S/V Sea Witch. Polynesian outrigger Inspired Trimaran.

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  • 12 Feb 2017 00:10
    Reply # 4604799 on 4602302

    I just looked at the photos and sketches on your profile page.  I assume you are aware that you will need much bigger amas (aras) than the motorboat version, which looked like a Philippine Banca design.  For a sailing double outrigger, the amas need at least 100% of the main hull's bouyancy, and many modern cruising trimarans have used up to 200% (measured when the ama is submerged to deck level, which you should try and avoid in reality!).

  • 12 Feb 2017 00:02
    Reply # 4604798 on 4602302

    Pete Hill has a Bernt Kohler catamaran (see my Hall of Fame article about him in issue 72) and he initially built it with the anti vortex panels.  He found the boat had a seriously heavy helm and would not self-steer, so after crossing the Atlantic from England to Brazil, he cut them off and fitted mini keels.  This resolved his steering problems.  He did extend the design during construction, which may have affected the performance of the panels, but it is hard to see how.  I'd prefer the minikeel anyway, so you can beach the boat on it and scrub under the main hull.  With the vortex panels, the bottom of the boat would sit on the sand.  With dagger board in the amas (or aras as you call them) for windward performance, you would have the best of both worlds.

  • 11 Feb 2017 16:54
    Reply # 4604317 on 4602302

    We have created two albums. One of Aurora Delfin, the boat that inspired us. The other are some of the planning whiteboard madness and the MS Excel drawing. Don't take these drawings as the plans, they where done early on with just a base idea of what the Sea Witch would look like. We most likely start the build, stand back and say "we don't like that" and change it. Best part of building you own boat, you get to change a few things here and there. Nothing major....we hope.

    To Graham:

    We are thinking of a mini/micro keel on the main hull and Centerboards on the Aras. Centerboard will most likely be use too when beaching the boat to keep her level.

    We are also looking in on Bernd Kohler's (a designer we found on Duckworksbbs.com) Anti Vortex Panels as a option. We want to keep our draft as little as possible, so this might be the option.

    To Antoine:

    Thanks for the correction. We weren't sure what it was called (didn't do our homework all the way it seems), so we started calling it Twin Sails so not to confuse it with the schooner or ketch.


    By the why we think it is the sail plan we will be building. The Schooner rig with identical sails....our Twin Sails. Now with our minds pointing this way we can start piecing things together.

    (But still busy moving, so will have to wait)

    Last modified: 12 Feb 2017 06:46 | Anonymous member
  • 10 Feb 2017 12:54
    Reply # 4602365 on 4602302

    Very interesting I will follow this closely as it was one of my dream option before I bought WaterBear.


    Technically what you call Twin sails is still a schooner, as for a schooner the foremast has to be shorter or equal to main mast.

    Wish you all the courage and all the best for your project. Please feed us with pictures to follow.


    Antoine

    WaterBear

    Last modified: 10 Feb 2017 12:55 | Anonymous member
  • 10 Feb 2017 12:22
    Reply # 4602348 on 4602302

    Thanks for your informative post.  I am looking forward to seeing the drawings.  What will you do for foils?  Will you use a mini keel, centreboard, or foils in the amas or main hull?  The rig choice may come down to sail size.  My boat, Arion has a single 35 sq metre sail (just under 400 sq ft) and I find it quite big enough.  500 sq ft is manageable but will be hard work, and 600 sq ft has proved a handful for some short-handed junk sailors.  I like a schooner rig, with a solid foremast and robust sail, that way you can use it as a storm sail, with or without a deeply reefed mainsail, at least with the wind forward of the beam.  Many junk schooner sailors prefer to use the mainsail when running downwind, even deeply reefed in strong winds,  and sheet the foresail in flat to keep the boat from rounding up, and to inhibit rolling.

    Plywood is a good material if well sealed with epoxy, and quick to build.  It is so easy to repair as well.  If you keep the interior "Polynesian", that is very basic and open, the boat should be reasonably cheap and quick to build, compared to other methods and styles.  Good luck!

    Last modified: 10 Feb 2017 12:28 | Anonymous member
  • 10 Feb 2017 11:32
    Message # 4602302

    Greetings all.

    As some of you might know from the Introduction section, we are Martin & Sandy, from South-Africa. We are busy planning and designing a sailboat ourselves. We have decided a junk rig would work the best for us, and that’s why we joined JRA. (Who wouldn’t want to junk their boat? Easy to handle and maintain, and looks hot too!)


    The Sea Witch

    As per title you can see our boat is a Polynesian outrigger (canoe) inspired trimaran. We got the idea while searching the internet for our boat (the boat we didn’t find or couldn’t afford).  We came across a picture of a boat called Aurora Delfin II. She was built by a  surfer named Thomas Ritchie and his family. Okay she is built as a powerboat, not a sailboat, we will not hold that against her. There weren’t any plans or much info, other then she is a 40 footer, but the picture and videos was enough to get the wheels in motion for us. (If you are interested you can find more info, the little there is, on this boat on Reefrider.net or look at Aurora Delfin on YOUTUBE)

    This toke us down a whole new path, one we didn’t consider. Rather than just looking at sailboat, we started looking at canoes too. We came across one free canoe plan from Bateau2 which gave us the long narrow floor plan we started to envision. Then we found the bayou skiff plan on Uncle John’s General Store site, this gave the increasing beam shape we looked for. We also had a few back and forth mails with Uncle John, he helped a lot.


