But why would there be water drag if they are in the fully "up" position? Maybe a little air drag.
And being able to flip them up briefly would help to get grass off the rudder blades. Grass is a major problem in many areas of the United States.
I thought maybe the reason for needing a casing so the rudder can go straight up and down was because the foils cause increased stresses on the transom?? Or maybe too much stress or "drag" for existing rudder systems to keep from kicking up??
The problem is that you have to be at a complete standstill to kick them up - or the foil will want to drive the rudder down as the boat moves forward. The solid rudder trunk does also allow very precise control over the angle of the t-foil while under way - and that's got to be really important. This kind of trunk is used on skiffs like the 49'er
(throwing stones <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />). Even our I20 style kickup rudder systems will allow the rudder to angle back just from loading (especially when the springs wear a little).
