The fog has come and gone these last couple weeks here in Qingdao. Most days we’ve had to live without any direct sunlight and visibility of a mile or less due to the low clouds. But a few days ago, just when we were losing hope altogether, the clouds broke, the color blue spread across the sky, the fog lifted and the breeze filled. From noon to four in the afternoons we have had anywhere from 6-10 knots and a decent little swell (enough to make Graham Biehl our US 470 crew feel a little queasy). In the theme of our training we’ve been heading out to make the most of what we had on hand but still were up against the odds. Massive swaths of algae are still the dominant factor in our training. The green ‘fairways’ as we call them are aptly labeled. Sometimes hundreds of yards long and up to a hundred yards wide, the blobs creep the water in massive waves of weed spoiling any racecourse in their path. It’s our own personal version of the sci-fi movie: the Blobs!!! They never go fast enough that you cannot outrun them (you are moving in the same current the blobs are). However, if you have to go through a line to get to a mark or get back to the beach, you may be swallowed alive and not make it back in before dinner. We’ve watched the Dutch Yngling team, coach boat and three boats in tow get stuck so badly they had to be hooked and hauled out by a local fishing trawler. Acres of the nasty stuff are the target of an increasing number of fishing craft and rumors are filtering through the boatpark that more help is on the way in the form of a Chinese Navy destroyer and some offshore fishing fleets from other ports along the coast.??
The current has made as big and impact as we expected it would. With a knot to a knot and half of current running across a six knot breeze, it can skew a racecourse very easily and force you to spend as much time racing against the moving water as much as you race against the moving fleet. I thought maybe a good way to put a good spin on the few weeks we’ve had over here is to re-publish a post debunking the myth of the mysterious Lee-Bow Effect that I posted a few years ago in the Monday Morning Tactician column:
One theory that must be put to rest without hesitation is the famed Leebow Effect. Many revered and heralded sailors have presented cases for such an effect and the Monday Morning Tactician wishes to drag into the light all those under the spell of vile Leebow Effect. I will put my hypothesis forward with full knowledge of the possible outcry and controversy: The widely acknowledged theory of the Leebow Effect is decidedly FALSE!Buddy Melges, the Gold medalist, Champion and ambassador for the sport co-authored a great book, published in 1979, called Sailing Smart: Winning Techniques, Tactics, and Strategies. Many an evening have I spent squinting at its pages, well after my ‘bed time’ reading every word and studying its figures and theories. One that I wish I had never read comes leaping off of page 110. According to Mr Melges and his co-author Charles Mason (former editor for Sail Magazine):
Lee-Bow Effect: This brings up the famous lee-bow effect. If the current is coming at you at an angle that is very close to the course you are sailing and if, by pinching just a little bit, you can get your lee bow into the flow of the current, the movement of the water is going to push against the hull, the keel, and the rudder, and it is goign to drive you up to windward even though you are going slower over the bottom. If you are on the other tack the current is going to be hitting you broadside and pushing you down. If you can get the lee-bow effect to push you to windward, I feel you also increase the wind pressure on the sails. If I am on the tack that goes across the current I feel I am losing speed and distance to the mark. That is why, unless there is an obvious way to get out of the current entirely, or at least to a slower flow, I think you should always make your longest tack to the next mark sailing in the lee-bow position. And I would do this even if it meant pinching a bit to do so.
This seemed appealing enough to my young, malleable, Naples sabot sailing around current-less basins in Southern California brain. I was willing to believe anything out of the Wizard of Zenda’s mouth, or written on the pages in front of me. The idea that a boat sailing alone with its bow slightly above the angle of adverse current would gain distance to windward makes sense, relative a stationary object like a shoreline or a mark anchored in the water. This idea is sufficiently flawed when you either of two things: add another boat to the situation, or remove the mark from the racecourse. At the risk of being flicked into oblivion as I tug on Superman’s cape, the lee-bow effect does not exist when racing against other boats.If two boats are sailing upwind on opposite tacks. According to Melges, the boat with its lee-bow facing the current will gain distance. to windward, and the boat with its windward hip facing the current will lose distance to leeward. In the following diagram. The boat gaining the mythical advantage is in red, as the current crossed the picture right to left. The critical issue is that two boats sailing together upwind are affected exactly equally by the current! Imagine that the two boats are dead in the water. There is no movement whatsoever up the racecourse or towards each other, but there are 2 knots of current running beneath them from right to left across the racecourse. As Mr Melges points out, the red boat is traveling over a distance to windward which happens to be to his left. Likewise, the green boat is traveling distance to leeward. However, there is no advantage to being the red boat or the green boat because both boats are moving at exactly the same speed in exactly the same direction, that of the current. Simply because the red boat is moving to windward, does not mean that the boat is gaining, it only means (in the demonstrated scenario) that it is gaining distance to the left. The green boat is likewise not losing anything, in fact it is gaining the same distance as the red boat toward the left.
Now if we add breeze to the situation and the boats start moving up the page and towards each other, nothing changes! The current is still affecting their movement pushing both boats from right to left across the course, and they meanwhile sail up the racecourse as if they were sailing on a lake with no current. Their paths sailing forward, upwind on closehauled are the same as they would have been without current. Because of the additional current vector in the motion of the boats, the resultant vectors place the boats slightly to the left of where they would normally be, but makes no difference between the boats relative each other.
If we add a mark to the mix, little changes in our revised theory. The red boat will in our diagram will be pushed closer towards a port-tack layline, and the green boat will proceed the same distance, in addition to the forward progress he would have made anyway.
Monday Morning Tactician Says: The best way to look at current while racing is as if the water your sailing on is a conveyor belt moving across the racecourse. The marks are moving relative your normal sailing tracks. It is important to realize, if the current is different on one part of the racecourse than on another, then the strategy becomes significantly more complex, and may be worth discussion in future MMT columns. However, if the current is moving across the racecourse in a uniform fashion, then it is better to not even worry about the current EXCEPT for dealing with 1. Laylines, 2. Mark Roundings, 3. Starting strategy.
Original post by Andrew and software by Elliott Back
