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A customised technique to produce high performance boats
Figure 6: Infused bottom.
A customised technique to produce high performance boats Italian boat builder Agostini Nautica has developed a customised infusion process to suit its production. Simonetta Pegorari reports.
B
ased on its experiences of various infusion processes and materials (including the Seeman composites resin infusion process (SCRIMP), DIAB infusion technology, and others), Italian boat builder Agostini Nautica has developed a system suited to its own requirements. This tailored technique aims to get the best
32
REINFORCEDplastics
rp5101p32_37.indd 32
January 2007
performance out of products especially designed for the infusion process (resins, core materials, fabrics) as well as systems designed for flow control (peel-ply, injection points and lines, distribution net, vacuum bag, draining system etc; see Figure 1). The main reason why the shipyard has invested in the optimisation of its own
infusion production technique has been the opportunity to offer its clients new methods for producing higher performance composite products which can comply with higher specifications. The Italian company already manufactures composite boats using the traditional technique of hand lay-up. 0034-3617/07©2007 Elsevier Ltd. All rights reserved
09/01/2007 11:03:35
Feature
Figure 1: Infusion materials.
Using the infusion technique, hulls have been manufactured with different characteristics, both in terms of design (monolithic bottom rather than with a polyvinyl chloride [PVC] core, bulkheads and infusion structural panels or traditional ones), and in terms of materials (from knitted fabrics to quadraxial, through to woven roving). In every case, the finished products have always matched the design specifications and have also demonstrated improved impregnation ratio and weight compared to products manufactured using manual production methods (hand lay-up).
Infusing a hull The better mechanical characteristics and weight reduction provided by the infusion technique are the main reasons why a shipyard is going to choose to manufacture a boat using this technique. In fact, to be able to gain
Figure 2: Sketched distribution lines.
January 2007
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Feature
all the advantages offered by the infusion processes, the boat should be designed taking into account the type of finished product which can be obtained.
The better mechanical characteristics and weight reduction provided by the infusion technique are the main reasons why a shipyard is going to choose to manufacture a boat using this technique. Early on, at the start of the design stage, information exchange between the technical office responsible for the craft and the manufacturer responsible for the construction process is very important. In fact, there are detail aspects which, once they have been established, are strictly linked to the infusion process model. For example, frameworks shorter than the floor-plates do not infuse
all at the same time, while monolithic areas, usually found at the window frames, need a particular distribution net lay-up (Figure 2). Once the construction details have been defined, it is essential to check in the laboratory the behaviour of all the materials which are required to manufacture the finished product, carrying out practical infusion tests on the side and bottom panels, planning and testing the fabric application, the core material, the reinforcement layer and the tooling materials. A crucial element to be kept under strict control is the resin gel time (Figure 3). Together with the resin suppliers (in this case Polynt), the laboratory should develop the different catalysts to be used throughout the infusion lines, considering three particular parameters: • temperature and humidity conditions during the production process; • the resin flow between the lines; and • the permeability of the laminate that the resin flow has to run through. Another working step requiring great attention, and a preliminary theoretical study of the component to be infused, is the
positioning of the lines for the resin flow. These should be positioned by calculating distances related to the fabrics which the laminate is based on, but also according to the geometry of some of the areas that the resin flow meets along its way (window frames, sea water intakes and others). Generally speaking, the objective is to make the resin flow progress homogeneously, from the middle of the mould to the external perimeter, where the vacuum intake ring is normally positioned. Finally, the production process can start. The infusion process can be outlined through the following steps: • hand lay-up of the skin coat; • laying up of the reinforcement fabrics of the external dry skin; • laying up of the dry core material; • dry lay-up of the external skin; • peel-ply positioning and resin injection lines and flow; • vacuum bag installation; • resin flow line and vacuum system positioning; • calibration of the resin infusion time; • infusion line opening; and • catalysis and end of the process.
Figure 3: Gel time control.
