Mariner’s Web

Flat is Fast (or is it?)

Sailboat balance is a result of Center of Effort from the sail plan combined with the Center of Lateral Resistance provided by the keel appendage. While in a racing seminar sailing J/24’s in Florida’s Key West, I first heard the term “flat is fast” – in reference to angle of heel. Minimizing heel angle is almost always the goal of our race crew. A couple of exceptions to this rule that come to mind are: when sailing in our typically light and rarefied Rocky Mountain air we heel the boat enough to assist in sail trim when the wind Gods are not cooperative; and we may heel the boat to weather to project the asymmetrical windward and sail deeper. But with that said it is a fact that in sailboat design and theory the keel or centerboard provides lift (like an airplane wing) and so as a boat heels more, less lift is generated, hence a decrease in speed and/or more leeway. The same is true for lift on the sail plan.

Alas, since a monohull sailboat is more difficult to sail flat in winds of 12+ knots, designers take heeling into account with hull form and appendage. There are some general rules to take into consideration for maximum efficient heel angles for different boats as follows:

• One and Two person dinghies: 0 to 5 degrees heel – essentially flat!

• Larger, heavier dinghies: 0 to 10 degrees. I consider my last two raceboats, a J22 and an Ultimate 20 (fractional sloops with small jibs) fall mostly into this category.

• Scows (Flat-bottomed dinghies with two rudders): About 20 degrees – to the point where the leeward rudder is vertical and the wetted hull surface reduced.

• Catamarans: Just enough that the windward hull skims the water.

• Keelboats: 10 to 25 degrees – so that the ballast in the keel appendage can get some leverage to prevent further heeling.

I think a case for an asterisk has been made: Flat Is Fast*