Best known as the designer of fast IRC yachts – and a mighty good ACC design for Shosholoza done on a shoestring – Jason Ker is now taking a look at the ORCi rating system...

Earlier this year we had reason to take a fresh look at the VPP-based ORCi rule, which continues to be popular in the eastern Mediterranean and Baltic, and subsequently carried out an in-depth analysis of the rule’s strengths, weakness and opportunities, using Numeca’s highly accurate FINE-Marine RANS CFD code on our own computer cluster to probe for errors and opportunities within the algorithms.

An effective process we use for designing to any rule is to first identify the unrated aspects and maximise or minimise accordingly, then using a combination of judgement, experience and analysis we maximise the underrated attributes and minimise the overrated effects, all while meeting the client’s brief in terms of size, budget, competition and ease of use.

Designing to ORCi requires a totally different approach to IRC. IRC has a similar number of measurements to a typical box rule, so after setting our own box limits according to studies of the design space, we proceed as if it were a box rule design and we simply maximise performance within the limits of the box...

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