A 3D Model of the Venetian Galeazza

ContourShip_J

Alessandro Cavinato,   Beat Geissmann,   Konrad R. Vandevelde

INTRODUCTION

During its thousand-year lifespan between the 7th and the 18th centuries, the Republic of Venice played a leading role in the Mediterranean commercial activity, with a trading empire that spanned from the lagoons of the northern Adriatic Sea to the shores of Syria and Lebanon. The secret of the Venetian domain on the Eastern Mediterranean was certainly the power and efficiency of the Serenissima’s fleet. The Venetian Arsenale in fact, with its assembly line structure, was capable of building and equipping ships that were both suitable for commerce and battle purposes.
Among the most successful ships of the Venetian fleet is the Galeazza, whose superior maneuverability and deadly firepower led to the victory of the Holy League in the battle of Lepanto (1571).  Such galleass represent the masterpiece of the shipping technology of the 16th and 17th century, and it is the symbol of the Venetian domain on the Mediterranean sea during this period. In this project we built a detailed CAD model of a Venetian galleass of the 16th century, including interior and exterior design, in such a way that model’s parts can be reused for other reproductions. Moreover, the completion of the model allowed us to perform several calculations and estimations related to the galleass that might partially explain the secret of its success. In this report, we fist describe the modeling and the rendering approach that we exploited to build our ship reproduction. Then, we will expose the quantitative data and estimates that we were able to extract from the 3D model. Finally, we will show some renderings of the Galleazza, as well as two sections that might be useful to understand the structure of such ship.

MATERIALS AND METHODS

In order to model the galleass in detail, as a first step we had to find reliable and precise documentation about the structure, the proportions and the materials of such ship. In order to do so, we purchased the following exhaustive material from a well-furnished bookshop in Venice that is specialized in the venetian nautical field:

  • Eleven plans of the Venetian Galeazza issued by the Associazione Navimodellisti Bolognesi. These detailed drawings served as the primary source of information in the construction of the main structure of the ship.
  • The book Galeazze, un sogno veneziano[1], which is about the history and the evolution of the Venetian galleass during the different epochs of the Republic of Venice.
  • The book Navi veneziane[2], a catalogue containing several ancient original drawings about the Serenissima’s fleet since the 13th century.

With this documentation we were able to start the modeling procedure, which has been carried out entirely in Rhino 3D. The import/export possibilities of this software proved to be extremely useful in the different modeling stages. In particular, Rhino 3D allowed us to automatically obtain the 2D contour of several pieces of the ship directly from the scans of the 11 plans of the Galeazza. In order to obtain such 2D curves, we first had to scan at high resolution the eleven existing plans of the ship and then, by using Adobe Illustrator CC, we extracted the polygons defining the shape of the parts. After importing the 2D polygons in the CAD software, we only needed to scale the contours to the right size and extrude them to obtain 3D objects.                                                           Scan with RhinoScan with RhinoFigure 1: Screenshot of an extrusion in Rhino 3D.Scan with Rhino

Once all the main components have been modeled, we could start the assembly process by combining together all the parts. We deduced the exact position of each piece by looking at the plans of the galleass and at the original drawings contained in Navi veneziane. In this way, we could achieve a highly detailed and reliable reproduction of every deck and compartment of the ship. The assembly process started with the positioning of the keel, which represents the main part of the ship’s geometry. Then we added all the sections which define the profile of the boat, by placing them on the keel. After this step, we added the rudder at the end of the keel and we modeled the hull using the “Loft” function of Rhino 3D, that requires the reference curves on the sections to generate a surface along the length of the Galeazza. Having completed this, the main shape of the ship was defined, so that we could start to add more detailed and specific substructures, such as the masts, the front and the after castles.
The next stage was to model the interior of the ship and, in particular, to recreate reliably the compartmentalization of the lower internal decks with the different materials that could be found inside. The information that we needed for this step was gathered after an extensive inspection of the ancient drawings contained in Navi venetiane and in Galeazze, un sogno veneziano. Therefore, after creating different volumes in the lower decks, we filled them with materials and tools, also adding several details like anchors, fences and ladders to fulfill the appearance of our galley. In the following video it is possible to appreciate a 360° external view of the final 3D model.

In parallel with the modeling of the last parts of the ship, we started the rendering process. This task was carried out by using Maxwell Render, a very powerful and intuitive software that easily interfaces with Rhino 3D through a plugin. In order to produce a final result as realistic as possible, we had to select each piece of the galleass and consult the literature[3] to identify the material it was made of. Thus, we had to apply the correct material to the piece, after downloading the proper texture from the Maxwell Render online material database. Finally, we created a model of the water with the tool Maxwell Sea, in order to render the ship during sailing. This extension for Maxwell Render permits to simulate realistic ocean waves from a simple plane just by setting a few parameters (wind speed, wind direction, water depth, …). We report some rendered views of the inside and outside of the ship in the results.

