Influential Battens

Full Battens and Sail Shape

In this blog we pose some questions and outline some answers.  The black art of batten technology and its complexity s demonstrated by the multiple answers given to any challenge by different people; therefore, an open mind and ability to analyze benefits and losses is as important as the knowledge of battens themselves. This is NOT a “give me the solution, not the problem” blog, but an effort to make the reader more inquisitive in this matter – an easy to define area of measurable performance returns.

The effect of battens on sail shape is often an under investigated area in racing, and indeed sailing in general.  In a conversation with a friend, it became apparent that in windsurfing the extremes of the effects of batten weight have become very influential indeed – battens change the shape of sails enough that exactly the same Pryde production sail can be used as a high wind sail for heavies and a light wind sail for others, just by changing battens.  Bear in mind that the usual layout and cut characteristics of light and high wind sails are very different to each other.  At this point we thought a blog would be good to discuss the reasons why this can occur.

What do battens do?  Prior to the introduction of full length battens, they were regarded as a way of supporting the leech roach (the area of the sail aft of a straight line between the clew and the mast tip) and controlling the return (how a sail is shaped at the leech).  On a pin head sail, battens were still used to “stabilize” the leech, which meant that as the mast bent under load and the leech fluttered that the battens would prevent the flutter, whilst also giving some control of return.  It therefore follows that the larger the area of leech roach, the more influential battens can be.  For this reason with the introduction of the block head sail the influence of battens on speed and height has become greater, yet the average good racing sailor seems curiously uninformed about their effects.

The influence of full battens is almost a separate topic within a topic.  We can move the point of maximum draft fore and aft with different battens, and we can even influence that depth with both stiffness of battens and the tension that we apply to them.

So, you say, in a one design rig we are stuck with the battens that we are given.  Yes, strictly true, but the “one design” battens vary considerably.  Battens are measured with a strain gauge (often a fishing scale for dinghy battens).  Essentially they are stood on end and measured for length.  A weight is applied to bend them to another length, which is a fixed percentage (set by the person who is measuring, and usually around 70-90%) of the original length.  The batten is then marked with the weight needed to bend it to the team’s standard.  Most “one design” battens vary by up to 30% in stiffness.  We need to know how stiff the battens are prior to assessing the sail for different conditions, as we believe battens  make a light wind rocket or a high wind Exocet, but never both!!

An interesting feature of battens is that there is no need to make them perfectly “fair”.  It has been found that there is a wave effect on battens, so filing them at the quarter and half length is considered fine for the purpose of altering bend characteristics.  If we consider the effect of wings being trimmed, we can see that this theory is probably quite correct.

This information brings us to the point where we are able to play with battens and understand some of their features.  It also means that we can test how different battens will alter the way we are able to sail.  Theories are one aspect of sailing which are interesting, but practical testing is still the best (only??) way of establishing improvement or loss.  Any number of sailors make changes which slow the boat up, but they fit in with a theory as to why the boat should go faster.  However, with battens you need a reliable tuning boat that you can measure your speed against, and do so whilst you change and compare different battens.  Testing them in a variety of wind-strengths is also important, and you may find that tension and stiffness give a distinct preferred wind range for each set of battens.

The best way to find out about battens is to change them.  Make notes about the perceived difference, then weigh them.  If you know the weight difference it can influence the outcome of the tests – if you don’t, you will learn both about battens and how to test.  At Toplevel Sailing we do as much blind testing as possible.  If the results do not match our expectations, we investigate thoroughly.  Knowledge never comes cheaply!

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