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January 2007
09/01/2007 11:03:59
Feature
After laminating the skin-coat, the side and bottom external skin coat fabrics, the core material, and finally the reinforcement layers, are positioned (Figure 4). All the layers placed in the dry mould should be adequately staggered and overlapped. Once the lay-up of the skin materials has been performed, the peel-ply is positioned. The peel-ply has the double purpose of allowing the vacuum bag extraction from the laminate, and of guaranteeing the adequate porosity of the laminate. The next step involves applying the lines for the resin flow (Figure 5). This completes all the stages of dry material installation. After sealing, using a vacuum bag, the vacuum line is connected to the intake pumps, and the air is extracted from the mould until 1 bar is reached, and all the reinforcement materials are compacted against the mould. Before starting to inject the resin, it is necessary to check bag integrity. At this stage, it is possible to open the resin flow lines, starting from the keel line and, as the resin reaches the subsequent lines from the middle toward the external perimeter of the mould, the resin infuses the bottom (Figure 6), the stern, and at the same time, the two sides. The infusion process has been correctly performed when the external boundaries of the mould along the whole perimeter are reached by the resin almost at the same time, without producing any 'dry' areas (areas without resin). In order to ensure this, drilled and grooved PVC can be used,and also materials which can help the resin transport to critical areas, either interlaminar materials or surface distribution nets (Figure 7).
The infusion technique is precise. The infusion technique is precise: the time to infuse the laminate and the resin catalysis are calculated and at the end of the process, when the resin has completed the catalysis, the vacuum bag and the peel-ply are extracted. Contrary to the traditional lamination processes, with infusion it is not possible to
Figure 4: Laying up of dry materials.
visually check for proper adhesion of the different layers and the possible presence of air bubbles. To determine that a laminate meets the design specifications, it is necessary to test its consistency thoroughly, highlighting the possible critical areas. The boats constructed by Agostini Nautica are tested by the Q.I. Composites Srl, which uses an ultrasound technique to verify and certify the following aspects: • adhesion between the skin and the core; • thickness homogeneity; • symmetry between the laminates of the two sides; • proper compaction of the fabrics; • no resin accumulations; • total filling of the PVC cube-shaped cuts. After passing these tests, it is possible to state that the finished product meets the design requirements.
Infusion costs The comparison of infusion process costs compared with the costs of traditional lamination must be tackled carefully since the infusion process affects the various
production steps differently. A shipyard's moulding costs could be divided and analysed in terms of the following categories.
Tooling materials One aspect to be taken into account (obtained through the average cost for the construction of the various units produced) is the cost of the tooling materials (peel-ply, injection points and lines, distribution net, vacuum bag, drainage system) as well as the waste materials (residual resin in the lines) to perform the infusion moulding. This figure can be compared with the costs of the tooling materials which might have been used for the traditional lamination process (rolls, brushes, cleaning acetone), also considering that in this case the quantity (that is the amount of material used for the lay-up) would have been higher. The quantification of these latter costs varies from shipyard to shipyard as a function of the different tooling methods. Another element to be kept in mind is that in Italy, the infusion technique is still rarely used. If the technique becomes more widely used, it is reasonable to foresee a January 2007
rp5101p32_37.indd 35
REINFORCEDplastics
35
09/01/2007 11:04:04
Feature
Figure 5: Installation of the distribution lines.
decrease in the unit costs of the tooling materials.
In-mould handling The lower weight of an infused laminate leads to a lower amount of materials to be installed, and therefore to a lower cost as a result of the reduction of the installation time. In fact, it is not the moulding hours that decrease but the assembling time, which, depending on the type of boat, can drop by up to 16-18%. This makes it possible to shorten the moulding time (from the gel coat to the extraction step) for the same size of boat. For boats of 60 ft or longer, the time required is over 20% less than for the traditional lamination process.
Bodywork handling The finishing of infused parts is more expensive than for components manufactured by traditional hand lay-up. The main problem is the possibility of shrinkage where the resin has accumulated; this can be improved with experience and by some measures taken during the installation steps of the dry materials. At the present time, we can say that
36
REINFORCEDplastics
rp5101p32_37.indd 36
the bodywork for infused hulls takes 10% more time compared to hand laminating. Improvements in infusion materials and new construction methods (for example, the application of a barrier coat between the skin coat and the laminate external skin) can make this extra cost drop.
Quality tests
Production staff
General considerations
Based on its experience, Agostini Nautica points out that the introduction of the infusion technique does not require the employment of workers devoted to the supervision of this process. Of course it is necessary to adequately train the staff, especially the technical office operators, the shipyard chief operator as well as those who are responsible for the purchase of the materials, to make each of them aware of the main issues. The additional activity foreseen consists in carrying out tests on the panels or the mould parts for the analysis and the optimisation of the distribution net, of the catalysis ratio, of the infusion time, but also of all the details of each part in terms of geometries and of materials to be infused.
Everything considered, with the data available nowadays and according to the current experience, it can be stated that the infusion process is still 5-8% more expensive than traditional lamination for the same size of product to be constructed. Nevertheless the following observations deserve attention: • the finished infusion product has better mechanical characteristics; • the finished product produced is of a better quality as the result of a better glass/ resin ratio; • this technique is still hardly used, and surely when more shipyards start using it prices will drop; • further process optimisation is needed, involving investment in research, development and manpower; and
The laminate quality is evaluated from samples. The cost of this service, which in the case of Agostini Nautica is carried out by an external company, is counterbalanced by the possibility of offering its customers a more reliable production process.
