"Tender"
Tender relates to how far and quickly a boat heels in a gust or wind change. It's determined by hull shape, and the location and amount of built-in ballast. With low mass and no built-in ballast, all dinghies are tender, especially if the helm and crew do not anticipate and respond quickly to gusts. The response involves moving to ballast the boat, sail trim, and helming in that order to keep the boat flat. Most boats sail faster when they are flat. When I raced a Sunfish, flat meant literally flat - 0 degrees of heel. Other designs are meant to heel 5 or 10 degrees, but all designs slow significantly under excessive heel - usually more than 15 to 25 degrees depending on the design. Dinghies can be rolled over by the wind, mostly because the mast out-weighs the dagger/centerboard, and the "ballast" or crew is ineffective when the dinghies are knocked down, with sails flat on the water. A boat with built-in ballast, on the other hand will not roll over based on the wind. The ballast exerts a mighty righting force as the mast approaches the water, so keel boats can only be rolled over by a wave taller than the beam of the boat. Keel boats with a more "V" shaped hull, or higher ballast (a shoal keel, or water ballast both place ballast high, and closer to the center of displacement of the boat) are more initially tender. The narrow V type hull is simply easier to tip than the flat hull shapes used in many modern designs. Modern designs also tend to have a wide beam aft, which gives more initial stability (less tender) while allowing big cockpits, and big after berths. Water ballast places the ballast high, within the hull shape. As a result, the lever arm - the distance from the ballast to the boat's center of displacement - is shorter, and the boat needs to heel more for the ballast to come into play. So a water ballasted boat might roll to 20 to 25 degrees before the ballast is really effective, making it "tender." Nevertheless, excessive heeling of a ballasted boat also slows it down. Control of heeling in a keel boat can be slower because the ballast, mass of the hull, and high inertia of the more massive, taller rig slow heeling in a gust. Heel in a gust is controlled with sail trim, and helming, because movement of the crew to the rail is too slow (and difficult). In a keel boat, keeping it flat (usually around 15 degrees of heel) in average (versus gust) winds is accomplished with the crew moving to the rail, sail trim, and then sail reefing. Reefing so the boat sails flat increases speed in higher winds because of the sail area lost and increased drag of the hull at a heel of over 15 to 20 degrees. Also, while some crew may enjoy the roller coaster feel of excessive heel, my experience is that most (including my admiral) become increasingly uneasy at heels over 15 degrees. And keeping the admiral and crew in love with sailing is a major objective of mine! David Lady Lillie
