This is largely because winch manufacturers love complicated mathematical formulas. Simply put, this is how many pounds of pulling power you will get from a winch for every pound of pressure that you put in. In reality, this is only a rough guide. There are other things that need to be factored in, such as the number of turns in the sheet, the friction produced by the lead blocks, and the operation of the winch itself. However, as a basis of comparison, the ratio is useful.
Most manufacturers make size recommendations based on boat length.
While this is useful, a better option is to use the sail area of a boat, since this is a better guide for determining a craft's power. There are also other factors to be considered. The smaller sail may seem like an odd choice, but bear in mind that it's used in heavier winds, so the sheets are subjected to higher loads. 0.00431 SA is the sail area, and V represents the apparent wind in knots. Therefore, a 300 sq.