    The design

    We know that we will have limited resources and even fewer funds. So the design and build needed to be simple, fast, use mostly things we could find in our small town, and…cheap. With the K.I.S.S (keep it simple sailor/stupid) philosophy, much like the junk rig itself, we started drawing lines on a whiteboard. We toke the two canoe plans we had, mashing them together, and changing the scale a bit.

    The result, a ply over frame design, covered with fiberglass, with 11 (six-sided) bulkheads. Starting at the bow(stem), the bulkheads increasing in size till bulkhead 6, from there deceasing to the stern again. This gives us a narrow double ended shape. Bulkheads are 750mm apart (this is from center of bulkhead to center of next bulkhead) with the stem and stern extending by just under 1m from the last bulkheads.  This gives the drawn waterline length (of the main hull) 9.5 meter, a beam of 1.6m, and a draft of 300mm. (True draft would most likely be closer  500mm, water length 9.85m and beam 1.77m)

    The internal layout is also simple. Each section/area lies between four bulkheads. 1-4 The Head; 4-7 The Settee; 7-10 The Galley. Okay for those that followed all this so far might see there is only 1 bulkhead , number  11, left and still no cabin. Well 10-11 is walking space, and the aft cabin (1.9m in length x1.9 in beam x 1.2 in height box shape) with the cockpit on top of this cabin, will be attached on bulkhead 11(400mm above the drawn water line). This places the Cockpit floor at 1.7m above the drawn waterline, plus a 1.85m high hard top above the cockpit.

    The Aras or outriggers is a 50% the size of the main hull, minus the cabin top. They will be at a 20degree lift from the drawn water line allowing, the boat to heel at max 20degrees. The will also be close to mail hull, about 1.6 m from max beam (making total beam of boat 5.85m). This will give the boat a narrow look when seen from bow or stern.  At this stage thinking of using U-channel to attach the aras to the main hull. (Planning and Ideas still been thrown around) A support frame, most likely also of metal, will be inside the main hull to attach the aras to.

    We have a basic drawing of the boat, done in MS Excel that we would insert here (as soon as we figure out how to insert picture in post). David suggested we use FreeShip and we are busy modeling it with the software. Progress is slow as we need to learn to software, plus we are still moving house too. Hopefully soon we will have a better picture for you. Thanks David for the advise.


    The Junk Rig

    Now we can start with the Junk rig. The reason we joined JRA.  So we are thinking we can place the mast(standard round tube) anywhere from Bulkhead 1-6. Bulkhead 6 is dead center of boats water line. If mast is placed at bulkhead 1 this will gives us a maximum length of 7.5m.

    We have a few sail plans open to us. Using Wikipedia picture of junk rig sail plans, we will talk about these options.

    1.  The Cat

    This is a single elongated (longer then in Height) sail with mast at bulkhead 1 stretching all the way back to cockpit.

    Pro’s are. Cheaper to make and maintain. Fewest lines in cockpit

    Con’s are.  More weight to lift on halyard. Fewer sail options. On a run the end of sail will extend beyond the out riggers

    2. The Yawl

    Like the Cat Slightly smaller mainsail and the mizzen mast in front of cockpit on bulkhead 10.

    Pro’s are. More Sail options during sailing. Lighter Halyard on main as mainsail is slightly smaller. And one can use the heavy reefed mizzen sail as a type of anchor riding sail. (small sail on stern of boat to help keep the bow into the wind while at anchor)

    Con’s are. More cost as there are now two mast and more battens. More lines in cockpit. Driving force move slightly aft but not much we think

    3. The Schooner

    This is the rig we first drew when we talked about adding a junk rig. This is a small foremast mast at bulkhead 1 and the larger mainmast at Bulkhead 5.

    Pro’s  are:  Lighter mainsail halyard then the cat. Smaller sails to make, and handle off the rig. Driving force moves  forward. Again more sail options because of the multi sails configuration. Mast sizes can be same for both foremast and mainmast just length differ.

    Con’s are:  Like yawl , more costs, more mast, more battens, more sails, and more lines used and in cockpit. The foremast halyard heavier than one would have on a yawl due to sail size.

    4. The Ketch

    Much like the Schooner except the mainmast is now in front (bulkhead 1) and the mizzen mast behind (bulkheads 7)

    Pro’s are:  Same as the Schooner except the drive force moves more aft.

    Con’s are:  Again same as the Schooner.

    5. Twin Sails

    This one is not in the picture but is one to consider. Two masts and sails of same size.  Masts at bulkhead 1 and 6.

    Pro’s are: Sails and masts are same, so just a case of two of each. Only need to design one sail. Drive force also moves forward but not as much as schooners. Both halyards pulls the same weight. Again more sail options due to multi sails. On a dead run sails are spread evenly port to starboard. And lastly we can, if needed, move the sails between the masts without  any worry as they are the same

    Con’s are:  Same as with any of the other multi mast sail plan, cost, lines and control

    6. The Ship

    A Triple masted sail plan. Looks like a mash up between a schooner and yawl.

    Pro’s are. Smaller sails than a schooner. Increased sail area. Smaller masts. Lighter halyards. And loads of sail options.

    Con’s are: Highest cost. Three sails to design and maintain. Three masts of different sizes end length. And lines and lines and lines. Oh and more control lines too.


    So there are the 6 options. Our hearts lean towards the Schooner. Our heads towards the Twin Sails. And our pocket the Cat or Yawl.

    Sorry for the extremely long post, but the more info one has, the better decision one can make. We are of course open to suggestions and input. That is why we are here at JRA

     

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