Cat ketch/scooner

Discussion in 'Sailboats' started by J.D.Hogg, Jul 13, 2006.

  1. J.D.Hogg
    Joined: May 2006
    Posts: 49
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Richmond, Virginia

    J.D.Hogg Junior Member

    I'm still looking for a design for single handed voyaging, and leaning towards the 8m designs like the Didi-26 and Kavalier-800.

    However, I am also very attracted to the simplicity of cat rigs. I believe, and correct me if I'm wrong, that they provide the following benifits. Unstayed masts using conventional materials, reduced complexity, self steerage and easy handling.

    Can a given single-mast design be well adapted to two masts.

    Any opinions on whether ketch or schooner is better? Scooner rigs seem like they would be more predictable when reducing sail.
     
  2. BOATMIK
    Joined: Nov 2004
    Posts: 296
    Likes: 15, Points: 28, Legacy Rep: 190
    Location: Adelaide, South Australia

    BOATMIK Deeply flawed human being

    Generally it can be a little tricky to change a sloop over to an unstayed rig. You would be wise to pay for professional help if considering it.

    I have Sailed Bruce Kirby's Norwalk Island Sharpies a lot - Ketch rig. Reef like a dream. Slab reefing. Generally don't have to reef mizzen at all - at least until it is getting pretty fresh. Sail can be well eased and still not flap because of full length battens and sails can be well flattend because of flexible masts.
    NIS Boats (www.nisboats.com) have developed a tabernacle system that allows the boats to be trailed and one person on a winch to wind up the mainmast in about 2 minutes with complete control. Rigging time is about 14 minutes to launch because booms and sails right through to lazyjacks are ready to go because boom is mounted to tabernacle - not the mast.

    Regards
    Michael Storer
     
  3. Eric Sponberg
    Joined: Dec 2001
    Posts: 2,003
    Likes: 206, Points: 73, Legacy Rep: 2917
    Location: On board Corroboree

    Eric Sponberg Senior Member

    It depends on the design of the hull and the interior. For a cat-ketch rig, you want a little more buoyancy in the bow to support the weight of the forward mast. Therefore, a raked stem with a long overhang won't work well. You need more of a plumb stem and somewhat fuller sections. The interior has to be set up so that the masts don't come down through the middle of seats, tables, and berths. One also has to be aware of balance so that the center of the sail area is in an appropriate position in relation to the underwater profile (the "lead", as we say).

    The Sea Pearl boats at 21' and 28' both have two masts (to my design). So it certainly can be done.

    Generally, ketches are more weatherly (point higher) than schooners, so if weatherliness is one of your goals, then the ketch is the way to go. Schooners are faster when reaching because generally they carry more sail area than ketches. Downwind I think they are about the same, although on a schooner the main (aft) tends to blanket the foresail more readily, so you likely have to gybe through wider angles.

    I don't know how much money you intend to spend, but you obviously have focused in on the mid-20' range, probably partly due to the size of your budget. The smaller the boat, of course, the harder it is to live on and go voyaging. You want at least standing headroom. If you haven't already, you might want to look at the Globetrotter 45 on my website, and the article on free-standing rigs:

    http://www.sponbergyachtdesign.com/Globetrotter45.htm

    http://www.sponbergyachtdesign.com/StateoftheArt.htm

    Good luck on your endeavor.

    Eric
     
  4. BOATMIK
    Joined: Nov 2004
    Posts: 296
    Likes: 15, Points: 28, Legacy Rep: 190
    Location: Adelaide, South Australia

    BOATMIK Deeply flawed human being

    This is part of a two longer posts on freestanding rigs that are at ...
    http://www.boatdesign.net/forums/showthread.php?t=11939

    I agree with almost everything you have written Eric - and well explained too - easy to read and technical enough to explain correctly.

    One issue though.

    We have raced Norwalk Island sharpies a lot. When we want to maximise speed broad reaching and running we goosewing, But not as most people go about it with cat ketches

    For PERFORMANCE you can whip almost any spinnaker boat on a broad reach by running goosewinged - but almost everyone does it wrong. They let the mainsail choose its side and then push the mizzen over so it is by-the-lee. This configuration means that the mizzen is simply blanketting the mainsail unless your are on a really square run.

    Doing it the right way you let the mizzen flip to the side it wants and run the main by the lee - sounds scary but on an unstayed rig you can let the main out 10 degrees forward of the normal running position. Use lots of vang on both sails and watch her go. If you have attached flow (it will be reversed from back of sail to the front - Laser style - tufts on the main flowing crank the foot up to a 1 in 7 camber (upwind it should only be a tame 1 in 10 or a bit fuller depending on the boat)

    The air that is forced either side of the mizzen results in accelerated flow on the windward side of the mast - which goes straight at the mainsail. Same effect as running downwind with the fleet astern but to one side.

