: Hi all,
: I'm in the process of designing an internal rudder.

: What would be the best placement of the rudder? Would the same position as a
: skeg be the best, the last 18"-30" section, or is there a
: science attached to it?

Well, there is a science, but its not complex. A rudder wants to be as far back as you can have it without making it very vulnerable to damage. Rudders of the type you describe are rare on kayaks, but the North Shore Calypso II has one. This is a commercial fibreglass double. Unfortunately, North Shore are a very
small outfit and don't have their own website. They cater mainly to local paddlers in the UK, sales by word of mouth, and to retail trade in Scandinavia, where you will find that the web sites are not in English. However, there is a picture of the Calypso II, with its rudder in the lowered position, which will give you an idea of the placement:

Andy