The 2022 ORC champion Intermezzo in the shed for major alterations to the original Landmark 43 keel… actually not so major when the cost of this solution is compared with the expense of replacing the original keel with a brand new one. For a competent builder with reasonable composites experience this procedure is straightforward, and by diligent use of machined templates the results should accurately match the designer’s new profiles. While the fin is given modern hollowed-out aft sections, the keel area is being enlarged to make lane-holding easier and make a heavy-ish 43-footer more forgiving, particularly speed-building out of a manoeuvre
in ORC is a combination of high stability, deep draught and low weight. ‘You might argue that these are the main
factors to make a boat go really fast, so why would the rule make them unattrac- tive? I think the answer to that is that the rulemakers want to ensure a situation where the majority of existing boats always remain competitive. And most boats on the market are more conservative designs that spend their lives in displacement mode. ‘Or put it another way: the rule works
with formulas that are supposed to predict performance – for example, how weight affects performance. To develop a formula or set of formulas that can handle all the parameters you would have to look at the majority of the actual fleet; there will be some outliers, but the majority of the boats are pretty close and react the same way to certain changes. ‘So when you enter a boat with a radi-
cally different design the rule may now suddenly be a lot less accurate. This focus on “the majority” does also act as a kind of cost control factor. I imagine that the people who wrote the rule made sure that you couldn’t win by going to the extremes. ‘Eventually I think that would have killed the ORC rule. Any rule actually.’
Faster or slower? So to sum up: if you want to do well in ORC or IRC the first thing is to choose the right boat from the beginning. There are certain boats that will have an advantage, and others that will have a disadvantage. If you have a well fitted-out boat, let’s say an X-41, which is an older design that can be purchased in good shape for around ⇔150,000, what can you actually do to give it an extra edge? ‘First of all,’ says Nielsen, ‘there are
basically two kinds of optimisation: one is about optimising your experience of the
50 SEAHORSE
boat, to simply make it sail better with no attention to any rating rules. The other is to look at the rating and see where a gain on the certificate could be bigger than the loss in seconds on the racecourse. Often this results in making the boat slower; less often the opposite can also be the case.’
Keel, rudder, internal ballast and sailplan ‘But let’s look at potential speed gains first. For that I would start under the waterline,’ says Nielsen. ‘The keel and rudder are areas where large gains can be made, they are comparable to the tyres of a car and most people tend to neglect this fact. Optimisations of the appendages are not just to obtain a better rating, but to improve overall performance. ‘I would also take a closer look at the
ballast situation under-deck, to see if there are gains to be made by increasing, reducing or moving internal ballast. This could mean reducing stability to obtain a better rating; an old story we are too familiar with! And last, but certainly not least, the sailplan is obviously very important. Currently we are working a lot on the size and type of ORC spinnakers. Of course jibs and mainsails can also be optimised, often quite simply by adjusting the location of the head or tack, or by making new sails bigger or smaller.’
Gut feeling is (still) necessary ‘I usually test different scenarios by run- ning them through the ORC VPP and then compare the results to the output of the other VPPs that I can access. ‘Of course it is the ORC VPP software
that ultimately decides the rating. I can test every parameter on my computer, so I can, just as an example, change the P measure- ment and see what the consequence would be for the rating. Whether this is a good idea or not – in other words, to estimate
how this will affect real speed potential on the water, and under various conditions – well, that is to a large degree a question of gut feeling, based on experience, judge- ment and common sense. Yes, there are modern tools that help here, but even in 2023 the wind and waves are hard to model to a respectable scientific level. ‘We can measure and quantify certain
things, though, with reasonable confi- dence. For example, we know that a bigger spinnaker gives a better performance at open wind angles, and we also know that this is not punished very hard under ORC. Largely this rule also has a hard time esti- mating when a boat is capable of planing… ‘But other things are more a question of
belief. Of course it helps to have the right tools. In my toolbox I have something a lot of other designers still haven’t got, my own Computational Fluid software (CFD). This allows me to visualise flow and calculate lift and drag in different scenarios more precisely… but much of the practical value is still in the interpretation.’
Back to appendages… I would like to hear a bit more about how keel and rudder optimisation is actually done. Nielsen immediately starts sketching on the notepad. ‘Mostly we laser scan the boats to get a
digitised version of the design – our high- profile projects like Intermezzowill always begin with a laser scan. Often the keel turns out to be asymmetric or crooked, as it comes from the boatyards. The original keel fins are usually cast iron, and they can easily distort a little during the casting process. So with our digitised version of the boat we are able to start our actual design work with more confidence. ‘There are several ways to create a new
or optimised keel profile. The easiest – and cheapest – is to simply put a new profile on
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