Seaworthiness

Heavy Weather Dynamics: Too Fast on the Run

Heavy Weather Dynamics: Too Fast on the Run

This article is a follow-up from Heavy Weather Dynamics: Yachts in Following Seas published some months ago. It has since become one the most read items on this site. While the original article applied to most sea-going monohulls, the following discusses more specifically fast modern hulls, or yachts in very fast following seas, such as can […]

Heavy Weather Dynamics: Upwind Sailing, Windage and Resistance

Heavy Weather Dynamics: Upwind Sailing, Windage and Resistance

With tropical cruising becoming increasingly popular and accessible in the last 2-3 decades, trends have developed in outfitting yachts for ocean cruising. Some of these trends that originated from sailing in moderate settled weather areas have resulted in significantly increased risks when a vessel is caught in severe conditions. Many of today’s cruising yachts, whether […]

Heavy Weather Dynamics: Yachts in Following Seas

Heavy Weather Dynamics: Yachts in Following Seas

This article deals with some of the physics involved when a yacht is running before the sea, especially in heavy weather when waves are long and their front faces become steep. Yachts running in heavy weather and following seas face challenges that are very dependent on the characteristics of the design; the ability of the crew […]

Transverse Stability, Part 4: Sailing Yachts at Sea

Transverse Stability, Part 4: Sailing Yachts at Sea

This article follows Transverse Stability, Part 3: Dynamic Stability Part 3 of this series dealt with changes in transverse stability taking place once a vessel starts travelling through the water. This article discusses the way the stability of sailing yachts can be challenged at sea as a result of wave action. Wave action doesn’t reduce […]

Transverse Stability, Part 3: Dynamic Stability

Transverse Stability, Part 3: Dynamic Stability

This article follows Transverse Stability, Part 2: Stability Curve and Knock-Down Energy If you are looking for information regarding the stability of monohull yachts hit or capsized in beam seas, the subject is treated in the next part, Transverse Stability, Part 4: Sailing Yachts at Sea. In the case of monohulls, regardless of the type […]

Design Overview

Design Overview

The sloop Nordkyn is a 13-metre (43′) round-bilge alloy yacht with a displacement of about 8600kg half-loaded in cruising trim. It features a fixed bulb keel with a draft of 2.35m (7′ 9”) and a single deep spade rudder. The alloy construction is very robust without being heavy and the deck is integral to the aluminium […]

Offshore Weather: Sailing Near the Limit

Offshore Weather: Sailing Near the Limit

Sailing over 55,000NM in seven years on board the 9-metre sloop Yarra between the Arctic and the Antarctic resulted in a fair share of strong winds and rough seas at times. I managed to wear a set of hanks on my storm jib and pull my new #2 jib out of shape. Even so, wind […]

Development

Development

Hull shape is the largest contributor to success or failure in yacht design. Appendages can be replaced, rigs modified, but a bad hull is usually where the buck stops. It is just as true for motor vessels. The design of the Nordkyn hull was underpinned by two key objectives: exceptional seakeeping properties and excellent light […]

Transverse Stability, Part 2: Stability Curve and Knock-Down Energy

Transverse Stability, Part 2: Stability Curve and Knock-Down Energy

This article follows Transverse Stability Part 1: Fundamentals The most relevant way of expressing the relation between heel and stability for a given vessel is plotting the GZ-curve or the righting moment curve. Ships and load-carrying vessels start from KN-curves, because they allow taking into account large variations in trim and loading, but at the […]

Transverse Stability, Part 1: Fundamentals

Transverse Stability, Part 1: Fundamentals

Transverse stability is the ability of a vessel to resist and recover from heeling over. It important in the sense that this is what prevents a vessel rolling over and capsizing. For sailing vessels, stability is also needed to develop power under sail other than downwind. Stability is a force moment, i.e. forces separated by […]