Sunreef's naval architects team deals with hull design, stability, weight and all structural calculations, construction material integrated testing as well as sails and deck plans. Then, production drawings are made in 2D and 3D tools and forwarded to technicians and engineers supervising the production process.
Hull design
Designing the hull shape so that the yacht can be performant, seaworthy and comfortable is a complex process involving a large number of important decisions about shape, structure, materials and processes. The purpose of the design process is to optimise the performance and reliability of the hull, taking into account the structure as a whole, and also to minimise the cost price and reduce weight.
In the design stage, the greatest challenge is to find the perfect balance between aerodynamics and hydrodynamics, combining all the elements into one single unit. The aerodynamic properties are crucial in determining how well the sails can extract energy from the wind. The hydrodynamic properties define how the hull can transfer this energy into speed.
Design, materials and processes are closely linked, and this is particularly clear in the development of Sunreef yachts models. With the necessary know-how available in-house, we can take into account specific hull performance requirements right from the beginning, in the early stages of when a mould or other production equipment is developed. The fact that we have this expertise in-house also lets us benefit from the experience acquired in all the different phases of developing and producing a new hull design. Similarly, optimizing the production process can have an important influence on the overall design.
Integrated calculations
Applied aero- and hydrodynamics
At the start of a hull project, our customer shares with us the specifications for the yacht's purpose. We can use these specifications to perform initial calculations of the geometry and structure.
The hydrodynamic design of the yacht's hull defines its wetted surface area, under water ratio of the hull and the profile of the appendices. It is a matter of finding the best compromise between water and air flow, strength and weight (aerodynamics, hydrodynamics and structure). The purpose is to optimise performance while minimising weight and loads.
All Sunreef's hydroaerodynamic models and calculations are kept in our design database. This allows to provide our customers with preliminary designs in a very short time and to a high level of precision.
CFD 3D Calculations
CFD calculations are performed in the design phase in order to determine the interaction between the hull and the sails. Computational Fluid Dynamics (CFD) simulations can be used to determine how the wind and water forces affect the boat. The results are used to adjust the hydro and aerodynamic design of respectively the hull and the sails.
Sunreef's Naval Architecture bureau prepare the integrated calculation of aerodynamics, structure, loads and the control system jointly with best specialists in the domain.
At Sunreef Yachts, all information is collected in a single database. This translates into a consistent dataflow:
- greater precision and more refined calculations
- greater clarity (tracking the design process)
- faster calculations.
FEA Calculations
During the last few years, Sunreef Naval Architecture Bureau have worked with reliable partners on Finite Element Analyses, in order to help the design team face the main critical issues ensuring that structural regulations are met and to assess, by means of direct calculations, compliance with regulations for alternative design. FEA is applied to the whole or to a part of the yacht's structure to have an accurate analytical prediction of its structural behavior.
This methodology allows the strength of the yacht structure and the dynamic behavior in typical load scenarios to be studied by using the currently available data; in particular, considerations are made on: the ultimate strength of yachts, the response to the slamming load and the global vibration analysis.
Advanced Composites Construction materials
The philosophy behind the way Sunreef Yachts selects materials is basically very simple. It is based on stable, well-tested materials that provide the best possible balance between price and performance. Via smart engineering, we ”stretch” what the materials are capable of and continually expand the envelope of what can be achieved.
Fibre technology:
Glass fibre is a strong, versatile material, and it is important that we develop these properties still further. This will help boost the quality of the hull we produce and also keep costs down. We achieve this via the analysis of both the glass fibre and resin. This provide us with in-depth knowledge about the exact properties of these key materials, as well as a clear picture of how they will perform in large-scale composite structures. Our current focus includes the tensile strength of the fibres and the overall structure.
Our testing and analysis work helps us find any weak points in existing materials, so that we can eliminate them. It also leads us to requirements for improvements in specific materials properties. We pass these on to our suppliers, and work closely with them to make it all happen.
Resin:
Glass fibre and polyester or carbon fibre and epoxy play a key role in Sunreef's construction technologies. Our starting point is low-cost materials that we can get to perform even better. We have decided to invest in "smart engineering". Via research into design, materials and processes, we focus on optimising cheaper technology so that we can reduce the overall price of the hull while at the same time maintaining the best performance properties.
Resin's properties have an impact on both the efficiency of the process and the quality of the end product. We have therefore involved our suppliers in focused efforts to set out specifications for optimising resin and fibre for our own processes.
