Staying Safe While Sailing Nacra 17

Keeping safe while sailing is a core value of the Nacra 17 Class Association. As the fastest and heaviest Olympic sailing event, we are dealing with higher energy levels than many of our sailors have sailed with in the past. The higher the energy levels present on a boat, the greater the potential there is for a serious safety incident, with energy being equal to mass times velocity squared. We strongly encourage all sailors to report all safety incidents on the World Sailing portal so that we can all gain access to direct knowledge of the risks encountered while sailing.

The sailors on the Nacra 17 circuit are typically highly experienced in complex and potentially dangerous styles of sailing. Many sailors and coaches have experience in elite professional sailing circuits, like the America’s Cup, Sail GP, Volvo Ocean Race, GC32, and M32. They bring and share this experience to the Nacra 17 circuit, and as a class we aim to provide a safety culture suitable for this higher risk style of that comes with foiling and speed.

Highest Risk Case

The highest known current risk for Nacra 17 sailing is from a severe cut to a sailor after falling off the boat and being hit by the rudder and/or elevator. There have been roughly 20 foil strike incidents since the class went foiling, with at least 5 requiring stitches to the sailors who were struck. Three of these incidents required more than 30 stitches to repair large cuts. There are two things sailors should do to decrease the likelihood of a serious incident from the rudder strikes.

a) Reduce the frequency of falling overboard. Sailor should diligently and professionally set up and maintain their trapezing equipment. Each piece of equipment in the trapeze system, from the fitting attached to the mast to the trapeze being worn should be regularly inspected and be specified to handle the impact and point loads that are applied to it. Sailors should pay particular attention to the trapeze bails and trapeze hooks, as to date these have been the more common points of failure, though there have been other points of failure as well.

b) Wear protective clothing to reduce the risk of bad cuts. Falling overboard is a part of our sport. On the Nacra 17 it is most likely from missing a tapeze clip, or being knocked out of a trapeze by a wave, or falling off during a maneuver when not clipped in. Sailors should wear cut resistant clothing and/or impact protective clothing to reduce the risk of a severe cut. Most of the cuts have been to the backs of sailors legs, and therefore this area should be protected at all times while sailing.

Root Causes

When the Nacra 17 was evolved to full foiling, a number of changes to the specification of the boat were introduced, some of which have lead to the increase in serious foil strike incidents.

a) The rudders are now fixed.

The 2016 Nacra 17 rudders were a ‘kick up’ style, and when they were struck with large force, would kick up. This is typical in catamaran design. When the boat evolved for 2020, a kick up style rudder is no longer possible, with the large upward forces derived from the elevators, and need for secure rudder mounting from foiling at high speeds. There is no known kick up system that handles the loads of foiling and breaks away upon impact. As such, when sailors now fall overboard and are struck by the rudder, it impacts with the full force of the boat onto the sailor, unlike before.

Furthermore, kick up style rudders are not deemed a suitable option for foiling catamarans, as the moment a leeward foil kicks up, the boat can become uncontrollable by the sailors on board. This can have serious safety implication for those sailors and any other boats in the vicinity of an incident. Therefore, kick up or breakaway style rudders have been ruled out as an option for the Nacra 17.

b) The rudders are mounted at the outboard edge of the hulls.

The placement of the rudders is at the extreme outboard edge of the hulls, to keep the rudders operating in water unaffected by the wake of the daggerboards. For sailors falling overboard, this make foil strike incidents more likely, as the rudders are closer to the area that sailors might fall into.

c) The rudders have a T elevator, it is sharp, and has a torpedo in the center.

T elevators are more efficient than L elevators, both hydrodynamically and structurally. As such, a T design was chosen for the 2020 Nacra 17 spec. This puts the most outboard edge of the elevator farther outboard than the rudder vertical, and closer to the area a sailor is most likely to fall into.

The center of the T elevator protrudes forward like a ‘torpedo’, which helps in structure and hydrodynamically. This element has also been implicated in some injury reports due to increased point loading of an impact.

For the 2024 update, it is likely that the rudder design will change to an L shape, so more the most outboard elements of the elevator are brought inboard. Additionally, the torpedo will be removed, and the overall leading edge shape will be blunter than the 2020 version. In November of 2018, active sailors were surveyed about the option of introducing a partially asymmetric elevator, without a torpedo and with a blunter shape for use until Tokyo, but rejected the change by a 3:1 ratio.