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What About the Junk Rig...?
The 32' Junk Rigged Tahiti Ketch - Click for Larger ImageCopyright 2001 - 2016 Michael Kasten
Is the Junk Rig Suited to Modern Cruising...?
The junk rig shares many of the virtues of the gaff rig. The junk rig or "Chinese lug rig" is easy to handle, very easy to reef, easy and inexpensive to build, easy to rig, has no complex hardware, requires no winches, is easy to maintain, involves very low rigging stresses, provides a low center of effort so requires less beam or depth of keel, and at least in my view, looks great!
That is quite an impressive list of positive attributes... The following is not intended to be a comprehensive guide to the junk rig. It is however a good introduction to a few of the advantages offered by the Chinese lug, or junk rig. Due to its excellent qualities for blue water voyaging, I believe the junk rig has much to offer.
Some Advantages Specific to the Junk Rig
Reefing: The ease of reefing a junk rig is legendary. Perhaps it is best illustrated with a brief story about sailing one quite windy day off Port Townsend on Migrant, sister ship to Colvin's Gazelle. This was in 1979, when I was considering the junk rig for my own boat, then under construction.
Naturally curious, I asked the skipper about reefing the junk rig. He had just passed around fresh mugs of hot chocolate, so I expected a brief discourse on the subject. Instead, without saying anything he walked over to the main mast and with one hand released the main halyard just enough to let it slip over the belaying pin, paying out about half of it and then belaying it again. The boat was reefed. He did not put down his mug of hot chocolate... and he did not spill any.
Suitability to Cruising Boats: Many hull forms will handle the junk rig very nicely. As we are now seeing, fully battened sails are the "state of the art" on high performance sailing craft, for example on the America's Cup contenders. Given proper design, there is no reason the junk rig cannot be adapted to performance oriented cruising boats. An excellent combination is also the use of a fairly traditional hull form with the junk rig.
As with any rig, there must be correct balance, and sufficient sail area, with an efficient plan form given to the sails. In my view, there will ideally not be any "western" sails such as a jib, and the rig should approach that of a true ocean going Chinese junk. Among our designs that are able to make good use of the Junk Rig are the 44' Valhalla and the 42' Zephyr. That said, the Junk Rig can be adapted to most of our sailing designs, and even to a few of our motor yacht designs.
32' Tahiti Junk Schooner - Click for Larger Image
Suitability to Motor Sailors: A motor sailor can make excellent use of the junk rig. A motor sailor can be 100% sailing vessel, as well as being 100% capable under power, as we see in the 48' Jasmine. There are many other approaches as well, such as that taken by the Gulliver 46, the Greatheart 48, the 50' Renegade and the Greatheart 60 designs. These types have an emphasis on sail that is more on the order of around 60% or so. In other words, the sails are provided primarily for the purpose of auxiliary propulsion, rather than primary propulsion. The sails serve the function of being the "get-home" motive power in the case of engine failure. In addition, the sails provide extra boost while motoring when the wind favors. As a bonus, the sails and rig provide excellent roll dampening. For this purpose, the junk rig is ideal.
Simplicity: With a schooner or ketch configuration arranged in true Chinese junk fashion, therefore not having a western jib, there would be just two junk sails, therefore just two halyards total. For a larger vessel, a small mizzen or small fore sail can be used, or both, also ideally a junk sail.
Ease of use: On any cruising vessel, be it a sail boat or a motor sailor, it seems particularly advantageous to have the ability to instantly reef the sails, or to lower them completely without any fooling around. Sail and battens collect neatly in the lazy jacks. Once down, you can go to the sail to throw a line around the lowered battens if necessary. With proper lazy jacks, there is absolutely no drama to this.
Flogging / Luffing: There is no sail flapping and flogging when passing through the eye of the wind, either while tacking or jibing.
