Technical Construction

INTEGRATED GLOBAL PROJECT

The integrated global project (IGP) is a new way of conceiving the rubber dinghy, it has the target to reduce environmental impacts, raise standards of quality and minimize costs.

The I.G.P. is based on the synergy of four thematic areas, which are daily being developed in Motonautica Vesuviana:

CAD-CAM design thrust
Research and experimentation in the laboratory of the hulls and materials and data comparison with tests at sea
Massive implementation of vacuum construction techniques
Search for new biodegradable raw materials

Design CAD-CAM

To develop the ideas, the technical department of MV, consists of three engineers for the design of CAD / CAM 3-D and a technician officer of at the center of CNC 5-axis milling numeric control.

The 3-D CAD software allow to: modeling the various design solutions, studying shapes and colors, enhance the water lines of the hull, evaluate hydrostatic and hydrodynamic parameters, check the ergonomics of every detail of construction, optimize space, check interaction with human beings, engineer production processes, evaluate during the project step the design of suitable materials and their use, to simulate the assembly of the various elements, use at most the benefits derived from new construction techniques.

After giving form to ideas, with the CAD, the second step is the materialization of the CAM in a virtual environment, through the milling center, running the models with a precision of a hundredth of a millimeter.

Here is that the foundations were laid for the reduction of weights, of powders, of processing times and quality of the R.I.B. (RIGID INFLATABLE BOATS). Thanks to this design methodology are used in a large scale the structures in sandwich, the cores are designed and milled on site.

The sandwich structures, laminated in infusion system, have high mechanical properties and reduced weight, the video shows the impact test, performed on different plates, 6 mm aluminum, in 12mm fiberglass, and 20 mm wood, compared with a laminated sandwich, with external layers of only 3 mm and a 20mm PVC foam core, as used in our hulls. The results are surprising, all monolithic samples are broken, with the exception of the sandwich, which absorbs the impact without suffering any drilling.

The vacuum sandwich structures allow to eliminate the structural frame, with a reduction of weight, up to 30%, to reduce the VOC (Volatile organic compounds) during processing, to break down the dust of abrasion, for the absence of the internal frame, to improve the quality of work and to reduce CO2 emissions into the atmosphere.

These techniques well used, reduce the processing time and further increase the safety for the sinking.

Research and testing in the hull and materials laboratory

After a careful design phase and hydrostatic simulation of hulls in 3D CAD environment, the various solutions, are tested with models in the laboratory of hydrodynamic experiments site in department of Naval Architect and Marine Engineering of University of Naples “Federico II”. Parameters are measured as the resistance to motion, the angle of longitudinal trim in stroke, the R.I.B. raising at sea and the acceleration in case of rough seas.

The data obtained are compared with “the parameters and the practical experience of the ribyard” and only at the end we proceed with the realization of the true model.

Technical Construction

For the lamination of a fiber composite material, fiberglass and carbofibre-reinforced plastics, there are several construction methods, those of greatest interest for the boating industry are: the RTM Light, infusion and prepregs. The latest techniques have been developed in the aerospace and automotive field, later applied in the marine industry. These techniques have been designed to reduce the weight and increase the mechanical properties of the artefacts, which are essential to build light aircraft with low operating costs. When the fuel price was lower, the yards did not give much importance to the weight of the R.I.B.. Today the owners are very careful to the consumption, weight and development of high performance hulls, play a key role in the market.

Infusion

The infusion is used by MV since 2005, is a processing technique in vacuum used for lamination of structural parts, which must have high mechanical properties, such as hulls, blankets, deckhouses, saddles. The fibers are lying dry in mold, including the cores of the sandwich, the whole is placed in a bag vacuum, for depression, the resin is drawn to interior of the fibers.

The resin enters only in the empty spaces and imbues at best fibers without excess, we obtain a laminate with a constant thickness, of very high quality and low weight. During processing operators are not exposed to the vapors of the resin, as they are conveyed in a closed environment. Emissions of particulate organic compounds (VOCs) in the atmosphere are reduced by 92% all for the benefit the environment.

From tests carried out in the laboratory is evident, that in two panels from 1 square meter with the same amount of glass fiber, a laminate by hand and the other in the infusion, we have a weight reduction of 32%.

RTM-Light

The RTM-Light, used in the production cycle from the MV since 2005, is a technique of lamination in closed mold in vacuum used for the lamination of the visible parts where you need a high degree of trimming, the tops off the peaks, the quarterdecks , the consoles are polished on both sides. It ‘s a more sophisticated technique than infusion, it works in male and female molds, and the tolerances are low. The great merit RTM-Light is to make complex parts, like the stern door of Vesevus 35, full of all the predispositions to the anchors and cables, with the foam core, making it hard and on weight content. This methodology allows very high levels of trimming and reduced production time. The pieces come already finished and after trimming, are ready for assembly.

Ecological production respecting environment

Comparing the two construction techniques applied by the MV, the infusion and RTM Light, with the manual lamination, it is clear that emissions of volatile substances in the atmosphere are reduced by 93% and dust by 80%.

The results of the integrated global project

The construction process of Mito 31, allows a reduction of 93% of emissions of volatile organic compounds (VOC) and 80% of dust. By comparing the MV Mito 31 with others of the same segment, designed with traditional methods, there is a difference in the finished weight of 800 Kg In navigation, at a cruising speed of 35 knots, it takes only 65 liters / hour of fuel, fuel consumption and CO2 emissions are significantly reduced by 25%. These results are due also to the efficiency of our hulls, to verify the goodness, the regression has to be calculated. We carry out sea trials, where it detects the real speed at various engine speeds. Knowing the pace of the propeller and the relationship to the foot, it is calculated at various speeds, the theoretical speed.

It is defined the theoretical step response (TSR), as the distance that the propeller runs, in a rotation of 360 °, screwing into a solid material, it is defined real step (RS), the distance that the propeller runs screwing along a liquid , the “regression” (r) is the percentage difference, the distance between the theoretical step (TS) and the real one (RS). As it is noted from the graph the values of the regression, are very low, because the actual speed is very close to the theoretical one. The MV builds R.I.B.s with efficient hulls which absorbs a little power and limits the consumption.

Search for a new biodegradable raw materials

The attention to the environment is always very high, the effort is also directed to the research. The MV in collaboration with CNR (National Research Council) and University Federico II of Naples, had work on a project “Biocomp-RB” for RIB’s construction in composite materials, through the use of biodegradable raw materials.

We are experimenting materials with fiber reinforcement and resins derived from natural substances, cores with recycled products, such as Polypropylene PP and Polyethylene PP completely reusable. The global integrated project (G.I.P.) is a new way of conceiving the R.I.B., directed to quality of product and environment.

Most of manufacturers, commission the fiberglass hull to subcontractors, who sell products by weight. Very little fiber and a lot of resin corresponds to more weight and thus with higher profits at the expense of quality. Building with vacuum techniques in sandwich, with fabrics in multi-axial and resins of high quality, can not be evaluated with the same parameter, the more the article is technological and light, the greater is the value.

The purpose of this statement is to answer the curiosity of fans, who want to know the building philosophy of the MV, in designing the rubber dinghies of present and future.