Originally Posted by fj007
So when is the right time to cleat the topping lift? do you raise the mainsail, which then lifts the boom to the proper height, then attach the topping lift line to hold it in place?
The topping lift need only support the boom a) when the sail is down, or b) when the wind is so light the weight of the boom drops the clew and 'closes' off the leech.
Under ordinary conditions the sail and the forces on it will support the boom, and the vang and sheet used to overcome that force to get the correct trim. Then the topping lift should be removed or completely slacked. It's common for an overtight topping lift to interfere with mainsail trim.