Drag

Also known as Resistance

Drag is the force that keeps a kayak from going as fast as you want. There are several sources of resistance in a kayak:

Total resistance = R_f + R_w + R_i + R_h

Skin friction resistance - R_f

Friction is one source of drag on a kayak. This kind of drag is due to the resistance of one material sliding against another. The friction of water rubbing against the surface of a kayak as it moves through the water creates a force which tries to stop the kayak. The best way to reduce friction drag is to reduce the wetted surface area of the kayak.

Wave-making resistance - R_w

Also called Form drag is one component slowing a kayak as it moves through the water. This force is largely due to the inertia of the water that is being displaced by the kayak as it moves throught it. Any water in front of the kayak must by pushed out of the way and then moved back in behind the boat. The energy imparted into the water during this motion is then converted to wave energy and can be seen in the wake of the kayak.

Induced resistance - R_i

The resistance felt because of leeway - the kayak is moving sideways, as in a crosswind.

Heeling resistance - R_h

The extra resistance due to maintaining an angle of heel. This can occur during edging.

There is also resistance from eddy making in the afterpart of the hull, but since this is not easy to separate from the skin or wave-making resistance, it is left out and is accounted for in the latter two resistances.

For kayakers, friction and form drag predominate most of the time.

See Also:

• Hull speed
• Optimal length

Udo Beier and Peter Unold have posted some data extracted on resistance from Sea Kayaker Magazine's kayak tests. The results can be seen on this web site. You can use the site to sort the kayak data by various factors.

References:

• Sailing Theory And Practice