Mark Your Deck to Check Rudder Drag

Feeling slow? Maybe you’re over-steering or have excessive weather helm, creating rudder drag. You can do an interesting exercise by marking tiller “boundary lines” to check rudder drag. Then go out and sail in a straight line, and see if you stay within the lines. You might be surprised.

How to Mark Tiller Boundary Lines

Most references suggest you avoid deflecting your tiller more than 4º from center for straight-line sailing. To mark your deck with 4º boundary lines, do the following:

Find the centerline of the boat
Measure the distance from the rudder pivot point to the location you want to mark (d in the drawing)
Multiply the distance (d) by 0.07. See the notes for the source of this calculation.
Measure and mark this distance on each side of the center at the chosen location.

Example:

Assume you want to mark your deck 24″ forward of the rudder pivot point.
24″ x .07 = 1.68″ or about 1-5/8″.
Make a mark 1-5/8″ on each side of the center line 24″ forward of the rudder.

Correcting Weather Helm and Over-Steering

If you find you have weather helm or are over-steering, below are some good references. We’ll cover more about these topics in future SailZing posts.

Striking a Balanced Helm: Sailing World. Good pictures showing how to balance weather helm with crew position and sail trim.
Tuning Guide – Buccaneer 18. Detailed discussion of tuning. Pages 24-25 have graphs and a discussion indicating that 4º of weather helm improves upwind performance in light to medium air.

Notes

The deflection from centerline is calculated using the formula deflection = d*sin(α), where d is the distance from the pivot point and α is the angle of deflection.