Spinnaker Pole Height

For Good Downwind Speed

    By Andrew Kerr

 

The spinnaker on the left has the pole a little too low - notice how the curl on the luff of the sail is a little high

 

One of the many aspects of good downwind speed is attaining the correct height for the spinnaker pole in the wide variety of wind and sea conditions that your team can encounter over the course of a race or series.

In my role as a coach I spend quite a lot of time watching teams sail from out side of the boat; Very often I am video taping them or taking pictures for later  review and critique.  This perspective is a unique one and has helped with a lot of the sail shape visualizations that are more difficult to see when actually on board.

Every photograph of a boat with a spinnaker up reveals something about pole height and the shape of the sail. A casual flip through a sailing magazine can illustrate all the differences and pluses and minuses of spinnaker shapes.

Let’s look at the different conditions that your team will encounter and what to look for with pole height and the overall spinnaker shape that it creates.

General shape- what to look for.

The old maxim “get the clews even” is not very effective as spinnakers are designed differently and if one was to abide by this the spinnaker clews would be raised far too high as the breeze increases causing the head of the spinnaker to blow out flat and for the sail to lose a lot of directional power as well as it’s stability.

Instead what you are looking for is the sail to be breaking or curling on the luff around the center panel area on the luff, the sail to have a vertical profile and for the center seam of the spinnaker to be vertical.  There are exceptions to this which we note later in this article.

Adjusting pole height can be compared somewhat to adjusting the Cunningham on the mainsail – as it helps controls the position of the draft of the sail as well as luff tension and how open or closed the leech is.  If the pole is too low the luff will be too tight and the draft too far forward on the sail (like having the Cunningham too tight,) if the pole is too high the luff is too loose, & the draft too far back that is akin to having insufficient Cunningham – sometimes the case when there is a lot of backstay on.

In picture # 1 we can see the vertical profile of the sail, the center seam vertical and the luff breaking evenly in the middle panel on the luff of the sail.

 

If the pole is too high you will notice the sail will curl on the lower portion of the luff and the center seam will not be vertical, this is because the tack of the sail is too high forcing the luff of the sail to be too loose which in turn makes the luff collapse down low as the clew of the sail is lower and the draft is too far aft in the sail. If the pole is too high the sail will tend to be very unstable and the top of the sail will be blown out flat.

If the pole is too low you will notice the upper part of the sail on the luff will curl this is because the tack of the sail is being forced too low and the clew is riding too high causing the sail to luff up high. The advice is to adjust the pole height until the curl is in the middle part of the luff and be ready to adjust it in any subsequent lull or puff.

When proper pole height is accomplished for sailing low angles the sail will have a vertical profile as in picture # 2.

On Disaster Area all 3 of us are conscious of correct pole height, either Bill or I will adjust the topping lift or out board end if necc. Depending on who has a free hand. The topping lift on our boat is located on the starboard side of the mast on a swivel cleat and is accessible from most angles.

To keep your team on the same page and communicating – try asking “what do you think of pole height?” once in a while (or vang tension or mast rake etc.).   This helps keep the productive boat speed communication open and ongoing.

Keep an open mind at all times – it’s easy to fall in to the trap of “this is how we do it”; Typically you find you don’t get any faster that way and very often a team  get’s slower. 

 

 

 

 

When running try to keep the inboard and out board end even

On some types of boats this does not apply – some classes, (like one design 35’s for instance) like the outboard end of the pole higher than the inboard end as it accomplishes a faster shape. 

On the Santana 20 and boats similar too it we try to keep the inboard and outboard ends fairly even for max projection of the pole length. Some S20’s have an adjustable track on the inboard end of the pole (Altitude sickness, DA, Head First and others) which can be commensurately adjusted as the outboard end is adjusted; most boats (Cal trans, Mini Me to name a few) have two spinnaker pole bale rings at different height’s for the pole on the mast to accomplish the same thing – both systems are very effective so no radical changes are needed!

Let’s look at pole height in a variety of conditions:

Pole height in Light air:

Typically the advice is to lower the out board end of the pole ( and the inboard end) to pull the daft forward in the sail and create more stability in the luff of the sail as well as open the leech of the sail – by virtue of raising the clew of the sail. We are essentially changing the shape from a symmetric one to an asymmetric one.

