!

Construction techniques

Integrated global project

The integrated global project (P.G.I.) is a new way of conceiving dinghies, with the aim of reducing environmental impact, raising quality standards and containing costs. The P.G.I. is based on the synergy of four thematic areas, which are developed daily by Mv Marine technicians:
1. CAD-CAM push design;
2. Research and experimentation in the laboratory of hulls and materials and comparison of data with tests at sea;
3. Massive implementation of vacuum construction techniques;
4. Search for new biodegradable raw materials.

CAD-CAM design

The technical study of the MV consists of three engineers for the CAD / CAM 3-D design and a technician assigned to the CNC milling center with 5-axis control. The 3-D CAD software allows you to: model the various stylistic solutions by studying shapes and colors, optimizing the hull water lines, evaluating the hydrostatic and hydrodynamic parameters, verifying the ergonomics of every construction detail, optimizing the spaces, verifying the interaction with the human being, engineering production processes, evaluating suitable materials and their use during the design phase, simulating the assembly of the various elements, making maximum use of the benefits deriving from new construction techniques. After giving shape to the ideas in a virtual environment through CAD design, we move on to materialization with the CAM, through the milling center, which executes the models with precision to the hundredth of a millimeter.

And it is here that the foundations are laid for the reduction of weights, powders, processing times and the quality of the boat. Thanks to this design methodology, sandwich structures are used on a large scale, so even the cores are designed and milled on site. Sandwich structures, laminated in infusion, have very high mechanical properties and reduced weight.
The sandwich structures in vacuum allow to eliminate the structural frame, with a weight reduction, up to 30%, to reduce the V.O.C. (volatile organic components) during processing, to reduce abrasion dust due to the absence of the internal frame, to improve the quality of work and to reduce CO2 emissions into the atmosphere.
These well-used techniques reduce processing times and further increase sinking safety.

Research & experimentation

After a careful hydrostatic design and simulation phase of the hulls in a CAD 3D environment, the various solutions are tested with scale models in the hydrodynamic experiments laboratory of the Naval Engineering Department of the Federico II University of Naples. Parameters are measured such as resistance to motion, angle of longitudinal motion in the race, raising of the boat during navigation and acceleration in case of rough seas. The data obtained is compared with “the parameters and the practical experiences of the construction site” and only at the end does one proceed with the realization of the true model.

Lamination

For the lamination of a fibrous composite material, fiberglass and carboresin, there are several construction methods, the ones of greatest interest for the nautical sector are: RTM Light, infusion and pre-impregnation. These most innovative techniques have been developed in the aerospace and automotive sectors, subsequently applied in the nautical sector. These techniques have been designed to reduce weight and increase the mechanical properties of products, which are essential for building light products with low operating costs. When the price of fuel was lower, the yards did not give much importance to the weight of the boat. Today shipowners are very attentive to consumption; the weight and development of high-performance hulls therefore play a key role in the market.

The infusion

The infusion, used by the MV since 2005, is a vacuum processing technique used for the rolling of structural parts, which must have high mechanical properties, such as hulls, blankets, deckhouses, saddles. The fibers are laid dry in the mold, including the cores of the sandwich, everything is placed in a vacuum bag, by depression the resin is sucked inside the fibers. The resin enters only the empty spaces and impregnates the fibers without excesses, obtaining a laminate with a constant thickness, of very high quality and reduced weight. During processing the operators are not exposed to resin vapors, as it conveys in a closed environment. Emissions of volatile organic particles (V.O.C.) in the atmosphere are reduced by 92%, all in favor of the environment.
The tests carried out in the laboratory show that in two 1-square-meter panels with the same amount of fiberglass, one hand-rolled and the other in infusion, we have a weight reduction of 32%.

The RTM-Light

The RTM-Light, used in the production cycle by the MV since 2005, is a closed-mold rolling technique, in vacuum used for the rolling of visible parts where a very high degree of finishing is needed, the lids of the lockers, the formwork , the consoles are shiny on both sides. It is a more complex infusion technique, it is worked in mold and counter-mold and the tolerances are low. The great value of the RTM-Light is to realize complex parts, such as the stern hatch of the Mito 45, complete with all the predispositions for the wiring and the anchors, with the foam core, which make it rigid and by weight content. This method allows very high finishing levels and reduced production times. The pieces come out already finished and after trimming, they are ready for assembly. Comparing the two construction techniques applied by the MV, the Infusion and RTM Light, with the manual lamination method, it is clear that the emissions of volatile substances, in the atmosphere they are reduced by 93% and dust by 80%.

!

Search for new raw materials

Attention to the environment is always very high, the commitment is also aimed at research. The MV in collaboration with the CNR and the Federico II University of Naples, worked on the “Biocomp-RB” project for the construction of rubber dinghies, in composite material, using biodegradable raw materials.
Materials with fibrous reinforcement and resins obtained from natural substances were tested, cores with recycled products, such as Polypropylene PP and Polyethylene PE, completely reusable. The result of these studies is the Mv 620 Eco-Tech, a boat made with flax fibers and resins derived from vegetable oils that are still sailing today.

!

The results

The construction process of the Mito 31, allows a 93% reduction in emissions of volatile organic substances (V.O.C.) and 80% of dust. Comparing the MV Mito 31 with others of the same segment, conceived with traditional methods, there is a difference in the finished weight of around 800 Kg. At sea, at a cruising speed of 35 knots, only 65 liters / hour of fuel are needed, fuel consumption and CO2 emissions are significantly reduced by 25%.

These results are also due to the efficiency of our hulls, to check its goodness, the regression must be calculated. Sea tests are carried out, where the real speed is measured at the various engine speeds. Knowing the pitch of the propeller and the relationship to the foot, the theoretical speed is calculated at various regimes.
We define the theoretical step (PT), as the distance that the propeller travels, in a 360 ° rotation, screwing itself into a solid material, is defined as a real step (PR), the distance that the propeller travels, turning into a liquid , the “regress” (R) is the difference in percentage, of the distance between the theoretical step (PT) and the real one (PR).
As can be seen from the graph, the values of the regression are very low, as the real speed is very close to the theoretical one. The MV builds boats with efficient hulls that absorb little power and contain consumption. Building with sandwich vacuum techniques, with multi-axial fabrics and high-quality resins, makes the product technological, light and of greater value.

The integrated global project is therefore a new way of conceiving inflatable boats, aimed at the quality of the product and the environment.