It's often talked about and rarely changes on any boat once set. But it's an important tool that needs to be changed between light and heavy airs. Rake defines the balance (Lead) of the boat and how it sails upwind and downwind.
Any helmsperson will tell you that it is easier to keep a boat sailing upwind in a groove if there is a touch of weather helm. That "feel" lets the boat find its natural track through the water and will require less rudder to steer the boat. Too much helm, either windward or leeward, requires more rudder movement to steer, which hurts boat speed. How do you set up your boat, so you achieve the proper amount of helm? You do it by raking the mast aft or forward.
If you have zero degrees mast rake, your mast is standing straight up. 3 degrees of rake would indicate your mast is leaning aft at a 3-degree angle. A negative rake would have it leaning forward (an unusual circumstance for most boats unless you're a catamaran).
To establish your boat's optimal mast rake settings, and this is the same for all boats, start with where you set the mast heel. Position it wherever the designer or latest tuning guides for your boat sets the mast step. (Note: if you intend to use SparTite to seal it at the deck, set your mast step and base rake before sealing the SparTite.) Follow this by adjusting the headstay length to what you believe would be a base setting with firm tension on the rig. Then go out in 10 knots of breeze and try sailing upwind for a while. If you have too much weather helm (the sail plan's centre of effort is aft of the hull's centre of resistance (Lead), making the boat want to turn into the wind), shorten the headstay and try again. These headstay adjustments may be as slight as a few turns on a turnbuckle to achieve a different feel. Mark where you have set the headstay length for your base, whether it is counting exposed threads, measuring with a calliper, or whatever method works for you.
Meridian Salona 45 tracking perfectly in medium conditions with here XD Carbon sails
It is easy to see and feel if you have too much weather helm. If you watch the boat's track on the horizon, you can see if you're gaining ground to windward or losing it. How much pull or weather helm is critical at this point. If you let go of the helm, does the boat come to windward? If the boat goes straight or bears away clearly, you need to lengthen the forestay a few turns to get a little weather helm. If the boat shoots to windward and almost tacks. Then take turns on the forestay to balance this. You should have enough, so the boat tracks upwind but not close to tacking. Note your rig tension and mast can be set once the rake is set so you can fine-tune that later. But the caps should have tension on them when testing the rake.
Once you have that 10-knot base setting, go out in heavier winds and conduct the same assessment. You will probably start off with too much helm using the base setting as you will have the mast relatively too far aft. Progressively take up a few turns on the headstay until you experience just enough windward helm to keep you in a groove while sailing. Then, do the same thing in winds less than ten knots where you will lengthen the headstay past the base setting. Capture the positions of all three settings and keep a record of them on the boat for easy access. You may want to have additional intermediate settings.
J 109 Outrajeous in light air showing her heels unwind with her Titanium sails
But for most boats having a light, base, and heavy headstay setting should suffice. Note it is mostly turning on or off the forestay to get you these settings. As in light airs when you add rake you want the rig soft. And in heavy airs, you want the rig tight, so you will be taking turns on the forestay.
Theoretically, you can't increase rake without adjusting the length of the headstay. You can crank down on the backstay to move the tip of the mast aft, but that basically creates more prebend and not rake. That prebend, when attempting to depower the boat, can have the same effect on the centre of effort, but not as dramatically as if you were to shorten the headstay and reset the mast's angle of rake.
Just as having the right headsail can dramatically change the performance of your boat as the wind increases or decreases, so can adjusting your angle of rake. Most boats will set up to a base, heavy or light setting at the beginning of the day and not make adjustments as the day progresses. If the wind speed changes and you're sailing multiple races, don't be afraid to adjust your headstay on the water to reflect the present conditions. Some modern boats, it should be noted, have systems that allow you to adjust the length of the headstay and mast rake during a race. This is not that common but can be very effective in maintaining rig balance.
When you get to the right balance of setting, make notes of where they are so you can replicate them when sailing in similar conditions in the future. And remember, the less you use the rudder to keep the boat in its groove, the faster you will go...and the best way to balance the boat is through proper mast rake.
Slack Allice GK 34 moving along perfectly in 12 kts with her Tape drive silver sails
If you have questions on how to set up the headstay on your boat to achieve optimal rake settings, contact UK Sailmakers Ireland today.