By combining optimisation of the resin with
vacuum infusion, we have been able to create a very strong, uniform laminate with no defects. We have also achieved more rapid hardening, which has reduced production time by several weeks.
Aluminium materials
For the production of aluminum hulls, superstructures and other yacht equipment, we use widely known and highly appreciated types of aluminum alloy such as Sealium® and Alustar® among others which have become the international industry standard for large cruising yachts. These types of alloy optimise the overall performance of vessels in general as they make them more robust, safer, and user-friendly.
Sealium® and/or Alustar® alloy advantages:
- Higher welded yield strength than standard 5083 alloy
- Proven improved corrosion resistance
- Increased fatigue strength
- Same usage proprieties (formability and welding) than 5083 alloy
The characteristics of aluminium provide the best safety guarantee for the yacht:
- Rigidity : an aluminium hull is an extremely rigid object that does not suffer from
distortion caused by the ballast, the rigging or the sea state. This is the ultimate
guarantee of safety for your yacht and the durability of your hull and of its interior
fittings.
- The capacity of aluminium to absorb shocks without rupturing is one of the biggest
advantages of aluminium hulls in encounters with containers, tree trunks, etc.
- The density of aluminium (2.7) is low and offers the benefits of the other advantages
of aluminium without increasing the weight of the boat.
Working on Aluminium:
Preparation
Before any workshop actions performed, complete set of drawings and instructions is being prepared in our Naval engineering department. All parts of construction are carefully designed. Our naval engineers are considering all load cases that not existing construction will have to take. When we are sure that everything is in its place we are sending full set of elements for CNC cutting.
Depending on size, type of material and destination of element we are using different machines for cutting: water, laser or plasma. All materials used (plates and profiles) must be certified so we are sure that they comply with mechanical characterisctics used for previous calculations. Materials we are using have been approved by the major classification societies: American Bureau of Shipping, USA , Bureau Veritas, France, Det Norske Veritas, Norway, Germanisher Lloyd, Germany, Lloyds Register of Shipping, UK, Nippon Kaiji Kyokai, Japan, Registro Italiano Navale, Italy.
Building process
All welds of construction are done according to plans and instructions previously approved by Certifying Society, in our case usually it's Bureau Veritas (BV). All welders working on construction are aluminium welders cerified by BV. We are taking care to create welding friendly environment: dust free, low humidity and themperature close to 15°C
Quality control of built sections
All prefabricated elements are checked up if they were built in accordance with workshop instructions. Depending on area, type of weld and level of stress in certain area our Naval engineers and/or independend certified specialists are performing non destructive tests on welden construction. All welds are checked up for welding failures by visual test with penetrant fluid.
All butt welds on the shell of the boat are checked with ultrasoud scanner and areas of highest risk of welding failure are x-rayed to be sure that everything is according to high quality standarts. If its requaired by notified body (BV) independent specialists are carrying out tests and prepairing report of results.
All actions performed from designing construction, cutting, building are carried out in a way to build high quality aluminium construction which will serve its owner for many years.
Integrated testing
It's often the small details that lead to major technology breakthroughs. That's why test a bank of materials before choosing the optimal ones which apply to the highest standards of yacht building, as part of our analysis of their overall properties. This helps reveal how these materials will perform when used in large-scale composite or aluminum structures, paving the way to achieving the best possible quality.
To study these properties, we work with specialised companies to create a special test model, which then undergoes a range of different tests. Part of these involves a special pull-and-push testing machine that uses computer-controlled servo-hydraulics to test the strength and stiffness of a particular material.
Boundary areas, such as glued joints and interfaces between laminates and the core material, have a critical influence on the overall structural strength of a hull. Sunreef Yachts production complies with Bureau Veritas quality requirements as for testing mechanical breaking strength. This method introduces different loadings using force moments, which makes it possible to apply well-defined loads in several different axes at once. These correspond to the forces that act on the hull while in real-life operation.
Non-destructive testing (NDT):
NDT is a general term that describes test methods that do not damage the item tested. At Sunreef Yachts, we use different kinds of electronic NDT to complement visual and manual quality assurance, for example during the final inspection of the adhesive joints, laminates, aluminum welding and geometry of the hull.
Composite hull testing:
- Ultrasound scanning of the laminate
- Digital hammering
Aluminum hull testing:
- X-Ray scanning
- Ultrasound scanning of the butt welds,
- Visual test with penetrant fluid
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