Can Modern Sail & Rigging Tech Improve a Ketch Rig?

Discussion in 'Boat Design' started by CloudDiver, Jan 31, 2016.

  1. CloudDiver
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    CloudDiver Senior Member

    I have been doing a great deal of book reading and forum research on the pros and cons of ketch rigs as well as other multiple mast rigs. Because of my love for classic lines and old wooden boats I've come to greatly admire multiple mast rigs in general, but particularly the ketch rig.

    So as I gather the pros and cons are (generally) this;
    - Ketch Rigs (and Yawl) were more common and favored in older designs before the invention of modern sail handling equipment. Stronger materials and gear allow for handling higher loads and sail area on a sloop rig.
    - With the above noted, a Ketch still offers easier single handing and more options for a balanced sail plan.
    - Some hull designs still favor a ketch rig, others not so much (too many variables in this statement to go into detail, hull design beyond the scope of my question).
    - To the wind the Ketch will not perform as well, the mizzen will be blocked by the main and cause more drag than provide lift.
    - Downwind performance is better
    - Mizzen makes a great riding sail at anchorage
    - With divided sail area, lower loads (or at least loads more equalized) across rigging

    Thats the short version I supposed. Essentially, my question is; Can improvements in design and sail handling technology improve some of the cons?

    I have a design in mind for a 30 ft hull with a moderate (narrowish but not skinny) beam. I have envisioned it as a ketch rig. I know there will be a higher initial cost in rigging but I am prepared for that. I believe, but not totally certain until the design is fully realized, that the higher rigging cost will be off-set by savings else where... Plus it helps when you buy wire by the spool, get your swage fittings at wholesale, and have unlimited access to a swage machine to build your own stays and shrouds after-hours for the cost of a few beers and some stainless steel welding repair jobs.

    Thoughts and suggestions? The design I have in mind can always be completed as a Sloop rig, but I have plenty of time to think it over.
     
  2. bpw
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    bpw Senior Member

    Steve Dashew wrote about this quite a bit. He is a big fan of large mizzens on his designs. They are quite a bit bigger than 30ft though. In a boat that small it is hard not too mess up the deck layout when adding a mizzen.

    The extra rigging can be a real killer when trying to get upwind in a blow while reefed down on a small boat.
     
  3. CloudDiver
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    CloudDiver Senior Member

    Thanks, I'll have to look that author up and have a read...

    Larger Mizzens eh? Kind of like a Schooner in reverse?

    I'm not married to the ketch rig on a 30 ft design, but I think its worth investigating, especially if modern rig tech can help.
    Cherry Lees and Westsail Ketches are in the 32 range, maybe worth stretching a bit to see if it can work. Those boat have fat beams, I'm hoping for a slightly more slender beam...
     
  4. Jonathan Rosa R
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    Jonathan Rosa R Never give up!

    Hi CloudDiver!

    I would also add the following pros and cons:

    PROS
    ------

    - The major advantatge of ketch rig is that it allows you to reduce heeling when sailing upwind. I mean: for a given sail area and sufficient lenght (that is quite important to move freely around deck), with a ketch rig you are distributing sail area more horizontally while in a sloop is distributed more vertically. So doing that, you are lowering the Heeling Arm (CPV-CLR) which means that for a same wind intensity for a given yacht, the heeling moment will be lesser and so you will sail with less heel.

    This is a great way of reducing heel when your yacht is not to beamy (beam gives you great initial stability to withstand greater sail areas). And remember how badly heel affects to comfort when it happens for a long time.

    - The other PRO is about aesthetics: be the colest sailor in your marina with a fashioned ketch. All sloop owners will be green of envy!!

    CONS
    ------

    Space matters:

    1) In small yachts (lets say something under 24 feet) I believe it is better to go for a single masted rig beacuse you need to move around the deck and cockpit and mizzen mast has to be positioned somewhere more or less fore of the rudderstock (in the case of the ketch).

    2) Ketch rig ocuppies more space and free-height around the deck. The number of stays, backstays, shrouds, on so on will increase and turnbuckles are fitted in the deck, so if the yacht is not to beamy and not to big in lenght, it will result in a lot of wire disturbing free movement. A triatic stay will help reducing wire between mizzen and main masts, but tensions and interaction between the two mast have to be studied throughly, since you are connecting those two masts via the triatic.


    Regards,
    Jonathan Rosa Ruiz
     
  5. FAST FRED
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    FAST FRED Senior Member

    The only advantage of a Ketch over a true Cutter rig in that size is the mizzen is a nice place to lean against taking a sextant shot.

    A huge mizzen stay sail would be an advantage , BUT most folks use the iron topsail in 5k or less of breeze.

    In a bigger boat , where the main may be over 400sq ft , a ketch is a fine idea , but so is a schooner in that size.
     
  6. bpw
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    bpw Senior Member

    Pretty sure this isn't true once you account for drag. Otherwise race boats would have multiple masts.
     
