When Brazil Solar Challenge was created, a class of solar boats was specially designed for the competition to take place. Thus was born the class catamarans Polo Nautico, created by the Naval Engineer Rafael Coelho, former pilot and member of the team.
Currently, the Solar Challenge Brazil also has the Open class, which defines for the craft project only the maximum dimensions allowed by rule and covers, mostly monohulls of 20 feet.
For the 2015 competition, the ESB was dedicated to take to the competition a prototype of the Polo Nautico class, since the vessel designed and built to join the Dutch Energy Solar Challenge (2014), ESB-1 doesn’t have a satisfactory performance in the sea conditions in which the DSB is performed in Armação dos Búzios – RJ. The ESB-1, in turn, is designed to navigate in Dutch canals, or in shallow water conditions, sweet and a low incidence of waves.
Added to this the fact that the Polo Nautico class did not have, so far, mold to produce more prototypes for the competition. It was then decided to make a mold to build a new prototype for the participation of the team in the Brazil Solar Challenge 2015.
The construction of a mold is a complex and expensive process, which is only worthwhile when the construction method requires it or the number of parts to be produced makes it feasible.
Traditionally, molds for boats are of female type, in which the last touches are required on the external side of the product. The mold is manufactured, usually from a piece (plug) with the exact shape of the desired product.
Figure 1 – Positioning shapes
The manufacture of the plug , which requires accuracy about the design dimensions , can be done in several ways. The method that was used is called Strip- planking, widely used in the construction of boats in wood and also in the manufacture of plugs . The method basically consists in fixing wooden battens ( strips ) positioned on the plug shapes to be manufactured. Having fixed the strips, the outer caulking is made with a fiberglass layer , and finally the plug reaches its final shape with mass application finish following the external template, with a subsequent layer of gel coat for finishing.
Figure 2 – Insertion of the strips on the shapes to generate the plug shape
It is noteworthy that the shapes combined with the strips are the basis for the shape of the hull, so the alignment and leveling of the shapes, which are to be made as accurately as possible, and the choice of the dimensions of the strips have a key role in the hydrodynamic performance of the boat.
Figure 3 – templates on the plug
With the plug ready, we began the construction of the mold, which compared to the manufacture of plug, is a faster and simpler process. This step was the lamination of successive glass fiber layers onto a gel layer so applied to the plug, produced in order to give the mold the resistance required to receive successive laminations without losing its original shape and holding the obtained finish on the plug to future hulls to be built. Production of the mold took into account the fact that numerous prototypes can be made for a longer period, encouraging the expansion of the competition in the country.
Figure 4 – terminated Plug
With that our team was able to build an essential and quality mold to manufacture the catamaran that will go to the competition this year in Buzios.
Figure 5 – terminated Mold