Gemini Catamaran Center Board Repair

In my opinion, much of Tony Smith’s design elements for the Gemini catamaran were brilliant. (English man, English term- that ‘brilliant’.) Take the centerboards as an example. Being able to raise the boards certainly makes entering shallow water easier. Lowering the boards enhances the ability to point closer to the wind during sailing. Also while motoring at slow speed, having the ability to drop a single rudder creates a pivot point to better maneuver.

Partially dropped Gemini center board

Partially dropped Gemini center board

On the other hand, Tony’s allowance for future maintenance of the ropes used for raising and lowering- shows less brilliance in execution. The access port, to view and replace the lines, is damned small on our 1997 Gemini catamaran. A smaller access port, however, allowed the installation of drawers for storage- a typical boating trade-off. In fact, I do use the drawers daily. The line I replaced was 19 years old.

While on the hard at Jarrett Bay Boatyard, I removed the access lid and with a flashlight was able to look into the centerboard box to observe the lines’ conditions. The starboard board’s lines were relatively new- as is the board itself. The original equipment port side line showed a fray near the up-haul attachment point.

Gemini Center Board repair line damage

If one is to repair a centerboard, far better to do so while the boat is on the hard.

Our sequence was pretty much:
Raise the board as far as possible, and secure it with a dedicated “prop stick”;

Remove the screw which holds the knot-tail from jamming between the board and its box;
Gemini Center Board repair up haul knot

Untie the knot;

Note the funnel and tube. Soapy water was needed to aid in loosening the knots. The blades were used to saw thru the down haul knot.

Note the funnel and tube. Soapy water was needed to aid in loosening the knots. The blades were used to saw thru the down haul knot.

Tie on a fish line for pulling the new line;

Gemini Center Board repair fish line

Dig a small trench below the board so as to then drop the board all the way down;

Saw thru the haul-down knot at the board’s “knuckle”;

Gemini Center Board repair sawed knot

Unscrew the spool’s compression nut;

spool bolt hole

spool bolt hole

Pull the bolt;

Wiggle, tug, and cuss the spool out of the box;

Gemini Center Board repair spool

Trace the winding of the line;

Remove the center of spool line locking screw;

Remove the line.

Starting with the haul down attachment point, install the new line.

Gemini Center Board repair zip tied knot

Gemini Center Board repair new knot

Note that I wrote “line”. The system uses one line which is tied at the up and down haul points. The line functions in great measure due to being spooled and passing over and under a non rotating smooth bolt.

My suggestion is that you watch a Gemini factory video linked at
I watched it twice before executing the project, and referred back to sections of it as I did my work.

Replacing the line was fairly straight forward. My only (known) glitch was in not getting the line as tight as possible before assuming the job to be complete. Be sure to reinstall the center of spool line locking screw before trying the success of your effort!

Also, leaving a little extra tail on the haul up end of the line will aid in retightening the line should you find (as I did) that it is necessary. The tail gets screwed to the rudder stock anyway.

As has been many of our “new to us” maintenance issues- the biggest hurdle is building the confidence to tackle the job. With the right tools, the job goes easier- once begun.


The story / blog of Yacht A Fun, a Gemini catamaran sailboat, traveling the ICW and east coast with insights to the extended cruising life. Gemini Catamaran Center Board Line Rope

Comments 4

  1. Thanks for the information. I find it very helpful. Would you know how to remove the boards from the boat? Any help will be very appreciated. Thank You. Victor

    1. Post
      1. Have you removed your center boards yet? And if so how’d you do so? This is Dr Tim and I own a 1997 Gemini 105. The center boards are showing some delamination and would like to repair or replace at this point.

        1. Post

          I have used West System Six-10 epoxy in a caulk tube. The “knuckle” of the port board (original I believe)was deteriorating. A dental pick cleared the rooted soft wood. I then let it dry for a few days while doing other items. By placing cardboard between the board and trunk walls, I avoided bonding board to boat.

          Two years later the knuckle was holding up well.

          Feel free to send me images of your issue at alex dot yachtafun at
          I’ll be happy to comment.

          Thanks for being a YachtAFun reader / contributor.

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