Play the Curve

Hey I was thinking about contour breeze and how it directly relates to sailing at our end of the river, the Charles River Lower Basin (but because we are at the top half of it, it may be referred to as the Upper Basin). Think about that, the basin, why is it the "basin"? First consider that the Charles River snakes eastward from Hopkinton, MA. until it dumps into inner Boston Harbor. Coincidentally, Hopkinton is the starting point of the Boston Marathon and in a straight line it would run 29 miles (just longer than the twenty-six point something mile marathon). But the Charles River meanders some 86 miles! It has very many dams along the way to control its flow. I've kayaked the last 30 miles (from a starting point only 12 miles away as the crow flies) and had to portage a half-dozen of these dams, though there are many more of them up river. Still, there can be a crap load of drainage that spills into our basin. The Cottage Farm Bridge (you know it as the BU bridge) is the spigot, our faucet. The sluices (dam gates) at the Charleston Bridge is our drain plug. We are truly sailing in a water basin or sink, though the way the wind swirls, some consider it a toilet basin.
We don't usually feel the tug of the water in our basin because the drain plug is usually in and because of all the dams upriver. Occasionally, often before an expected big rainfall, they open up the sluices and the water drains out of our basin. It still drains at a moderate pace and we may not notice in the middle of the basin but at the BU bridge, where it narrows like an hourglass, there may be a knot or more current flowing eastward.
Our concern is not with the water flow but rather the air flow in regards to the shape of our water playground, as it drastically expands and forms the top of the Basin. Remember, air in motion (wind) is a fluid, and fluids have a trait of typically flowing around more solid barriers, not through them. We must also realized that air pressure build up around more solid barriers can in itself become a form of resistance, hence even the near windward side of barriers can create poor air flow. Fluids like to take the path of least resistance, and where wind is concerned on a confined race course, we may dub that a "Contour Breeze" as it follows the contours of the river bank, trees, and buildings and flows along its merry way.
You have to learn when to play the curve.
Wind-wise, while many may consider our biggest obstacle the bridges to our east and west, it really is the drastic reduction in the river's width at the top of the Basin combined with the fact that there are large structures to the north and south (the Hyatt Regency and BU Law Building) to define this gateway, or best described as a "funnel tube". When the wind flows from the west to east, out of the tube, the wind follows the contours of river banks, changing more southerly on the northern shore and more northerly on the southern. Now you may say dude, that's a crock of doo da because you have not noticed it on the race course. That's because we mostly sail lower in the Basin where the contour straightens out. However, on regatta days if the wind is westerly and if the course is set longer, leaving the whether mark closer to the gateway, you must be aware of the contour breeze. You may deal with this phenomenon more often than you realize when you sail out and back from practice.
Conversely, when the breeze is in an easterly direction, the wind goes from funnel to tube. Again, we don't usually deal with this on the race course but there is certainly one exception and I need only look to last year's Morris Intersectional at BU. The weather was cold, rainy, and a bit breezy. It was nasty enough that I decided to race out of our boathouse and had the starting line beneath the Hyatt and the Law Building. The line was so long for the 18 boat fleet that there was little room between the marks and the shoreline. There was also very little room to sail upwind before you would hit shore. Coincidentally, there was a little bit of current running to the east because they had opened up the sluices for the rain but that's not the crux of it (but had the wind been lighter instead of heavy and creating lots of leeway on floggings sails, the starts would have had more recalls from the current).
More of a concern was how the contour breeze effected the first half of the beat. You needed to get to the shoreline and take the lift on the opposite tack (which took you away from the shoreline) up the course. As you sailed away from the shore you would get knocked and then thrown into a mix of disturbed air mixing at the base of the funnel (and disturb more by the boats in the middle of this confined beat). You needed to short tack the the shoreline, either shoreline. If the mad gangsta recalls (Matt Conover), we talked about the contour breeze effect. Matt and Maddy were averaging above a 9th in the first six races but it was all about starts and route decisions not boatspeed or boathandling. After our chat he had a little more direction ("start at an end, short tack the shore, and don't make the cross until at least halfway up the beat and on the lift"). If memory serves, Matt had 1, 5 set and then had a hiccup set of a digger and a 9th due to some entanglement with the competition, and then came back with a 1,2 set. I don't believe I ever got around to talking to Bobby and Erin about the contour breeze but they were starting at the pin and when they won it they were playing the left shore and when they lost it they would tack and duck and sail to the other shore (there were no corners on the playing field of this race course, just long lay lines at the top). They effectively handling the contour breeze anyway and they won A division for the regatta. Of course there were more wind characteristics to deal with than just a contour breeze but it was part of the equation and worthy of note.
There are more examples of contour breezes, like how it effects the northeasterly as it bends around the MIT tower dormitory to the east of the Hyatt or how the southerly swoops in, to the east of our changing dock. We may see it when the wind is diagonal to the river and one edge of the blast rolls more along the windward shore, and more often see it divert along the leeward shore and flow along the bank (the curve). We see it along the sea wall in some wind directions at MIT and certainly as it funnels through Boston's Back bay streets and creates wind streaks coming off the shoreline when racing at Harvard. Its existence may be recognized at Tufts, coming out of the cove or how it relates to the backwash effect against the small hillsides and the Tufts boathouse itself.

Read the breeze.
Watch it oscillate, pulsate, bounce and flow.
And play the curve when you're in the know.


-Coach