| Instrument | : | Cross-staff, baculus Jacob, Jacob's staff, ballastella, arbalestrille, fore-staff, graadstok, graadboog,... |
| Manufacturer | : | N. de Hilster (original unknown). |
| Country of origin | : | The Netherlands (Original probably Sweden) |
| Manufacturing year | : | 2005 (Original: 1661) |
In 1998 a very special cross-staff was found on board of the Royal Ship Kronan, a Swedish ship that sunk in 1676 of the coast of Öland in the Baltic sea after fierce battle with the Danish-Dutch fleet. This particular staff was the first ever found with the so called spoon shaped vanes. Until then all known cross-staffs, like the cross-staff replica I made before, were equipped with straight vanes. The spoon shaped vanes were only known from paintings, cartouches and prints.
In order to be able to make a copy of this instrument I needed to measure it. As the staff has been under water for well over 300 years the wood has become quite fragile, so taking measures of it required a special technique. For this I used photogrammetry, which allowed me to measure the whole instrument with a minimum of physical contact.
In the spring of 2005 I went to the Kalmar Läns Mmuseum for the measurements. From these measurements I first created a 3D model and from this model I made the CAD drawings necessary to build the copy. Thanks to cooperation of the NISA (Dutch Institute for Underwater and Ships Archaeology) and the ROB (Dutch National Service for Archaeological Heritage) the wood of the staff was identified as pine (Pinus Spec.). The vanes could not be examined as no loose samples were available, but by the structure of the wood it is believed that these were made of beech (Fagus sylvatica).
Materials used on this reproduction are pine for the staff and beech for the vanes.
I'm very grateful to Willem Mörzer Bruyns (Scheepvaartmuseum Amsterdam) for recommending me to the Kalmar Läns Museum and to Lars Einarsson and Max Jahrehorn (both Kalmar Läns Museum) as without their help and information a detailed reproduction of this instrument would never have been possible.
Want to know if your staff belongs to a spiegelboog (mirror-staff) or cross-staff (and if it is a cross-staff you can check if the vanes are right)? You can check it yourself here.
If you like to know more, don't hesitate to contact me.