19.11.23 The short trip aloft, gybing around the high pressure , and some Sunday school theory
Good afternoon or morning or evening, people, hope all is good with you and your loved ones!
I‘d like to mention first that my climbing trip up the rig yesterday afternoon was short and nor very productive. I did climb up and just under the second spreders I realized two things: 1) my right ancle hurt and 2) the pitching was pretty bad and I simply couldn‘t hold on well enogh while climbing, leave alone working 10 more meters further up. So, I just quietly decended, leaving everything in place to wait for a better moment. I‘ll fast forward and will tell you that earlier today I stowed everything away and that better moment has now been posponed indefinitely. I did run a spare halyard through a block at the masthead, installed months ago during my preparation when the mast was safely placed in a horizontal position 1 meter off the ground. So, to hell with that tail dangling in the air. For the moment, there‘s nothing I can do about it.
Shortly after I had resigned I to Neptune‘s decision to punish me for presumptuously cutting corners too close, around noon yesterday the wind picked up as I mentioned to you right away.
However, come 10 o‘clock UTC, the breeze decisively backed to the NW and that caused some worries in me. The forecast clearly showed northerlies, backing slightly to the north-west much later. I was already a bit jumpy, having brushed not only the High but the possibility of spend a few days drifting aimlessly around so I immediately gybed. The new course was taking me mostly south, away from the cursed high pressure system even though at times I was actually going a tiny little bit to the west as well. The VMG didn‘t look great at all but the fear of getting sucked into the high‘s tentacles and becoming becalmed for days made me treat this as a tiny pebble of inconvenience in my shoe. As the new day was about to break, I realized that the wind had veered back north north west, and after a brief thought and weighing the pros and cons, I decided we gybe again and go east. Actually, so far it’s been very rewarding: we‘ve been able to sail even south of our general course to the Cape of Good Hope, some 2550 miles away with a stable 15-18-knot breeze.
So far so good with 8.5 -9.5 knots of boat speed, blue skies with puffy clouds – totally idyllic. Gotta watch out though and gybe the very moment something smells fishy or, rather, anticyclonic.
I mentioned VMG earlier and I do think I owe you an explanation of what this misterious VMG, this sacred abbreviation in sail racing, actually is. Fellow sailors, please excuse me.
Like most things at sea (and so often in life in general), this is also pure math. I like saying that mathematics is God‘s language and I‘m sure you‘ll admit it rings true. I mean, EVERYTHING out here: waves, wind gradient, atmospheric pressure, navigation, celestial navigation, aerodynamics, etc. Is best described by mathimatical formulae and statistical models, which are also pure math and calculus.
So, back to the matter at hand. Velocity Made Good, or VMG, is reveered by racers in a religious way: pretty much like the Holy Trinity is reveered by Catholics or the teachings of Buda – by a few hundred million people in the Far East.
It is actually a vector: remember what that was? It is a length of a straight line with an arrow at one end. In other words, it has a linear value (meters, feet, miles, whatever) but it also has direction.
When we want to reach point B from point A with a sail boat, it almost never happens to be in a straight line. If the wind is against you, you‘ll ned to tack your way to point B, zig-zagging along the course. That is because a foil or wing needs to have some angle of attack relative to the air flow. Thats why we can‘t go directly upwind. So, while happily tacking, our boat poins some 40-45 degrees away from the spot we want to go to. The vector of our speed can be projected along the line between point A and point B, and that, ladies and gents, is the VMG. In simple words, its the speed you‘re making towards the mark while not going there directly Got it? Imagine your course is at a right (90 degrees) angle relative to the line between A and B. No matter how many months you tack and how fast, you‘ll never reach pont B because your VMG is ZERO. On the other hand, if you can go directly to point B, your VMG will be exactly equal your speed over ground (SOG being you boat speed plus/minus current, or as you call it: GPS speed).
