Code zeros are all the rage; choosing between masthead or fraction code zeros can be tricky writes, Barry Hayes of UK Sailmakers Ireland.

The code zero is a reaching sail to be used between 45 and 110 degrees apparent wind angle, usually in winds below 20 knots. These sails fill the gap between reaching with a jib or a spinnaker. 

Regardless of whether you're cruising or racing, the options are more or less the same. It all comes down to a few key factors. Does your boat have masthead or fractional headsails, and are the headsails overlapping or not? And, how strong is your mast?

Masthead headsail rigs

Most boats with masthead headsail, whether overlapping or not, have no options but to go masthead code zeros. The question to be answered for these boats is how large a code zero they can carry. This comes down to the boat's weight and what headsail they currently use. Usually, a code zero is 165 % overlap. So if the boat has enough weight in the keel, it can take a bigger coder zero.

Boats with fractional headsails, however, have the choice between code zeros flown from a spinnaker halyard at the top of the mast or one from the hounds. A fractional boat interested in a masthead code zero has a lot to consider. To start with, the size of their current headsails - overlapping or non-overlapping.

If you can go masthead and your rig can take the load, a code zero would be a winning sail when reaching regardless of whether you are cruising or racing. You can almost double the sail area of a non-overlapping jib.

As you can see in the attached photo of the First 44.7, the code zero is more than double the area of their non-overlapping headsail giving Lively Lady loads of power on a reach into Dun Laoghaire.

Fractional, overlapping headsail rigs

If the fractional headsails are overlapping, then the extra sail area gained by setting a code zero will only make a slight difference. Typically, a fractional code zero would only add about 25% to the sail area compared with a genoa. In reality, this is not a significant gain, and it is hard to justify the extra expense of the sail and systems for this incremental sail area. Also, code zeros add extra points to your IRC rating. In cases like this, it can be more efficient from cost and rating perspectives to go with a very flat A3 that you can carry at very tight angles, particularly if the sail has a Kevlar luff rope to get the luff nice and firm.

Talk to your sailmaker and discuss the pros and cons of a fractional, overlapping headsail boat using a code zero vs a flat A3. The objective is to optimize reaching at relatively tight angles to the wind. Hard on the wind, your genoa will be much more efficient, and your VMG will be better.

If you are fractionally and your mast is strong enough to take the lateral loads of a masthead code zero, you can gain a lot of sail area vs a genoa.

In this drawing, you can see the difference in area gained with a masthead Code zero or A3 over a fractional Code zero. Also, notice the headsail area to compare.

Fractional, non-overlapping headsail rigs

It's normal enough for fractional headsail boats to have a code zero as they don't need the power of the overlapping headsail when reaching. They also save massively on their rating and only add a minimal amount for a code zero. This is very true of both white sail cruising or racing as it saves rating and HSA on IRC. Going to a code zero can nearly double your headsail area, giving you a massive power boost when your need it most.

Just because your headsail is fractional, that doesn't mean you can't set a code zero from a masthead spinnaker halyard. Your mast builder will be able to tell you if your mast can carry the loads of a masthead code zero. This is easy to work out, but if you cannot go masthead, there are options to be considered.

The above photo is of Wow, a Farr 42 with a non-overlapping headsail with no fractional spinnaker halyard

Wow (above) wanted a code zero because they needed more power reaching. They couldn't go masthead, so they took the masthead spinnaker halyard down to the top of the forestay and led it through a ring on the forward edge of the mast. This allowed them to set a fractional code zero while keeping the boat easy to sail. This set-up transformed the angles at which the boat was weakest, and it's still easy to sail.

In all instances

Whatever your rig set-up, getting the furl right when you retrieve your code zero is the most important thing. If the sail is furled properly you get a tight furl. To achieve this, the furler itself must be a high-quality furler like an Ubi Maior top-down furler with a ratchet lock. You then need a cable to get the furl right. With these cables, you can't go wrong. Perfect furls every time.

In the above video of the First 34.7 Black Velvet, you can see how tight the furl is on the cable and Ubi furler. If you have a tight furl on the sails, it creates almost no windage at all.

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