A New Beach Trimaran

Discussion in 'Multihulls' started by Chris Ostlind, Oct 22, 2008.

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  1. Chris Ostlind

    Chris Ostlind Previous Member

    OK, guys... I stuck it out there and competely revamped a design that I had been kicking around for a few years now and came to some very satisfying conclusions.

    Here's the boat... Essentially, this is a beach style trimaran that is capable of near shore coastal cruising (anywhere, really, that you'd be willing to take a large fast beach cat) Not Blue Water, please, save for short jaunts in known conditions.

    It is designed for easy setup and take-down and once taken apart, fits easily on any beach cat trailer that is hefty enough to handle one of the bigger beach cats (Nacra, Prindle, Hobie20, etc.)

    Here are the specs:

    Cardiff 21
    Sport Trimaran


    LOA …………….. 21’

    BOA .……………. 15’ (with amas)

    BOA …………….. 32” (vaka hull)

    Draft ……………. 12” (board up)
    52” (board down)

    Displacement … 1200 lbs.

    Sail Area ………. 216 sq. ft. and up depending on desires of owner

    The boat is designed for strip building in Western Red Cedar if you are in North America, Pauwlonia if in OZ and who knows what if you are anywhere else... (to be determined on a case by case basis if you can't get these woods)

    It's a simple, form driven stripping process for each half hull along the longitudinal line of each hull. The interiors are glassed, they are joined together with thickened epoxy with bulkheads in place and then glassed on the exterior set in epoxy. Hatch openings as suggested.

    The rig is from a harvested beach cat from H16 to H20 in size (depending on the thrill quotient desired) which also supplies the sailing hardware, the trailer, rudder and a whole bunch of other stuff. The board can be either a centerboard style of solution, or a daggerboard for those who are into limited compromises.

    The amas and akas are bolted together with the tramps in place. They fit into built glass tubes on the main hull and are pinned in place. The ama'aka structure is further stiffened with waterstays from the ama/aka junctures to the main hull above the waterline. The tramp is hooked to fixed pints on the integrated hiking benches and tightened-up for a solid, unified structure.

    Raise the mast with the winch handle on the trailer and a gin pole and you are in business in a flash.

    The traveler comes straight off the donor cat, so there is total compatability with the hardware.

    The boat will weigh between 500 and 550 lbs. all-up, if one is fairly judicious with the epoxy and will accomodate a nice bit of kit for a camping weekend on the water with a buddy, or even someone special.

    I expect some fairly lively performance with this boat, whatever the rig and it will be an easy in, easy out, affair at the chosen launch ramp or beach.

    I'd love to hear from you guys about the design, any limitations you might see in the details, such as they are, and just plain commentary from those who know about boats of this type.

    Best, as always...

    Attached Files:

  2. Gary Baigent
    Joined: Jul 2005
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    Gary Baigent Senior Member

    It's difficult to fault the design and anyway you end up with subjective viewpoints ..... which are just that. However in a beach tri design I think you could simplify, strengthen and lighten the design by not having a cockpit and perhaps make a lower wooded boat, reducing freeboard. But then my orientation is towards simple, high performance by reduction of size and materials, a minimalist approach - and that is not every bodies cup of tea. However on a daysailer you are going to have to take some cool weather gear because you are out in the elements perched on a trampollne so the "shelter" of the cockpit is not going to make much difference. But I can understand that many people like the conventional idea and illusion of a cockpit's safety. Whatever, the design is attractive and neat and is going to be an adequate to high performance boat anyway - so good luck with the design.
  3. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    I built a trimaran about that length years ago, with a cockpit - but much uglier.

    I suggest you make the cockpit self draining - that was always a nuisance and a danger in decent waves (like off the beach). It also makes outdoor storage less problematic - it wont fill up with rainwater.

