Rationalized Manufacturing thanks to Standardised Design - Application of Composite Sandwich Panels in the Shipbuilding Industry

 Produc tion and Process technology Application of Composite Sandwich Panels in the Shipbuilding Industry Rationalized Manufacturing thanks to Standardised Design Large-size GRP-sandwich panels allow the economic and high-quality production of ships which need only half of the fuel of traditional models. This example of the construction of catamaran describes impressively the possibilities such standardised panels open up. T he application of lightweight construction technologies in comparison to other new custom built ships is shown on a pilot's opens a huge energy-saving potential in the production catamaran (picture 2) which is under development. The P240: With of fast ships. Today‘s constructions are practicable with 2 x 368 kW the consumption of fuel at 20 knots service speed is on- the considerable fuel savings that can be achieved. The Baltec ly about 6 litres/nm (sea mile). In the individual cases the fuel econo- shipyard in Lübeck produces high-strength sandwich ships by my can cover the leasing rate of the ship. innovative lightweight construction. By comparison to conven- tionally made models with the same water lines length they are The TechnOLOGy half the weight and also see as much as 50 % reduction in fuel The production of the large-size GRP (fibreglass-reinforced plastic)- usage (Picture 1). sandwich panels occurs in 12 x 2.4-metre-heatable vacuum press (picture 3). The core and deck layer materials can be assembled The ShIPS according to the intended purpose of the panel (picture 4). The deck Baltec shipyard in Lübeck builds light weight composite vessels for laminates are made of pre-cast, pre-impregnated laminates (epoxy- different purposes, but has specialised particularly in the construc- Prepreg) which can be pre-defined depending on the required tion of fuel-efficient catamarans for professional use. The newly de- structural properties, fibre specification and direction. This guaran- veloped “Ocean Runner” design is tuned and specifically tailored to tees consistent structural properties producing quality, standardised meet requirements, which come from the lightweight construction. panels. To ensure the panel‘s unlimited use during the building The design of the ships also reflects optimised forms which are process, they are sanded on both sides after the post cure process. necessary to be able to build in panel construction method. To do This ensures that there are no defects within the epoxy surface of the justice to the final intended purpose, layout and specific require- panels. ments for the ship must be worked out in detailed collaboration with For the construction of ships, the big sandwich panels are cut pre- the customer and be integrated into the design. The potential saving cisely to size according to cAD drawings of the outside skin of the »In comparison to models made conventionally today, the modern GRP ships use only half the fuel. « Dipl.-Ing. (FH) Tina Kohn, Baltec Werft GmbH, Lübeck www.lightweight-design.com Produc tion and Process technology  FIGuRe 1 Thanks to logical lightweight construction Baltec have succeeded in producing ships which use half the fuel of a contemporary model of the same water line length. Above on the left: A200 Workboat with a consumption of 5 litres per sea mile with 20 knots service speed, on the right: P200 pilot boat with a consumption of 5 litres per sea mile with 20 knots service speed FIGuRe 2 By modern lightweight construction draughts de- respective ship, its frames and other individual parts. Due to the veloped pilot‘s catamaran method of construction used spherical and formed surfaces are on- ly available over long sections. Panel manufacturing and cutting is carried out in different workshop areas and can be prepared as se- parate working processes, this optimises time and man hours. In the manufacturing hall the pre-cut components are arranged and posi- Saving potential, covered to 20 years of service: tioned ready for assembly. Ships are constructed in the same way as shipbuilding is commonly carried out- from “inside out” (picture 5). → app. 5.500 tons less CO2 emission yachts and moulded vessels start with the out skin and then cons- → app. 2.000.000 litre less fuel truct the internals. epoxy resin and hardener is mixed in exact → min. 2.000.000 € less operating costs rations by machine and delivered to the joints by hose delivery to join the panels with fillet joints that do not require finishing by hand. The nozzle delivers the correct mixture of resin and hardener under pressure to the joints creating a uniform structural fillet join to join FIGuRe 3 The production of large-size GRP (fibreglass-reinforced plastic) panels together. sandwich panels occurs in a 12 x 2.4-metre heatable vacuum Building the vessel in this manner reduces the amount of liquid re- press. sins and hand laminates within the construction process. The prefor- med panels are already cured thus reducing the exposure of em- ployees to touching the resins or breathing in the gasses hand lay up causes. Reducing hand contact to resins helps in the reduction of sensitisation to the resins and stops skin irritation. hand lay up is only used where additional strengthening is required, mainly on the outer skin of the vessel too increase stiffness and rigidity. composing the ships occurs in a clean sphere with only little amounts of liquid resins and hand laminates. Thus thanks to the dry panel construction method none of the boat builders is exposed to much to liquid resins and their gases, the contact of resin to skin as well as working clothes is minimised and the accident and allergy FIGuRe 4 core materials and deck laminate risk is strongly reduced. The use of liquid resins by hand is limited to materials can be manufactured strengthening laminates, for example, in the outer hull area or in according to the requirements of constructive stiffening. the panel and its intended use. 3/2008 lightweightdesign  Produc tion and Process technology FIGuRe 5 In the shipbuilding it is worked from “inside out” (on the left: Positioning of the individual parts; middle and on the right: constructive gluing of outside skin to frame by means of epoxy resin) The quALIT y ASSuRAnce of a 20 years service period, GRP sandwich strips were put out in to Das The most frequent failure of the GRP core panel is – as in the a test bed and 10 million dynamic load changes were exerted picture 6 shown – core failure due to shear stresses over a 2-month period. At the end of the test cycle (equivalent to 20 years service) no fatigue symptoms were visible on the external deck laminates, nor in the core material. Also no remaining distortion was recognizable; the material still retained its original shape. A final comparison bending test was also carried out at the end showing only about 10 % less strength, which given the fact the material was 4 times stronger than originally required is insignificant in the scale of longevity of the products life.