This helps widen the slot between the mainsail and spinnaker and also accommodates the higher angle you are sailing in order to maintain pressure on the spinnaker sheet and the apparent wind across the sails. In very light air (and particularly if there is chop) it will be beneficial to have the sail curl higher on the shoulder of the sail (above the mid panel in the upper area of the luff)

 

 

As the breeze increases the pole can be raised for more projection - but keep an eye on the shoulder of the sail and where it is curling so as to not over do it.

If it is puff/ lull, then puff/ lull make sure the sail has loaded up sufficiently before raising the pole so as not too disrupt air flow, as the wind fades, lower it as you sail a higher angle to maintain speed.

In these conditions it is super important for the trimmer to be feeling the pressure on the spinnaker sheet and critiquing the position of the curl on the luff of the sail as small adjustments can bring large performance gains over teams who are not conscious of these necc. Adjustments.

Running – medium air – flat water:

This is when you are looking for the classic shape – center seam vertical – a vertical profile on the luff of the sail (best visualized by watching boats sail from outside the boat and looking at pictures) and the sail curling in the middle panel of the luff of the sail. Try to have the inboard and out board ends of the pole even as well for max projection.  

It is really good to have the bow person calling out the puffs and lulls so that you can anticipate pole height adjustments – slightly lowering the pole in lulls and raising it slightly for more projection in the puffs.

Picture # 3 is an example of excellent spinnaker shape in these conditions.

 

 

 

 

 

Running – medium air with Chop or in swells:

These are difficult conditions! What can help here is to lower the pole a little to pull the draft forward and create a slightly more stable and forgiving shape. In this instance you will go for a slightly higher curl on the luff of the sail than in flat water.

Having the pole a little further forward also helps maintain air flow attachment to the sail and helps accommodate the widely changing apparent wind speeds and angles – a whole other article unto itself! 

Running – very heavy air:

We can use the Cunningham analogy here – lower the pole a foot or so from the norm (with the curl on the luff above the mid panel toward the upper area) this will depower the sail by virtue of tightening the luff, pulling the draft forward and opening and splilling the leech by virtue of raising the clew of the sail. This will give the sail more stability and the helm a lot more control and a wider steering groove.  

This was perfectly illustrated by team Alinghi in the America’s cup final, when Team New Zealand suffered breakdowns in the windier races – Alinghi set the spinnaker with the outboard end of the pole lowered for better stability and sailed conservative sensible downwind legs under perfect control.

Reaching:

One can also make good pole height analogies with the mainsail Cunningham adjustment – typically one will lower the outboard end (and inboard end if possible) of the pole (sail breaking high on the mid panel toward the upper area of the sail) to tighten the luff of the sail, pull the draft forward for a larger steering groove & open the leech and create more of an asymmetric reaching oriented sail. The more open leech and wider slot enables the mainsail to be eased more (without luffing) for more forward power. The lowered outboard end applies for reaching in light air, medium air with chop and heavy air (for depowering).

 

 

A case can be made for raising the pole from the very lowest mode on the setting to help increase pointing ability in medium air and flat water (by virtue of moving the draft aft and closing the leech on the sail) – this does however depend on the cut of the spinnaker and doesn’t work on running (broad shouldered) sails but can work on flatter cut shapes with narrower shoulders in flat water. 

Make sure your leeward twing is long enough to allow the spin sheet to go all the way outboard so the slot is as open as possible. If the twing is too short   the spinnaker will sheet will close off the slot and drag the boat side ways and you will be forced to over trim the back winded mainsail.

The Twings:

 On the S20 most teams do not use a downhaul (or foreguy as it is sometimes referred too) as the twings are positioned well forward to effectively be a downhaul, because of this we tend to always have the windward spinnaker twing pulled down all the way in all conditions to keep the spinnaker guy and pole as stable as possible. This does make the guy adjustment & topping lift adjustment a little harder but it really is worth it.  Some teams run the windward twing 6 inches or so of the deck which makes adjusting the guy easier and is perfectly acceptable in very flat water and medium air.

In heavy air - running downwind we pull the leeward twing all the way down to choke the spinnaker down and reduce its oscillating tendency. In lulls we are quick to ease it all the way off to power the sail up.  

 Conclusion:

 Spinnaker pole height adjustment is another dynamic speed control that is worth reviewing as a team both on the land (looking at photographs and videotape) and through constant observation on the water, making the correct adjustment will help your team makes gains in the variety of conditions that you encounter when sailing downwind.  

 

 

 

Here we can see the center seam is verticle as a result of correct pole height.

 

The pole height shown here is giving the spinnaker maximum forward power and projection

 

This picture shows a good uniform luff shape & a vertical profile