Friday, July 20, 2012

Passage from Arbatax to Sicily - Technical Notes

The theme of this blog post can be summed up by (sung to a Willie Nelson tune) "It's on the Nose Again". (Marina here...for my buds...you will likely be happy to give this one a miss, unless you are into the technicalities of sailing...then go for it! But keep in mind, there are no pictures. Back to Matt...).


An all too familiar sight the last couple of days ...
 a very thin slice of wind to be sailing into.
My sailboat racing friends might relate more to this .... you know on when you're approaching the starboard tack layline in a westerly on Port tack about 100 yards from the mark and you keep getting lifted, and lifted and lifted -- so you never quite are able to lay the mark on starboard ... we call it 'The Great Circle Route' on Scarlet ..... that's kind of what we had, only in reverse ... for the last 24 hours all we have needed is a 20 degree lift (shift towards the stern) .... could we get a lift? No. Did we try to sail? Yes. Did we give up? Several times. In the last 36 hours we have travelled 240 miles -- first to Arbatax, then to Sicily, and the apparent wind has been 15-20 degrees off the nose the entire time!
For those non-sailors -- 2 concepts I'll try to explain -- apparent wind and VMG or velocity made good. Apparent wind is the wind you feel when you're sailing. When you're driving along at 100KPH and stick your head out the window it feels like the wind is blowing 100 kilometers per hour, even though the actual wind might be calm. If you have ever ridden a motorcycle through the Cassiar Connector, you realize that the wind must blow in there at close to 80KPH because it's like there is no wind when you're riding along -- a very strange sensation indeed.
Sailboats work the same way .... if you're in a 10 knot true wind (if you were stationary) and you sail at 7 knots into it, the wind you feel (and the wind the sails feel too) is 17 knots. If you sail downwind at 7 knots in that same wind it feels like it is blowing 3 knots. Got it?
The second concept is VMG or velocity made good. I love to tease my sailing buddies when they get new sails -- I tell them that with new sails they'll just go faster in the wrong direction. Sailboats can't really go directly upwind (kind of obvious if you've ever tried peeing into the wind ... somewhat futile). Strangely enough, sailboats cannot go directly downwind either -- or at least not very efficiently. Back to Apparent Wind .... if there's a 10 knot breeze and you are going 7 knots downwind your apparent wind is only 3 knots .... and of course a 3 knot wind isn't going to push a boat at 7 knots so you end up going r-e-a-l-l-y slow. Ideal wind for a cruising boat (read "Cruising Boat" as heavy ... just our anchor chain alone weighs more than our racing boat Scarlet; under-canvassed -- Scarlet also has about twice the sail area to weight ratio as Tara has -- just like having a bigger engine; and old, ugly sails -- racers replace their sails when they lose their shape -- usually after 2 seasons or so, our 10 year old sails have 'plenty of life in them'). Suffice it to say that Tara excels in conditions where the wind is between 15 to 30 knots and somewhere between a close and a broad reach ... this beating into a light headwind stuff is best left to racing boats.
So the wind was from the wrong direction, too strong to power directly into -- generating waves that slowed the boat down at the same time.
The end result of this thin wind is that you end up with GPS-course- made-good numbers that are somewhat pathetic and look like this: 40 degrees off course doing around 7 knots ... will we ever get there?
Come to think of it the last time we experienced this exact phenomenon was .... going north from Marzamemi Sicily to the Straits of Messina .... maybe we have to give some payola to the local Mafiosi if we want the wind to go our way .....

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