Rudder problem

[UNCIVILIZED]

There is a fairly easy way to tell if the shaft is bent without pulling the rudder out.
~ Get a sheet of some stiff, thin material about 2’x2’. Say some 1.5mm plywood, perhaps with a thin layer of glass on one side to stiffen it, ditto a piece of formica etc.
~ Cut a hemispherical notch the diameter of the rudder shaft into the center of one edge of it. So that it looks like someone took a bit out of it.
~ Attach a fine point marker, nail, or scribe point to the upper tip of the rudder’s trailing edge.
~ Slip the sheet in between the rudder & the hull, positioning it so that the half moon cutout is firmly up against the rudder shaft.
~ While holding the sheet flat in this position (perpendicular to the rudder shaft), move the rudder through as much of it’s range of arc as you can, thus inscribing a radius onto the sheet material.
~ Slide the sheet out, & fix it in place on a table top or work bench.
~ Stick a nail or tack into the bench top where the center of the shaft would fall on your template were the cutout not there.
~ Attach a string to the nail, & knot it at a length equal to the radius of the arc.
~ Swing the knot over the template sheet in a circular motion, noting if it doesn’t follow the inscribed line, & if so where & by how much.

If the curve on the template proves to be out of round, then assuming that you were holding the template sheet perpendicular to the rudder shaft, then there’s a bend in the shaft. And frankly, I wouldn’t worry much about any small deviations. But if there’s quite a bit of difference between the arc which the rudder traced on the template sheet, & that followed by your knotted sting, then some more intensive analysis of things is called for.

BTW, this test should work whether the rudder is in the boat straightly (vertically), or not. Even if it’s the type of rudder that’s purposefully built with some forward or aft rake to it. At least this will be the case so long as the template sheet is held fully perpendicular to the shaft on both the X, & Y axis during the test. It’s just simple geometry. Make sense?


EDIT: You probably want a couple of helpers to assist you with this. And too, glue as many stiffeners onto the backside of the template sheet as you can, & yet still be able to fit it where it needs to go for the test.

Also, were it me, I'd repeat this test at least 5x to rule out human error & variances when conducting it. So you might tape a sheet of paper onto the template, & use a pencil pointing upwards on the rudder's trailing edge instead.

Which if you use sheets of tracing paper, & different colored pencils, or marking pens, then you can overlay the various test result sheets atop one another in order to best compare them. Thus giving you a fully composite, combined "picture" of the arc. One that'll be much, much more accurate than doing the test but once or twice.

One other thing. The test shouldn't be affected by any asymmetry in the rudder, so long as your scribe point or pencil is firmly affixed to it's traiing edge, in exactly the same spot each time if you do the test more than once.