You have an ERNST water rudder. It SHOULD kick up when it meets any resistance. But the mounting tab provided on the GeeBee floats is not the way the Ernst floats are designed to mount. They are transom-mount.

You don't want the rudder in the water after you start your takeoff run. It just adds drag, and full-power prop blast over the air rudder is plenty effective.

Also, the flex-cable linkage for the water rudder is popular, but not very accurate. Clearance between the inner cable and the sheath lets it have play, and friction keeps it from centering well. But a water rudder is only for low taxiing anyway, and it can be sloppy and still suffice.