  7. CloudDiver
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    CloudDiver Senior Member

    I'm enjoying the responses to this thread, but I must point out the original question is can the cons of the ketch rig be improved by modern sail & rig tech?

    I am sure that for a 30 to 32 ft LOA with a narrower beam it is a bit of a hard sell to make that rig work, but I am keeping all of these same arguments in mind for a 40ft LOA design that will have no restriction on beam.
     
  8. Stumble
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    Stumble Senior Member

    Sure modern design and materials could improve on a smaller ketch, but I doubt it would come close to the efficency of a modern sloop or cutter.
     
  9. PAR
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    PAR Yacht Designer/Builder

    The choice of this rig means upwind ability isn't as big a concern and convenience and balance are higher up the priority list.

    Two changes to traditional ketch proportions can help. First is separation between the main's clew and the mizzen and next improving effective area once upwind.

    Effective area upwind is a difficult nut, unless you're willing to go to extremes. I have a canting mizzen ketch and it's very close, to masthead sloops of similar size upwind, but there's the complication of canting the mast to windward. Without the cant, the lower 3/4's of the mizzen is blanketed and back flowed by the main, all but rendering it useless upwind. With the mizzen canted (about 15 degrees), the upper 2/3's of the mizzen now breath in clean flow and really crank the bow up, meaning you can sheet the main in tighter.

    The other option is a large separation between the sticks. Several offshore racers have tried this, usually with nearly equal height poles and it does work, but you dramatically cut into aspect ratio, with this approach, even if the mizzen is now more effective. You do have more staysail hoist, but the basic issue still remains.

    Personally, if going the ketch route, I wouldn't worry so much about how much better it can be, unless you're willing to spring for carbon, freestanding sticks, semi rigid luffs and other go fast stuff, which seems self defeating on a ketch.
     
  10. Jonathan Rosa R
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    Jonathan Rosa R Never give up!

    What about old well known stimulators?



    Hi CloudDiver!

    You're right, we are talking about different topics :D. So what about stimulators? Is not something that new of course, but they help reducing some of the aero-drag around the section of the mast. I also recall the studies done by Pierte Gutelle about mast sections and their performance, although those studies were done decades ago and probably there have been new and more accurate studies.

    And I believe there is something about the optimitzation of a ketch sail system in order to reduce aero-drag in Principles of Yacht Design. But haven't work on it, just had a look some time ago.


    What is sure is that the interaction of 3 wings (genoa, main and mizzen) is normally translated into more drag than sloop rig (probably drag increases considerably after wind being driven through mizzen mast). Up to what I know, sloop will always perform better in comparison to ketch: when being both competitors, and both fully optimized, I bet ketch has nothing to do against sloop (at least sailing upwind).

    Regards,
    Jonathan Rosa Ruiz
     
  11. Jonathan Rosa R
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    Jonathan Rosa R Never give up!

    I know few companies designing nextgen ketches. In Spain Barrucada Yacht Design has worked in the design of a cruiser more or less like a nextgen ketch. And I think Dykstra Yacht Design (Holland) has also developed some of these yachts.

    The exterior style of this 55 m ketch from Dykstra is obviously neoclassical but ketch rig configuration is that of the nextgen type as you say, right?

    http://www.dykstra-na.nl/bestanden/aquarius_sailplan_515x335.gif

    And nobody has metioned it, but what about cutter-ketch rigged yachts? Does anyone know the result of this sail system?
     
  12. PAR
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    PAR Yacht Designer/Builder

    I'm not sure what you're asking Jonathan, but the evolution of the ketch in modern times, is much like the Dykstra approach. As much separation as practical and a proportionally taller mizzen. They still suck upwind comparatively, but it's an improvement over traditional proportions.

    [​IMG]
    [​IMG]

    A double headsail rig is a practical decision, not a performance concern, as the twins up front, just make things worse aerodynamically. With modern sail handling gear, I think double headsails are a novelty at best. If you're a cruiser, some rasional could be used for the double headsail rig, so you can pole out genoas in the trades. A real cutter rig, would place the main too far aft to make a ketch workable, though a yawl proportioned rig would be possible
     
  13. Jonathan Rosa R
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    Jonathan Rosa R Never give up!

    Thanks for answering PAR! I meant if ketches with double headsail perform better than traditional ketches... You have already answered.

    Project Amazon from Sponberg! Very nice one.
     
  14. Stumble
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    Stumble Senior Member

    What I think is being lost is that there is a massive difference in a 55m design and a 30' design. At 55m rig height and sail size quickly become serious limitations or problems that a 30' boat simply doesn't have. Things don't really scale well.

    Just as an example and 55m boat is certainly using carbon sticks tapered to the engineering. Almost no 30' boat is going to do the same, so the 30' ketch is going to have double the weight, double the windage, and may gain 30% in sail area at the most. Likely the total sail area will remain close.

    The 55m boat also has real issues like bridge clearance and the number of yards that could destep a sloop rig that big, while with two smaller ones it isn't quite as limiting.
     

  15. pogo
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    pogo ingenious dilletante

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