Faced with a sudden fierce chop, I did my best to steer around the worst of the waves, but trimmed the sails as I always had for flat water, with perhaps a little more power thrown in. Then I happened to read an article by the late Larry Klein on learning to sail a Soling in big seas and started thinking a little bit harder about the differences between the best sail trim for flat water and the best sail trim for waves. Sailing in waves downwind can be an exciting challenge, but for now let's concentrate on getting through waves upwind. Two major elements distinguish the two conditions. The first and most obvious distinction is that the boat does need more power to get through, or, more accurately, to get over the waves.
Any bicycle rider knows it takes more energy to ride up and down hills than to pedal along the flat.
Even though you get back some of the energy you expend on the uphill coasting down the other side, the net output is a lot more. But because big waves are more often than not accompanied by wind to match, extra power is usually not that big an issue. The second big distinction between flat water and waves is that the top of the boat's mast moves around a lot more in waves than it does in flat water. That means the sails are moving around, too. As your bow lifts to climb an oncoming wave, the top of the mast moves aft or at least moves forward more slowly than the boat beneath it.