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Carving Turns

PostPosted: Thu Dec 01, 2011 10:13 pm
by GregS
ACA Freestyle canoeing guru Charlie Wilson offers the following introduction to Carving Turns

The term carving a turn comes to paddlesport from skiing, where the ski is placed on edge and the deformed shape of the sidecut turns the skier. In paddlesport, we heel the boat to one side or another, inside or outside the intended turn to “carve” a turn.

Most paddlecraft, say 90%, are designed with their stems in the water. It is instructive to block any average hull into a heeling angle in a driveway or parking lot and run a piece of chalk around the hull indexing it at, at both dimension with a 2X4 stub. The resulting banana shapes traced on the ground leave no doubt as to which way the hull will turn most easily.

Art, after T MacKenzie

This tendency is also observable on water. Once achieving neutral forward motion, remove the paddle from the water and heel the hull to one side. Touring and recreational hulls may take a few seconds to respond, but invariably turn away from the heel. [Note that any yaw from straight ahead always induces a yaw couple and a turn towards the yaw.] The banana shape is only one aspect of carved turns, and no turn is a pure carve for long.

Another factor in carving touring hull turns is bow plane deflection. When the hull is level, both bow planes exert equal deflection away from the plane as it is angled to the water at a negative angle of attack. As the deflections counter each other, hulls tend to run straight. [There’s more to course keeping than that, but let’s move on.]

When a touring hull is heeled, the down-side bow plane’s surface area increases and the up-side bow planes surface area in the water decreases. The imbalance in forces deflects the bow towards the up-side bow plane. In combination with the curved shape of an outside heeled hull, the “Carved turn” becomes aggressive. As the bow continues to offset or carve inside the turn a Yaw Couple is initiated. The paddler’s mass, located at the Center of Gravity of a solo boat, continues on course. [Newton was pretty much right about that.] The stern breaks into a skid. This is illustrated on water if the paddler holds the unpowered heel long enough.

Carving turns always end in a skidded turn as the bow moves to one side of the direction of travel, the paddlers mass moves forward in the direction of travel and the stern skids around the Center.

Whitewater and some recreational hulls may carve differently, carving on an exaggerated chine, even a stern chine, and the bow planes are often clear of the water. This is boat situational, but chalk on the driveway will always tell.

Developing the paddle sensitivity to initiate a yaw couple and drive the hull in a circle towards the paddle side or in a straight line without correction is the goal of the Inside Circle Etude.

As ever, this is best read in context: see ACA Freestyle canoeing guru Charlie Wilson offers the following introduction to here.