If you are having trouble keeping the boat under you, I would suspect initial stability, not secondary. Or more specifically the relative difference between initial and secondary. You will not increase secondary stability by moving the stringers towards the keel, however by decreasing the initial stability, you will make the secondary more pronounced, even if the absolute value of the secondary is reduced. Like you say, it is a ratio thing.

Without knowing exactly how the boat gets squirrly in waves I'll suggest one possiblity: You say that it hard to keep the boat under you, but you aren't saying you actually are capsizing. This could be because of relatively too much secondary. As you sit on the slope of a wave the boat tilts easily relative to the water surface until the secondary kicks in, thus trying to throw you. This could be due to a sudden increase in the slope of your stability curve.

I don't think that reducing the "pinching" near the ends would necessarily increase your secondary. The pinching creates a boat that is effectively a little shorter. This can help in choppy conditions because the boat will fit between waves a little better. A long boat that tends to bridge between waves can feel very unstable when the ends are supported in seperate waves.

It is possible you would find the boat more comfortable with less secondary as it will be less effected by waves. Keeping the same waterline beam while reducing the overall width would reduce the secondary without effecting the primary.

Below is a link to a long article on stability
: Last weekend, I discovered that my boat is a real handful in confused chop
: and it seems that a lack of secondary stability is the culprit. It's
: really tiring just keeping the boat under me. Two days later, I paddled my
: Nordkapp for the first time since I built the skin boat and the difference
: is night and day. It is MUCH more comfortable and relaxing to paddle in
: rough conditions.

: I want my next skin boat to be somewhat different in shape (more like the
: Nordkapp) in order to increase secondary stability. For starters, I'm
: going to add a foot in length (to 18' 6"). In looking through the
: various books I have, I've noticed that many boats built by Greenlanders
: have little or no pinch in the ends. While I like the swoopy looking,
: reverse-curved gunwales from pinched ends, it seems that this really
: reduces the flare of the hull and volume at the bow and stern. I'm
: surmising that this negatively impacts stability and makes the boat a very
: wet ride. Does this make sense?

: An addtional benefit to a less pinched shape is that it increases the width
: at the foot brace, providing more foot room.

: I'm also considering moving the chine stringers in toward the keel more. I've
: read that this will decrease primary stability, but increase secondary
: stability due to more flare in the hull shape. However, I wonder if it
: actually makes the secondary stability higher or does it merely change the
: ratio of primary-secondary stability?

: Thoughts? Ideas? Wild-ass guesses?