You might think wind just blows you across the water, and while this might be partially correct, there are other forces at work – the same forces that allow birds to fly. Both bird’s wings and your sails are built to the same design. There’s a leading edge where the wind first hits it, then a curve that forces the wind out of its normal pattern. As the wind travels around the curve, it has farther to go, so it travels faster on the wing’s top edge – or the sail’s downwind edge. Just like wind passing over a mountain range, it speeds up, creating less pressure – a vacuum. The bird’s wing, or a sail, is sucked into that vacuum creating forward movement. That’s right, when you tack, your sailing into a vacuum.
Birds have developed many ways to help them fly, to adjust their speed, allow them to stall before landing, trim as wind increases, glide, take off – they even prefer to launch into the wind like a sailor quickly learns. Sailing mimics all this when you reef, flatten or loosening sails to change their shape, spilling wind when things get rough. And just like sailors, birds ‘sails’ wear out, so every year most grow new feathers to replace the ragged ones. Next time you’re at the marina watching the gulls make off with a bag of French fries, notice their wing shapes. Compare them to a good sail. Watch them as they land and notice all the activity that goes on with all those feathers. Boy, I sure wish I could fly!
Larry Eifert paints and blogs about wild places at larryeifert.com. His art can be seen in many national parks across America.