Tight groove
Would tend to agree with Alan. The X-yachts IOR boats are designed very much to that rule. Look at the entry, forward. It is likely flat - like a NY 36. Large sections of the hull bottom are also likely to be flat or straight because of the way hulls are measured under IOR. Other parts of the boat are designed to be fast, so in order to sail to its rating, it has to be positioned exactly xx in yy amount of wind, with sail adjustments ww and zz to match. A large & heavy crew is needed to keep track of, and make all the necesary adjustments and to keep the boat flat. (Earlier X-Yachts tend to have cast iron keels instead of lead - making hiking more important.) On deck, systems & sailhandling are typically well thought-out and seamanlike - but they need to be in order to have the boat perform. X-Yachts IOR designs haven't done as well as they perhaps could, because you have to be quite good to get the most out of them, and really keep at it, because they sail in such a narrow optimal groove. Nice boats, though.
