I have spent many years coaching people around the race course and continually looking for a scenario to help explain sailing angles down wind.  Everyone knows you have to sail higher in light air and lower in heavy air but why does this work? I would often get people questioning the reaching in light air theory.  I even had an engineer stay up all night and come to me with diagrams on how a spinnaker should be made to sail directly down wind.  Then I asked him if an ice boat that is capable of sailing at 3 times the wind strength would get to the leeward mark faster by going directly down wind at the same speed as the wind.  He quickly did some calculations and realized a flaw in his theory for his design. So how do you compare sailing down wind to something that almost everyone has done in their life?  How do you simplify the theory so that people understand?

One evening I was heading home here in San Diego, driving up the hill from the loft, 2 kids were riding their single speed beach cruisers up the hill in front of me.  They were crisscrossing the street back and forth to get up the hill without having to get off their bikes and push them since beach cruisers only have one gear.  I was reminiscing about when I was a kid in the same scenario.  We would ride back and forth up the hills having to ride a lot further but being able to still pedal up the hill.  The more you went sideways to the hill the faster you could go but travel more distance.  You would build up more speed before making your turn to the other side so you did not stop in the middle of the turn.  Watching these kids made it clear that sailing down wind is exactly the same.  These kids had VMG (Velocity Made Good) figured out and they had probably never even heard the term.  Sailing a boat down wind in light air is just like riding a bike up a steep hill.  Sailing a boat down wind in heavy air is like riding a bike on a flat hill.  Looking for more wind is like finding the flattest hill to ride up.  Jibing back and forth is the same as crisscrossing the street.  The more wind (flatter hill) you can take a more direct route.  If the wind is light (steeper hill) you have to sail more perpendicular to the wind (street) until you find an angle that still gets you to your destination but also keeps your speed up and sails full.  The higher speed potential of your boat (higher geared bike) the more you have to reach (crisscross at steeper angles) to get the best VMG.  If you have a slower boat (or a bike with a low gear) you can go straight to your destination at a slow steady pace.

Figuring out your optimum angle can be a little tricky but is one of the most important resources you can have to gain peek performance on the race course.  It is always faster to have a target boat speed on the run even if it is not 100% correct than allowing the boat to slow down and have to get back up to speed again.  There are many target boat speeds available on the internet and from your local sailmaker or naval architect. It is best to find polar charts that match your boat or a similar boat and take notes on what works and what does not.  In a short time you will have the optimum numbers for sailing down wind and your performance will improve.