Another boring one. Move on. Nothing to see here, folks.
The mainsail is a big triangular piece of incredibly sophisticated cloth. The front edge, called the luff, attaches to the mast with a series of slides that run in a UHMW polyethelene track. The lower edge, called the foot, is stretched straight because it’s tied to the boom, an aluminum tube that is hinged to the mast. When the sail is up, it holds up the boom, but when the mainsail is dropped, it sits in a big pile on top of the boom. Then the free end of the boom is held up by the boom topping lift, a small line that runs from the top of the mast.
At anchor, the boom wants to flop back and forth as the boat rolls in passing waves and wakes. Movement makes noise inside the boat. Noise inside the boat makes us crazy. We used to make a triangle between the boom topping lift, the main sheet, and another line to secure the end of the boom to minimize the flopping-around-itude.
The Boom Topping Lift is 60′ of small diameter Dacron line. The more the wind blew, the wavier the anchorage, the tighter we pulled on everything, the more the line turned the entire boat into a bucket bass. It got extremely loud and high-pitched, sometimes even vibrating the mast.
We install the crutch, tighten up the sheet and the opposing line (which are thick enough and short enough that they won’t sing), and leave the topping lift loose enough that it won’t resonate. As a bonus, the crutch keeps the boom horizontal, giving Bright Water that “well-cared-for” look we treasure.