TY - THES ID - 148646615 TI - Master thesis : The Hull Optimisation for an Open 60 IMOCA Single Handed Race yacht AU - Gournay, Lazare AU - BARKLEY, Giles AU - Gentaz, Lionel AU - Bonnefoy, Fabien AU - Boote, Dario PY - 2022 PB - Liège Université de Liège (ULiège) DB - UniCat KW - Sailing yacht design, Open 60 IMOCA hull form design, hydrofoil design, Velocity Prediction Program (VPP), performance prediction, foil lifting-line theory, theoretical model development for hydrofoil performance prediction, hull optimisation, experimental hydrodynamics, tank testing. KW - Ingénierie, informatique & technologie > Ingénierie mécanique UR - https://www.unicat.be/uniCat?func=search&query=sysid:148646615 AB - This paper investigates the benefits of using modern foils on an IMOCA 60 sailing boat. This was achieved for a designed IMOCA hull form, and designed foils, using different approaches.

A parametric study and researches on existing IMOCA 60 was first realised. Different hull forms were then modelled in the nurbs-based hull form modelling software Maxsurf. They were investigated through VPP analyses to determine the fastest design. Two of them are the reversed engineered hull forms of Hugo Boss and L'Occitane. They were used as reference to validate the design, by comparing the boat speeds found using the designed hull and these reference ones, in various sailing configurations (headings and wind speeds) chosen in the VPP.

The selected hull form design was manufactured at model scale (1:10) using composite materials, to be tank tested with its keel and foil. Tank tests were realised with and without the foil, at different boat speeds, heel angles, and leeway angles. The data recorded during the tests comprises the total drag, the side force, the roll (or righting) moment, the heave, and the pitch of the boat.
The data measured without foil was subtracted from the one measured with foil, which allowed to determine the effect of the foil on the boat. 

Meanwhile, a theoretical model was developed under the assumptions of the lifting-line theory, to try to predict the hydrodynamic forces generated by the designed foil, and their influence on the overall righting moment of the boat. The results were compared to the experimental foil results, which allowed to validate the model.

Finally, “direct experimental“ VPP analyses were performed based on the experimental data found with and without foil. It enabled to find the gains in boat speed due to the foil, in various sailing configurations. The influence of the righting lever ($GZ$) was also investigated.

%Add the main findings!!
After two iterations including a re-design process, the designed hull form proved to be relatively fast compared to the reversed engineered hull forms. 
Moreover, it was found that the developed theoretical model provides realistic trends when compared to the experimental foil results. The theoretical foil results generally overestimated the experimental ones, which means that the foil was slightly less efficient than predicted in theory. 
The direct experimental VPP analyses showed that the designed foils globally increased the boat speeds, when the increase in $GZ$ was accounted for. 
However, a few boat speeds were smaller with foil than without it, regardless of the $GZ$ values used. It was found to correspond to configurations (boat speeds, heel, and leeway angles) in which the foil ventilated in the tank.
The downwind speeds were unchanged since the foil was not immersed at the corresponding small heel angles. Hence, a design modification was proposed to solve that issue, and also benefit from the lift of the foils when sailing downwind. ER -