The only really accurate way of positioning the car on a genoa sheet track is to close-haul the sail then sight up it as the helmsman brings the boat slowly above a close-hauled course. The luff should ‘lift’ evenly all the way up. If the lower part breaks first, move the car aft; if the upper section goes, slide it forward.
Tell-tales make this job easier. The ‘inside’, or windward one, of each pair will lift before the sail itself shows signs of breaking. When the lower, middle and upper ones all go together, the car is spot on.