January 2007
09/01/2007 11:04:09
Feature
Figure 7: Completed infusion.
• the infusion process leads to a cleaner environment for workers; in fact, costs of complying with health and safety directives are decreasing. When the infusion process is more widely used it is reasonable to expect a large decrease in the costs over the traditional construction procedure, although the reason for choosing the infusion process should not be the decrease in the moulding costs, but the higher quality, performance and mechanical properties it results in. There are several factors related to the infusion process which require more attention. Based on practical experience, the following points should be thoroughly investigated by those who are going to use this technique. The engineering of the boat construction by infusion is very different from the hand lay-up one in terms of the technical specifications. The main differences are listed below. Traditional technique: • lamination data tables; • cost estimate;
• construction design; and • construction details. Infusion: • construction details; • construction design; • lamination data tables; and • cost estimate. Using the infusion technique it is possible to solve right at the beginning of the process many technical production problems thanks to the constructor’s involvement at the design stage; moreover, this factor allows the constructor to develop a close partnership with the customer. According to the data collected so far, it is possible to say that in a finished product, manufactured using the infusion technique, a 30% weight reduction can be obtained over a finished product of the same size laminated using the traditional technique. The process results in a decrease in emissions to the atmosphere (the styrene loss with the infusion process is less than 1% weight compared with 7-10% for manual lamination) and allows staff to operate in a better working environment.
The process results in a decrease in emissions to the atmosphere, and allows staff to operate in a better working environment. To summarise the advantages offered by the infusion technique, one could say that using this technique the production of the fiberglass finished products approaches more the industrial-type supply, leaving less room for the subjective variables that a craftsman approach obviously involves, although carried out very accurately. ■
Agostini Nautica; Via Bevano, 16 - cap 48010, Castiglione di Ravenna (RA), Italy; tel: +39-544-554227; www.agostininautica.it
January 2007
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REINFORCEDplastics
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A customised technique to produce high performance boats Italian boat builder Agostini Nautica has developed a customised infusion process to suit its production. Simonetta Pegorari reports.
B
ased on its experiences of various infusion processes and materials (including the Seeman composites resin infusion process (SCRIMP), DIAB infusion technology, and others), Italian boat builder Agostini Nautica has developed a system suited to its own requirements. This tailored technique aims to get the best
32
REINFORCEDplastics
rp5101p32_37.indd 32
January 2007
performance out of products especially designed for the infusion process (resins, core materials, fabrics) as well as systems designed for flow control (peel-ply, injection points and lines, distribution net, vacuum bag, draining system etc; see Figure 1). The main reason why the shipyard has invested in the optimisation of its own
infusion production technique has been the opportunity to offer its clients new methods for producing higher performance composite products which can comply with higher specifications. The Italian company already manufactures composite boats using the traditional technique of hand lay-up. 0034-3617/07©2007 Elsevier Ltd. All rights reserved
09/01/2007 11:03:35
Feature
Figure 1: Infusion materials.
Using the infusion technique, hulls have been manufactured with different characteristics, both in terms of design (monolithic bottom rather than with a polyvinyl chloride [PVC] core, bulkheads and infusion structural panels or traditional ones), and in terms of materials (from knitted fabrics to quadraxial, through to woven roving). In every case, the finished products have always matched the design specifications and have also demonstrated improved impregnation ratio and weight compared to products manufactured using manual production methods (hand lay-up).
Infusing a hull The better mechanical characteristics and weight reduction provided by the infusion technique are the main reasons why a shipyard is going to choose to manufacture a boat using this technique. In fact, to be able to gain
Figure 2: Sketched distribution lines.
January 2007
rp5101p32_37.indd 33
REINFORCEDplastics
33
09/01/2007 11:03:47
Feature
all the advantages offered by the infusion processes, the boat should be designed taking into account the type of finished product which can be obtained.
