Secondary stability

Secondary stability is harder define than primary stability. In general it seems to be a perceptual thing. A kayak that feels like it gets harder to lean at higher angles it is said to have good secondary stability. If you look at the stability curve of a boat like this, the slope of the curve will increase at higher angles for a while before the slope starts decreasing again.

Another way to look at secondary is to look at how hard it is to lean it to the point that the righting moment starts decreasing. This is indicated by the area under the stability curve up to the maximum point on the curve.

Unfortunately, there does not seem to be any real agreement as to what exactly secondary stability really is. People just know it when they feel it.

Beginners tend to prefer high secondary stability, since it leads directly from high initial stability and results in a feeling of comfort. More experienced kayakers prefer lower levels of secondary stability due to the behavior of a kayak in rough conditions.

Stability in calm water means that the kayak stays level - specifically perpendicular to the water surface. However, if the water surface is sloped, as on the face of a wave, being perpendicular to the water surface means being tipped. Thus, a kayak with high stability will tend to rock with the waves more than one of lower stability. Since experienced paddlers prefer to remain upright in waves, they will forgo stability in favour of the ability to edge into a wave.

In one extreme, high stability actually makes a kayak less stable in waves. Specifically, if the waves are breaking, the higher the stability and the beamier the kayak, the more likely the kayak will be to upset if it broaches. Thus in very rough conditions, wide, stable kayaks can be a liability.