The question new sailors often ask when they first experience a sailboat heeling is, “What stops it from going all the way over?” to which the usual answer is something like: “That big lump of lead underneath us.” However, while stability lies at the very root of sailboat design, ballast is only one of the many factors that influence it.
In practice, a boat’s stability is contingent on the relationship between two key factors. One is the (CG), through which (CB), the midpoint of the underwater volume of the boat, whose upward thrust counteracts the effect of the CG (see figure above).