Junk rig on modern hulls

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

  1. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 98, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

  2. sharpii2
    Joined: May 2004
    Posts: 1,902
    Likes: 105, Points: 63, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    From the looks of it, the one cat rigged boat was really moving.

    It also appears that there was some curved shape to sail panels. Not an airfoil shape exactly, but most likely better than a pure flat sail. A pure flat sail is supposed to be one third less efficient than a good airfoil shaped sail. I suppose any curve at all, as long as it doesn't resemble a open trash bag, is an improvement on a flat sail. So, if you split the difference, a sail with a non airfoil curve is, say, half the difference between the efficiency of a flat sail and an airfoil one, it is then one sixth less efficient.

    Now, consider the fact that a single sail is almost always more efficient than multiple sails, then you've pretty much eaten the efficiency deficit by having just one sail.

    Then, when you consider this efficiency counts mostly going to windward, which few cruising boats spend much time doing, you may end up with no deficit at all, but a real advantage instead. You have a sail that is infinitely easier to reef than a more conventional sail which enables you to do two things:

    1.) wait longer before reefing, and
    2.) have a larger rig to begin with.

    Almost every junk rig presentation drawing I have ever seen has sported a considerably larger junk rig than the conventional one offered.

    The only disadvantage I see is the extra weight of all those boomlets. Such a rig would be too heavy for my 'Lola' design

    It would be interesting to race a junk rigged boat and a more conventionally rigged one with the same hull design, around the cans with just one crew each, with the boats being in the thirty foot range. The more conventionally rigged one would probably win until reefing weather set in.
     
  3. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 98, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    http://www.leow.de/chinese/stavanger/
    Here is a link with pictures of "shaped" chinese sails. Don't care for it myself as I think it makes little difference.
    The blue sail in photo here just looks stretchy, not shaped.
    BERTIE has sailed against various gaff rigged boats of her size and design and always won. She often ghosts as well as more modern types due to her big rig. Sail is cut flat.
     

    Attached Files:

  4. Tad
    Joined: Mar 2002
    Posts: 2,303
    Likes: 185, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

  5. MastMonkey
    Joined: Oct 2009
    Posts: 92
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Cali

    MastMonkey Junior Member

    Any comments on mixing Junk sails with western sail types? I am really curious about using a jib with a junk sail versus the typical ship rig the Chinese use. Though I have seen photos of native junks with sails like spinnakers and jibs flying, it seems some designers feel mixing the sail types compromises the effectiveness of both.
     
  6. Tad
    Joined: Mar 2002
    Posts: 2,303
    Likes: 185, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    Who? Why?

    This is the standard Colvin Gazelle rig, I don't know exactly but more than 100 boats out sailing......

    colvin.jpg
     
  7. MastMonkey
    Joined: Oct 2009
    Posts: 92
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Cali

    MastMonkey Junior Member

    I am familiar with Colvin's Gazelle. I ask the question because there is so much disinformation/opinion about the topic. And it relates closely to the topic of this thread. The Gazelle is a shoal draft cruiser with inboard ballast. The Junk rig seems to match the hull characteristics. Even Colvin though writes that the junk rig, while handy has drawbacks including the inability to heave-to. And the owner of "Migrant," the second Gazelle built, has written in another forum that it performed abysmally to windward and couldn't do so against any weather. This could be due to the the hull or also being a multi-masted vessel. I am not one obsessed with windward performance, but these experiences have characterized the Chinese rig to western observers. I guess the original intent of my question is why or why not to include western type sails on Chinese rigged boat? I have read in some forums that lacking a jib misses out on the potential slot effect it generates. Yet others retort that the forward sail in a multi-masted setup can create a similar effect. Contradicting what Colvin says, others write that a Junk rigged boat can be made to heave-to in a configuration like a yawl. I would think a jib would help in the ability to heave to and possibly to point, but this doesn't seem universally so.

    I am just trying to gain insight into the numerous discrepancies.
     
