Cras Rule or Breton Plotter?

This question often comes up when starting a training course such as the Offshore boating licence: is it necessary to use a Cras rule or a Breton plotter? What are the advantages of one over the other? 

The Cras Rule

The Cras rule is the emblematic rule of the French Navy because it was developed at the beginning of the last century by the French Admiral Jean Cras, who was also a music lover and composer who was quite famous in his time. Widely used in the military navy, it quickly took its place in the commercial navy and then in yachting and pleasure boating, since the instructors in these fields were often former professionals. 

It is made up of two half-plotters on a transparent surface allowing to draw or measure any direction or course on the chart. The main advantage of this rule is its accuracy when you perfectly master its use! On the other hand, reading and using the original Cras model is made difficult in the overlapping area of the two plotters. Fortunately, at Flash-Tide Instruments we have redesigned various improved models of the Cras rule to make it easier for novice sailors to use: overlap area layout, three-color printing, etc...

It is true that learning how to use it can put off some novice sailors, but it is nevertheless very useful to master it because many French houseboats are still equipped with this rule today. With the development of electronics, mastering traditional techniques remains important if only to be able to prepare a navigation !

To learn more about the Cras rule, please check out our video tutorials!

Breton Plotter

The Breton Plotter was developed in the 1960s by Yvonnick Gueret on the basis of a model originally used by the commercial navy and then the U.S. civil aviation.  Today, this model is widely used in Anglo-Saxon yachting. Indeed, with the decrease in the size of chart tables in houseboats, the traditional parallel rules has been replaced by plotter rules.

By simplifying and rationalizing its manufacture, the navigation plotter quickly became popular in France but also in England. It is composed by a rose of the capes movable on the axis of the rule. The big advantage of this model is the simplicity of reading angles or the tracing of roads or bearings, resulting in less risk of errors and more ease of learning for users.

Some trainers reproach the disc plotter for its lack of precision due to the mobility of the rose: in reality, you just have to be precise in using the rule. Today, many candidates for the offshore licence pass their exams with a Breton plotter and many school boats are evolving and now work with a disc plotter: New Breton Plotter or Brocémer Plotter.

To learn more about the Breton type plotter-rule, please check out our video tutorials!

If you are still hesitating, we propose our new Antares plotter rule: a Cras rule and a Breton plotter on the same rule. 

This is a Flash-Tide Instruments exclusivity!