    Every square inch is working in a beautifully flat projected area. Compare with a spinnaker which has almost half of its area hiding behind the mainsail and poor projected area because of the large camber.

    When the wind gets up so that control becomes an issue it is probably best to drop the goosewing scenario incase a wave turns the boat and an all standing gybe is the result. With a freestanding rig it is a lot less traumatic and a lot less potentially damaging to boat, crew and gear, but not really the sort of behavior one should be cultivating well from shore.

    Best Regards
    Michael Storer
     
  5. J.D.Hogg
    Joined: May 2006
    Posts: 49
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Richmond, Virginia

    J.D.Hogg Junior Member

    Thanks both.

    I unfortuneately cannot afford one mast of the globetrotter much less the whole thing. It's the type of boat I've been sketching only bigger.

    How big of a hull can you build before the masts of a reasonably powered, free standing sail-plan, can no longer be made of wood or aluminum?

    Are all freestanding rigs keel stepped?

    Small is fine as long as it doesn't give up too much to a racing/daysailing cockpit, as the intent is not to cruise, liveaboard style, but to transport me around the world. One thing worth mentioning is I want to be able to unstep the masts and raise the keel for canal and inland waterways.

    Are sharpies well suited for deep water?
     
  6. Eric Sponberg
    Joined: Dec 2001
    Posts: 2,003
    Likes: 206, Points: 73, Legacy Rep: 2917
    Location: On board Corroboree

    Eric Sponberg Senior Member

    To Boatmik,

    You hit the nail on the head regarding running downwind. I have discussed just that point and those advantages in many of my discussions on free-standing rigs. In my comments above, I was also including stayed rigs in my thinking where setting a sail forward of the beam is not possible because the shrouds get in the way. But certainly, in my discussions of free-standing masts and the Globetrotters, free-standing rigs have the very advantages you discuss--wing-and-wing downwind for balanced, high-speed sailing with the ultimate in safety. The sails in this configuration are generating lift downwind, whereas a spinnaker on a conventionally rigged boat generates only drag. Lift is many times more powerful than drag, and that's why free-standing rigs downwind are so fast--there is just so much more power there. I wonder when the rest of the world will open their eyes to this advantage???

    JD Hogg's questions: The Nonsuch boats up to 36' all had aluminum masts, and most (but not all) of those have survived. Many of the Nonsuch 36s are going over to carbon fiber now. The early Freedom 40s and a vast number of free-standing rigged boats in the early 1980s all had aluminum masts. I think by 40', you need to go carbon fiber. For a wood mast, you are certainly below 30' LOA for a mast of reasonable weight. The early Herreshoff cat-ketches--28', 31', and 38' all originally had wood spars, they were square built-up box sections. They were very heavy, and weights varied a lot due to the wood soaking up moisture. Ultimately, all the Herreshoff cat ketches, including the later 45'er, went to fiberglass and carbon fiber which I designed for them.

    All free-standing masts must be keel-stepped, or, if you want to step on the deck, you need a compression post between the deck and the keel and some kind of support about 4-6' above the deck (tall tube socket, tripod, or some kind of structure) to hold the mast up. That is, you need two support points, obviously, a few feet apart.

    The Sea Pearl 28 design has an aluminum tube that holds each mast and each of the tubes include a tabernacle so that each mast can be tilted down when stowing the boat on the trailer. The forward mast tilts down aft, and the aft mast tilts down forward. This can be done by two people. A similar arrangement could be figured out for your boat.

    I am not that familiar with sharpies in deep water. Boatmik can probably fill you in there. Usually, you want a hull that has good carrying capacity, a decent keel, and adequate stability. If a sharpie has those features, then it should work OK.

    Eric
     
  7. Seafarer24
    Joined: May 2005
    Posts: 228
    Likes: 2, Points: 18, Legacy Rep: 22
    Location: Tampa Bay

    Seafarer24 Sunset Chaser

    A few boats you may have missed:

    Herreshoff 31
    These boats were constructed in the cold-mold WEST method (wood core, 'glass skin)
    Offshore 33
    Freedom 33
    There are two versions of this boat, the centerboarder and the keel. The keel model began in 1983 and is considered the better of the two.

    I'm currently working on the design of a 32' Cat Ketch with equal-length masts for single or double-handed offshore cruising. All the work I did last month is in New Jersey still, while I'm back home in Florida. It should be here later this week and I'll try to take some pictures for you.
     
