hinged rudder for my Dufour T6

Discussion in 'Sailboats' started by peterhull418, Aug 6, 2015.

  1. peterhull418
    Joined: Aug 2015
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    Location: Watchet

    peterhull418 New Member

    I have a trailer sailer a Dufour T6. It is 6metres long and weighs about 800kgs.

    The existing rudder is very long and does not fold up when I go into shallow water.

    I want to make a GRP rudder for the boat that will swing up when I go into shallow water.

    I am wondering if I can adapt a large sailing dinghy like a Fireball with a GRP rudder to work on my Trailer sailer.

    Any design advice would be appreciated.
  2. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    welcome to the forum,

    That would be an easy thing to make work as long as it is large enough. the rudder size is determined by a number of factors, usually for smaller dingys and day sailors they use a rule of thumb of about 2.5 percent of the sail area. In most cases that is good enough, but there are a few other factors that might affect size.

    Usually the larger the rudder the more control authority you will have, particularly important in light air when hardly making any head way. A larger rudder would also have more drag of course, and be more trouble to stow when trailering, so the 2.5 percent number is just something that balances these and other factors fairly well.

    Another factor is on a really beamy monohull the rudder tends to lift out of the water when heeled over, so a longer rudder makes sure you still have enough rudder in the water to control the boat when heeled over. And on a hull design that tends to porpoise in heavy seas, a short rudder might lift out of the water occasionally, with possible momentary loss of control. Usually not a big issue, but sometimes it is possible broach very quickly when this happens, taking the crew by surprise.

    If you are happy with the performance of your existing rudder, it would not be that difficult to just copy the design but build a new one with a kick up feature. Search the internet for "kick up rudder" images for ideas, you might even find free plans somewhere, and instructions Or find a used one from something large enough to adapt if that is cheaper and easier.

    There is no magic formula, it just has to be sturdy and reliable, and large enough to control the boat in all sailing and sea conditions. Erroring to a slightly larger size usually is a safe bet.

    Good luck.
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Your boat should have come with a cassette style of rudder assembly, which works pretty good. I like kickup styles better, but this is a skinny water guy thing. There are a lots of examples to copy. Drop me an email (click on my name) and I can send you a few versions you can adapt to your application

  4. peterhull418
    Joined: Aug 2015
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    Location: Watchet

    peterhull418 New Member

    Thanks Petros and PAR for your posts. mY boat does have a cassette type Stainless frame into which the rudder slides which I remove when I want to use the outboard.

    The design of boat has a good sailing performance. When I am on hols with it the existing rudder is quite unwieldy to remove when on the move, hence my need for a kick up or hinged rudder
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