Is this doable?

Discussion in 'Multihulls' started by SeaLegs, May 26, 2007.

  1. SeaLegs
    Joined: May 2007
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    SeaLegs New Member

    Here is what I want to do: I want to build a skin on frame trimaran. Size is less than 17 feet. I want to be able to disassemble or fold it and put it on the top of my car. What I want to end up with is something similar to the smaller tris like the Astus or Challenger or that one in a current thread. I want a tri because I am a paraplegic. Throwing myself around a monohull just gets old and because I'm limited in my ability hiking out and can be slow switching over I often end up in the drink, at least when single handed. In light winds though I can be tough to beat!

    Designwise I was thinking of something like a sailing kayak or canoe. I like the sailing kayaks I have seen, like the Triak. I want to do it skin on frame because that would mean a lightweight boat with a fast build time. And construction would be simple, which is a big plus for me. I have all the tools needed for it too. I am handy and do not think I would have problems with a SOF.

    Really what I want to be able to do is put this thing together with enough time left in the summer to take it to the local lake where some friends often race and win hands down. They race Catalina Capri 14.2s. If it also happens to be a challenge to other similiar sized boats even better.

    I am not a boat designer though and would welcome other's experience. My over all concept is a main hull based on a SOF kayak with amas also either SOF or I was thinking of fiberglass over some foam. Do sailing kayaks have good sailing characteristics? How would this thing perform? Can I do it or should I explore a different route?

    Thanks for your comments,
  2. longliner45
    Joined: Dec 2005
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    longliner45 Senior Member

    yes you can do it ,,look at the american eskimos fishing boats ,,you will see neat little trickes like putting bone ,,or something else between the ribs and skin to stop wear and tear ,,being handycapped ,means you just have to improvese,,,,,you gotta , go with what you got,you can lay down and die ,and waller in self pity ,or you can build a boat that suits you ,,,I think your gonna build a boat ,,as far as your time frame ,,be readdy for setbacks ,,,,I have at least one a month,,,3 years and still building ,,and I dont think you will ,,but dont let someone tell you you cant,,,if I can help further pm me ,,,longliner,,,,,,,buy the way welcome to the group,
  3. tspeer
    Joined: Feb 2002
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    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    The Catapult catamaran is an inflatable beach cat similar to what you describe. Catapult hulls could be used as amas if you built a center hull that was tailored to your needs. If you could find a used Catapult for sale, that would provide you with the mast, sails, and all the necessary rigging hardware, too. The same goes for any hard-hulled beach cat, such as a Hobie or Nacra.

    A Hobie Wave might be adapted by sewing a fabric pocket to the tramp to hold your legs and hips in the center, along with something like a stadium seat to support your back. I've seen Manta landyachts adapted for paraplegic sailing with a seat belt, leg pocket and hand tiller - it worked very well.

    An existing trimaran that might be adapted is a Windrider 16. It's almost exactly what you've specified, except for the skin -on-frame construction.

    The Aerolite geodesic boats are skin-on-frame and very light. However, the center hull of a multihull is very highly stressed. The good Mr. Monfort may be able to design a hull for you that would fit the bill. It might require a vertical shear web down the middle to stiffen it against the compression and bending of the mast and forestay.

    There are a lot of special design requirements you may want to consider. I've had paraplegic friends that actively raced landyachts and I have a friend that is a paraplegic (almost a high-functioning quad) and owns a Rave trimaran, so I've seen some of the difficulties you have with a boat in this class. Instead of rushing to get something built to race this summer, I'd recommend you take your time to design a boat that you can sail for years, build it over the winter, and take your secret weapon to the lake next summer.

    You have to work out the whole boat as a system, and the land-based operations are at least as important as handling the boat on the water. A suitable boat is going to depend a great deal on your particular ability and circumstances. For example, do you have full strength in both arms or does the boat have to be set up primarily around one arm? Do you have helpers to get you in and out of the boat, or will you have to do it largely on your own?

    Are you launching from a beach, ramp, dock, or crane? The shore facilities will have an impact on whether you man the boat before launching, or do it after the boat is launched. Although you want something that is light enough to car-top, I suggest you consider a light-weight trailer - your type of boat can be pulled by any car. That will save a lot of assembly and disassembly, and make launching much easier. It also makes it easier to man the boat on dry land where you can approach it from any aspect and it is no problem to roll it into the water for launching compared with pushing it off of a beach or ramp.