Safety: Individual "sheetlets" are lead to each batten, a full set of sheetlets on each side, so the sails are self tending. The sail shape can be controlled very effectively. This is quite a safe arrangement as well. The multiple sheets, one to each batten, make jibes very gentle, so there is no drama if someone inadvertently puts the helm too far over. This "soft jibe" effect is augmented by there being a fair sized portion of the sail forward of the mast, as a counter force. This makes the junk rig very forgiving for family sailing.
Sail Stress: Having multiple battens, the sails can be made of somewhat lighter material. Sail "cut" is not usually regarded as being critical, and most often junk sails are built "flat" rather than being cambered.
Appearance: In my view, the junk rig looks "right" on many vessels, especially so with a somewhat "traditional" hull form. Given the right match to the hull form underneath, in my eyes the junk rig is very handsome. This can be applied especially well to motor sailing types. For example, the junk rig would be a perfect companion to a vessel like the 50' Renegade.
Sheet Schematic - 5 Batten SailSpars & Rigging
Spars: Spars can be solid wood as is quite traditional, or, without much fuss hollow wooden spars can be made. Alternately, as with the gaff rig, the junk rig can take excellent advantage of welded aluminum tube or pipe for spars. When painted properly the aluminum spars are nearly indistinguishable from traditional round wooden spars. Compared strictly on a strength to weight basis, aluminum spars are much better. When compared on the basis of maintenance, the aluminum spars win again. In terms of longevity... aluminum is far and away the best choice. In terms of first cost (the cost to fabricate the rig), again aluminum wins hands down - all fittings being fully welded and therefore integrally a part of the spars.
48' Junk Rigged Schooner JASMINE
Standing Rigging: Most often, there are shrouds and stays to support the mast, as in the design shown above. However... the junk rig gains a terrific benefit from free standing spars, as can be seen in the Jasmine sail plan shown above. The reason for this is to simplify; to eliminate or greatly reduce chafe; and to allow the sails to have a much greater range of trim - highly useful for running downwind when the sails can be set at nearly 90 degrees to the centerline.
Battens: Many types of battens have been tried, varying from the obvious use of wood (easy to make but somewhat heavy for the required stiffness), to the use of ABS pipe (cheap but brittle when cold and limp when hot), to the use of fiberglass rods or bars (strong but somewhat heavy for the stiffness, and fairly expensive). Each material has an advantage and a disadvantage. Although fiberglass battens are a bit heavier and more costly, they will usually outlast the others listed by a substantial margin. Bamboo though is likely to be the ideal for battens: light, flexible, strong, relatively unaffected by heat or cold, inexpensive... and - big surprise - it is the preferred traditional material aboard Chinese junks...!
Running Rigging: The junk rig is friendly to use. For example, just as with a traditional gaff rig, one will be handling soft Dacron lines and multi-part tackles rather than harsh stainless wire and mechanical winches.
Proportion: The drawing shown below is very generic, and is intended only as a schematic to illustrate the approximate layout of a four batten junk (upper yard and boom not included in the batten count). In most applications, and especially for the optimum windward performance, the sail's proportions would be stretched in order to be somewhat taller and less wide. In other words, the rig would ideally have a somewhat higher aspect ratio, very much as can be seen on the 48' Jasmine.
Generic Four Batten Junk Sail Plan - Click for Larger Image
A Few New Terms...
A minor advantage of familiarity with the junk rig is being able to impress dock side wags by knowing all about lizards, sheetlets, euphroes, snotters, and bowsing tackles....!
Sail shape is controlled by each of the individual sheets. Each "sheetlet" runs through a "euphroe" which acts as friction block to keep the tension set as intended. In the drawing above, I've made use of a simpler arrangement using a fiddle block and separate "lizard" eyes in order to allow the sail to self adjust when it is reefed.
Once the sail is raised, if it is desired to tension the sail vertically, it is hauled downward by a "bowsing tackle." If it is desired to move the sail forward or aft, it can be done by controlling the "out haul" which in this case leads forward to the leading edge of the battens. The top yard can be controlled via a line called the "snotter" to move the spar forward or aft, or to snug it against the mast, as needed.
