I have started to think about how I can make a rudder for my Nomad (Design by Björn Thomasson). I could of course just buy a commercial rudder in a kayak shop, but I don't think it looks good on a wooden kayak.

I Nicks book, The Strip-Build Sea Kayak, he describes how to make a rudder and in figure 9-23 there is a description of the rudder mechanism. Like most other rudders, it has a horizontal piece, called the "T" and vertical piece, the rudder support. The rudder support is a little different from most other rudder mechanisms I have seen extends below the "T". Does anyone know what the purpose of the lower part is?

The rudder in the book only rotates about 135 degrees, but I think it can easily be modified to rotate 270 degrees by adding a disc on each side of the top of the rudder blade and let the rudder lift-robe go around these discs (like many commercial rudders).

I will also have to figure out how to shape the rudder blade. I have heard of NACA foils, but I am not sure which one I should choose. Some people mention the NACA 0012 profile, where the thickness is 12% of the width. I have no idea why this specific profile should be good for a rudder but I somehow got the impression the choice of profile has something to do with the speed of the vessel. Most of information I have found about NACA rudders has been related to yacht and other larger boats, so I am not sure if the NACA 0012 is good for a sea kayak rudder. According to the specification on the Nomad it has an average speed of 4.8 mi/h (7,8 km/h) and a max speed of 6.9 mi/h (11.2 km/h).

I will also have to decide how wide and long my rudder should be, the relation between these measurements (called the aspect ratio) and the rudder area. Is there any method to determine this based on the dimensions of the hull? The length of waterline of Nomad is 17.32´ (5.28 m), the beam of waterline is 20.82" (53 cm), the drag is 4.3" (11 cm) and the wetted surface is 24.3 sq ft (2.26 m2)
Here is the full description of the Nomad: http://www.thomassondesign.com/en/catalog/my-kayaks/nomad#details

Any descriptions of how to make a wooden rudder will also be appreciated.

Palle Dam, Denmark