When do we reef our main sail on a Lagoon 440 catamaran.

When planning to come to Indonesia from the Gold Coast Australia, we purchased new sails from Evolution Sails Gold Coast.

We were told there would be little or no wind in Indonesia and therefore we invested in a large genoa, a large screecher and a large square top sail.  Little did we know that this year was going to be different and we have had frequently winds of 30 -35 knots with a maximum of 52 knots recorded.  This calls for some serious reefing  and some of our friends have sent us questions regarding when we reef.

I actually have quite a serious alarm system : It’s called Ana – when the admiral yells she is uncomfortable I know it’s time to reef 😀

Usually we hear the term being quoted by sailors on catamarans : ‘Reef by the numbers’ i.e. we cannot feel the power on the boat so just do what the manufacturer handbook recommends.

I agree that one should be looking at the numbers but for us there is so much more to it so rather we use it as a guide more than an absolute.

At any rate, the numbers in our opinion are very conservative, in addition to a manufacturer sail size also being built to conservative dimensions.

On Impi we have a substantially larger genoa and main sail designed and manufactured along with a large screecher, Asymmetric and spinnaker sails.  In spite of this we still have found in some conditions the numbers are conservative whereas in other conditions we would have to reef much sooner.  The decision to reef is dependent on point of sail, sea conditions, boat weight and resistance on the helm.

Point of sail

We are more aware of the need to reef sooner on a close point of sail versus a broader point of sail.

Sea conditions

In rough seas when sailing off one wave into the next the forces exerted by the resistance of the bows ploughing into a wave is significant. There are untold stresses exerted on the mast and shrouds, the support structure at the base of the mast and other parts of the boat through the wind power in the sail pushing a heavy vessel through the ocean, sometimes surfing the hull, in addition to  the boat sailing into the back of a wave, the ‘stopping force’ of the craft versus the pushing force of the wind in the sail.

So for us it’s important to pay attention to when we need to reduce sail based on sea state and how well the boat copes with it. When we find ourselves ‘caught’ in sudden squalls we turn on the motors to help push the vessel through the water to ease the pressure on the sails by reducing the vessels resistance in the water.

Boat Weight

Sometimes when stocking up the boat for long distance cruising we add weight through provisions like food, diesel etc. Sometimes we make water and fill the tanks to give the boat a fresh water rinse.

When the boat is heavily loaded the added resistance puts more force on the shrouds and other parts of the vessel along with the fact that our sails take more pressure so we take all that into consideration.

Resistance on the Helm

I can say that ultimately our big decider is resistance on the helm or the rudder angle in the water relative to the boats heading.

The boat should feel light and comfortable to maintain a heading without struggling for it. So from time to time I release the auto pilot and feel the helm and steer it for a while. Of course the rudder angle indicator is also telling, although there are times when you have a heavier helm like in currents.

The angle of the rudders in the water is a good indicator for us of being overpowered in what would otherwise be ‘neutral conditions’ :  do we have a ‘heavy helm’ and would reefing or taking the pressure off the sails reduce it.

After trimming all the sails to get as close as possible to having the boat gliding along with little resistance to the helm we would reduce sail to see if it brings the rudders to a more neutral position.

We often find that by reducing sails the boat actually picks up speed, and a large part of that is because we are not dragging the rudders through the water at as much of an angle to maintain a heading.

On monohulls its quite easy because of the heeling motion of the boat but on multihulls rudder angle is quite a ‘tell tale’ we’ve found.


  1. Great info. Sailing downwind in strong winds – you are happy to still have 3rd reef main up vs reduced Geneo only? I’m not very experienced but always thought downwind with main up not a good idea. Appreciate your thoughts? Thanks David sv Nomad Davina


    1. It all depends on where exactly the wind sits I guess. If the wind is dead downwind you can put the sails wing on wing. In strong winds too it equalizes the pressure on the mast.


  2. HI. Only new to catamaran sailing but I thought it was not a good idea to have main sail up when sailing downwind in strong winds and just go with geneo only. You are happy to sail downwind with reefed main in strong winds? Any more comments on how you reef main without turning into wind?Thanks David


    1. Hi David and thanks for engaging here with us.
      Agreed that on a catamaran one should not as a rule be sailing with the main up downwind (usually on long passages we use the genoa in strong blows, two genoas side by side or a spinnaker in lighter winds), but with a bit more experience, the right sail configuration and sea state, it can be done. I would not recommend it for folks new to sailing catamarans.
      I refer to reefing downwind where one is caught in a squall for example – often on a long passage one is caught in squall lines and in this situation we reef the main sail or even bring it down under way.
      On the other hand, with sailing downwind in controllable seas, it really depends a lot on the sail configuration and sea state and we do often sail wing on wing with the main and genoa, however, this has been a lot easier and less likely to gybe the main since we have gone to a square top main.
      Our square top main is longer (on the top) than the standard rule of 1/3rd of the foot which means we have a lot of power keeping the main open and holding it there – we sail with the main against the shrouds. Some folks feel its not right to have a main sail touch the shrouds but in actual fact, on cats we often do.
      One would also sail the boat favoring the wind in the main slightly more than wind in the genoa and the genoa would be set out on a barber hauler.
      With our previous main sail which was not a square top we ran the risk of gybing the main easier with winds aft the boat and we very seldom kept the main sail up downwind – as mentioned – rather a double genoa or spinnaker or genoa on barber hauler set up.
      I should write a blog on how we reef the main sail without turning the bows into the wind but lets see iff I can share some of this without using picture illustrations.

