Why controlled gybes are important

whoops-gybe

I've had chance recently to sail with some skippers that did uncontrolled gybes, on purpose.  As in, that's just how they gybed.  We're going to unpack a lot here.  What is a controlled vs uncontrolled gybe?  Why does it matter?  What can go wrong with an uncontrolled gybe?  Before we can even define controlled vs uncontrolled, first I want to talk about different types of gybes and when they're appropriate.  But before we can do that, first we need to talk about two different modes of sailing: planing vs non-planing.

We'll keep this quick and simple.  Non-planing is the "normal" mode of a sail boat, and especially most of our boats, most of the time.  The boat is pushing its way through the water, reluctantly and (relatively) slowly.  The dinghies we learn and teach on operate in this mode, except for in extreme and exciting circumstances.  When you get into more high-performance boats, like our RS500, they are made to plane, which means they pop up on top of the water and, almost literally, start flying across the top of the water.

Why is this relevant to gybes?  Because you gybe these two types of boats very differently.  On a planing boat, its fastest point of sail is, by far, on a broad reach.  And often you're flying a gennaker, because that's what they're made for, so you're moving at near (or above) wind speed.  To gybe, you go from a broad reach at really high speed and drive down fast onto a dead run, at which point the apparent wind drops to almost nothing (because you're still planing and moving fast). As you keep turning through the wind, you just let the main sail flop over on its own, because there's very little pressure on it (pressure on the sail is determined by wind speed minus your speed.  i.e., apparent wind speed).  Then you keep turning up onto the new broad reach, maintaining your speed, and continue on your very merry way (or you don't do everything perfectly and you capsize, but ssshhh we don't tell people about those).  This is often referred to as a racing gybe, as you're doing it at high speed and with minimal loss of speed.

But on a non-planing boat, or more accurately, on a boat in non-planing mode, you want to gybe differently, which is from a stable dead downwind course.  This is how we generally teach gybing in our lessons.  Get on a dead run, grab the main sheet falls and pull the main across.  Here is how I like to teach it.  Now, what you DON'T want to do is perform a racing gybe when you're not planing – which would be an uncontrolled gybe.  Let's talk about why this is significant.

Remember, the reason a racing gybe works on a boat that's planing is because the force on the main is fairly low, so the actual flop of the gybe is relatively gentle.  But if you're not flying downwind at high speeds with the kite up, the force on the main sail is much higher (due to the higher apparent wind), so if you just turn through a downwind course and let the wind catch the back of the main and flop it across the boat, it's going to do so with MUCH more speed and force.  Several things happen here:

1. As soon as the wind catches the back of the main, the sail and, more importantly the boom, start accelerating.  If that starts while the boom is all the way out against the shroud, by the time it's halfway across the boat (i.e., over the cockpit) it's moving at incredibly dangerous speeds.
2. The next, and worst, thing that can happen is it hits someone's head.  We all yell 'ready to gybe?' and wait for a response, and we hope everyone ducks, but sometimes people don't duck enough, or they responded 'ready' without really being ready.  If that boom has been accelerating from the shrouds in high winds, any contact with a person is going to... well, let's just say if all it does is end your sail for the day, you had a lucky day.
3. If no one's in the way and that's not a concern, the next thing you as a skipper will probably try to do is grab the falls as they come across to try to slow down the sail so it doesn't slam to a stop on the other side.  Not good on your shoulder.  Please never do anything to put yourself in harm’s way.  We can fix boats.  People are harder to fix.  But even more importantly, please don't do things that are going to purposefully put you in harm’s way, like a questionable technique that requires dangerous maneuvers to pull off.  If you find yourself doing so, step back and ask, 'is there a better and safer way for me to do this?'
4. Ok, so you've learned not to try to grab a flying sail and risk ripping your shoulder out.  So now the main and boom fly across the boat at full speed and slam into the far shrouds.  At best it's excessive wear on the rigging and boom.  At worst, you just dismasted.
5. Say no one and nothing broke, but you probably had a high chance of capsizing.  Because a sail with that much force slamming to a stop carries something with it: momentum.  Momentum that wants to keep spinning, and will take the boat with it, so now you're fighting the urge of the boat to turn up into the wind and subsequently capsize.

These reasons are why we pull the boom to centerline to gybe.  Ideally you want to be sailing at an angle to the wind so that when you pull the main across, the wind catches the backside of it when it's close to the center of the boat.  That's when it starts accelerating.  Which means 1) people's heads are safer, 2) it's much easier and safer to hold onto the falls to keep the sail controlled and moving slowly, and 3) when the sail settles into its new position, it does so gently and with minimal effect on the boat itself, allowing you to calmly start sailing on your new tack.

As with anything sailing, always ask yourself, ‘what could go wrong if things don’t work out how I expect them to?’.  If you don’t like the answer (or don’t know the answer), ask around.  Sailor’s love ‘what if?’ scenarios, and especially explaining why what other people are doing is wrong ;-)