  8. pdwiley
    Joined: Jun 2008
    Posts: 1,002
    Likes: 86, Points: 48, Legacy Rep: 933
    Location: Hobart

    pdwiley Senior Member

    Tom is drawing me a junk schooner rig for my stretched Saugeen Witch hull at the moment. As far as he's concerned it works with a jib. MIGRANT did over 100,000 sea miles under the original owner and when I saw her for sale a few years back over in Malaysia the hull still had a junk rig so who knows? I think that Tom said over 700 Gazelles have been built now, not all rigged as junks but a lot of them.

    As my hull was first designed in 1964 IIRC I don't know if anyone would call it 'modern'.

    PDW
     
  9. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 98, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    Here's one that has worked successfully using a Swatow, very high peaked 1000 square foot sail in place of a gaff rig, with a slightly taller mast, jib and staysail.
     

    Attached Files:

    1 person likes this.
  10. Tad
    Joined: Mar 2002
    Posts: 2,303
    Likes: 185, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    There will always be "discrepancies" because every hull/keel/rig combination works differently and the reports are all biased based on previous experience and expectations....."The Gazelle performed abysmally", compared to what? A 12 metre or a Tahiti Ketch? Under her original owner Migrant is reported to have sailed 17,000 miles at an average of 142 miles per day, that's good going for a 33' waterline. Colvin has written (in reference to sailing his own Gazelle) that, "for ocean cruising, the closest anyone would chose to sail would be five points or more to the wind, why stress the ability to point higher at the sacrifice of efficiency, ease of handling, and efficiency on other points of sailing?"

    Certainly I find no reason to expect that a very shallow draft (3'10") flat-sided box keel design would be any kind of windward machine.
     
  11. MastMonkey
    Joined: Oct 2009
    Posts: 92
    Likes: 3, Points: 0, Legacy Rep: 43
    Location: Cali

    MastMonkey Junior Member

    Bataan: I learned quite a bit by reading your posts and descriptions of your vessel. She is a fascinating craft. I too love historic designs and really envy the experiences you have had researching and building them. One thing is often said about the Junk rig; that it is principally suited to old hull designs like yours because performance to weather is already restricted by hull characteristics. Do you feel this is true of your boat? I know you have said in the past that Bertie tacks through about 120 degrees. Do you notice a difference in pointing between having the jib or not?

    Tad: Of course you are right. But, I was attempting to relate my question to "modern" designs, as the thread title suggests. And I feel it is important to acknowledge that many modern designs are marketed for those that are day sailors and weekend cruisers. We do not have the luxury of trades always at our back. Considering that, I do not regard Gazelle's ability to crack of many miles that much of an accomplishment. Off the wind, with the amount of sail a junk carries it should crack on, especially considering Gazelle is also fairly narrow. Wouldn't nearly any designs with a reasonably hydrodynamic hull and a bunch of cloth to catch the wind? Would you honestly buy a boat that couldn't point tack through 160 degrees given there are many other designs that have much better well rounded performance? Would you design one as such? Again, the thread is based on modern hulls and that is what I base my questions on.

    I asked my first question because of how seldom one sees a junk conversion with the jib. The videos above shows none that do. Instead the mast is well forward. Partly, I understand that it is to maintain the ease of handling characteristic in the junk. But is there a scientific reason for such?

    One other consideration is that there is likely much variation in the difference Gazelle hulls built in terms of weight and displacement. Gazelle itself, and migrant, are actually quite lightweight I believe. Did you explain to you the purpose of including a jib, why he felt it works?
     
  12. Tad
    Joined: Mar 2002
    Posts: 2,303
    Likes: 185, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    MM.......regarding modern sailing cruisers and their use.....I've written before that in light of the way these boats are used by the majority, their exclusive adoption of the high-aspect sloop rig is pointless.....they never sail to weather and only reach or run, and that only occasionally. On any given day (this week, the past month, and maybe next week) I can look out the window in perfect sailing weather and see 20 sailboats under power. The three under sail are reaching/running across the gulf, the rest are going north or south (ie either with the NW wind or against it).

    T. Colvin has written (in Cruising as a Way of Life) that the jib on his junk schooners is considered by him a light weather sail and is the first to be taken down as the wind increases. As to heaving to he says that a junk has more reefing options that retain good balance than western rigs so it's not a major obstacle (in his view). Of course there are many modern fin keel boats which will not heave to in the traditional sense either.