The better mechanical characteristics and weight reduction provided by the infusion technique are the main reasons why a shipyard is going to choose to manufacture a boat using this technique. Early on, at the start of the design stage, information exchange between the technical office responsible for the craft and the manufacturer responsible for the construction process is very important. In fact, there are detail aspects which, once they have been established, are strictly linked to the infusion process model. For example, frameworks shorter than the floor-plates do not infuse
all at the same time, while monolithic areas, usually found at the window frames, need a particular distribution net lay-up (Figure 2). Once the construction details have been defined, it is essential to check in the laboratory the behaviour of all the materials which are required to manufacture the finished product, carrying out practical infusion tests on the side and bottom panels, planning and testing the fabric application, the core material, the reinforcement layer and the tooling materials. A crucial element to be kept under strict control is the resin gel time (Figure 3). Together with the resin suppliers (in this case Polynt), the laboratory should develop the different catalysts to be used throughout the infusion lines, considering three particular parameters: • temperature and humidity conditions during the production process; • the resin flow between the lines; and • the permeability of the laminate that the resin flow has to run through. Another working step requiring great attention, and a preliminary theoretical study of the component to be infused, is the
positioning of the lines for the resin flow. These should be positioned by calculating distances related to the fabrics which the laminate is based on, but also according to the geometry of some of the areas that the resin flow meets along its way (window frames, sea water intakes and others). Generally speaking, the objective is to make the resin flow progress homogeneously, from the middle of the mould to the external perimeter, where the vacuum intake ring is normally positioned. Finally, the production process can start. The infusion process can be outlined through the following steps: • hand lay-up of the skin coat; • laying up of the reinforcement fabrics of the external dry skin; • laying up of the dry core material; • dry lay-up of the external skin; • peel-ply positioning and resin injection lines and flow; • vacuum bag installation; • resin flow line and vacuum system positioning; • calibration of the resin infusion time; • infusion line opening; and • catalysis and end of the process.
Figure 3: Gel time control.
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REINFORCEDplastics
rp5101p32_37.indd 34
January 2007
09/01/2007 11:03:59
Feature
After laminating the skin-coat, the side and bottom external skin coat fabrics, the core material, and finally the reinforcement layers, are positioned (Figure 4). All the layers placed in the dry mould should be adequately staggered and overlapped. Once the lay-up of the skin materials has been performed, the peel-ply is positioned. The peel-ply has the double purpose of allowing the vacuum bag extraction from the laminate, and of guaranteeing the adequate porosity of the laminate. The next step involves applying the lines for the resin flow (Figure 5). This completes all the stages of dry material installation. After sealing, using a vacuum bag, the vacuum line is connected to the intake pumps, and the air is extracted from the mould until 1 bar is reached, and all the reinforcement materials are compacted against the mould. Before starting to inject the resin, it is necessary to check bag integrity. At this stage, it is possible to open the resin flow lines, starting from the keel line and, as the resin reaches the subsequent lines from the middle toward the external perimeter of the mould, the resin infuses the bottom (Figure 6), the stern, and at the same time, the two sides. The infusion process has been correctly performed when the external boundaries of the mould along the whole perimeter are reached by the resin almost at the same time, without producing any 'dry' areas (areas without resin). In order to ensure this, drilled and grooved PVC can be used,and also materials which can help the resin transport to critical areas, either interlaminar materials or surface distribution nets (Figure 7).
The infusion technique is precise. The infusion technique is precise: the time to infuse the laminate and the resin catalysis are calculated and at the end of the process, when the resin has completed the catalysis, the vacuum bag and the peel-ply are extracted. Contrary to the traditional lamination processes, with infusion it is not possible to
Figure 4: Laying up of dry materials.
visually check for proper adhesion of the different layers and the possible presence of air bubbles. To determine that a laminate meets the design specifications, it is necessary to test its consistency thoroughly, highlighting the possible critical areas. The boats constructed by Agostini Nautica are tested by the Q.I. Composites Srl, which uses an ultrasound technique to verify and certify the following aspects: • adhesion between the skin and the core; • thickness homogeneity; • symmetry between the laminates of the two sides; • proper compaction of the fabrics; • no resin accumulations; • total filling of the PVC cube-shaped cuts. After passing these tests, it is possible to state that the finished product meets the design requirements.
Infusion costs The comparison of infusion process costs compared with the costs of traditional lamination must be tackled carefully since the infusion process affects the various
production steps differently. A shipyard's moulding costs could be divided and analysed in terms of the following categories.
Tooling materials One aspect to be taken into account (obtained through the average cost for the construction of the various units produced) is the cost of the tooling materials (peel-ply, injection points and lines, distribution net, vacuum bag, drainage system) as well as the waste materials (residual resin in the lines) to perform the infusion moulding. This figure can be compared with the costs of the tooling materials which might have been used for the traditional lamination process (rolls, brushes, cleaning acetone), also considering that in this case the quantity (that is the amount of material used for the lay-up) would have been higher. The quantification of these latter costs varies from shipyard to shipyard as a function of the different tooling methods. Another element to be kept in mind is that in Italy, the infusion technique is still rarely used. If the technique becomes more widely used, it is reasonable to foresee a January 2007
rp5101p32_37.indd 35
REINFORCEDplastics
35
09/01/2007 11:04:04
Feature
Figure 5: Installation of the distribution lines.
decrease in the unit costs of the tooling materials.
