Upwind in Very Strong Breeze
When sailing an RS Aero upwind in fresh conditions, conventional wisdom would dictate a firm vang, lots of cunningham and a reasonably taut outhaul. This results in a flat, efficient sail shape with low drag. But what should the sail trim be as the wind builds and exceeds your comfort level?
For each sailor, there is a peak wind strength beyond which, sailing becomes difficult and slow. Below this point, the sailor is the master of their boat. They hike hard and can sail efficiently and fast. But above that point, it seems that the wind and boat conspire to become the master. Staying in control becomes increasingly difficult. The boat staggers with each gust, slipping sideways and going much slower.
What the limit is, depends on the sailor's experience, weight and sea state. For more experienced Aero sailors that peak wind limit may be quite high up to 20-22 knots of breeze. For newer and lighter sailors, the limit may be much lower down to or below 15 knots.
In the Aero, you can extend that peak wind limit by raising the centerboard a little and by flattening the sail as much as possible by maximum use of the cunningham, vang and outhaul. But what should you do beyond that point?
Before explaining the solution, we must first examine the Aero mast. This is not a Laser!
The Aero mast is very bendy, so much so that in very strong breeze, it is easy to over bend (fore/aft) beyond the maximum curve cut into the luff of the sail. When that happens, you will see diagonal overbend wrinkles in the sail starting at the clew near the boom and extending along the inner end of the battens toward the mast. Bending the mast beyond this point does not flatten the sail any more rather it creates an inefficient shape with the leach collapsing, hinging vertically on the inner edge of the battens.
In the picture below on the left, a normal sail in medium winds without overbend wrinkles. On the right, a sail with max vang and starting to get overbend wrinkles.
The Aero mast is also bendy laterally, so that with each gust, the mast will bend sideways at the top, opening the leach to spill wind up high. Sideways bend allows the Aero to automatically reduce power in gusts without you having to compensate solely by easing the mainsheet. In this manner, rather than heeling or staggering, the boat accelerates forward in gusts and is much easier to control. This is very desirable as the boat will automatically reduce power and self-tune to the dynamics of the wind. However, the tighter the vang, the less the mast will bend sideways and the less power will be spilled.
Vang is Good to a Point
The vang (kicker) on the RS Aero achieves two purposes:
- It flattens the sail by bending the mast
- It tightens the sail leach by reducing twist in the sail
These are both desirable in medium conditions, but in strong breeze when consistently overpowered and the boat is staggering, the tight leach becomes a problem. The top of the sail becomes too powerful and difficult to ease quickly in gusts. In really strong breeze, a different approach is more effective where you vang less and use the cunningham more.
The Aero cunningham (downhaul) also bends the mast, but in a different way to the vang. It stretches the sail to pull the draft forward and flatten the sail, especially at the top. The cunningham will compresses the aft end of the mast and because it is so flexible, it will very effectively bend the mast to flatten the front of the sail. When pulled to the maximum, you can completely flatten the top of the sail. This is essential in strong breeze. In very strong breeze, you cannot pull the cunningham on too much. It can be somewhat scary to pull on the cunningham this hard (two hands required), but it is fast and essential in these conditions.
When used in combination, less vang and more cunningham is very effective in reducing power and making the boat much more manageable.
More Twist Please
Consider these two images taken on the same day in 22 knots of breeze. Look at the angle of the top batten in both pictures.
The first image is with traditional strong breeze trim. Lots of cunningham, vang and a flat outhaul. The leach has little twist and is fairly straight. There is power in the sail throughout.
The second image is with a vang eased about 10-15cm, the cunningham on max and a 1-2cm ease on the outhaul. The sail has much more twist and the top of the sail is very open. The power is in the bottom half of the sail.
On this day, the more twisted trim was significantly easier to sail and had greater acceleration out of the waves.
Why More Twist Works
Using less vang means more twist and the top of the sail is more open at a lesser angle to the wind. This means less power up high and a lower center of force from the wind. This makes the boat more stable and easier to control.
Less vang helps the mast to bend sideways which releases the leach up high in gusts. This helps the boat auto-tune in gusts and changing wind speed over waves.
Using maximum cunningham flattens the top of the sail and also helps twist the sail open. Easing the outhaul a small amount helps give the boat a bit more low down power which is useful in big waves to re-accelerate.
The centerboard should be raised 10-15cm to stop the boat tripping on the centerboard in gusts. The boat will feel a bit "squishy" as it slips sideways a little, but this is primarily a different feel and does not seem to impact performance. Amazingly, you will actually make less leeway with the board raised compared to a sailor that lets their boat heel with their board all the way down.
Finally, sail the boat very flat -- almost no one sails the boat flat enough. Flat is fast. It is faster to ease the sail too much, even luffing and keep the boat flat, vs having the boat heel in gusts.
Finally, if it becomes survival conditions for you and you need to abandon the race or just get round the course, ease the vang a lot (50% or more) when going upwind or reaching. Keep all the other controls on hard. The top half of the sail will completely depower and you'll be much more in control. You'll be slow, but safe.
Downwind, ease the vang more than you would normally, but not too much. Too much twist can make the boat quite tippy. Trim the mainsheet so the boom is only 60% out. Keep the centerboard down and move right to the back of the boat. That will be your most stable configuration.