The Ugly Side of Pinching

Pinching is bad, but what happens next is worse…

After just moments of noticing they are sailing too close to the wind, the helms person bears away back to the correct angle.  What they don’t know is that they are slipping sideways due to something even worse: stalling of the sail.  The reason? a shift in apparent wind.

First we should understand the difference between pinching and stalling.  Pinching is when the boat is sailed too close to the wind direction, causing the angle of attack on the sail to be too narrow.   The creates a large separation bubble of flow on the windward side of the sail, indicated by the luffing just behind the mast.  Stalling is the opposite, when the boat is sailed with a wider angle of attack usually from bearing away too far from close hauled or having the sail trimmed in too tight.

Why pinching is bad:

Whether the boat sailed into a header, or steered too high to the wind indicated by backwinding of the luff in the sail caused by a narrowing in the angle of attack, it is critical that the boat not stay this course.  Almost immediately the relief of pressure on the sail will lower the drive force on the sails and foils combined output, allowing for drag to manipulate the performance of the boat.

The 4 types of drag that play a big role on sailboats are:

  1. skin drag: boat bottom surface friction
  2. form drag: The boat shape in the water and how the streamline may optimize performance or create drag
  3. bow impact drag: waves or chop hitting the bow
  4. aerodynamic drag: windage on the hull, sails and everything else above water

But how long does it take for pinching to make a difference on the boat?  Obviously the longer you pinch for the more the boat slows, and less the sail maintains function, which is compounded by the drag components, but even a mild amount of pinching has some pretty big affects to the performance.  For those who have great focus and avoid pinching at all costs know that if you even notice the pinch occur, it is too late and your speed is being affected.

When the angle of attack is narrowed so much to create the pinching effect, so much drive force is lost that the boat is already losing speed.

How should one react to pinching?  Avoid stalling the sail by sheeting out while bearing away.  Since the boat speed has decreased, the apparent wind moves aft, meaning that bearing away back to close hauled will widen the angle of attack, creating some level of stall on the sail even though it is the correct angle for VMG.  This is usually not noticeable from the sailors point of view, but from behind the boat will slip sideways until the apparent wind settles forward and the foils grip again.   Depending on how long the boat was pinched for, this stall can be much worse than the pinching itself! So be sure to bear away quickly, and drop sheet for the wind angle to adjust.

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The second, and equally important tip about getting off the pinch is:

A lot of people criticize use of rudder as adding drag to the boat.  I would say that it is very true, but rudder drag is only one small type of drag amongst four greater types of drag mentioned earlier.  Try pushing a canoe up a swell and into the wind and through chop and it won’t make it very far due to drag.  When the angle of attack is narrowed so much to create the pinching effect, so much drive force is lost that the boat is already losing speed.  My suggestion would be to use as much tiller as you need to get the boat off the pinch ASAP! *pro tip: if you can bear away down the back of a wave you will get the benefit of reducing impact drag and getting off of the pinch at the same time.

How should one react to pinching?  Avoid stalling the sail by sheeting out while bearing away.

Lastly, don’t bear away with windward heel.  When sailing to windward, boats track best with some degree of weather helm.  Pinching will result in a loss in pressure in the sails and foils, having a flattening affect that contributes to lee helm.  Lee helm is when your boat wants to bear away.  Sailing upwind with lee helm is BAD! What makes things worse is sailing with lee helm and bearing away with your rudder! pulling your tiller to windward when your boat is windward heel upwind is likely one of the worst looking things from a performance perspective.

So it’s simple right?  If you accidentally pinch, or sail into a header, adjust your course to the new close hauled AS soon as you notice it! While bearing away ease some sheet, and move your weight inboard slightly (if needed).


Vaughn Harrison

When Vaughn isn't coaching sailors at our week long, all-inclusive Laser clinics in Mexico, he continues his work with countless Olympians, youth and masters sailors. He coached at the 2016 Rio Olympic Games and founded ISA in 2008.