the angle of the dangle

Merf Owen from Owen Clarke Design takes you inside the world of design fine tuning

angle of the dangleThe IMOCA60 Class has a complicated set of appendages: with canted and tilted keels, cambered dagger-boards that can be designed to be fitted to the hull in different orientations and toed in and twin rudders that can also be configured in different orientations. The relative balance between the appendages varies with boat speed and is also affected by the running trim of the boat, which varies with the hull design and ballast tank usage.

This paper describes the development process that was followed to tune the appendage configurations for a new Owen Clarke design, starting from the known performance of previous designs, through VPP predictions and sail selection charts for different sailing conditions to tank test setups and CFD calculations of relative appendage loadings. Results from tests and calculations will be presented with discussion of correlation of findings, tempered by the reality of knowledge from sailing these high-performance ocean racing yachts. Read on.