The Double Ended Cruising Yacht - VALHALLA 44 - Click for Larger Image
Converting an Existing Western Rig to Chinese Junk Rig...?
Is it worth it...? That is the fundamental question.
Although the junk rig has many benefits, those benefits are realized most dramatically for actual voyaging. For day-sailing, the Western rig is likely to perform better to windward – and on smaller sail boats, reefing Western sails is no big deal.
That said, if big water sailing over long distances is being considered, especially on a larger boat, there are definite benefits with regard to safety and peace of mind with the junk rig. The rig is after all very simple and easy to build. There are also the practical aspects of there being considerably lessened forces on all parts of the rig, in particular with free standing masts.
Outside those specific justifications, I’m less convinced of the benefits of converting to junk rig - mainly due to the effort required to effect the change. But if voyaging is in the cards, then a much stronger case can be made for effecting such a change.
For that process, the best source of information on the junk rig is within the book ‘Practical Junk Rig’ by Hasler & McLeod. It is well worth the price. There is also 'The Chinese Sailing Rig' by Derek van Loan, a book which I've seen but not studied. If you can find it, there is a very good guide to building junk sails by Tom Colvin, to my knowledge only available from the Colvin family, or in a good used bookstore.
DESIGNING THE RIG
For a variety of reasons, I don't favor mixing Western sails with Junk sails (for example, adding a jib, etc.). As for the shape of the junk sails, Hasler & McLeod seem to prefer a rectangular shape to the junk sail profile, with the battens more or less parallel. However I favor a fan shape to the junk sail as is more common in China. In other words, a fan shape similar to the the ‘Reddish’ rig in the H&M book, or like the sail shapes in the images shown above.
Regarding the best location of the mast and sail, the junk rig's CE and overall sail area should be approximately the same as the rig that is being replaced. Cardboard cutouts of the existing sail profiles can be made and balanced on a straight edge in at least two directions in order to find their common center. Alternately the CE can be calculated. Ditto for the proposed junk rig.
With that information in hand, the mast location (assuming a single sail and no jib), will be automatic, assuming a vertical mast. If multiple masts and sails are required, there are more options with regard to sail size and mast location.
‘Practical Junk Rig’ has all the information one will need for calculating the mast dimensions as well as the rest of the rig, plus good instructions for how to build a free standing wood mast.
NOTE: One caveat however is that in calculating the mast diameter I prefer to use a first principles approach, treating the mast as a uniformly loaded cantilevered beam, then secondarily as a point loaded cantilevered beam (with the point load at the halyard), both with a safety factor of 4 acting against the vessel's maximum righting moment. In so doing, I have found the Hasler & McLeod mast diameter calculations to be a fair bit under-sized for free standing masts.
H&M do not consider the vessel's righting moment (only mast length) therefore no attempt is made to actually determine the maximum load imposed on the mast. Because of this, I'm not too surprised to read that a few of their mast designs have 'carried away' in rough conditions, which Hasler & McLeod attribute to glue joint failure. In my view, since the H&M calcs yield masts of a relatively smaller diameter than a first principles calculation will require, their masts are simply more highly stressed.
H&M do make a good point however regarding preserving a certain amount of flexibility in the masts. Deflection at the masthead should be limited to no more than 2% of the panel length (partners to halyard attachment). Using a first principles approach with a safety factor of 4 does bring the masthead deflection into compliance with that limitation.
I submit that the cutter & ketch rig divisor of 7.1 used by H&M in their mast diameter equation is too aggressive. In my view, the more conservative divisor of 6.3 should be used (the same as H&M use for a schooner's fore mast). Doing so will yield a mast diameter much closer to a first principles approach. In my experience, the result will still be slightly under-sized, but that very much depends on the vessel's actual righting moment...
INSTALLING THE RIG
With the above information in hand, two remaining questions arise…
- How much more will the junk rig weigh than the original rig, and how will that affect stability and sailing stiffness…?
