Choosing the Right Spinnaker


With the increased use of asymmetric spinnakers, both in sprit boats and in conventional rig pole boats, I get lots of questions on what type of sail a customer should be using. With sprit boats the choices are easier because all the spinnakers will be asymmetric so it is just a matter of matching the sail design to the conditions the sail is to be used in. With conventional rig boats the choices aren’t always so clear and will vary depending on the rating system you sail under, the type of racing you do and the displacement of your boat.

So first a quick look at the current naming system for spinnakers, and their uses. You have all probably seen asymmetric spinnakers named things like Code 2A, 3A etc. and similar names for symmetric sails; Code 2S, 3S etc. In this case the “A” stands for asymmetric and the “S” indicates symmetrical. Odd number sails are reaching sails, even numbered sails are running sails, and the numbers indicate the wind range of a sail with a Code 1 being for light air and the higher the number the more wind the sail is make for. And of course there are the Code Zero spinnakers which are specially designed sails for extremely tight reaching, will have very nearly straight luffs, and be built the minimum mid-girth the rating rules allow for a spinnaker. The chart at the bottom of this page shows the general range and overlap areas for both asymmetrical and symmetrical spinnakers.

Conventional rig boats will often use a combination of symmetric and asymmetric spinnaker, however in some areas such as Southern California more and more of them are using almost entire inventories of asymmetric sails. This is because their PHRF rules allow slightly bigger asymmetric sails with no change to the rating. Traditional symmetric spinnakers have luff and leeches equal to .95 times the square root of I squared plus J squared. = .95*SQRT((I squared)+(J squared)). However their rule for asymmetrics allows a the luff to be 1.03*SQRT((I squared)+(J squared)) or slightly over 8% longer than a symmetrical luff, and the leech only has to be 5% shorter than the luff so it can be about 3% longer. This is a fair amount of additional area at no extra rating. Their Code 2A sails (your AP type running sail for medium air) will be shaped pretty much just like a symmetrical AP spinnaker (Code 2S) with and additional luff and leech length area added on the bottom. They are flown of the standard spinnaker pole exactly the same way a symmetrical is flown, the pole comes just as far back and they can be sailed just a deep. Most areas have rules that allow the use of both asymmetric and symmetric spinnakers on conventional pole boats but in most cases the rule requires the two types of sails to have the same area. Even in those cases using asymmetric running sails can have some advantage, first even though they are the same area the luff is going to be a little longer than a symmetrical spinnaker while the leech will be a bit shorter to keep the area equal, so the sail will have a bit more area out on the windward side where it does you the most good. Second, if you do have to reach up with the sail they will perform better than a symmetrical sail at the tighter angles.

The one slight draw back to asymmetric spinnakers on conventional pole boats is that they are a little bit more involved to gybe and especially in heavier air are a bit slower gybe. Crews that sail with them on a regular basis can very nearly overcome that with practice. If you sail offshore races, or longer point to point races having asymmetric runners makes a lot of sense because you don’t gybe very often, while if you sail short course buoy races they are instances where having the symmetrical sail that you easily gybe, or even sail without a pole for short distances while you gybe back and forth, can give you some nice tactical advantages. In either case sailing with a Code 1 asymmetrical for light air is generally preferred. In winds under 8 knots true wind speed most boats need to sail at quite hot apparent wind angles, usually between 70 and 90 degrees depending on the wind strength, even with trying to sail dead down wind. Any time you have the apparent wind forward of 100 degrees the asymmetric sail is going to be better because it will have much flatter leech sections than a symmetrical sail that has to have just as much curve in the leech as it has in the luff. The flatter leech sections allow the sail to be trimmed tighter when needed and always keep the slot more open between the backside of the mainsail and the spinnaker.

     Code 1A for light air
     Code 2S for running
     Code 4S for heavier air running.

     Code 1A for light air downwind, up to 7 knots of wind, and for light to medium air course that are reaches
     Code 2A or 2S for medium are downwind 7 knots to 18 or 22 depending on your boat and crew.
     Code 3A for heavier air reaching, it will be a smaller sail with a max girth of around 165% of yor J rather than a full size 180%
     Code 4A or 4S for heavy air downwind

In addition to these sails, depending on the size of the boat, the area you will be sailing in, and the possibility of widely varying conditions boats will often carry additional sails.

     Code Zero for very tight reaching, 40 degrees apparent to 65 degrees apparent
     Code 5A for very heavy air reaching
     Code 6A for very heavy air running (in the old days that would be your chicken chute)