Topping lift vs. boom vang - For Tim
The purpose of the topping lift is to support the boom whenever the mainsail cannot do so, for example when the sail is being raised or lowered. The topping lift is not really a sail control, although some people tension it in very light air to prevent the weight of the boom from pulling the sail down and tightening the leech. When sailing, the topping lift should be loose enough for the sail to support the boom. As you found, it doesn't have to be completely free.When sailing upwind, the boom is held down by the mainsheet tackle. However, off the wind, the mainsheet is no longer as effective, and the boom tends to rise in response to the wind pressure, reducing the sail area presented to the wind. Tensioning the boom vang opposes the boom's tendency to rise when sailing off the wind.The vang can also be used when sailing upwind to "float" the boom in heavy air. I believe the technique is called "vang sheeting". It allows the boom to rise in response to a gust, depowering the sail by reducing its area slightly and helping to prevent the boat from being overpowered. As the gust passes, the sail reverts to its original trim and power is restored. I hope this helps.PeterH23 "Raven"