Until electronic strain gauges entered the leisure marine world, setting up a yacht’s standing rigging was more art than science. While the dinghy and small keelboat scene had basic mechanical devices for measuring static loads in wire shrouds, bending the wire and seeing how it deflected a simple metal indicator didn’t translate well to bigger diameter wires, let alone rods.
The launch of Spinlock’s Rig Sense gauges changed all of that. The devices still worked by deflecting the stay and still provided a reading by purely mechanical means, but they provided actual load readings without the need for a look-up table and were far more consistent than conventional gauges of the day.
Yet even these devices (of which there are two models) couldn’t scale up to the wire standing rigging of large cruisers and racers, let alone rod rigging.
Here, once you’re looking at boats of over, say, 11m (36ft) LOA it is difficult if not impossible feel the load by hand. Typically, the correct tension is assessed when under sail by checking the load in the leeward shroud when the rig is fully loaded and generating maximum power.
Even then, the popularity of aft-swept spreader rigs has meant that much higher pre-tension is usually required than for masts with in-line spreaders, making it even harder to establish when a mast has been set up correctly.
The new Rig Sense Pro changes that. The mechanical unit still clips onto the shrouds, but it is based on an electronic strain gauge system that can measure the actual load in the stay, be it wire or rod, under any load condition from at rest to under way.
As you might expect from a company whose products are developed through innovative thinking based on a fresh approach to the problem, the unit is both ingenious and simple to operate.
Rig Sense Pro measures wire stays from 5mm to 20mm diameter and -6 to -60 in rod rigging, making it suitable for boats of up to around 15-20m (50-65ft) LOA. By selecting the stay size and type from the integral database that is accessed via the control display, the unit is set up by moving a simple slider to the appropriate position.
This establishes where the deflection will be made within the unit itself to ensure that the actual load can be displayed. It also takes into account the variety of technical factors that relate to the way a particular size and type of stay will deflect. For example, the movement of the individual strands within a 1x19 wire as it is deflected will mean that the stay behaves differently from a solid rod.
Locking the unit onto the stay using the long lever applies the deflection, activates the strain gauge and attaches the Rig Sense Pro to the stay securely from where it can deliver the reading on a digital display. The unit can be left on the stay while other adjustments are made either to the rig or the boat trim itself and so provides a constant read-out of the load.
Among the many useful functions that are included, the Rig Sense Pro’s internal database of stay sizes and load limits means that it can deliver warnings automatically when maximum working loads are exceeded both visually and with an audible warning.
The unit also stores load readings and can transfer the data to a dedicated app which allows loads to be logged, tracked and analysed. Over the air, firmware updates can also be downloaded to the unit as new cables and rod types join the calibration database. Rig-Sense Pro is also delivered with a “Check Calibration” function that allows users to validate the device’s accuracy before performing certain jobs.
There are plenty of reasons why this rig measurement device is welcome in the marine world, but it is not anticipated that all sailing yacht owners will want to carry a Rig Sense Pro unit aboard. Instead, the project started with a request from spar builders Seldén, who wanted to establish a more accurate and repeatable way of setting up and assessing the pre-load that they had designed for their rigs.
With the growth in the average size of new cruising yachts and the distance that many are now travelling, being able to specify the correct rig settings and to measure them anywhere in the world through the global network of riggers was important both to Seldén and to cruising yacht insurers.
This required a device that was easy to use, reliable and capable of dealing with the middle ground between large maxi cruisers, which often have their own integral measurement systems, and smaller cruisers where the loads could already be checked with existing technology. As these parameters were described so the design brief was created.
Today, the Rig Sense Pro delivers a practical solution to a challenge that has gone unanswered for many years.