In-mould handling The lower weight of an infused laminate leads to a lower amount of materials to be installed, and therefore to a lower cost as a result of the reduction of the installation time. In fact, it is not the moulding hours that decrease but the assembling time, which, depending on the type of boat, can drop by up to 16-18%. This makes it possible to shorten the moulding time (from the gel coat to the extraction step) for the same size of boat. For boats of 60 ft or longer, the time required is over 20% less than for the traditional lamination process.
Bodywork handling The finishing of infused parts is more expensive than for components manufactured by traditional hand lay-up. The main problem is the possibility of shrinkage where the resin has accumulated; this can be improved with experience and by some measures taken during the installation steps of the dry materials. At the present time, we can say that
36
REINFORCEDplastics
rp5101p32_37.indd 36
the bodywork for infused hulls takes 10% more time compared to hand laminating. Improvements in infusion materials and new construction methods (for example, the application of a barrier coat between the skin coat and the laminate external skin) can make this extra cost drop.
Quality tests
Production staff
General considerations
Based on its experience, Agostini Nautica points out that the introduction of the infusion technique does not require the employment of workers devoted to the supervision of this process. Of course it is necessary to adequately train the staff, especially the technical office operators, the shipyard chief operator as well as those who are responsible for the purchase of the materials, to make each of them aware of the main issues. The additional activity foreseen consists in carrying out tests on the panels or the mould parts for the analysis and the optimisation of the distribution net, of the catalysis ratio, of the infusion time, but also of all the details of each part in terms of geometries and of materials to be infused.
Everything considered, with the data available nowadays and according to the current experience, it can be stated that the infusion process is still 5-8% more expensive than traditional lamination for the same size of product to be constructed. Nevertheless the following observations deserve attention: • the finished infusion product has better mechanical characteristics; • the finished product produced is of a better quality as the result of a better glass/ resin ratio; • this technique is still hardly used, and surely when more shipyards start using it prices will drop; • further process optimisation is needed, involving investment in research, development and manpower; and
The laminate quality is evaluated from samples. The cost of this service, which in the case of Agostini Nautica is carried out by an external company, is counterbalanced by the possibility of offering its customers a more reliable production process.
January 2007
09/01/2007 11:04:09
Feature
Figure 7: Completed infusion.
• the infusion process leads to a cleaner environment for workers; in fact, costs of complying with health and safety directives are decreasing. When the infusion process is more widely used it is reasonable to expect a large decrease in the costs over the traditional construction procedure, although the reason for choosing the infusion process should not be the decrease in the moulding costs, but the higher quality, performance and mechanical properties it results in. There are several factors related to the infusion process which require more attention. Based on practical experience, the following points should be thoroughly investigated by those who are going to use this technique. The engineering of the boat construction by infusion is very different from the hand lay-up one in terms of the technical specifications. The main differences are listed below. Traditional technique: • lamination data tables; • cost estimate;
• construction design; and • construction details. Infusion: • construction details; • construction design; • lamination data tables; and • cost estimate. Using the infusion technique it is possible to solve right at the beginning of the process many technical production problems thanks to the constructor’s involvement at the design stage; moreover, this factor allows the constructor to develop a close partnership with the customer. According to the data collected so far, it is possible to say that in a finished product, manufactured using the infusion technique, a 30% weight reduction can be obtained over a finished product of the same size laminated using the traditional technique. The process results in a decrease in emissions to the atmosphere (the styrene loss with the infusion process is less than 1% weight compared with 7-10% for manual lamination) and allows staff to operate in a better working environment.
The process results in a decrease in emissions to the atmosphere, and allows staff to operate in a better working environment. To summarise the advantages offered by the infusion technique, one could say that using this technique the production of the fiberglass finished products approaches more the industrial-type supply, leaving less room for the subjective variables that a craftsman approach obviously involves, although carried out very accurately. ■
Agostini Nautica; Via Bevano, 16 - cap 48010, Castiglione di Ravenna (RA), Italy; tel: +39-544-554227; www.agostininautica.it
January 2007
rp5101p32_37.indd 37
REINFORCEDplastics
37
09/01/2007 11:04:13