Written by: Adam Cord and Adam Caldwell
This is the third chapter in the Introduction to GUT series.
This chapter discusses a few concepts behind “moving with efficiency” on a slalom ski. Top level skiers have the ability to travel extremely fast behind the boat and carry a lot of speed throughout the course. They can do so mainly because they move with good Center of Mass (COM) positioning over the ski, not because they have super human strength.
The Skateboard Example
When riding a skateboard, your COM must be very close to perpendicular, or what is called “normal”, to the board in the fore/aft plane. As long as your COM is positioned somewhere between both feet, you will be fairly well balanced. To turn the board, you simply shift your weight laterally while still maintaining your COM position in that normal fore/aft plane and the board turns and moves with you. However, if you lean mostly on the back leg as you turn, with your COM behind the rear wheels of the skateboard (like the infamous “drop to the tail” style turn on a water ski), the board will shoot out in front as you fall to the ground. In this situation, thanks to gravity, your COM moved in a direction no longer supported by the board.
In slalom, positioning your COM in the normal plane on the ski is the key element to achieving efficiency in the course. Even though it is possible to ski the course with your COM positioned toward the tail, relying excessively on the rope for support, a tremendous amount of effort is wasted. With enough strength it is possible to survive at longer line lengths with a “back seat” COM position, but progressing into shorter line lengths will be extremely challenging.
The Efficient COM Position for Slalom
Let’s look at what an efficient position should look like on a water ski. From a side view, the COM should be positioned over the ski such that a line drawn normal to the ski’s top surface would pass through the skier’s COM, similar to what is described in the skateboard example above. Additionally, this normal axis must intersect the ski at the midpoint between the balls of the front and back feet. The overall attitude of the ski as it rides in the water is primarily controlled by the location of your COM over the ski. Settings can be used to fine tune the ride characteristics, but the COM position is the primary factor. Figure 1 below shows how the ski attitude flattens out as the COM moves from a back position (red circle) to the target normal plane (green circle).
|Figure 1: COM Position and Efficiency|
There are significant disadvantages when the COM is either too far forward or too far back. If the COM moves too far toward the red zones shown in Figure 1, it causes the ski to ride with an inefficient attitude in the water where there will be either not enough lift, or excessive drag.
COM Positioning for Balance
An additional benefit to this position is the improved ability to balance on the ski. Your body senses pressure through the soles of your feet, and uses that information to help you balance. With your COM positioned between the balls of your feet you have effective use of sensory input from both feet, in addition to the ability to articulate both knees and ankles productively, which greatly improves your ability to maintain balance. When your COM shifts too far forward or too far back, your ability to balance diminishes greatly.
TEST: COM positioning can be easily tested on dry land to help understand how much it can benefit or hinder your balance. Stand up tall with your feet in line like you would on a slalom ski. First lean back and put your COM over the heel of your back foot. Notice how your balance feels, and how difficult it is to hold a steady position. Now shift your COM forward, by flexing at the knees and ankles so that your COM is balanced between the balls of your feet. There is a huge difference in fore/aft balance, lateral stability, and your ability to control and change positions athletically when you stand like this. This is the same stable feeling you want on a slalom ski. Just like being too far back, shifting the COM ahead of the ball of the front foot will also reduce balance, and more importantly make you more susceptible to an out-the-front type of fall.
Application on the Water
A real life perspective of the normal plane is represented in light-blue in Figure 2 below. In both pictures, the normal plane is located at the midpoint between the balls of the feet. The red dot in Figure 2: A shows the skier having his COM too far behind the target. In Figure 2: B, the green dot shows the skier’s COM being at the target, which is an extremely efficient position.
|Figure 2: A: “Back” & inefficient – COM over back foot||B: Forward & efficient – COM at midpoint between balls of the feet.|
With his COM further back, the skier in Figure 2: A is putting the ski between his COM and the boat, effectively putting the brakes on. This “back seat” position causes the resulting ski attitude in the water to be tip high, with the tail digging, and the water-break very far back. His effort is being wasted plowing water and fighting the boat. This ultimately reduces cross course acceleration while increasing load.
With his COM significantly further forward and within the target normal plane, the skier in Figure 2: B gains the benefit of having much greater leverage over the ski’s edge, further driving the tip down, rolling the ski to a higher bank angle, and putting more ski in the water. This greatly improves cross-course acceleration and increases the speed at the course center-line. With this high speed and reduced load, he will be able to transition to the turning edge much earlier and more easily, with ample energy to achieve the primary objective of GUT (i.e. taking the handle as high on the boat as possible as fast as possible).
Utilized effectively, ideal COM positioning will help you greatly reduce load, increase cross-course acceleration and improve both fore/aft and lateral balance in the slalom course. Positioning your COM to be near the target plane requires general awareness more than physical effort. Doing so will help the ski carry speed and keep you moving in the direction you want to go, without having to rely so heavily on the rope for support. Being able to enter and finish a turn with the COM in an efficient position will significantly improve your ability to sustain that position into the first wake, and help you accelerate much faster with far less effort.
