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Competitive Sailing Sailing To Win Yacht Racing

Rig Tune Relationship to Get Better Performance.

Firstly, I would like to correct an error in last weeks Blog regarding using the compass to establish Line bias. Phil Crebbin, a UK 470 Olympian kindly pointed this out and has provided the correct method which is copied below in bold.

Everybody knows that it is the wind direction vs the line direction that defines the bias of the line (subject only to other things like any variation of current at each end of the line, of course). The direction to the first mark has absolutely nothing to do with it, except in the extreme case when the mark can be laid in one, without having to tack.

One clear way of demonstrating this is if you have a shifty wind, with the line laid to be approximately on the average wind direction. Say that the wind is periodically shifting ca. 10 degrees on either side of this mean direction. When the wind is on its maximum left shift of 10 degrees, clearly the port end of the line is now favoured by that 10 degrees. Conversely, when the wind is on its maximum right shift of 10 degrees, the starboard end of the line is now favoured by that 10 degrees. 

 RIG TUNE –The four main elements to rig tune.

Mast Rake is measured from the masts vertical position to how far aft that the mast is angled. Angling the mast aft shifts the power aft and forces the bow to windward and creates weather helm.

Forestay length determines how much rake you have and how much rake a boat needs to generate the right amount of weather helm is a function of hydrodynamics being hull form, keel shape and placement (or in the case of a dinghy, centreboard position or rake if your class has a pivoting board).

In most one-design racing classes, sailmakers and class stalwarts have put a lot of time figuring out what works best and creating tuning guides that specify headstay lengths and thus rake for different conditions.

These are readily available by doing a Google search of your class.

Mast Bend –  After setting the rake turn your mind to mast bend. Mast bend changes the mainsail shape, the more bend the flatter the mainsail which in turn gives less power. 

No matter what type of rig you have, you want to start with a little mast bend or pre-bend and this is the amount of bend you have with no backstay tension.

Lengthening the headstay increases the bending moment and adds pre-bend and this is why it’s important to set rake first.

If your mainsail develops diagonal wrinkles from the clew up to the luff,  you are over-bending the mast for the amount of luff curve in your mainsail.

Athwartship Tuning the rig must be centred in the boat otherwise performance will be different on each tack. Using the main haliard and taking the loose end to the gunwale on each side will give you a side to side reference.

The tension on the shrouds needs to be firm, the same on both sides and if you are sailing a dinghy, the use of a tension gauge when setting up on the beach gives great results. 

In a keelboat, when sailing in 10-12 knots of breeze, sight up the aft face of the mast to check whether the tip is falling off or not. If it is, you need more upper tension.

The next step on a boat with lowers or with multiple spreaders and diagonals is that you need to work on the lowers and/or diagonals next.  

In over 10 knots, you want the mast to be straight but for more power in light air, you can let the middle of the mast sag a little to leeward to increase the depth in the mainsail. 

It is common in one-design classes to ease tension on the lowers (and diagonals if relevant) in light air to create a smooth sag.

 Headstay Sag  When the headstay sags, the headsail becomes fuller and more powerful, which is great in light conditions. As the breeze builds, you’ll want to reduce the amount of sag as much as possible to de-power the boat and help with pointing.  

When you pull on the backstay, or in the case of swept spreaders with no backstay, sheet tension and/or pulling on the sidestays (if they are adjustable) will initially tighten the headstay, but because you are also compressing the rig, the more backstay or rig tension you pull on, in turn, cause mast bend which increases headstay sag.

To counteract this some classes have a strut or chocks to lessen the bend and keep the headstay sag to a minimum and in other boats, you have check stays to change the bend and thus control headstay sag to match the rig and sails to the prevailing conditions.

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SAILING TO WIN!

 

Categories
Competitive Sailing Sailing To Win Yacht Racing

How To Work Out The Favoured End Without Instruments

Getting a great start in clear air can be the most important part of your race and knowing the favoured end and determining how much it is favoured will help you settle on your starting strategy.

Some of the many considerations to ensure a great start are current, where other boats are congregating, the size of the fleet, wind speed and any anticipated shifts.

Of course, there are many other factors to take into account as well so a lot of thought and preparation needs to be given in the lead up to the gun going off.

Instruments to ping the line (if legal in your class) can be of enormous benefit but I believe that you should also be able to use your compass only to work out the line and a couple of methods are set out below.

Going Head to Wind on the Middle of the Line: To carry this out, sail down the line from the boat end about a couple of boat lengths to leeward, when you get to the middle of the line, ease the sails and point directly into the wind. Once you are on the line and at right angles to it, see which end the bow is pointing to, that will be the favoured end. 

A variation of this is to carry out the same procedure but a number of lengths below the line. Doing this will make it easier to determine which end the bow is pointing to and will also keep you clear of heavy traffic on the line in large fleets. A disadvantage here is that there may be boats above you feeding back bad air making it harder to get an accurate reading.

Going Head To Wind On the Line But at an End:

The leeward end is probably the easiest end to carry out this check as generally there is less traffic there. Go head to wind beside the pin and use the angle of your transom to the line to determine the favoured end. If the imaginary line at right angles to your heading is above the start boat the pin is favoured and vice versa if the line is behind the start boat.

This will also give you an idea about how favoured one end is from the other and if the bias is not that great you may decide to start a little away from the favoured end where the chances of a clear air start are greater.

Using Your Compass:

Sail accurately down and on the line from the boat end noting the compass heading, then add 90 degrees to that. Compare that number to the course to the first mark displayed at the back of the start boat and the difference if any will show you which end is favoured.

If your number is less then the pin is favoured and conversely if your number is higher the boat end is favoured.

A Method to Use if You Don’t Have a Compass:

Often referred to as the Sheet and Cleat method. Once again, sail down the line from the start boat end and set your sails until they just start to luff. Either cleat them or take a note of exactly where the sheet is through the turning block. When you reach the other end of the line, tack or Gybe and head up the line in the opposite direction without adjusting the sheets. If the sails are luffing, the start boat end is favoured and if you need to let the sails out to get the telltales flying, the pin is favoured.

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SAILING TO WIN!