Monday, June 3, 2013

back and forth

To use a more specifically maritime language, it is called tacking. In fact it is not obvious for everybody that a sailboat cannot progress directly into the wind. So, to reach a destination which is directly upwind, sailors use a techniue called tacking. The boat has to create an angle between the lead side of the sails and the wind, that creates a lift effect, just as th method used by aircrafts to make heavier than air fly. That angle, ideally should be around 20 degrees. To that, you have to add the angle between the lead portion of the sail and the axis of the boat. The addition of those two angles are the angle of the wind to the axis of the boat. It means that to cover the distance between A and B directly upwind, you have to cover a greater distance. For example, when Papy Jovial is set up the way it used to be, with the genoa sheets going from the bow to the cockpit outside the shrouds, That angle was around 60 degrees. The cosinus of 60 degrees being 0.5, the progreesion towards the target was half of the distance covered through the water. To go 1000 miles directly upwind, Papy Jovial would have to sail 2000 miles. The pace of the progression towards the target is called the VMG (for Velocity made Good), and the smaller the angle between the course of the boat through the water and the angle of the wind, the closer the VMG gets to the speed through the water.
My dear friend Jean-Paul, who is helping us sail to Rouen and is a racer, has redirected the genoa sheets to go inside the shrouds and outside the lower shrouds. This in turn improved the angle between tacks, which went from 120 degrees to 100 degrees. That then converts into an improvement of 29 % of the VMG. Very significant. I think it means that cruisers could learn a thing or two from the racers and I am graterful that Jean-Paul is with us.
Last night was miserable, Temperature in the 50s, the boat again slamming and throwing us all over the place, and sleep becomes very problematic. Fortunately today, blue sky, sunshine, calmer seas.
At noon, we were by 47:49 N and 9:13 W. The distance to Rouen on a direct course is 389 miles, but we will probably cover a great deal more miles as we are expecting the wind to remain on an easterly direction, i.e. against us. We are now hoping that we could get to Le Havre, at the mouth of the river Seine on the 8th afternoon and in Rouen on the 9th.
No guarantees of course.
We are still doing good in terms of provisions and drinks.

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