  8. Vega
    Joined: Apr 2005
    Posts: 1,606
    Likes: 26, Points: 58, Legacy Rep: 132
    Location: Portugal

    Vega Senior Member

    For a 26ft, a cat rig can make sense, but a Schooner or a Ketch seems to me a lot of trouble for no reason. The rig that comes with the Didi 26 is certainly more efficient and simpler to run.

    About the boat, the Didi-26 is a great boat and a lot of fun to sail, but as the designer says, it is a : " high performance trailer sailer... high performance racing for Dad... comfortable weekending for the family.

    This is not a boat designed to be a voyager.

    If your main goal is not weekend cruising, but a small boat designed for voyaging, with available plans pointing to the amateur boatbuilder, I would take a look at the Vagabond 26.

    http://www.bateau.com/studyplans/VG26_study.htm

    http://www.bateau.com/studyplans/VG26_study.htm#BOM
     
  9. GregW
    Joined: Jul 2006
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Toronto

    GregW New Member

  10. J.D.Hogg
    Joined: May 2006
    Posts: 49
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Richmond, Virginia

    J.D.Hogg Junior Member

    Thanks everybody for the replies

    For unstepping or folding the masts, having them shorter and lighter is an advantage, as well as not having to deal with the rigging. There would be less heeling force for a given sail area and they can be self steering. While the didi is not perfect for my intents, it's hull and keel are what I like. The cabin is too small and the cockpit too large, but it's a starting point.

    Actually I was hoping to get away with two equal length masts from a one-design class like a laser or similar (perhapse not large enough), and use them with narrow, fully battened sails.

    Does a cat rig such as a nonsuch has, run a spinnaker? It would seem less than stable with all of the sail to one side or the other on a run.

    Prehapse I sould post a description of my ideal boat. It's slowly forming.
     
  11. BOATMIK
    Joined: Nov 2004
    Posts: 296
    Likes: 15, Points: 28, Legacy Rep: 190
    Location: Adelaide, South Australia

    BOATMIK Deeply flawed human being

    Hi all,

    I haven't been back here for a while ...

    All excellent information in your unsnipped post above Eric.

    With ocean work there is no difference between a sharpie and any other boat.

    You need good righting moment and a good range of stability.

    If the boat has them - then it is probably OK - but it is certainly more difficult to get them in a sharpie - but probably not impossible.

    But then again the accepted stability range of racing yachts has been reduced and reduced - some sharpies hugely outperform them in this area. Bruce Kirbys NIS31 has around (I can't quite recall) 140 to 150 degrees of positive stability, whereas many offshore racers run out around the 115 degree mark (unless they have changed the requirement while I wasn't looking!

    I would certainly rather be on the ocean in rough weather in a well designed sharpie than many of these offshore racing yachts.

    There are sharpies I would be worried about going across a bay in a decent blow and there are others in which I would be prepared to risk facing bad conditions at sea.

    But they do have to be judged on the same grounds as other boats.

    Enough blathering on my part

    Best Regards
    Michael Storer
     
  12. Eric Sponberg
    Joined: Dec 2001
    Posts: 2,003
    Likes: 206, Points: 73, Legacy Rep: 2917
    Location: On board Corroboree

    Eric Sponberg Senior Member

    Some Nonsuch's do have spinnakers, but you really should have running backs from the height of the spinnaker block to prevent the mast from pumping. Spinnakers are light air sails, and usually set well ahead of the boat, so heeling is not really an issue. Certainly, as you come more broadside to the wind, with so much sail area up (main and spinnaker) you are going to heel more. But the stability of the boat is pretty much the same. If the heeling is too much, douse the spinnaker.

    Eric
     
  13. dougfrolich
    Joined: Nov 2002
    Posts: 661
    Likes: 21, Points: 28, Legacy Rep: 225
    Location: San Francisco

    dougfrolich Senior Member

    Here is an example of a carbon fiber free standing cat rig with a spinn.
    The boat is a Wylie 44
     

    Attached Files:

  14. mattotoole
    Joined: Nov 2004
    Posts: 200
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Potomac MD, USA

    mattotoole Senior Member

    I saw a Freedom 25 in BC last month, carrying a spinnaker on a reach on its "Gun Mount" pole. I've always been interested in this boat, but I had never seen this setup in action. It looked like it was working well, but of course everything looks good on a reach in 10 knots of wind. BTW, it did have running backstays to support the chute.
     

  15. chandler
    Joined: Mar 2004
    Posts: 378
    Likes: 2, Points: 0, Legacy Rep: 16
    Location: U.s. Maine

    chandler Senior Member

    anybody have anything to say about offshore 33 cat ketch, good bad, quality of build. Anything? Links to offshore forums?
    Thanks
    Chandler
     
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.