Monday, August 06, 2012

Sail setting for speed

I've read many books and sat through many coaching sessions on how to win races and it seems to me that simply put there are two key aspects- sail the boat fast and sail the fastest route around the course. That's probably where the simplicity ends and things become a little more complicated.
Sailing a boat fast is all about boat handling and sailing the fastest route is all about strategy and tactics. This simple division helps identify the where a crew can initially contribute to the speed of a boat and that is boat handling. Strategy and tactics can be handled by the helm whilst the crew focuses on learning the basics of boat handling. Later the crew can begin to help in the task of finding the fastest route around the course but more on that another time.

Sailing a boat fast requires optimising the power generated by the wind in the sails and turning it to the maximum speed through the water. So whatever direction or manoeuvre that the helm and crew take the boat through they must trim the sails correctly to the wind and at the same time make sure the boat is controlled to minimise drag and use its hull shape to best advantage. This requires a teamwork as well as knowledge of what needs to be done because without a coordinated approach the looked for boat speed will not materialise.

To begin with the crew must understand some basic principles of boat manoeuvres, specifically each point of sailing and then tacking and gybing, because they will need to control a number of aspects of the boats equipment as well as moving to the appropriate position in the boat. 

Points of sailing
This diagram shows the relative angles between the direction of the boat's travel and the wind direction.
The sails need to be set to the right angle to fill and drive the boat through the water. If the sail is not correctly set then it will not work efficiently. Each point of sailing has a name which helps because for each one the controls have general settings and the helm need only say which point of sailing for the crew to know what they should be doing. So for example on a beam reach the jib sail doesn't need to be pulled in tight but just enough for the sail to fill and the centreplate will be about 50% down. On the Albacore we also have shroud levers to let the leeward shroud go slack which helps the mainsail set better and the crew is responsible for this control. (The crew's position will depend upon wind strength and perhaps sea state but the key factor is keeping the boat upright - but more on this later.)

Setting the jib
Setting the sail correctly does require fine tuning, which is always a continuous process because the relative direction of the wind to the boat is always changing and so the crew needs to know just how to set the jib. The first stage is to trim the jib so that it is just filling completely which means that the front edge (the luff) is not backwinding. Then the sail is adjusted to ensure that the jib telltales are flying correctly. The tell tales are small strips of material that are attached to each side of  the sail's surface and they respond to the movement of the air over the surface and so indicate how well the sail is set. The diagram shows the three states: trimmed (just right) luffing (sail need to be pulled in a bit) and stalled (sail needs to be let out a bit)

The crew should be constantly adjusting the sail in and out small amounts whilst watching the tell tales to ensure that the sail is trimmed optimally.

The diagram shows tell tales at different points up the jib and the crew needs to find the best optimum point for all of them which sometimes requires a bit of compromise because the sail's angle to the wind changes because it twists. This twist can be controlled with a jib pole which when deployed pushes the clew of the sail out and down to get the get the best angle of the sail to the wind from the top to the bottom.
This picture shows the jib pole in action. The jib pole is adjustable so needs to be controlled by the crew to get the best out of the jib which can be seen when all the tell-tales are flying right showing that the sail is correctly trimmed all the way up its luff and this maximises the effectiveness of the jib.

When sailing close hauled the jib is normally trimmed fully in and when running downwind the jib is poled out to catch as much wind as possible so on those points of sailing the crew does not need to adjust the sails except when tacking or gybing. But more on that on the next post.


fareastsails said...

Thanks for providing valuable information about sails setting up for speed.

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