Foto: Werner Karrasch; © Vikingeskibsmuseet.

Turns

When tacking against the wind it is important that the turns are as efficient as possible so that no time is lost or, in narrow waters, to avoid the ship going aground. In this exercise we will find out how efficient The Sea Stallion is at turning.

Download, unzip and open the navigation data from the voyage. Find stages where The Sea Stallion has tacked against the wind, either with the aid of the map on the website or by opening the data set in a GIS programme. Plot the positions around the turns on a co-ordinate system and note the speed at each point. Now try to answer the following questions:

  • How does the ship behave in a turn? What is the appearance of the trace following a good and a less successful turn respectively?
  • How long does a turn take? How quickly does the ship regain its correct course? How quickly is it up to speed again on the new course?
  • What influence does the wind speed have on the efficiency of the turn?

A series of exercises has been produced which aim to analyse The Sea Stallion’s handling abilities under sail and oar power respectively. In other words, the pupil is able to carry out him- or herself much of the research which the Viking Ship Museum is to embark upon after the voyage to Dublin. The exercises are best tackled in the order shown, and it is a good idea to present the results together in a final report.

The data set to be processed comprises the ship’s geographic co-ordinates (recorded with the aid of a GPS) as well as a series of other navigational and meteorological measurements. All of this is assembled in a zipped, semicolon separated text file Datalogger which can be downloaded from Tools in the right hand column of the exercise. This table can be used as the basis for a large number of exercises involving data validation, source criticism, searching and sorting, calculations and column updates and much more. The exercises are best executed with the aid of a spreadsheet and/or GIS and can be incorporated in a wider teaching context dealing with, for example, the GPS system, statistics and cartography.

Turns is an analysis of how much speed The Sea Stallion loses in a turn. The exercise can either be solved on paper or the route can be drawn as a graph in a spreadsheet but it is a good idea to use GIS. For example, a thematic map can be drawn with the speed as a z-value depicted by a colour or symbol. When solving on paper it is a good idea to convert the geographic co-ordinates to a metric co-ordinate system. It is easiest to concentrate on an actual tacking attempt: see 30th July and 2nd August.

Subjects: Maths, physics, geography, general study.

Level: Sixth form/A level.