    Likewise, a bit of of a splashguard on the foredeck ( or maybe a moulded foredeck)

    The flat seats along the side will tend to drain splashes into the centre hull. I found curved "seats" more comfortable to sit on, and if you design the lip to empty before the edge of the hull, it will make a much drier boat.

    You havnt drawn a net out near the bow. I found the narrow foredeck a real nuisance, and until I put a bit of netting up there, a bit hazardous.

    It might seem a bit impure - but provision for a small outbard will make the boat have even more useful. On a windless day you can get back to port, or even go fishing when there is no wind. Put the motor at the end of the stern, not hung offcentre from a beam. The motor will be "drowned" by waves if it isnt behind the hull. The trimaran made a much better fishing platform than small, narrow rocking "tinnies".

    The other thing I found usefull, was a bit of a "wash line", a slight horizontal ledge just below the gunnel, to deflect bow wash away before it sprays up on the crew.

    I think you will find the "screecher" a complete overkill on a small boat this size - I dont even think Tornadoes have anything but a jib, and with smaller ama's, you could easily be overpowered.

    See if you can figure out a way to keep the mainsheet traveller out of the way of the tiller and extension. I ended up running the mainsheet traveller on a steel cable, so the tiller could pass underneath the traveller. Having to backhand the tiller after every tack was a real pain.

    Finally, a self tacking jib was a great asset. It made single handling a much easier job.

    I look forward to seeing some pictures of it being built. Good luck
  4. Doug Lord

    Doug Lord Guest

  5. Fanie
    Joined: Oct 2007
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    Fanie Fanie


    I can confirm what rwatson mentioned. A foredeck and the netting to the bow. I also prefer the ama's rather too large than too small.

    Fishing (thanks rwatson ;)) from such a rig is something to consider. I myself is not interested in having the fastest rig around, just the fastest fish on my line :D Personally I think there is a huge market for sailing fishing rigs, just nobody provides for that. Keep in mind fishing is the most common sport in the world, fuel is expensive and not everyone buys a pesky ski-boat which is heavy and an unsafe outfit in my opinion. If the option is there, many will go for it.

    Easy to use sails and a small outboard for the odd no wind conditions. Also consider a trolling motor. Perfect fishing rig, cheap to maintain and use, easy, spacious, safe, go anywhere.

    Nice hull shapes.

    Dough, nasty fall-out there, good language expressions too, sounds like me trying to be a sailor :D

    I don't think Chris posted here with anything other than ask for opinions on his mind. I would like to honour that. The debate can continue in the other forum, and has no bearing on this one.
  6. Chris Ostlind

    Chris Ostlind Previous Member

    I guess this means we're not going steady anymore... is that right, Doug?
  7. RHP
    Joined: Nov 2005
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    RHP Senior Member

    Hear hear.
  8. Doug Lord

    Doug Lord Guest

    Fanie, I think he posted with the idea of selling plans and that makes Farriers comments very appropo......
  9. Chris Ostlind

    Chris Ostlind Previous Member


    While I do sell plans for some of the boats I draw, it is not the sole motivation for my design work. Selling something is rather far down the list, in fact. The Cardiff was presented here to gather input from the assembled readers who have a sum total of knowledge far greater than that which I will ever attain. I asked for their input because I wish to explore the potential of a given design genre such as the Cardiff and come to a much fuller understanding.

    Your comment above, about the selling of plans, would suggest that my efforts are driven by the desire for money. I would suggest in return that if money is the singular energy source that drives a person to design, then they are in for a very rude awakening in their quest.

    I've been a professional cameraman in the fields of still and motion picture work for more than 35 years, now. If my desire to create imagery would have been inspired by the pursuit of cash, instead of the inner need to create through the use of the tools in the medium, then I would have failed at my quest a long time ago.

    I have been fortunate to be able to work at the thing I have always loved to do and, yes, make a dandy living from the process. But, if I were to be driven only by the sketchy income potential when I first started in this career, then my craft would have suffered and I would have been quickly left for dead by those who would hire me to visually represent their needs.

