My prior experience with commercially-made kayak sails has been mostly with the Pacific Action sail and the Spirit Sail. I used them both for more than a decade on my previous kayak, and loved the versatility of being able to raise either or both so I could sail in anything from strong winds to gentle breezes. They were especially fast on broad reaches. But they are functionally square rigs, optimized for downwind sailing. On my new kayak, I wanted better across-the-wind performance and some upwind ability. So I upgraded to a Falcon Sail.
Apparent wind speed — the wind you actually experience — is the real wind speed, plus or minus your speed against or away from it. So if I paddle my kayak at 3 knots* into a 9 knot headwind, I feel the resistance of a 12 knot wind working against me. “That’s OK”, I used to think. “I’m only paddling into it until I stop for lunch. Then I’ll be heading back, and I’ll get as much push home as I had drag on the way out.”