Sailing can be seen as a recreational and competitive sport.
For recreational sailing we are enjoy having control over our boat, and the elements, so the role of choosing the right sails and rig for our weight is secondary.
In competitive sailing, we are looking for every advantage we may get if we want to win. Speed is a very important advantage to have – the gains from using the correct sails are more than just marginal!
Though there are many aspects to going fast, a crucial one is the power settings of our boat, many sailors knows how to adjust power in their boats with a given sail and mast but are unaware that sails are different and rigs are different.
There are flatter sails or fuller ones, there are softer masts and stiffer ones – even in the strictest “one design” we usually find 15-20% difference in mast stiffness. How they impact our power control over the boat has one principal rule. Heavy teams/sailors will require more power in light to medium winds to compete with the lighter teams/sailors, and will not require to depower their boat as much in stronger winds. Therefore, they will require stiffer masts and fuller sails. Lighter teams/sailors will not require as much power as heavy ones in light winds but will require a lot of depowering in medium to strong winds, hence will require a softer mast and flatter sails. Throughout this blog, please bear in mind that the key aspects of setting up your sails having chosen them are critical to performance. However, how you use cunningham, kicker and sometimes outhaul is what makes a real difference to your speed. Sail selection is the beginning – not a magic bullet!
The principal of depowering a boat is by bending the mast, softer masts will bend easier and more than stiffer masts, and hence will depower more easily. Stiffer masts will maintain their shape and hold better power. It is important to note that some masts are soft at the bottom and stiff at the top – and vice versa, so always bend test a mast at the halfway mark, and measure at each quarter what the deflection is.
Now we will discuss specifics for some key classes sailed around the world. We differentiate between unstayed masts, where the mast is not tied to the boat with shrouds, and stayed masts which means we can adjust the shape of the mast by having shrouds and spreaders. We will begin with unstayed masts.
The main area we are interested in bending is from the middle of the mast up, as this is where the sail is and will stretch the fabric, so depowering the sail. We would mainly be interested to keep the bottom of the mast stiff and straight as when it bends it will move the centre of effort backwards and will cause a change in airflow over the sail, as well as causing the boat to develop a tendency to luff up (creating pressure on the rudder).
Starting with the Optimist, where the mast is very short it will not bend in light to medium winds but may start to bend in strong winds (usually around 20 knots).
Luckily for optimist sailors there are many different types of masts, heavy sailors should choose a mast that will not bend much at all and lighter sailors should choose a mast that will bend early and allow them to depower the boat.
The shape of the sails varies massively depending on the model, and again heavy sailors should choose deeper sails, with the risk of losing height and lighter sailors should choose flatter sails with the risk of being underpowered in light winds.
The Laser, as much as it is perceived as a one design class has big variations in mast stiffness and sail shape. Although it is pretty hard to determine which sail is fuller (and the quality control of sails is relatively good) it is very easy to tell the difference between masts.
A stiff top section will prevent the sail from depowering and keep a tighter leech, so will be better suited for the heavier sailors and a softer top section (that bends a lot more) will bend very quick and allow the sail to depower easier and also help open the leech. Testing mast stiffness is very easy as you only need a weight and a string to compare masts. The bottom section is recommended to be a stiff one to prevent the mast from bending at the bottom while we put on kicker tension. If we use a soft bottom section, as soon as we start pulling the kicker it will cause the bottom of the mast to bend, change airflow over the sail and move the centre of effort backwards causing the boat which already have a tendency for rudder pressure generate even more rudder pressure as the boats tendency will be to luff up pretty hard.
Stayed masts can be divided into fully stayed masts which means they have caps that connect to the tip of the mast, like in the 49er and 49erFX, and to a semi-stayed mast, which means the shrouds are connected to a spot somewhat above the middle of the mast such as 470 and 420.
Let’s start with the fully stayed mast as in the 49er/ 49erFX, as it is a one design class there is not much difference between the sails and even if there is it might be very hard to spot the difference to a non expert. The rig, as in the Laser, is easy to measure and to determine stiffness.
Whilst we can bend the mast with a lot of control using shrouds, lowers and caps, the stiffness still matters a lot. The head will want to bend off to depower, and a stiff top mast will make that happen later. Again we can relate this to crew weight. Whilst the lowers and shrouds are easily adjusted to give is the sail shape we want, where we want it, running too soft a mast low down leads to compression problems for light crews, so it’s rarely a good idea to use soft lower or middle sections.
A semi stayed mast is a different story, we treat it as a stayed mast up until the shrouds, but from there up we will treat it as an unstayed mast, in classes such as 420 and 470 when you buy a mast you will receive its exact characteristics by the manufacturer.
If the bottom of the mast is soft, we can harden it by putting in chocks, but the top will give way to pressure and bend. Lighter teams will require a soft one, especially in gusty conditions it will allow the leech to open at the top and maintain the same level of power as before. The heavier ones can handle a much stiffer top as they can handle more power in their rigs.
At TopLevel sailing we deliver that information to our sailors allowing them to develop their own ability to determine the best mast and sails for them based on their feeling of the boat and their knowledge of their needs.