2. Technological Tools used
FoX is at the forefront of advanced technology, using the latest and most efficient tools available in yacht design.
3D-Conception and drawings (CAD):
Every project undertaken uses 3-dimensional design from the first to the lastest steps, from the initial hull design to the deck equipment details. These computer powered tools can calculate very quickly and efficiently the volumes and hull parameters, therefore enabling significant time savings and efficiency gains for the designer.
In more concrete terms, hull shapes can be defined by their parameters as much as by their lines; hull parameters are thus easily and efficiently modified and optimised. Furthermore, the inside and outside geometry of the yacht can be modelled directly in 3-dimensions, enabling a better evaluation of distances and volumes.
Structural analysis and scantlings:
Because the reliability and lifespan of our designs are our primary concerns, all the structural work is done accordingly with the classification society rules and guides. We work particularly with the ISO 12-215 and the ABS (American Bureau of Shipping) guide for most of the wood and composite yachts.
Such an approach can guaranty the strength and integrity of every boat designed and makes easier the necessary ratifications.
When a deeper analysis of the local stresses on complicated structures, FEA methods are used to refine the structural layout and details towards a lighter weight and better response to the loads.
Performance predictions – VPP:
Racing yachts projects are all developed using velocity prediction software. (VPP) Such programs are able to simulate and synthesize the forces applied to the yachts (aero and hydrodynamic lift and drag, heel and yaw angles) and to predict their performances. This enables the designer to choose and validate critical design parameters. (for example estimating the gain obtained by a wider hull that will increase stability but also increase the drag)
FoX Tech works on developing its own VPP software.
Experimental techniques: Towing Tank and Wind Tunnel:
FoX Tech is also able to undertake series of tests in the towing tank or in the wind tunnel. Our engineers are able to perform the experiments and use numerical scaling procedures to predict full size performances.
Aero and/or hydrodynamic performances can thus be obtained accurately and fed into a VPP program in order to obtain more accurate predictions. A fine and detailed analysis of the yacht performances can hence be performed.
The towing tank is a testing platform to test hull shapes or several appendages layout.
(Courtesy from C. Leflot)
Wind tunnel tests enables evaluation of the performances of sail plans, allow the testing and comparison of different shapes as well as finding the optimum range of use and the best trim.
Efficiency of particular appendage geometries can also be evaluated.
Flow modelling and simulations – CFD :
Postgraduates in CFD (Computational fluid dynamics), most of our engineers are familiar with the numerical methods and several modelling schemes that enable the modelling of flow streamlines around bodies. (Sails, appendages, etc...) Such techniques can be used in the development of appendage sections and planforms, bulb shapes, sail plans, etc.
Several types of CFD tools can be used: Lifting line, Panel codes or commercial R.A.N.S. flow solvers.
(2D Flow past a cut of mumm30 sail plan while reaching)
(3D Flow around Spinnaker + Mainsail)
We are able to handle panel codes as well as RANSE flow simulation tools and are experienced at using the main commercial software such as Fluent or CFX. We also develop as much as we can our in-house tools and optimisation programs, such as FoX VLM.
For sails and sail plans evaluation and optimisation, the panel code FoX VLM, developed by our engineers in collaboration with DELTA voiles divides the sail plan into small panels and analyses the air flow on both side of each panel. The flow speed is then calculated and the pressure on the surface of each panel can be found and computed over the whole sail plan so as to find the forces experienced by the whole sail plan. Such a tool enables us to calculate the lift and induced drag of a sail plan, taking the root and tip vortex into account as well as the sails interactions.
Upwind performances of a sail plan can thus be calculated and several sail plans can be compared.
