Sea Scout Ship 502

We love to sail.

Mar 1 Racing Program: Some Basics -Given by Nick

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These are the three most important principles every racer should keep in mind while sailing.

1. Sail Trim

When sailing upwind, the sails should be close-hauled.

To review how sails move the boat when going up wind: sails work as an airfoil. Air going around the windward side of the sail has less distance to travel and will have less speed; this creates low pressure on the windward side of the sail. Air going around the leeward side of the sail has a long, curved distance to travel and will blow across faster, creating a high pressure on the leeward side of the sail. As with the wings on an airplane, the two pressure cause a force, called lift, to push the boat in the direction of the high pressure, or towards leeward; This force to leeward is called leeway. The boat is able to move forward because the centerboard and rudder resist moving sideways against the water and will redirect the leeway force forwards. However, for all of this forwards motion, there is always some drift in the leeward direction.

Adding a jib can make the two sails more effective. If the jib is trimmed correctly, it will channel more air between the sails to go even faster around the high pressure side of the main, resulting in an even greater difference in pressures and a greater force.

If the jib is too tight in comparison to the main, it will channel its wind directly onto the back of the main sail and disrupt the high/low pressure system.

To make sure the jib is set correctly for a close hauled close, keep both side’s telltales streaming straight back. If the inside telltale is not flying straight, then the jib needs to be adjusted out. If the outside telltale is not flying straight, then the jib needs to be trimmed in.

Also adjust the jib so that there are no wrinkles in the foot of the sail.

2. Heading

When sailing upwind, you should sail as close to the wind as possible (which, as you know, is about 45 degrees from the wind). You can tell if you are pointing too high if the sails start luffing, meaning that they are not smooth and flat and may have a bubble in the luff of the sail. Remember, when close-hauled, the sails should be smooth and tight.

Keep in mind that the upwind mark might not always be directly upwind from the starting line. Sometimes the wind will shift to come from another direction, and the boat’s heading will need to be changed as well. If the wind shifts, use the tack that will provide the most direct path to the windward mark.

3. Crew Positioning

On upwind legs, most small racing boats sail fastest when perfectly balanced and flat on the water. Certain conditions can cause the boat to lean or heel in different directions. However the weight of the crew can be placed to keep the boat flat.

Because the pivot point of the boat is the centerboard, the crew should be seated as close together as possible over the centerboard. The crew usually sits forward of the jib cleat, and the skipper just behind the jib cleat. This will prevent the boat from plowing (the bow dipping lower in the water) or dragging (the stern dipping lower into the water).

Heavy wind will shift the pivot point further back, behind the centerboard; so in heavy wind, both skipper and crew should move further back, but still sit close together.

When sailing close-hauled, the boat normally heels over to leeward. To counteract this, the crew should hike out so that their bodies are parallel with the water.

Keeping the boat flat in this situation makes the boat sail faster because more of the leeway force will be converted into forwards movement. Recall that the sails create an airfoil that pushes the boat to leeward, perpendicular to the line of the boat. However, the surface area of the side of the center board resists movement in the leeward direction and redirects the force forwards. When the boat heels over, less of the centerboard surface area is resisting the leeway force and the boat will drift more to leeward.

At the meeting, we never got to learn how each of these three principles change for each different point of sail (reaching, wing-on-wing, etc.). I actually went much more in depth than we did at the meeting, so it is a lot more information (albeit much of it review material) than should be presented all at once. So ya know, oops… But I hope it was helpful nevertheless. I probably could have found real pictures for this lesson, but I find Microsoft Paint far too much fun:-) Click on the pictures to make them larger.

Tongue-twister a la Kim:

“How many tales could a telltale tell if a telltale could tell tales.”

written and posted by Kelly BMA


Written by ship502

March 2, 2010 at 22:23

One Response

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  1. […] sail upwind). Okay, so obviously we all already know how lift works (click here if you don’t:, but since school was out, we just wanted a fun activity that didn’t require any […]

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