length of rudder below the strut

[atlad]

I was wondering if there is a rule of thumb for the length of rudder below the strut. Or is it just a matter of keep trimming until you find what the boat needs to turn and run straight.

[fweasel]

On my 100mph+ SAW boats, I try to keep the rudder as short as possible and usually cut until it becomes a problem, then go back to the spare and cut less. On my sport boats, I usually start with about a minimum of 1" of rudder below the bottom of the prop blade. You can tell pretty easily if a boat has way to much steering input and when just turning the steering input down on the Tx isn't enough. On some boats if I'm using a water pick-up rudder blade, you can't run it any shorter than where the water pick-ups are drilled, so you adjust elsewhere if needed.