Rudder angle question

What is the maximum useful angle of turn on a catamaran rudder? Where should the stop be set? And what about getting out of irons? More rudder for that? Any feedback appreciated.

 

90 Degrees
The max. angle of attack is about 30- 40 degrees
but , The max angle of attack is defined by a/the tangente of boat's turning circle.

The boat's stern is drifting , direction outside the curve., so angles of 80degrees+ are possible and common ---one can see it on each tacking dinghy, keelboat, modern yachts a.s. o. ----especially on match racers.
Limiting the angle to 40 degrees , or so , makes no sense, the turning circle would be enlarged massive--bad for sailing- and habour manouvers .

pogo

 

Thanks pogo. I am trying to decide how to accomplish the goal of having a kickup rudder that will kick up at any angle of turn. Photos and discussion over here:
http://www.boatdesign.net/forums/boat-building/kurt-hughes-daycharter-36-a-31846-20.html
Down around post# 294
I really appreciate all input.

 

My advice:
Build a kickup ,vertikal retractable transom hung rudder like I did. It performs all tasks.

http://www.boatdesign.net/forums/multihulls/planing-catamaran-30415-4.html

pogo

 

On my cats I usually max out at about 30-35 degrees. Your foils can only handle an AOA of around 5 degrees before they stall so you can't push them way over anyway. As you tack you can push the rudders harder as the stern starts sliding sideways keeping the angle of attack within the envelope the foil can handle.

I would not worry about ensuring that you can have your rudder hard over as the rudder comes up. I am happy with the cassette wherbey my rudders can only come up when straight and it works fine so you should be fine with the cutout you already have.

cheers

Phil