The 13-metre alloy sloop Nordkyn is the outcome a personal design and build project. In short, I wanted a new ocean cruising and voyaging yacht suitable for the type of sailing illustrated by the voyage of the sloop Yarra.
The project had a long gestation period and involved development far beyond what would have been commercially viable for a one-off. The result also reflects this.
The sloop Nordkyn was not designed to meet a long list of requirements. It was designed for sailing and shaped by experience at sea
Seakeeping performance and survivability considerations led to the design of the hull, appendages and rig. The rest is mostly details and, while those received plenty of attention, they were not allowed to interfere or compromise the essential.
An awesome sea boat first and foremost, superb seakeeping characteristics, a boat to go to sea, stay at sea and live at sea for extended periods. Long passages often go hand-in-hand with high-latitude sailing, they take you there in the first place and get you out once the season is over – unless you tuck away for the winter.
Conditions at sea in the high latitudes are not always good, and can be terrible on occasions. The opposite is also true, some areas are under the influence of the polar anticyclones and are notorious for endless very light and variable winds, and this prompts for a boat that is also able to excel in light weather.
- A boat fun and rewarding to sail, sharp, precise and responsive to tuning. A boat that would handle like a thoroughbred.
- A boat structurally strong and resilient in terms of construction.
- Good carrying capacity for food and supplies and decent room on board. The sloop Yarra could carry over a year’s worth of provisions for myself in addition to sailing gear, documents, tools and spares, but it was somewhat overloaded and couldn’t have accommodated another person on board.
- A comfortable boat: good motion at sea, no insane rolling or pounding, moderate heel under way, good living space, good insulation, a bright interior and a view outside from down-below.
- A simple, reliable, practical boat throughout: simple to manoeuvre single-handed, reduced interdependencies, no complex systems. In short, as little as possible that could go wrong, cause grief or require maintenance.
I didn’t want…
What I didn’t want was a huge boat
There is a relation between boat size, usability and enjoyment. It is not a case of bigger is better, there is an optimum that varies with people and the intended use for the boat. I would also suggest that – for hands-on owners undertaking personal cruising programmes – the peak moves to the left with experience and difficulty in the intended voyage, but it does remain a personal measure.
I like sailing short-handed to areas that are sometimes difficult and I designed Nordkyn to be as small as possible while still being everything I was after. It started at 14 metres, at some point I tried to bring it down to 12.5 metres, but I needed 13 metres to make it work. I gained a metre towards my optimum and I am glad I did.
The metre I lost was prompting a larger rig, larger sails and winches, without adding much of actual value to me.
Seaworthiness, understood here as dynamic handling or seakeeping performance, is still the non-quantified factor in yacht design.
The amount of attention that goes into the design of hull shapes today is often insufficient or inadequate
Since the early 1980s, systematic quantitative experiments have been performed to understand how hull resistance relates to shape over a range of speeds. This work, mostly carried out at the Delft University of Technology in the Netherlands, is still one of the most practically significant advancements in yacht design today. However, it deals with resistance of upright hulls mostly, in flat water or head waves mostly, and it has limited correlation with the seakeeping properties of the hull out at sea.
In other words, the geometric constraints over the volume distribution of a hull set out by the Delft Systematic Series are necessary conditions to obtain an efficient design, but they are not sufficient in themselves. They are extremely useful for developing potentially fast hull shapes, but the outcome at sea in terms of dynamic handling goes beyond this.
One key issue is that, once a hull heels, its properties can change dramatically from the design figures achieved in the upright condition. Heeled or upright, we are still dealing with an object travelling at the surface of a fluid and creating pressure waves while displacing it. The work from Delft University does not specifically quantify what the heeled hull should look like, but this is not to say that it doesn’t matter or should be left to inspiration.
Some design initiatives, such as the so-called and inept “powerful stern sections”, in fact result in hulls that misbehave significantly in a seaway, typically because they trim down by the bow as they heel.
The Nordkyn Project involved designing an ocean cruising yacht with a hull where the gradual change in characteristics due to heel would be deliberate and contribute positively to seakeeping, while promoting both excellent upwind performance and course stability downwind.
The sloop Nordkyn was designed with no regards whatsoever for racing, ratings or top boat speed, it was developed for seaworthiness and ocean voyaging. However, it was designed to fall into a certain performance class of boats as explained in much more details further and this condition was going to take care of the matter.
In terms of sailing performance, the point is not how fast you can go; it is how slow you don’t go
Speed offshore is a matter of average daily mileage over time. The 9-metre (30′) sloop Yarra was not extraordinarily fast, it just had an insidious way of outperforming a lot of boats over time, most of them larger, even though it would often only travel at around 6.3 knots and practically top out at about 6.8 knots only.
The difference was that it got there quite readily, it climbed upwind quite well and very seldom stopped completely. Over an ocean passage, it often achieved enviable daily averages.
Long ago, I read in an oceanographic magazine that the average wind speed over the oceans of the globe is below 15 knots. It doesn’t sound like much, but there is a huge proportion of light winds and gentle breezes out at sea. When it comes to designing a cruising yacht, it would be absolutely foolish to ignore this detail.
Yarra left northern British Columbia bound for New Zealand non-stop, 6600NM away and averaged over 140NM per day until hitting the Variables coming out of the SE Trade Wind. Some slow days ensued, interspersed with near calms almost all the way to New Zealand afterwards. We made land in Tauranga, after 55 days out, having averaged exactly 5 knots, or 120NM per day. Now, even though a lot of larger cruising yachts are capable of sustaining speeds of 7 or 8 knots, they need more wind than what we had to get to 6 knots and they stop much sooner when conditions soften. This commonly resulted in lower averages on ocean passages.
Daily averages on ocean passages suffer much more from light and variable conditions than bad weather, which is comparatively rare. Sailing ability in light conditions is primordial to achieving good passage times in comfort. A boat under way is much more stable and liveable than one rolling in the sea making no headway or motoring. Concepts such as autonomy under power or fuel carrying capacity are hardly relevant on an efficient sailing yacht.
|Hull Length||13.00 metres|
|Draft||2.35 metres, bulb keel|
|Displacement||8600kg half-loaded, ballast 2600kg|
|Shell material||5083H3 welded marine grade aluminium|
|Interior construction||PVC core/E-Glass sandwich|
|Sail area||Up to 105m² upwind|
|Propulsion||40-55HP diesel, shaft drive and feathering propeller|
|Subdivision||Lazarette, two aft cabins, galley, navigation station, saloon, toilet/shower, workshop area with bench, sail compartment|
|Berths||2 aft double cabins, 1 day bed|
|Ground tackle||45lbs CQR, 80 metres 12mm chain|