Boat design and shipbuilding are one of the oldest human activities. The entire history of civilization is marked by the human desire to sail, to discover new territories, to conquer or defend rich islands, to trade or, very recently, to feel the pure pleasure of sailing.
The Long History of Boat Design
History sources show us that boats served as transportation a long time before antic carriages. The oldest archaeological evidence comes from Indonesia where people were sailing between the islands using ancient canoes . The earliest evidence of sailing activities in the Mediterranean area was discovered in Crete and consists of various quartz tools dated 130,000 years ago .
A Mesolithic petroglyph from Gobustan National Historical-Artistic Preserve, Azerbaijan (12,000 – 7,000 BCE) is considered to be one of the first boat designs . Possibly the oldest recovered boat is a monoxylon canoe – made from a single Scottish pine trunk, discovered and exposed in the Netherlands. The Pesse canoe constructed during the early Mesolithic period sometime between 8200 and 7600 BC . The first mentions of wheels used in transportation come from Mesopotamian chariots built in 3200 BC .
The Art of Building Boats
Following the traditions of the ancient Phoenicians, Egyptians, Vikings, Greeks, Spanish, and Dutch boat builders, the construction of military and commercial vessels has become an art. Consequently, the boat design and construction of today is a tradition preserved for generations. Ships are designed primarily according to their destination. Depending on their capacity and the navigation conditions that they will have to face, boats are designed differently. There are fast-flowing ships designed for rivers, as well as marine vessels suited to sail in the backwaters. Whichever the destination, the boat design should be sturdy enough to face the waves, rocks, and currents in oceans and seas.
Boat Engineering Based on Simulation Methods
From a ship engineering perspective, there are several important factors to consider in boat design. The ship’s materials are highly important. The floating capacity, flexibility, ease of processing, and also the hardness and water resistance are the selection criteria in shipbuilding. Today, there are strikingly similar building designs and construction methodologies to those that were used in the past.
The main difference in design techniques regards prototype testing before launching the ship into the water. History and even old movies reveal that the new boats used to be launched into small basins or directly into the waters at the docks. The probability that a ship would immediately float was quite small, as there were many unpredictable factors.
In modern boat engineering, there is the possibility of testing the materials and boat profile in laboratory conditions or even virtually, using computer simulation tools. Computer simulation, known as Computer-Aided Engineering (CAE), makes it possible to qualitatively test thousands of models to select the best design. Its purpose is to test the boat early in the design process, make the design changes based on the simulation results, with as few physical prototypes as possible and saving both money and time.
The ship hull shape is one of the most important factors influencing the boat’s buoyancy and stability in water and the aspects of its design that need to be considered include:
Flare – water launch increases the boat’s displacement and creates a positive buoyant force to float the boat
Tumblehome – the reverse of flare and is the shape of the hull as it moves outgoing from the gunwale to the water line
Camber – a deck usually curves athwartships, making it higher at the centerline than at the gunwales so the water flows off the deck
Sheer – the curvature of the main deck from the stem to the stern
Length on the waterline (LWL) – the distance from the bow to the stern, measured at the waterline when the boat is stationary. LWL changes as the boat rides high or low in the water.
Length over all (LOA) – is the length of the craft from its stem to its stern in a straight line. LOA does not change according to the way the boat floats in the water
Draft – the depth of the boat from the actual waterline to the bottom of its keel
Draft appendage – the depth of the boat from the actual waterline to the bottom of its keel or other permanent projection.
5 Boat Design Simulations
Other key factors in a boat design analysis are the water flow properties. A better way to visualize the simulation features and advantages in boat design is to discuss the real models. SimScale’s Public Projects library offers thousands of freely available simulation templates across various industries, including shipbuilding. Here you can find already completed boat design simulations, copy them and change the CAD design and set your own specifications. This saves time and also make it easier to perform the simulation. Herewith are a few examples:
This is one of most frequent engineering issues associated with any kind of ship, from small boats to giant transportation or cruise ships.
In this project, it is possible to see how to simulate the behavior of sea waves around a frigate. The ship’s oscillating motion is modelled using the 3D0F solid body motion option, through which the ship’s roll (x-rotation), heave (z-translation), and sway (y-translation) can be specified. The geometry was uploaded to the SimScale platform and meshing was done using snappyHexMesh. Finally, the simulation results can be used to study the impact of waves on the ship.
In traditional boat design, the wave effects on different hull shapes and dimensions are simulated in artificial conditions, trying to reproduce natural environments. One such physical testing tool is the wave tank, a special water reservoir able to host a small or medium-sized boat.
The proposed project simulates the free movement of a floating boat under the influence of a head-on wave via a multiphase 6DoF (degrees of freedom) transient analysis. The model considers the boat as a stationary floating body in a water tank with an open top. A single wave is generated to create disturbance in the water and simulate the motion of the boat. For simplicity of the analysis, a laminar model is used.
The simulation investigates the instantaneous flow of water and the free motion of the boat under the wave disturbance. The results processed with ParaView show the transient changes in phase fraction of water and flow velocities along with the free motion of the boat due to the fluid forces. This simulation shows how the free-floating body motion can be predicted via simulation to provide insight and aid in marine vehicle design and development.
Here is another interesting subject for engineering simulation using a CFD analysis. In this project, it is possible to see how the transient wake formation behind a moving boat can be simulated.
The model highlights the capability of local time-stepping multiphase solver used on the platform. The boat simulated in this case is 4 meters in length. It sails at 3.5 m/s at a heeling angle of 5 degrees. The simulation enables analysis of Kelvin wake formation times and wake patterns within reasonable computation time. The pattern is clearly visible in the snapshots.
Another very interesting project is a multiphase flow analysis around a boat hull. In this case, however, we will not focus on the simulation results, but rather on illustrating the collaborative nature of the SimScale platform.
A user wanted to test the capabilities of the SimScale simulation software by performing a CFD analysis on his own CAD model of a boat. The initial model analyzed a free surface flow around a boat hull to predict the waterline and drag. Two other engineers joined the project initiator, running parallel simulation sessions on the same CAD model. After a few iterations, one of the SimScale engineers proposed a better alternative for the initial model. Eventually, an experienced boat design engineer joined the forum discussion and shared his expertise with the other project participants, improving the model and obtaining improved results for the multiphase flow analysis.
The main purpose of this powerboat study is to predict the resistance and trim angle of a planning hull. In the current sailing activities, one of the most important things for a powerboat driver is to try different trim settings in different sea conditions. Obviously, every boat is different, and the reactions to various trim changes are very different in varying conditions. Efficiency, speed, trim angle, and the smoothness of the boat’s ride are also the subjects of such studies.