RESULTS

Estimates and calculations:
Having a detailed CAD model of the Venetian Galeazza allows us not only to produce nice renderings of the ship, but also to obtain quantitative results that might be appealing to naval experts and the Digital Humanities community. To perform the computation of weights, center of gravity and waterline position, we exploited a naval simulation tool called Orca3D that runs as plug-in in the Rhino environment. However, since the complete model of the ship was too detailed to run on this software, we had to create a simplified model containing all the important structures, in which we defined the density of all the pieces. The biggest uncertainty we had was about the thickness of the hull. Since we could not find any information about this quantity, we estimated it to be 10 cm, as it appears to be a reasonable thickness compared to the overall size of the ship. The data that we have been able to calculate are reported in the following table and commented below.

Cattura

Table 1:  Estimated quantitative data regarding the Venetian galleass.

The length, the width and the height shown above refer to the maximal quantities, meaning that they take into account the aftercastle, the frontcastle and the masts.
The total sail surface is 1280 m2: this splits up to 283 m2 for the Trinchetto, 358 m2 for the Mezzana and 638 m2 for the Maestra sail.
Knowing that those ships were usually built from walnut wood with a density of approximately 700 kg/m3, the total mass of the empty ship can be estimated. The volume of the used wood that we extracted from the Rhino model is equal to 603 m3 which yields a total mass of 422 tons for the empty ship. These estimated data were necessary to calculate the center of gravity and the position of the waterline with Orca3D.
As it is reported on the table, the centre of mass of the empty ship was positioned approximately 3 meters above the waterline. However, without any ballast, the ship would not be stable. Thus, to keep the galleass upright, cannonballs were placed on the lowest empty deck of the hull, as it is reported in the literature[1]. In order to derive the maximum number of cannonballs that could be stored in this space, we had to compute the average ball size. According to [4], a typical canon ball of the epoch was between 5 and 30 lb heavy: using a weight of 12 lb (5.4 kg), we could derive that the average ball diameter was 11.2 cm. Given this size, the CAD model allowed us to estimate that the lowest empty space could store up to 3 layers of 8000 cannonballs each, which sums up to a maximum of 24000 cannonballs, with a corresponding weight of 131 tons. As this is already about 33 % of the mass of the empty ship, we could conclude that this volume was never completely filled.
After completing the modeling of the internal part of the galleass, we noticed the presence of a narrow empty space running under the rowing deck and along the whole length of the ship. Thus, after consulting the literature[1], we discovered that those Galeazze had a nonstandard way of storing the potable water: this essential good, in fact, was stored in boxes that were placed in the middle empty space mentioned above. This solution allowed sailors to transport more water (estimate of 52000 liters) and to easily refill the provisions, since water tanks were readily accessible. On the other hand, this exposed position increased the chance of the boxes to get damaged during a fight.
We also found interesting to estimate the time that the ship could stay away from harbor based on the potable water storage. Since the Galeazza had a very large crew of about 620 people (330 rowers, 120 sailors and around 170 soldiers, according to [5]) drinking roughly 2 liters per day, this water would last for 6 weeks. After such a long time, however, the water stored in boxes rather becomes bad than it runs out.
Finally, we estimated the internal volumes that can be used as warehouse: the hull encloses a total volume of 1090 m3 from which we have to subtract the lowermost part that was usually filled with cannon balls as ballast (160 m3). Thus a space of  930 m3 remained for merchandise, food and weapons.

Renderings and sections of the ship:
With the complete and detailed CAD model, we could produce some rendered views of the interior and exterior of the galleass. The following video shows several images reproducing what a person on board would see and allows us  to have a taste of life on such a ship.

From the images reported above it is possible to appreciate the great level of detail that we were able to achieve, especially in the reflectance and light scattering of the different surfaces. Despite the quality of the images is quite good, it is possible to produce even more realistic results by increasing the processing time of the Maxwell Render software.
Finally, in the following we propose two sections of the Galeazza in order to expose in a clear way the complex structure of this ship.
cut2_Jcut_JFigure 2: Top panel: transversal cut of the ship. Bottom panel: Longitudinal cut.
The first image shows a cut through the width of the ship. As we can notice, the galleass was organized into three main external decks plus an internal deck contained inside the hull. The top external deck was mainly used by sailors to maneuver the sails and to have access to the anchors and the six cannons placed on the front. The two corridors placed above the oars represented the main fighting station of the ship, since four cannons per side were placed in this space. Finally, the central corridor above the hull was exploited by oarsmen to have access to the rowing benches. It is also possible to notice the empty space in the lowest part of the hull that was used to store cannonballs for ballast.
Conversely, the second image is useful to understand the internal compartmentalization of the hull. Towards the front of the ship, there was the so called Giava dei Capi, a space used to store utensils and several tools to repair the damaged parts of the galleass. Right behind this room there was the Giava dei Compagni, a large space that was exploited to store anchors and ropes in the case the original ones needed to be replaced. One of the most important compartments, however, was the Santabarbara, where the gunpowder and ammo for the cannons were placed. Since this place was highly flammable, venetian ship builders designed the galleass in such a way that the Santabarbara always remained below the waterline, in order to be protected against cannonballs. Finally, towards the back of the ship we could find additional compartments to store goods and materials, as well as a very small chapel.

REFERENCES

[1] Guido Ercole, Galeazze. Un sogno veneziano, Gruppo Modellistico Trentino, 2010.
[2] Gilberto Penzo, Navi Veneziane, Lint, 2000.
[3] Guido Ercole, Duri i banchi!, Gruppo Modellisticio Trentino, 2008.