Thanks to Hill at North American Sailor for the tip.

If you sail a lot in light air, there are a number of upgrades you can consider. From new sails, to light-weight halyards, to removing gear from the boat. We’ve already talked before about the value of training as well. But one upgrade which will improve your performance – no matter how badly you sail – is making sure you’ve got a fair bottom. On many cruisers, thru-hulls are an important component of drag, and can be faired or recessed to improve performance.

Practical-Sailor highlights these two major options: fairing in or recessing the thru-hull. Definitely worth a read.

In light air, a major portion of the total resistance of a sailboat derives from skin friction. To oversimplify, the smoother the boat’s “skin” — the submerged part of the vessel — the less power is required to drive it to a given speed. Put another way, given two boats identical in every way, including sail area, the boat with the smoother bot­tom will be slightly faster than a boat with a rough bottom in light air.

Read more here.