To Reef or Not to Reef – That is the Question

The Lune Pilot Considers – When Should I Reef The Sail?

Easing back the power when the wind is up can be a tough decision especially for the keen sailor who is looking to blow away the week’s frustrations with an exhilarating drive through the waves. Every good sailor however should be reading the elements and making decisions based on his skill, experience and safety. Efficiency certainly is a high priority and there’s nothing like going fast. The two are linked but not the same.

So what determines the need to reef a sail. Basically, wind strength – sometimes wind behaviour. On a very windy day if you have too much sail up the boat will be blown very hard. This will make the boat go faster – that’s good isn’t it? Well, it also makes her very difficult to handling, makes her very uncomfortable and stresses the gear and not to mention the crew. Heeling is not the problem because most boats will sail well when heeled over but its the violent tipping and pitching that is the problem. I always think that sailing in gusty conditions is like “fighting” because you feel like you been in one and so does the boat.

Speed

Actually its a bit of a myth that the boat sails faster with more sail up. In the same way that a powerful car is not necessarily faster than one that is less so. Boats too have factors other than power which determine it’s speed. Boats have what is called a “Theoretical Hull Speed” and it’s different for every boat. Boats are designed with a pointed end and smooth lines in order to allow them to slip through the viscous (compared to air) substance called water. At slow speeds this happen rather effortlessly. As the speed increases the water struggles to get round the boat. It starts to resist causing friction and rucks up in front of the boat. This creates a bow-wave in front of the boat. This resistance starts to impede progress. The power in the sail however overpowers this and as the boats ploughs harder and deeper into the water the wave crashes past the boat breaking and foaming causing a very satisfying rushing sound. The white water speeds past the boat and out the back causing a wake. This is when the theoretical hull speed becomes an increasingly important factor. It’s all about the physics. There is a point at which the effort required to make even small increases in speed becomes enormous. It’s the same reason why cars burn more fuel at high speed. The problem then becomes stability and potential damage to the gear.

So the situation is simple, when you get near to the theoretical hull speed there is little to be gained from applying more power. On a very windy day you reduce the power by reefing the sail but you go just as fast – only now you are more comfortable, more stable and there is less stress on the rigging. I always find that once I have put the reef in I relax and start breathing again, but I’m still going fast.

Reefing Methods

On new boats reefing is achieved simply by rolling up the sails inside the boom or the mast or around the fore-stay. By doing this we are reducing the sail area, substantially. On older more traditional boats like the Lune Pilot  it is achieved by raveling up the bottom strip of the sail and tying it off with small lengths of rope. This is called slab reefing. (The knot used is called a reef knot – now it all makes sense doesn’t it.) The jib sail is just replaced with a smaller one. In a storm the sails are reefed or changed so that the sail area is tiny and that is all that is needed to make progress – hopefully.

When?

It’s always best, but not always possible, to decide on reefing before you encounter the need rather than after. In a lumpy sea and a strong blow taking in a reef is both difficult and risky. On the other hand shaking out a reef because it’s not needed is relatively simple and trouble free.

The reef points are shown in rows on the mainsail in the image below.

Lune Pilot Thumb

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