    The same is true for working in the field of boat design, Doug. The financial rewards are typically limited, but the emotional satisfaction of creating boats that not only work properly, but also have an aesthetic feel that brings joy to the eye, are what motivates my entry into this area of work. One key to the fulfillment in that fashion is in the asking of others... and then the listening.
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  10. Doug Lord

    Doug Lord Guest

    Money is not the issue: the issue is inexperienced people being taken in by nice renderings and winding up buying plans from an exceedingly inexperienced designer: the blind being led by the blind. This subject has been
    covered in great detail on the boatdesign forums. There is evidence both here and under "Sailboats", and on Dinghy anarchy and Multihull anarchy that you are ,in fact, using the forums to PROMOTE your designs-and I feel that is wrong-maybe dangerously wrong in the case of a KIDS boat!
    Nothing is stopping you from building and testing your own designs-but using others as your guinea pigs doesn't cut it. Ian Farriers experience with you IS relevant for that reason alone.
  11. Chris Ostlind

    Chris Ostlind Previous Member

    Regarding your insistance to go off topic in a very nicely communicated thread up until your totally unnecessary intrusion, I refer you to Post #37 of the New Cabrillo Skiff for Kids, thread.

    And I quote:


    As the person who started this thread, I'm going to have to ask you to put your comments back on topic, or please excuse yourself from the thread. You have made your simple foray into the netherworld as the water boy of record. Those so inclined, have already read the post from Ian Farrier and moved on with their own opinions.

    It's now time to move back to the topic of the Cabrillo Skiff for Kids, specifically, or even any other kid related entry level boat that have a direct relationship to the boat in question.

    How about you observe some Forum decorum and let this opinion of yours fall into whatever place you put lost thoughts?"

    Anyone reading this thread and finding Doug's recent antics to be well beyond the expected behavior on this Forum... please avail yourselves of the opportunity to report said infractions to the Moderator.

    There's a clean little button on the upper right hand corner of each post which allows you to make a written report of disruptive behavior directly to the Owner/Moderator. Since Doug has not responded like a gentleman to a kind request to let this type of hostility go, I would be very grateful if you would do just that.
  12. RHP
    Joined: Nov 2005
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    RHP Senior Member

    Guys, life is far too short to get diverted by these needless attacks.

    I buy old cars and motorbikes in good faith about the condition they are in and always end up paying twice what I imagined to fix them up, but thats life.

    I am one of the blind and if a designer stands behind his design should something go wrong then thats good enough for me. With a 20' tri this simple, if it looks right it probably is right.
  13. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    I fail to see why only one designer should have a claim on all tri's. Everyone else is free to do his own thing. If it was a copy of someone else's work for reselling it may have been different. I fail to see what this tri has to do with any of Ian's tri's.

    As far as I can see, many of the boat designers maintain a presense on various forums. They learn from us, and we learn more from them.
  14. Butch .H
    Joined: Apr 2008
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    Butch .H Senior Member

    RHP the voice of reason. Good on you:)

  15. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    Chris, instead of the side pipes tucked inside the hull for trailing, why not make them foldable ? The BOA of your design makes it very easy to do.

    If it is foldable, the ama's can stay connected to the side pipes. This will make the time to water a no brainer. Fold the ama's off the centre hull, insert the locating pins, raise the mast and you can launch.

    My tri also has to be assembled, but the beams and ama's is a pain in the butt to assemble. Not difficult, but a pain. My one friend has a windrider. Same story, his beams also disasseble from the ama's and hull, and is a pain to assembe and disassemble.

    On the drawing, if there is a piece of flat below the hull's 2 pipes it will keep the ama's beam from falling through. You can just hinge the amas off the hull and it rest in place on the flat. Insert the pins and they're set to go. The drawing is as seen from above.

    The trampoline can stay in place and you can just cover with a sail for protection when out the water.

    I plan to convert my manually assembled beams to semi automatic ones soon ;)

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