What about the VMG when the boat is sailing downwind? It should be all much simpler but it isn‘t. As the wind angle (on the nose being 0 degrees, exactly from behind being 180 degrees) increases, the boat speed starts going up. The so called apparent wind, which (here we go again) is a vector sum of the true wind and our own speed but pointing back (a dog with its head out of the window of a car doing 50 km/h on a windless day, will be enjoying exactly 50 km/h wind in its cute face, and will be having a ball with its tongue and ears flopping happily in the self-created breeze, hence boat speed in the oposite direction) will start to decrease at some point, and as the wind idirection becomes 180, the two vectors will be oposing each other. See, our own speed will be „killing“ the wind from behind. And, even though this may be the shortest course to a point exactly downwind from us, it is not the fastest. If you‘re happily cruising, who cares – you wing-and-wing or even drop the mainsail altogether so it doesnt spill your drink if it accidentally gybes. But when racing, we fix our eyes on the VMG value and zig-zag our way towards the leeward mark, gybing along the way, in an attempt to get there as fast as possible.
My boat was designed by the ingenuous Bruce Farr with symmetrical spinnakers in mind. It was also designed for crew of 12-13 people. As much as I love symmetrical chutes (spinnakers) I have to keep in mind nd that I‘m single-handed and make compromises. Asymmetricals (or gennakers = genoa+spinnaker) are easier to handle, can be furled just like a jib and are the obvious choice when you‘re on your own. But! They have one major disadvantage: they don‘t do don‘t handle „deep“ wind angles (150, 160, never mind 180) well at all. The reason is simple – since their tack is attached to some point on the center line the further downwind we go, the larger area of the gennaker gets blanketed by the mainsail. And, at some point the sail collapses and you need to go upwind to fill it up again. The lighter the wind and the higher the waves, the worse a gennaker behaves.
A symetrical spinnaker‘s windward clew is attachd to a spinnaker pole, which can be pulled as far back as 90 degrees relative to the fore-aft line so half of the sail area is clear of the shaddow of the mainsail, allowing the boat to sail much „deeper“ downwind. Sounds perfect, right? Well, not exactly. You have a lot more lines to think about and to rig out before you hoist a symetrical. The spinnaker pole, remember? Guys – forward and aft, a topping lift, too. And two lines leading to each clew of the sail. And this is just a start. Immagine gybing a 180-square-meter chute single-handed. With full crew, I have counted 7 people being involved in that manoeuvre. Seven! Well, I have practiced a lot and have been successfully gybing on my own up to 17 knots of true wind. Unfortunately, I can‘t even think about it now. My autopilot remote control died 10-12 days ago so its impossible to be on the fore deck dipping a 6-meter spinnaker pole and controlling the autopilot at the same time. A gybe woukd mean taking the chute down, folding it in the bag, and hoisting it again on the other side if I‘m still conscious. Because, folks, hoisting a symetrical chute is not such a big deal. Lowering and collecting it when single-handed, though, is a different cup of tea.
Let me put it this way: dropping a symetrical on this boat on your own equals 3 days in the gym plus an MMA-like grappling match in the course of several minutes. In other words, it‘s not something I look forward to and that‘s why it rarely happens to use a symetrical. But sometimes the wind and sea state tell you to go deep downwind – to avoid exposing your side to the waves or to avoid endless gybing, or just to honor Bruce Farr‘s genius as a designer and make the most out of your VMG.
So, for that reason alone, I carry 2 spinnaker poles and 3 symetrical spinnakers. Gybing now is out of question because of the permanently installed baby stay carrying the storm jib but a long downwind leg can be perfect for a symetrical chute. It looks like I may have to put my muscles where my mouth is in the next couple of days and I will definitely tell you how it’s gone down after (and if) I do.
I‘m pretty sure you have by now had your fair share of a lonely sailor‘s babblings for one day. So I‘m gonna leave you to your Sunday activities hoping that they are only pleasant ones and go check on sails, sea, wind, flying fish and the horizon. If all looks all right, I‘m going to get a new grib file on the weather ahead and take my afternoon nap.
Enjoy your Sunday and don‘t forget to tell people you love them if you really do. They can‘t always guess and they shouldn‘t.
Best!
Pav
