Making an Articulated-Stern Rudder

A Home-built Sea Kayak Rudder

Making a rudder for a sea kayak

I decided a rudder on my Fast Double would be a good idea, but I didn’t want to destroy the shape of the stern by lopping off the tip to mount the standard rudder system. I had the idea that I could incorporate the end of the boat into the rudder system, by making the tip of the stern articulate or pivot. This let me keep the basic shape of the boat and still have a rudder.

To do this I cut off the stern, made a vertical slot to hang the rudder and constructed a wooden hinge to let the rudder pivot. Start with a substantial endpour. This is so you don’t end up with a hole in the back of the boat when you cut off the end. The endpour should extend about 7" from the end of the boat.

Cut the stern off 6 1/2" from the end. Make this cut straight up and down and straight across, perpendicular to the centerline and waterline. A hacksaw is a good tool for this job. Then cut 3/4" off the end of the cut off piece to account for the size of the hinge.

Sea Kayak Rudder Pivot
The completed articulated rudder.

The front roller of a belt sander makes a good tool to make a rounded depression in the end of the boat and the cut-off piece. Hold the sander on its side so the roller is rotating around a vertical axis. Press the sander against the end of the boat. Check to see that it is sanding straight and vertically. You want to hollow that will let round disks rotate in it.

Keep sanding and checking the orientation until you have a semi-circular hollow all the way across the back of the boat. Clamp the cut off piece in a vice and repeat the sanding job on it.

Cut a vertical slot in the end of the cut-off piece about 1/4" wide and 4" deep. The slot should be parallel to the centerline and stem. Drill a 1/4" hole through the cut-off piece, at the sheerline and 1" back from the front of the slot. This will be the pivot hole for the kick-up rudder. Drill another hole at the sheer as close to the front of the cut-off piece as you can with out poking through the sanded section. This will be for the control arms.

Seal all the exposed wood with epoxy. Put a layer of fiberglass over the back of the boat for a little added strength.

Make four round disks out of mahogany or other hardwood. These disks should be the same diameter as the front roller of the sander. Make a test disk and try the fit in the sanded section on the back of the boat. You want a snug fit. If you need to make the disks bigger. Drill a 1/2" hole in the center of each disk and fill the hole with epoxy. Re-drill the hole at 1/4".

Glue two of these disks to the boat with thickened epoxy. The first disk should be right at the top of the deck. Use a spacer to get the second one spaced below the first with enough room between for a disk mounted to the cut-off piece. Run a bolt through the holes in the disks to keep them aligned. Try to clean up any squeezed out glue between the two disks.

Mount the other two disks on the cut-off piece so that it will line up like it was before being cut-off. Make sure the disks are parallel. When the glue has cured, try the fit. Clean up any squeezed out glue that gets in the way with a small chisel. You will probably need to sand the outer edge of the disks to get a smooth fit. Drop an bolt down through all the holes. Sand off anything that keeps the hinge from turning. Coat everything with epoxy.

Set the end straight and sand off any part of the disks sticking out beyond the extent of the boat. Drill a 1/4" hole through the bottom hinge for the rudder pull-down bungy.

The rudder can be a piece of aluminum, marine plywood or you can laminate on from fiberglass. I laminated in some veneer to make it look like wood. It takes at least a dozen layers of 6 oz fiberglass to make a stiff enough rudder. Make this oversized and cut it down to size later a rudder blade similar to what is shown in my book, The Strip-Built Sea Kayak, will do fine.

Use stainless steel bolts throughout. One bolt for the kick-up pivot, one for down through the hinge and two for the control levers. Get 6" bolts which are threaded on only the last inch. Clean any oil off of them and epoxy them into the holes you made. The threads in the epoxy will be enough to keep them in place. If the hinge is a little stiff, apply some wax to the moving pieces.

A loop mounted on the deck for the rudder lift control lines is a good idea. For the rest of the control system look in my book. I’d describe the system I used on my Fast Double, but it was not very good.

This system takes some work to make and may not be quite as strong as a commercially manufactured rudder system, but if you are trying to maintain the lines of a kayak with a long overhanging stern such as the Guillemot, Expedition Single, or Fast Double, it is a pretty nice system. I would not bother use this for a boat like the Great Auk or Guillemot Double.

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