      First of all one needs to have a full line reefing system ( a full block reefing system set up as some would call it). This means that the line would run from the boom aft, up through a block or friction ring on the leech, down through a pulley on the boom aft, through or along the boom to a pulley at the forward part of the boom, up to a block or friction ring on the luff and back down to the baser of the mast and back to the winch.
      One can do it with other set up’s but would require a different technique and a lot more effort.
      On our 440 we also have a downhaul line attached to the top of the main sail car which helps bring in the last part of the sail – a standard feature open the 440 out of the factory.
      Take the main sail traveller windward of center and relax the main sheet a bit.
      With the main sail up and in a blow, take the main halyard from the jammer across to the genoa winch – it will be offset.
      Wrap it around the genoa winch and release the jammer lever.
      On 1st reef, bring the reef line to the halyard winch (ours is electric which helps a lot but not necessary) .
      Now take the main halyard in hand (all it needs is two wraps around the winch and in a very strong blow perhaps 3 wraps, but I always manage with two. Ease out on the main halyard and if the reef is on electric don’t cleat off the main halyard, just ease it whilst pushing the electric winch button which is slowly pulling in the reef line.
      As you do this grab 3rd reef (leech) and tension it by hand – the sail will distort slightly but it keeps the head in.
      Keep easing out on the main halyard and keep winching in on the reef line.
      The trick is – we have a mark on the sail for each reef position and we have a mark on the mast. So when pulling in the reef the final block position will be where the reef mark meets the mast mark.
      Whilst doing this, the natural tendency will be for the luff block to come in faster (toward the boom) than the leech block.
      This is important to note since one wants to give a pause between to allow the lines to even out the block positions.
      This is why it’s good to have some slack in the boom as with the motion of the boat moving over swells, the movement of the boom helps equalize the block positions.
      Now pull in on the leech and start applying pressure to the main halyard as one gets close to the mark.
      When in position, jam off the main halyard and pull tension on the reef line allowing the forward (luff) and aft (leech) blocks to be close to the boom and equally spaced from the boom. As mentioned before this is where one works it in as the boat rides the swells – you will notice the boom tension and slightly release as the wind shifts with the swells and at this point you are tweaking the final positions.
      For the first reef, as mentioned before – its quite important to keep tensioning by hand the 3rd reef leech line to keep the head in.
      For the 2nd reef the process is much the same.
      For the 3rd reef Lagoon on the 440 rigged it with only one line pulling in on the leech and only a ring on the luff. This means one would need to walk forward and hook the ring on the luff which is not always possible in a storm if left too late. So we have installed a luff reef line that goes up independently with the luff and comes back to a jammer.
      So on 3rd reef, one can pull down on the leech reef line with the main winch whilst easing out the main halyard. Bring in the luff reef tension by hand until the leech reef is in position. Jam off the halyard and pull in on the luff reef line.
      The luff reef line (3rd reef) is also nice to have to ‘help the sail down’ in some ‘devilish conditions’.
      I’m not sure Ive explained this as well as I would like to have but without illustrating it is the best I can do.
      When hoisting the main sail reef by reef we do the opposite and we put the halyard on the main halyard winch and the reef lines offset to the genoa winch.
      We will make sure the leeward side of the sail stack pack lines are loosened off and pulled clear i.e. the slack lines tucked behind a cleat at the front of the boom.
      Working the sail up using leech line 3 tension is important to keep the head of the sail from ending up behind a shroud etc.

      It all sounds like a lot of technique – and it is – but with practice we now do it really fast and it’s second nature for us.

      I hope this is handy for you and others.

      Best wishes


      1. Fabulous. Thank you for your reply. It is really appreciated. I love the sailing community and how so many people are willing to help others. Safe sailing.

        David and Tina. Sv Nomad Davina. Lightwave 38 catamaran.


  3. Hi Brent. Thanks for this advice. We’re relatively new to catamaran sailing and we are finding some big differences compared to our quite extensive monohull experience. Your articles on handling heavy weather and reefing are very helpful. We have an Endeavourcat30, quite a different boat than your Lagoon 440 but still a cat. Cheers, Bas Dolkens.


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