Trimaran conversion

Discussion in 'Boat Design' started by brithowell, May 15, 2008.

  1. brithowell
    Joined: May 2008
    Posts: 3
    Likes: 1, Points: 0, Legacy Rep: 21
    Location: Stansbury Park, UT

    brithowell New Member

    I am new to this board, and am looking for some advice on a project I have been mulling over for a while now. There seems to be plenty of experience on this board.

    I have very limited design experience, but have built a few boats, both from purchased plans and from free plans (I will always recommend the plans that cost money from now on, but that's another story)

    I have a 14' strip-built kayak hull that has been hanging on the wall in my garage for almost 4 years now. The hull is complete, the deck is about 70% complete. One sunny day a couple of years back, I was inside looking at sailboats on the internet, and ran across a conversion kit offered from CLC for a kayak-to-trimaran sail rig. It peaked my interest, but I did not want a "snap-on" conversion. This is where it all started....

    I have been comparing technologies from one boat to another on this subject, and came up with what I thought was a pretty good design. I would lkie some feedback from some of you folks, good or bad. I already know the rudder is too small :)

    Attached Files:

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  2. TTS
    Joined: Jul 2007
    Posts: 112
    Likes: 3, Points: 0, Legacy Rep: 28
    Location: New Hampshire

    TTS Senior Member

    Look up Weta Trimarans. I think that there thought process on building is something that you could look at. Weta is a NZ company and you night have to try a couple of different searches to find them. If I can find the link I will post it. Meade Gougeon owns one and a company in North Carolina imports them.
  3. Chris Ostlind

    Chris Ostlind Previous Member

    Besides offering you as much info on the project as you might need, I can also offer you an opportunity to hang-out with kindred souls at my boat shop in SLC.

    The shop next to mine is also occupied by a small craft builder and we have a fairly large fenced yard directly in front of our roll-up shop doors for boat storage.

    There are something like 15 or 20 regular guys who float in and out of the shops over the year. We meet each Thursday evening on a regular basis and work on boats, talk shop, give each other a hard time and share tools and experiences.

    This weekend, there is a big self-made boating get together out at Starvation Reservoir near Duschene. Folks will be coming from all over the mountain states to sail, row, and paddle each others boats, camp out and share a righteous potluck dinner on Saturday evening. A great crowd of folks who will be happy to meet you and hear of your effort to build this boat you have planned.

    You are moving in the right direction with your design effort and with a few minor tweaks, you'll have a very nice sailing kayak once completed.

    Feel free to send me a private message offlist with your Stansbury phone number and email address and I'll get in touch with you.

  4. brithowell
    Joined: May 2008
    Posts: 3
    Likes: 1, Points: 0, Legacy Rep: 21
    Location: Stansbury Park, UT

    brithowell New Member

    Thanks for your responses.


    Found the site at Some good information to be gleened...thx


    Sent you an email.

    Everyone Else:

    Having some difficulty finding a way to figure out rudder size, short of guessing. Is there a formula for calculating this?

  5. Chris Ostlind

    Chris Ostlind Previous Member


    A lot of this will depend on the sail size you are running and the type of rudder control you have in the boat.

    I use the rudder shown below for a sailing canoe running a rig of 56 sq. ft. The immersed blade is 18" deep and just under 6" in width (chord) it uses a NACA 0012 section. The rudder cheekblock system is the kick-up variety made with simple components.

    I haven't had any stalling issues, it works well at the top end of boat speed and it is fairly simple to build from Northern White Ash.

    You will probably not get good results from a standard kayak rudder setup. The aluminum blades have a big tendency to bend-off (and snap) under load, reducing the effect of the foil and they are generally much too small of an area to create the kind of turning forces you will need with the proposed sail rig.

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