Does the force of the current a boat is feeling depend on the direction of the boat in relation to the direction of the current?
Dan Dickison responds:
This is always a topic of much debate among racing sailors, but the answer is NO! There is no such phenomenon as "lee-bow effect" from current. Essentially, if the current is constant from one moment to the nextand it usually isthen the effect is the same on either tack whether your keel (or centerboard) is oriented with the current or broadside it. If your boat had instruments indicating wind strength and apparent wind angle, you could prove this easily by seeing that the readings don't change from tack to tack or jibe to jibe when you're sailing. Dave Perry explains this pretty clearly in his classic book Winning in One-Designs. If someone challenges you on this, simply explain to them that no matter how fast or in what direction your boat is moving, if the current remains constant, then its effect on the boat's apparent wind will remain constant. I hope this helps you, but don't just take my word for it; go out and prove it to yourself. If you'd like to check out additional references in print, log on to the SailNet Store.