The Mystery of Masts

Why does the mast matter?

In terms of sailing boat “hardware”,  the mast must be considered one of the most dominant pieces of equipment when considering impact on performance.

We have many types of mast, and along with the evolution of hull design and the progression to apparent wind sailing, the mast has probably changed as much as any other feature of the sailing boat – it has certainly had an awful lot of research!  The unstayed mast found predominantly on sailing boats such as Laser dinghy, Finn class, Europe, Optimist etc. are a critical part of being fast, yet are considered one design by so many, and especially in the class rules of all but Finn class.

In terms of examples of masts being a critical performance item, the Finn class is a great example of gain.  In the late 90s the British sailing team focused a lot on the Finn class.  They began to understand the effects of mast bend in ways that others had not prior to this time.  Although unstayed masts are confined to their effective optimal wind range, masts can be built to suit the physique and style of the sailor.  For example, the simple example begins at the mast tip where the sail has greatest leverage on the boat.  A heavy sailor will exert more leverage on the mast (particularly at the tip) than a lighter one.  In order for this to achieve optimum bend in certain specific wind ranges, it needs to be stiffer for a heavier sailor.  The complexities of working around rake setting/sail design and technique can then be undertaken and improved.  The manner in which the mast bends changes the shape of the sail, which in turn can affect drive both positively and too often negatively.

The stayed mast is a different beast.  The stayed mast may be tuned to the sail and the sailor by bending it with the tension applied to the shrouds.  The pressure delivered to the mast can be enormous, and the mast responds by bending.  Interestingly enough the mast often suffers over compression, which results in an S bend when viewed from the bow, as well as the graceful curve produced when viewed from the side of the boat.  In boats like 470 class which have dynamically adjustable rig tension (tension can be changed whilst sailing) this can become problematic.  However the performance advantages of skilled use of these features are massive.  Conventional stayed rigs allow the mast above the hounds (where the forestry and shrouds attach to the mast) to be considered an unstayed section of the mast.  We then face similar challenges of mast selection when choosing an optimum performance mast for a particular crew.  To give an idea, the stiffness of these “one design” sections commonly vary by up to 15%, and sometimes a lot more.  There is a true story of the Israel 470 class in Sydney at the Olympic Games being hit on the mast tip by a seaplane.  At that moment the crew went from near favorites in the Games to also rans – they did not have time or opportunity to find how their reserve mast performed, and finished well down the fleet compared to their potential.  At the highest level masts are this critical.  The 470 class is a complex sail boat to sail at international standard, but understanding the mast is a critical skill to achievement.  It is well controlled by tension, adjustable spreaders, blocks and rake which leads to massive performance differences from the same mast by those sailors who are coached to understand the settings rather than those who blindly follow manufacturers settings.

The skiff mast as found on most skiffs affords even more control than the conventional mast with hounds.  Sailing skiffs are generally considered the wild beasts of the boat park, yet the mast is probably controlled better than on any other sailing dinghy.  There are three sets of shroud controls, lowers, shrouds and uppers.  The lowers can be thought of in the same light as chocks, and control the shape in the lower part of the main – the straighter the lower part, the more power low down on the mainsail.  This will “drag” sailcloth into the lower part and effectively tighten the upper parts of the sail.  The shrouds do what they do on conventional dinghy rigs – they control the overall power of the sail, usually set to the weight and height of the crew.  The uppers control the section above the hounds, and therefore introduce a new dimension where the sideways “fall off” of the mast tip may be controlled by tension rather than just mast stiffness, leading to a more precise tuning of the mast without resorting to manufacturer’s stiffness.  For certain the top section will be fully dependent on stiffness for bending aft, but the fall away which produces often unwanted leech tension is controlled by the uppers.

So, which mast do we choose, and how can we make a rig less “mast critical” than was previously thought?  Well, on an unstayed rig the mast will always dominate the way a sail boat may be sailed.  A classic example of (probably) a one design flaw was in Qingdao, where the great Laser sailor Tom Slingsby suddenly lost pace as soon as he got his charter boat.  There had to be something wrong with the mast – later he proved in Weymouth how blisteringly fast he is on charter equipment, but for the time in Qingdao, it all went wrong, and logically can probably only have been the mast.  The Europe used to be very mast critical, with a lot spent on manufacture, as is the Finn class.  The loads on the Optimist, combined with the gaff rig, make the mast not too critical, but still people claim differences.  As regards the other sail boats, playing with chocks, tensions and where possible unconventional rakes are the way to collect your own data.  Every mast change is felt through the tiller and through power differences, so learning to make a mast work is a critical skill in stayed boat classes.  If you rely on manufacturers settings, you don’t cope as well with mode changes, or even worse with equipment changes.  Time spent on the accumulation of this knowledge inevitably leads to big gains.

At Toplevel Sailing we encourage the knowledge gathering about masts on chosen classes in various ways, and particularly the understanding of what is good and bad bend, and how to tune a mast to your own individual needs.

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