It is extremely important to keep the COM “normal” to the ski and balanced between the balls of your feet at all times, regardless of the attitude of the ski in the water, where it’s pointing, or where you are in the course. Skiers who habitually lean too far back are in the red area shown on Figure 1, and this is a hard habit to break. Shifting the COM forward to an efficient position within the green zone on Figure 1 can be unnerving and unfamiliar at first. As awareness and confidence improves, having your COM centered over the balls of your feet becomes more natural. Maintaining ideal COM position will help you transfer the tremendous power of the boat directly into speed and acceleration with much less effort, allowing you to carry more energy through the turns and run an early, wide, up-course rhythm.
Entering it's 20th uninterrupted year with a world record to its name, GOODE Skis is once again transforming ski design and performance with the RéV 6, a giant leap forward for the FlexTail, a ski that powered Chris Parrish to the No. 1 spot on the IWWF world rankings list, won multiple Big Dawg titles and pushed skiers across the globe to countless new line lengths.
The magic in the all-new RéV 6 lies in it's highly refined length-to-width ratios. A rigorous R&D process discovered a longer length that works in perfect harmony with the lateral flex induced by the FlexTail - creating the speed and stability of a longer ski and the turning characteristics of a shorter one. The result is a ski universally loved by GOODE's testing and design teams.
"It's the best ski I've ever ridden," says Chet Raley, a world-renown coach, Men's senior world slalom champion and a key member of the R&D team. "The FlexTail to me was mind blowing, but there was more work to be done, as is always the case with all things, like cars, boats and skis. The work over the winter was relentless, but we took the FlexTail and made it a way better ski. This ski accentuates the FlexTail technology better than the original ski did. It's more stable, more balanced tip-to-tail and side-to-side. It maintains a really tight turning radius without destabilizing the ski."
The higher length-to-width ratio is manifest by an additional length between the boots and the fin, in essence elongating the tail of the ski.
"You have more ski behind you so you can ride a bigger ski, utilize the advantages that that offers, but still be able to turn it because the FlexTail technology is giving you a huge assist," said Dave GOODE, founder and president of GOODE Skis. "That extra length in the tail generates more speed from the buoy line to the first wake, leaving you up-course and ahead of the boat, all with more line control and less physical exertion and fatigue."
The RéV 6 is the result of an R&D process that began as soon as the FlexTail hit the market last year, with the testing and design team focused on taking full advantage of the industry-first lateral flex found in the FlexTail technology.
"Whenever there is a huge leap forward in technology in any industry or sport, it takes a bit of time - and a lot of hard work - to fully maximize the potential," says Goode. "The extra year of R&D has allowed us to do that with the RéV 6 and it's paying off for the test team in extra buoys."
For World No. 1 Regina Jaquess, the extra R&D led to a ski that is markedly better than the FlexTail, and has her skiing a preferred style of skiing.
"The FlexTail was a great ski, but now we have this 12 months of data from everyone skiing on it at different lengths and different conditions," said Regina Jaquess, the Women's slalom world record holder and two-time defending world champion. "The biggest thing is I feel it's lighter in the course, and of course we want to be light, we want to have that feeling of being light."
The RéV 6 will come with GOODE's standard five-year warranty and 30-day money back guarantee, and will be available in six sizes: 64", 65", 66", 66.5", 67", and 68".
Skiers wanting to order the RéV 6 can add their names to a waiting list beginning on March 3rd. Orders are expected to begin shipping in mid-March.
Written by: Adam Cord and Adam Caldwell
This is the second chapter in the Introduction to GUT series.
Thinking about skiing in terms of extreme limits helps us to understand the underlying physics. Let’s compare two different scenarios at the centerline (CL) of the course to help demonstrate the unique relationship between speed and load.
For the first extreme, imagine approaching the gates, but instead of pulling out to the left, you stay behind the boat and start right on top the left wake. The instant you reach the gates you slam the ski on edge and pull extremely hard to head toward one ball. For this example, let’s assume that you are able to reach 5mph of cross-course speed by the CL, with your ski angle 50° to the course. In a highly loaded position, you are moving much faster straight down the lake (36mph) than across it (5mph).
Now imagine the opposite extreme. Let’s say you are again coming into the gates, but this time you pull out to the left and get very high and wide, nearly passing the windshield on the boat. With a wide and early turn in for the gates you build a lot of speed and angle progressively, allowing you to reach a 40mph cross-course speed by CL, and like the first extreme, with your ski angled 50° to the course. This time you are actually moving faster across course (40mph) than down course (36mph).
Figure 1 illustrates the two extremes we discussed above. As you can see for Scenario 2, the 40mph cross-course speed translates into a 53.8mph resultant speed, while in Scenario 1, the 5mph cross-course speed translates into a resultant speed of only 36.3mph, almost the same as the boat. What’s important to understand is that even though the physical angle of the ski relative to the course is exactly 50° in both cases, the load acting on the ski will be completely different due to the speed and direction of water flow relative to the bottom of the ski.
|Scenario 1: 5mph Cross-course Speed, Ski at 50°||Scenario 2: 40mph Cross-Course Speed, Ski at 50°|
(Merced, CA) – Today both Centurion Boats (Centurion) and Supreme Boats (Supreme) announced that respected industry veteran, Paul Singer, has been appointed as their President.
