower sheet. This will give better control over twist.
  2. Halyard.
    • If you use unstayed mast, it is important that the compression force in the mast is kept low. On a 26sq.m. sail, I use a 4 to 1 purchase.
  3. Lazy Jack.
    • On a small boat, I will recommend a running system that is possible to adjust from the cockpit.
  4. Yard parrel.
    • This is a rope going from the halyard point on the yard, around the mast, back to the yard, via a block, and to the deck.
    • This parrel will prevent the yard from swinging around in waves, especially when the sail is reefed.
  5. Boom sling.
    • This is two ropes going down from the top of the mast, on each side of the sail, and fastened to the boom. It works together with the lazy jack, catching the bundle of the sail when you are reefing. In this way it is easy to swing the sail fore and aft.
    • Hasler/McLeod used only one rope on the outside of the sail, under the boom, and fastened around the mast.
  6. Throat parrel.
    • This parrel is working together with the yard parrel. It is going from the fore end of the yard, around the mast, back to the fore end of the yard, via a block to the deck.
  7. Batten parrels.
    • This are ropes going from the fore end of each batten and the boom, around the mast, and ends at the battens further aft. The distance between the fastening points must be big enough to allow the sail to swing forward the desired distance. If the batten parrels are too short, they will more easily catch when running up and down the mast.
    • Hasler/McLeod did not use batten parrel on the boom.
  8. Back haul/Down haul for the boom.
  9. May be combined with a kicking strap.
  10. Hong Kong parrels.
    • These are ropes used to prevent battens from "falling" forward, and create creases in the sail.

Some do not use batten parrels at all, but have a throat/luff parrel that comprises all battens, often divided in an upper, and a lower one. When the boat is tacking, the sail is hauled as far aft as possible, and when running, the sail is slacked off, so a greater portion of the sail is forward of the mast.

tr252