    In many ways the addition of a jib (or not) was apparently a style issue, with some practicality and balance gains added in. Godfrey (see above) was going on to me about how cheap his sails were (fabric purchase), thinking this would influence my rig choice. But he depends on his engine, I probably won't be doing that and thus will have a long bowsprit, some big jibs, and even a topsail eventually.

    My wife grew up on this Colvin pinky.....

    TemujinSP.jpg
     
  13. pdwiley
    Joined: Jun 2008
    Posts: 1,002
    Likes: 86, Points: 48, Legacy Rep: 933
    Location: Hobart

    pdwiley Senior Member

    If you're interested in Colvin junk designs you really should get copies of his books 'Cruising as a way of life' (out of print), 'Cruising Wrinkles' (available from Tom) and 'Sailmaking' (available from Tom). The latter has a chapter on sailing Colvin type junk rigged vessels and what sail/reefing options are available. There's no point in my paraphrasing it here. Suffice to say that, as Tad has already stated, the jib is the first sail to come off as the wind rises and that, reefed right down, the hull balances under the reefed foresail alone.

    Comparisons with a high aspect sloop rig are kind of pointless. If you want one of those, get one. You'll gain the ability to point high at a cost in dollars and convenience in sail handling.

    I was watching a 70 y/o single hander sailing a Jay Benford 34' dory with a junk rig recently (BADGER type). He easily managed the whole evolution, tacking, gybing and stopping to wait for a car ferry to cross a narrow channel, from his steering position. When he reached his slip berth, he released the foresail halyard and it folded into its lazyjacks, reefing finished. Once in his slip berth he did the same with the main. After he'd finished securing the lines and tidying up he stepped off & went ashore. Try doing that with your sloop rig without in-mast furling or equivalent. Even with it, try reefing down while your sail is plastered against the spreaders. If something breaks or jams, good luck.

    There's no perfect rig. Life is full of tradeoffs. For me, a hull & rig that I can build, maintain & sail short-handed at a reasonable cost outweighs one with more theoretical efficiency on certain points of sail. I can always motor-sail upwind.

    My hull is classed as a medium displacement hull but similar in concept to a Gazelle. There are some subtleties to the hull shape that, according to Tom, make quite a difference to sailing performance upwind. I know the bow was interesting to plate and I can see how some people might simplify it. This doesn't apply to MIGRANT which was built in Tom's yard, of course. The original owners kept MIGRANT for some 30 years, with the junk rig, so how unhappy with its performance could they be in reality?

    And yes, there's been a huge variation in displacement of built Gazelles. Tom quotes figures from 22,500 lbs (his Gazelle with engine & tanks) all the way to 36,000 lbs for something so overweight it was ridiculous. I've personally seen one that drew 5'6" and had its transom bottom underwater.

    Here's the blog of someone with a Colvin DOXY design. Still junk rigged after many years.

    http://www.blogger.com/profile/03344568204950269287

    My advice FWIW is to get what you want and rationalise it afterwards. Works for me; I've got 4 rigging plans for my hull and waited until I had the hull finished before settling on one.

    PDW
     
  14. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 98, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    BERTIE tacks through 120 degrees because of her hull, and would do pretty much the same with 1000 sq ft of gaff sail and topsail instead of her equivalent area in lugsail. She points about 100 degrees between tacks but the course made good is different due to 7-10 degree leeway, and this has little to do with the rig. Loading her down with 10 tons of bricks or something else profitable would help a lot, due to immersion of flat lee side.
    Remember, BERTIE works well due to her difficult-to-imagine amount of stability. "Stiff as a church on Sunday" as Pete Culler put it. And it is not all initial stability as we put the mast head in the very chaotic and rough water one difficult day off Punta Gorda, breaking two battens and the boom, but she snapped back up fast without a hesitation.
    The Chinese rig is heavy and when your craft is heeled and all that weight is over the lee side levering the mast, you should have some stability to compensate. Any boat designed for a different rig, being adapted, needs careful thought and design for it to work right. GAZELLE is a good example that works great when following the plans and balancing sail area to load, because the designer understood what was needed and what was not. But she is not a cargo vessel type like BERTIE so doesn't do so well overloaded.
     

  15. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 98, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    Port Townsend wooden boat festival.
     

    Attached Files:

Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.