Singer, an Air Force veteran, is highly respected for nearly three decades of work in the boating industry. He is best known for playing a key role serving as an executive at one of the boating industry’s largest manufacturers. During his time at the boat manufacturer Singer played an instrumental role building the organization from a start-up into a respected industry leader. Singer is universally respected and liked among competitors, dealers, vendors and customers.
Centurion and Supreme are both owned by Correct Craft and are built in Merced, California. For over twenty years Centurion has been the official boat of the Wake Surf World Championships and was recently chosen by the International Waterski and Wakeboard Federation (IWWF) as the official boat of their Wakeboard World Championships. Supreme is known for providing great watersports boats at an exceptional value. Singer will serve as President of both brands.
Singer, President of Centurion and Supreme stated “I could not be happier to join the Centurion and Supreme teams. Both brands have wonderful teams and we will work together to achieve great things!” Singer added “I am also happy to be part of Correct Craft. The Correct Craft culture is amazing and something we look forward to further developing at Centurion and Supreme. The future is exciting!”
Bill Yeargin, CEO of Correct Craft, announced Singer’s appointment today stating “Paul Singer is one of the most respected people in our industry and he will have a big impact on both Centurion and Supreme. Paul fully embraces the Correct Craft culture and he is a friend; Paul is one of the best guys I know and I could not be happier to have him joining our family.” Yeargin added “In the several months since Correct Craft purchased Centurion and Supreme the brands have released exciting new product, added nearly thirty new dealers, seen production processes improved, added key talent and seen Centurion selected as the official boat of the IWWF Wakeboard World Championships. Having Paul join the team tops this all off with the best news yet and begins an exciting new era at Centurion and Supreme!”
Denali Skis is a new USA based startup in the water ski community with a revolutionary approach to ski design, product support, and skiing philosophy. We at Denali are excited to announce the launch of our new 2016 Denali Ski, now available in limited quantities at Denaliskis.com.
Orders are fulfilled on a first-come first-served basis, and skis will no longer be available when order limits are met. By intentionally controlling volumes, Denali intends to grow organically, focusing on personalized technical support for each individual customer. Visit Denaliskis.com to learn about our asymmetrical fin settings, free-flex binding plate, measure-flat tail, and much more!
The team behind Denali consists of engineers who are also skiers. For several years, Denali has worked off the grid exploring the boundaries of water ski design. With the use of an exclusive rapid prototyping method, new concepts at Denali are drafted to a 3D model, machined into a mold, built and tested - all in less than 72 hours. As a result, Denali has evolved its ski design faster than ever before, putting the new 2016 Denali years ahead of the competition.
In addition to the most cutting edge design in slalom history, flex and torsion patterns are customized for each individual skier. Matching the skier’s size, weight, and ability to a tailored flex pattern provides ideal characteristics to optimize the delicate balance between speed and feel on the water, further improving longevity and performance.
Providing an unmatched level of support, Denali customers will have access to an online community where skiers can ask questions and share ideas about setup, technique, and training. This platform provides customers direct access to the Denali community as a whole, as well as the engineers/skiers behind the ski, allowing for continuous technical support to help all customers take their skiing to a whole new level!
Join the Denali community today, and order now at Denaliskis.com to get your limited edition custom built Denali ski! Skis will begin shipping May 1st.
QUINCY, WA (January 29, 2016) – We are excited to announce that Crescent Bar River Fest will include the first annual Herb O’Brien Memorial Cup this year. Radar Skis, MasterCraft Boats and Sunshine Marketing have partnered to celebrate the Godfather of waterskiing with this Cash Prize Pro/Am waterski tournament.
Our mission is to celebrate the spirit that Herb O’Brien instilled in waterskiing, the passion he held for water sports in the Northwest and his specific love of Crescent Bar. It’s these values that we wish to reinforce in the community through an annual professional ski event and pro skier tour through Western and Eastern Washington.
The Herb O’Brien Memorial Cup will feature and international field:
K.C. Wilson – 3X Jr. Masters Champion
Brooks Wilson – 3X Jr. US Open Champion
Freddie Winter – Pro Champion and British Record Holder
Jason McClintock – Canadian Record Holder
Stephen Neveu – World Champion Medalist
Chris Rossi – Professional Champion
Trent Finlayson – Canadian Record Holder
Terry Winter – Professional Champion
Herb O’Brien founded O’Brien Sports, HO Sports/Hyperlite and most recently Ronix Wakeboards and Radar Waterskis. In 1972, he built the second ever manmade waterski lake in Woodinville, WA which today remains one of the most famous lakes in the world. Anyone with the privilege of knowing Herb remembers him for his generosity and giving nature. There are endless stories of his compassion told by the hundreds of people who worked for him over the years.
|Rank||Skier||Event %||Score %||Combined %|
|13||Coble Eller April||21.43||7.14||14.29|