A small gun rudder has no relation in size to the scale rudder. A ship of class X gets Y square-inches of rudder area.
Sorry to revive an old thread but.... Another method to determine rudder shape given a set square inch size is to get a length of string and four thumb tacks. Determine the circumference of your area, mark this length on the string, tie the string together at the marks, and then use the tacks and string to play with rudder shapes all you want. Circumference formula: ( 2 * X ) + 2 where X is your square inch allowance. Example: for a three square inch rudder, 2 * 3 + 2 = 8 inches. No matter how you shape the circle of string, it will never exceed your max square inch allowance. Pre-cut strings could be used lakeside to check rudder size.
Umm...nope. Rather easy to exceed the max square inch allowed with that. Example 2 in^2 rudder so an 6 inch string by that method. A perfect square (highest area : perimeter ratio of any quadrilateral) with an area of 2 in^2 has a perimeter of ~=5.657 in. A perfect circle (highest area : perimeter ratio of all 2D shapes) with an area of 2 in^2 has a perimeter of ~=5.013 in. By that method I would be able to get away with: A perfect square with an area of 2.25 in^2 has a perimeter of 6 in. A perfect circle with an area of ~2.865 in^2 has a perimeter of 6 in. Dont get me started on crazy shapes like a 2 in^2 rudder that is 0.25"x8" (perimeter of 16.5")..
