By Richard Feeny, US Sailing Junior National Coach, Finger Lakes Junior Laser Champion
Introduction
The shape of the land to windward of the race course will affect the wind. The first thing to look for is any low area that will let the wind onto the race course. In a flat country with no valleys to funnel the wind, what will affect the wind? There will still be geographic sweet spots, and fairly rhythmic, yet unpredictable, shifts. In shifty conditions you can’t be right all the time.
Successful sailors punch out into the first shift, using their speed to stay in the front row half way up a first beat. In shifty conditions the middle of the starting line is usually a good home base. (Until one end is more than 15 degrees favored – then you have to get there). If the oscillations slow down then they become, effectively, persistent shifts.
To be world caliber you need an aggressive starting mode on a lake just as on salt water.
Geographic Effects
The land upwind of the race course will affect the wind. Trees and man-made features will cause wind shadows and holes, but also will create sweet spots that have more wind, more often, than the rest of the lake. The puffs tend to fan out as they hit the lake. Sail the edges of a fan puff to ride the lifts.
The land can also bend the wind, for example, the wind aligning with streets and buildings which tend to be perpendicular to the shore. Perhaps this is why it usually pays to head towards shore. If one shore is in or near the race course a smart sailor can usually make it pay. It is not as simple as hit the beach, but play lifts and headers on that side. Look for an acceleration of the airflow in a near-shore band, and/or a heading shift on the tack headed most directly toward the shore that permits a boat to shorten its course by tacking to the lifted offshore tack.
Generally, all other things being equal, the friction of a shoreline will bend the gradient wind left in the Northern Hemisphere compared to open water. So if there is a shoreline on the left side of the race course, the left will often (dare I say usually?) pay by providing port tack lifts.
To chase puffs or not?
The trick is to meet puffs, not chase them. The race is to the mark, so all speed should be directed in that direction. Small detours are permitted to catch or intercept puffs. Try to identify the geographic effects to find the places puffs touch down.
Conclusion
You will see oscillating, persistent, and geographic wind shifts on lakes, which is why lakes are more fun to sail on than open water.