A wooden or steel boat can accommodate the purchaser's detailed design changes up to a very late stage in construction. An FRP boat cannot. The shape is a faithfull reproduction of a mould which has been designed and usually made long before the purchaser appeared. Production is therefore locked into a single type of vessel, a “Standard Design”.
It is emphasized that a wrongly chosen design, or design with features unsuitable for a tropical environment, would not find buyers and would cause the yard to fail at an early stage. Some research into fishermen's needs would allow a person to select plants to begin from an informed position.
It may be tempting to purchase a licence to copy vessels already in production elsewhere, but fishermen would not be thankful if the design were inappropriate. A design specifically commissioned for the local area combining traditional requirements, appropriate technology for construction and use, which has a regard to the climate and probable lack of maintenance, will take longer to arrange but is more likely to produce acceptable results.
Methods for the construction of plugs, moulds and hulls have been described in previous sections and the reader must judge which route is most suitable for local conditions. Factors influencing choice include:
Yard facilities
Materials availability
Labour skills
Size of vessel
Number to be produced
In the early stages of the life of an FRP boatyard in a developing country when experience is in short supply, it is advisable to obtain as much technical assistance as possible and begin with a project of manageable size.
Importing moulds and an example of a finished model which has been designed for the local environment is recommended for the start-up of an FRP boatyard. Subsequent local production initially under the guidance of an accredited expert will ensure well built boats while building up experience. This transfer of technology is vital as it provides the basic “hands on” experience of building boats in a new way and with new materials. A joint venture with an established overseas builder is another method whereby moulds, FRP materials and technology transfer are provided by the foreign company for a longer period on a more stable basis.
It is unlikely that a newly established yard will attempt to introduce a wholly new design until experience has been gained. Even then it is advised that the opinion of a third party be sought to check the hydrodynamic and structural calculations of a new vessel. This procedure is normal in northern countries where Classification Societies are employed to conduct such tasks. A list of recognized societies who undertake this work worldwide is given in Annex 3. In the case of a yard which has been set up with the assistance of an Aid Agency then this on going contact should be used for advice.
Another example of where design understanding may be of use is in the case of foreign built vessel requiring repairs when the laminate schedule information is not available. The construction rules of the original Classification Society may be requested and used to maintain the vessel within class after repair, but if not available the laminate schedule of the Sea Fish Industry Authority (SFIA) UK, should prove adequate and not difficult to follow.
The SFIA recommends that the amount of FRP needed for the skins of hulls of various sizes be based on a SCANTLING NUMERAL obtained as a product of multiplying:
L × B × D which are defined as follows:
L: The length shall be measured in metres on a straight line from the fore part of the stem at the top to the aftermost side of the hull shell.
B: The breadth shall be measured in metres at the greatest breadth of the vessel to the outside of the shell moulding.
D: The depth shall be measured in metres at the middle of the length L from the underside of the keel moulding to the top of the shell moulding.
Weight of laminate given in Table 9 is CSM only. However, a WR/CSM laminate can be calculated by substituting some CSM with WR in the ratio of 2:1 by weight/unit area. Alternate layering of CSM/WR MUST be maintained.
For example lets take from Table 9 a Scantling Numeral equal 200. The required shell weight is 5 100 g/m2 (CSM)
CSM Only Laminate
| Layer | |
|---|---|
| 1 | 300 g/m2 |
| 2 | 300 g/m2 |
| 3 | 450 g/m2 |
| 4 | 450 g/m2 |
| 5 | 600 g/m2 |
| 6 | 600 g/m2 |
| 7 | 600 g/m2 |
| 8 | 900 g/m2 |
| 9 | 900 g/m2 |
| 5 | 100 g/m2 |
Totals: 9 layers requiring 9 applications given 5 100 g/m2
CSM/WR Combination
| Layer | CSM Equivalent | |
|---|---|---|
| 1 | 300 g/m2 CSM | 300 g/m2 |
| 2 | 300 g/m2 CSM | 300 g/m2 |
| 3 | 300 g/m2 CSM} | 300 g/m2 |
| 600 g/m2 WR} | 1 200 g/m2 | |
| 4 | 300 g/m2 CSM} | 300 g/m2 |
| 600 g/m2 WR} | 1 200 g/m2 | |
| 5 | 300 g/m2 CSM} | 300 g/m2 |
| 600 g/m2 WR} | 1 200 g/m2 | |
| 3 300 g/m2 | 5 100 g/m2 | |
Totals: 8 layers requiring 5 applications giving 3 300 g/m2 which is equivalent to the required 5 100 g/m2 of CSM.
This realizes savings of:
Reinforcement
Resin
Application time
