CARLO BORLENGHI/ROLEX
ORC
Peak VPP!
Each new year the ORC’s VPP and rules change according to what is discussed and approved in the autumn annual meeting of the various ORC committees. Much of this work will have been done by the International Technical Committee throughout the year, following a predefined research agenda along with new requests made by users of the system. This group of designers and technologists from around the world
is chaired by Andy Claughton, who has summarised the major changes to expect in the latest 2023 version of the rule… Seahorse:We may as well start with the 64 million dollar question… will the ORC fleet be happy when they see their 2023 ratings? Andy Claughton: As usual 50 per cent of the boats will feel OK and the other 50 per cent less so… to a lesser or greater degree! Altruism is not much in play when it comes to managing any handicap system. As a general policy ORC tries not to change ratings for the bulk of the fleet by more than 0.5% with each new iteration. This overall goal helps to stabilise changes year to year while still steadily improving rating accuracy based on our research. While it’s naive to think anyone will be cracking open the champagne, many design types that hitherto have sat some distance from the mainstream are more realistically treated in 2023 than in previous years. The three major improvements to this year’s VPP are: a further
upgrade to the Residuary Resistance force model; full implemen- tation of the CFD-based aero depowering model; and a further refine- ment of sail force coefficients for flying headsails. Taken jointly these refinements have got us to the point where there are no longer any ‘subjective’ elements left in our VPP code – a weakness in any system and an obvious target for customer complaints. Every force model is now based on plausible and appropriate
physics, with no areas left where we need to develop new concepts. With these tools and improved software we are now able to generate speed predictions for an enormous variety of raceboat types:
30 SEAHORSE
everything from sportboats to superyachts, foiling and non-foiling, and now multihulls too. In this sense I think we’ve reached ‘peak VPP’ in terms of what is and isn’t possible with current technology. SH:Peak VPP… what happens as new design innovations inevitably come into play? AC: I am simply referring to having done the heavy lifting in the research and modelling. We now have a VPP that could be refined further but it is doing a good job for the majority of the boats that we rate. To spend more time and treasure now on more refinements may not pay off in significant improvements in ratings. To borrow a phrase from Formula One, we have reached a ‘hygiene level’ for all parts of the VPP code; it’s not perfect, and is more perfect for some boat types than others. But there is nothing in there that is really holding us back. But it’s a good point to flag up around real innovations, because
new ideas are popping up all the time. I think because our VPP is complex and able to characterise the performance of our existing fleet reasonably well there is much less typeforming pressure and few avenues for work-arounds that are not already covered. For example, flying headsails: these sails with mid-girth to foot
ratios above 55% are very cost-effective for the owner who is both racing and cruising. We have worked hard to get the VPP to set these sails at the appropriate apparent wind angles so that the owners can build the sails that suit the boat, without taking an i - nappropriate handicap hit. SH:Can ORC overcome its reputation for being over-complex? There is still an awful lot to measure, plus the multiple options in scoring continue to confuse sailors and race managers… AC: The ORC system must necessarily be complex to predict the performance of any boat, on any point of sail in winds between 6 and 20kt. ORC measurements are complex because the more details we know the better we are able to model performance. For
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