BASIC PRINCIPLE OF SHELL DESIGN

Rowing shells, and in fact all paddling sports, utilize displacement hull designs that are focused on producing the maximum possible speed without enabling the hull to hydroplane. As a result, the theory of shell design is based on a few key factors.

1) Reducing drag created by the two drag factors of Wave Making Drag and Frictional Drag

2) Producing a stable and comfortable enough platform to support ideal athlete bio-mechanics

3) Creating a seaworthy platform that can sustain performance in a variety of different water and weather conditions

WAVE DRAG vs FRICTIONAL DRAG

Wave drag is unavoidable in paddle sports as the only way to eliminate this drag all together is to build a hydroplaning design which is prohibited under FISA design rules. This accounts for the general design of rowing shells being relatively long and narrow. Shorter hulls will create less friction but will produce greater wave drag and longer hulls will reduce wave drag to a minimum while increasing friction, Thus all designs are somewhat of a tradeoff between the two types of drag where the designers aim to find a sweet spot between the two AND ideally create a stable enough platform to perform. In most rowing shells the wave drag accounts for only about 15% of the total drag with friction accounting for the remaining 85%. Frictional drag is primarily a function of wetted surface area. In this area, builders have the ability to minimize wetter surface to some degree however the rower’s weight and the weight of the shell are far larger determinants of total wetted surface. Here the shell’s shape comes into play as well with deeper narrower hulls beating out wider hulls for speed but losing to them in stability (again a trade off) Boat builders were tempted in recent decades to build shorter/wider shells that had the same the wetted surface area but offered better stability (IE Resolute or Vespoli E Hull). Shorter hulls however produce greater wave drag and so most shell designs in recent years have sought to find a more happy medium to find a “sweet spot” that reduces BOTH types of drag at the maximum.

HULL TESTING

In the past, most rowing shells were developed using tank testing. This industry standard uses computers to map the shape of a hull and its effects on the water in a controlled tank where the elements of drag could be quantified and boat design parameters be tweeked. There are several problems with this methodology. First, these tank tests often neglected to test hulls in a variety of conditions such as wind, waves and currents all of which can have dramatic effects on hull speed. Second, and more importantly, these tests placed a hypothetical weight of the rower on the center of the seat deck. This, however, neglected the clear fact that rowers are moving back and forth on the seat during the stroke cycle which meant that their weight was rarely centered like in the tests.

PITCH AS A FUNCTION OF DRAG

With more complex computer modeling we are now able to understand that the pitching of the boat from front to back and side to side plays a significant role in the frictional drag of a displacement hull design. Rowing shells tend, at the catch, to pitch towards the stern while the rowers weight is on their feet while at the finish, they tend to pitch to the bow with the bow pressed down in the water. A considerable portion of modern rowing technique is based on this principle and rowing shell designers are taking on the challenge of building hulls that will diminish drag by helping to reduce the amount of pitching caused by the athlete and thus enable to hull to run as close to its designed trim as possible.

NELO ADVANCES IN HULL DESIGN

Nelo has been building displacement racing hulls since 1978 and, in the racing Canoe and Kayak community, has built a dominating reputation with 27 of a possible 36 medals at the Rio Games going to Nelo athletes. This reputation was been developed over the last 40 years, during which time Nelo has produced a number of design breakthroughs bringing new ideas and fresh creativity to the paddle sports market. In their entry to the rowing shell market they are bringing the full weight of their developmental resources to bear and implementing a number of their patented technologies to bring you a racing shell unlike any other. in 2015 NELO engineers developed 2 key aspects of their revolutionary K1 model kayaks that became the early sparks of their shell designs. As the design progressed, the designers found that these two attributes helped to increase the run of the boat on the recovery, a trait even more formidable in rowing which experiences much longer recovery time in the stroke cycle

INVERTED BOW “CINCO” TECHNOLOGY

Inverted bows have been present in the high performance sailing industry for well over a decade (pictured right is the state of the art America’s Cup Winner Oracle). NELO first began researching and using this technology in their revolutionary K1 CINCO kayaks in 2015 and shortly after obtained an exclusive patent to bring this design to the paddle sports market. The CINCO bow is less about the blunt shape of the tip itself and more about the narrow entry shape of the bow which produces less buoyancy in the forward section than a traditional design. This ensures that the longest part of the shell is always touching the water which maximizes waterline length to reduce wave drag. It can be compared to most swept-bow boats in which a substantial portion of the bow leaves the water as the rower approaches the catch. The resulting shape also pierces through waves more easily causing less disturbance to the movement of the boat AND, in unison with the flattened stern section works to reduce the pitching caused by the athletes fore and aft movement reducing friction and maintaining a long run and higher hull speed.

FLATTENNED MID-BOW AND TAIL

Along with the CINCO bow design, NELO designers sought to find ways to improve the stability of the boat in spite of the extremely narrow design. Here they discovered that by flattening the shape of the hull they could not only increase stability but produce a certain amount of lift when the boat was at speed. This shape not only provides excellent stability without producing additional wetted surface but helps to reduce the pitching of the hull towards the stern at the catch. Working in concert with the NELO CINCO bow, this hull shape produces a boat that resists fore and aft pitching as much as possible while the lift generated by the flattened sections creates a sensation of extreme stability and promotes the even trim of the shell creating consistently better flow, reduced wave and frictional drag, longer run, and higher sustained hull speeds.

QUALITY CONSTRUCTION

Nelo boats are built using high modulus carbon fiber. Hulls are built with both unidirectional and multi directional layers for strength and stiffness. Each hull is built with an outer layer of carbon, a middle layer of PVC Closed Cell Foam and and inner layer of carbon. The use of PVC is unique in the rowing world where lighter weight Nomex honeycomb is more common. PVC is only slightly heavier but provides considerably better stiffness and adhesion between layers while also providing better flotation and water resistance in the case of damage. This weight is saved in the use of lightweight carbon riggers and all Nelo boats are competitive with FISA minimum weight standards!

CARBON FIBER RIGGERS

All Nelo Racing Shells come equipped STANDARD with industry leading carbon fiber, bow mounted, wing riggers. Carbon riggers provide the same or better stiffness and power return as aluminum while reducing weight. Since rowing shells are built to a minimum weight standard, this means that additional materials can be used in the construction of the hull which improves hull stiffness and durability. Adding weight to the hull instead of the riggers also places more weight at a lower center of gravity which helps to improve stability. Nelo riggers are extremely strong and durable and offer exceptional adjustability to all levels of athletes.

INDUSTRY LEADING PARTS ARE STANDARD

NELO Racing Shells come equipped with industry leading parts standard with every shell. Easily adjustable carbon fiber foot stretchers allow you to customize your fit. Project B Shoes are the industry leader in rowing comfort and performance. Carbon fin system makes replacement a breeze. Convex seat tracks eliminate the need to constantly clean and repair seat tracks and reduce track bites. Best of all, ALL shells come equipped with a complete set of covers for no additional cost!