A customised technique to produce high performance boats

REINFORCEDplastics January 2007 32 0034-3617/07©2007 Elsevier Ltd. All rights reserved

A customised technique to produce high performance boatsItalian boat builder Agostini Nautica has developed a customised infusion process to suit its production. Simonetta Pegorari reports.

Based 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

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.

Figure 6: Infused bottom.

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33

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 1: Infusion materials.

Figure 2: Sketched distribution lines.

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REINFORCEDplastics January 2007 34

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 techni-

cal office responsible for the craft and the

manufacturer responsible for the construc-

tion 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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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

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

Figure 4: Laying up of dry materials.

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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

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.

Production staff

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 optimi-

sation 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.

Quality tests

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.

General considerations

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

Figure 5: Installation of the distribution lines.

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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

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