Once upon a time..................I was riding slowly with a strong steady tailwind. I sat up straight and held my windbreaker out on both sides like a sail. I started to accelerate a little. I could feel the wind was coming in from the rear quarter, not straight astern........uh......behind. I twisted my shoulders and turned my arms (boom?) perpendicular to the wind direction and started to accelerate even more.
Unfortunately I was closing in on an intersection and had to put my hands back on the bars just as I started getting up into the high teens in mph. Wish I had a real sail that day. Wish one of my friends had a camera.