- How should you support the mast (mast step, partners, shrouds if any, etc.)…?
The first question can be addressed by simulating the added weight by hauling a weight equivalent to the difference in mass between your existing rig’s mass and center up to the centroid of the new mast & rig and test it (securely please..!). This test is simple to do and involves very little if any cost. Such a test is empirical rather than theoretical, and if performed in a variety of conditions, as long as your calculations are correct you can depend on the results that you obtain.
One caveat is that the 'distributed mass' of the heavier junk rig and sails will behave somewhat differently than a 'point mass' as described for the above test. For an explanation of why this is so, please see our Beam vs Ballast article under the heading Roll Moment of Inertia.
As for the second question… its answer depends on where the new mast position is located with regard to surrounding structure. If part of the ballast keel is available on which to place the mast step, the main task is then to provide adequate support for the heel of the mast laterally, there being relatively little compression involved if the mast is free standing.
This can be done using built-up floors and fore and aft webs, with a secure means to hold the mast in place. Then do the same at the deck penetration with reinforcements of the structure locally; a secure means of holding the mast (slightly oversize tube); and cabin knees or deck knees outboard as needed…
All of this can probably be accomplished on one's own by a process of trial and error . However if the above described process leads to a point of uncertainty with regard to the centers, the loads, or the structure, please feel free to contact me as needed for assistance.
It is worth mentioning that 'rig conversions' can be relatively time consuming for me to specify (therefore potentially costly) since I do not have the actual boat to experiment with. I must therefore 'model' the vessel's form, its CG, and its structure in order to derive reliable information, and then specify and illustrate structure that will stand up to the calculated loads. On a larger boat, or if cost is not an overriding concern on a smaller boat, the cost of involving formal design will be much more easily justified.
A Junk Rig Testimonial...
This letter was received from the current owner of Migrant, one of the vessels mentioned above.
Dear Michael,
It was nice to come across your piece [above] on the Junk Rig and immediately see Migrant named and another story about Dick Johnson told.
I bought Migrant from Dick in 1991 after having sailed on her a number of times since meeting him in 1971 when he first sailed into Bellingham. In 1994, with the same sails that Dick Johnson had used to go to Australia, New Zealand, Pitcairn, Mexico, and back to Bellingham, I sailed Migrant from Bellingham once again, bound for Mexico.
I spent a year and a half in Mexico before sailing onward to French Polynesia, Samoa, Tonga, Fiji, the Marshalls, Micronesia, down to the Solomon's, Vanuatu, New Caledonia, and Australia. By then I had put four more years in the tropical sun on the same sail cloth, and it had become very fragile.
On the way up the Barrier Reef, the top panel started developing tears. By the time I had crossed the top of Australia and gotten to Ashmore Reef, the top panel was in shreds and only the bolt rope around the perimeter was holding the sail and yard together, yet the sailing performance did not suffer in any noticeable way.
By that time the sun damage in the lower panels was severe enough that a careless push with my hand would go right through the sail. Even in bad squalls, the rips did not propagate because of the low stress on the cloth.
I continued onward through Indonesia, Singapore, Malaysia, and Thailand. I finally replaced the sails in July of 2000 when they became too disreputable looking, even for me...
What other rigs exist where a rip in the sail is not of any great concern, or that you would be able to continue onward for that many miles using sails with cloth so old and fragile?
William Servais
Aboard the junk rigged schooner, Migrant
In Conclusion
There are many excellent resources for more information on the junk rig. Tom Colvin has written many good articles and a few books on the subject, as have Hasler & McLeod, among others.
If this kind of wildness is of interest, please inquire.
42' Zephyr - Click for Larger Image
Please see the AVAILABLE BOAT PLANS web page.
Home | Intro | Our Design Process | Stock Design Info | Motor Yacht Designs | Sailing Yacht Designs | Prototype Designs
Plans List | Articles | Our CAD Design Stream | Maxsurf | News..! | SITE MAP..! | Site Search | Design Team | Contact Us