    Getting into and out of the boat requires special consideration. If manning the boat on land, you can roll up to the cockpit and hoist yourself vertically up and in. If manning from a dock, you will need to traverse from the dock over the tramp to the cockpit.

    A tackle from the boom and a harness similar to a trapeze, windsurfing or hang-gliding harness would allow you to hoist yourself up, swing over the tramp, and lower yourself into the cockpit. But you will need to be able to raise the mainsail after you get in, so roller furling on the boom would be a good idea. Your tackle could have a wide fabric sling that goes over the furled sail and is removed once you're in the cockpit. Lines led from the harness to each side of the boat, with captive clam or cam cleats attached to the harness, will allow you to stabilize and pull yourself from side as you maneuver in and out of the boat. The boom topping lift should be led back to the cockpit so you can set the boom at the right height for entry and exit vs sailing.

    An alternate approach might be to use a spinnaker or jib halyard to the harness. A lot of mast rake would help position the halyard over the cockpit, or the side lines could be led to the sterns of the amas to provide the necessary triangulation to allow you to fly over almost any portion of the tramp and cockpit. Again, this will depend a lot on what kind of strength you have in your arms and your ability to handle more than one line at a time.

    Another possible way to go would be to look at something like the sliding seats used on the International Canoe. Although they slide the seat from side to side and use their legs to move their bodies to the end of the plank, you might consider a seat on a track that would roll from the ama to the center and lock into place for sailing.

    If you're sailing from a dock, you will want to have a means of capturing the dock when you come in. A single line led from the cockpit to the chainplate to the dock will allow you to snug the boat up the dock and control yawing until you can get bow and stern lines secured. A long lightweight pole may make it possible for you to lasso a dock cleat from the cockpit. A rubber band could hold a bight on the end of the pole and release it when the cleat is snagged.

    Small multihulls will capsize, so you need to design for that eventuality. You'll need to be able to free yourself from the cockpit and make your way to the surface. Being a paraplegic doesn't make this all that different from anyone else, but it has to be thought out. If you're normally sitting on top of the boat, you'll have some kind of restraint like a seat belt so you can pull on lines and not be dislodged when the boat heels. Even if you're seated in a deep cockpit, you may want to be restrained until the boat turtles completely, rather than falling out as the hulls go past vertical.
  4. SeaLegs
    Joined: May 2007
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    SeaLegs New Member

    Thank you for the very thoughtful reply. I don't have too many special considerations when sailing. I can single hand many monos just fine up to moderate wind. There are a few trouble spots but overall I have figured out ways to manage.

    Maybe a trimaran isn't the best word for what I have in mind. Maybe a better description is a kayak with training wheels and a sail. I was hoping that the easily driven hull like that of a kayak would get good speed with out piling on sail like in many tris. The amas would just be for stability, so they wouldn't have to be full size I think. I just don't know if this would still be fast. Because I am not piling on sail, I thought that might limit the stress on the main hull as well and simplify the rig. As much as I want to put up sail and and dream of fly the main and kicking up spray, I don't think this is the boat for it.

    Considering the stresses though, I was wondering if simply beefing up the keel in the frame of the kayak(main hull) and adding additional ribs would overcome some of these concerns?

    I want to get it done this summer, because I had the idea last summer and don't like the idea of putting it off again. I'm not to afraid to try it because it is cheap and if it doesn't work I figure I at least have a kayak. I can't afford to buy a manufactured boat and also don't have much room to store something on a trailer. So this desire has stuck with me.

    Thanks again,
  5. frosh
    Joined: Jan 2005
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    frosh Senior Member

    There is a an excellent range of kayaks and canoes with optional outriggers of various sizes. Some of the kayaks dis-assemble into shorter sections also. Sailing rigs of various configurations with the accessories needed, are also available. I have studied the excellent brochures and viewed the video. Seems a very well designed and engineered range of boats. Definitely worth a close look. Here is the link to their website:
  6. Chris Ostlind

    Chris Ostlind Previous Member

    Kayak Tri

    So, you're thinking of something like this except SOF for the kayak hull? The amas on this boat are inflatable and made from the same fabric that is used on whitewater rafts.


    Attached Files:

  7. garydierking
    Joined: Sep 2004
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    Location: New Zealand

    garydierking Senior Member

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