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Kite boards have taken technology from many different sports. Many different designs and concepts have been adopted from wake boards and even water skis. But due to the unique forces involved with flying the kite, the vectored forces from the kite does not really allow all the same principals to be adopted here. So, what do we really want from a kite board? Feel! We want the board to have smooth predictable performance. Not have it skipping out and not being able to control it in varying wind and sea conditions. The better it feels the more control you have. The more control you have the more you can push the limits with confidence. Following is just some of the design considerations that effect the design of a kiteboard.
Flex
flex diagramBeing thin, kite boards will flex to some extent when in use. Unfortunately flex directly affects the rocker line which as you know dramatically effects the performance and feel of any board. Many things effect the flex characteristics, construction, profile, materials, channels just to name a few. As you see on the left most boards when they flex bend in the middle and there is little bend towards the tips of the board. This kills the performance of the board as the tips basically become useless. Result, unpredictable feel. When I talk about 'flex' in my boards, I don't just mean a very soft board. If that was the case we will all be riding inner tubes. I mean using the flex properties to improve the ride of the boards.
Controlling the flex
widestanceI observe lots of riders at the beach testing the flex of a board by bending it right in the middle. This is an unrealistic test because the board is not loaded up this way when riding. There is a lot more that makes a board feel soft when riding, mainly rail shape, fins and thickness profile. There will be boards that feel soft on the beach and has a lot of bend, but when you ride it, it has a very stiff feeling. Like wise, there will be less bendy boards that have a softer feel when out on the water. It is a common thing to see riders checking out a new board by putting their knee in the middle of the board and bending the tips back. This really does not tell you much and all you are doing is potentially damaging the board but adding stress in areas that are not usually stressed when riding. Ride it to feel the Flex.
With the latest trend of widening the foot stance, ( which I think really improves your riding and control, it just takes a little getting used to.) the flex of a board has to be re evaluated. With a wider stance, you feet are closer to the tips of the board and there is a greater area of board between your feet. So the upward force from underneath in the middle of the board is increased and the upward force on the outside of your feet is reduced causing what I call 'negative flex.' The board bends upward in the middle and forces the tips downward really effecting performance. So the middle of the board , just the middle section between your feet has to be stiffened to preserve some of the rocker line between your feet, and the tips should accommodate most of the flex.
Using a combination of materials including d-cell foam core, balsa wood and a combination of carbon fiber (in strategic places) and s-glass with a constant taper profile shaped into the board, I have been able to control the flex of the boards. A positive, smooth carving feel under your feet with no 'skipping out' that you get with stiffer, less controllable boards. A board with good flex will handle gusts and choppy water better because it bends under load releasing pressure under the board and helps maintain a constant wetted surface and positive rail pressure. (which also helps going upwind) If your board is super stiff every time you get a gust or hit a little piece of chop the board is loaded up causing the board to either skip down wind a little (loosing upwind ground ) or you have to de-power the kite to absorb the excess load with the kite. Stay powered up and in control with flex.
wakeStyleWake Style boards
Putting bindings on a board greatly stiffens the board. Because of the large foot print of bindings the continuous/progressive flex is lost, the boards does not bend under the plate areas and all the bend happens in the middle and the tips become rigid. All control of the rocker line is now lost. So I decided to use this added stiffness to my advantage instead of working against it. I stiffened the mid section so that basically it will not just bend in the middle but spread the flex.. I managed to stiffen the middle using the board profile and not just by adding more glass in those areas. I just became aware of the change of the flex properties and used this to my advantage. With the added leverage you get from bindings there is not as much emphasis needed to fine tuning the flex and rocker line to achieve the feel and turning abilities that you require in a board that is ridden with foot straps only. You are powering yourself from rail to rail more with bindings. You can force the board where you want with the leverage you have form the bindings. With a footstrap board it is more important to have a more reactive board inherently designed into the board to work with you when foot/heel pressure is applied. This is achieved with progressive rocker line. So without this requirement here, I was able to use a more continuous rocker line and not my normal progressive rocker.
A continuous rocker is a rocker curve that has a pretty uniform curve from tip to tip. (i.e.. the curve does not increase towards the tips but is a uniform arc. ) Normally a continuous rocker reduces feel in boards that are more sensitive to foot pressures, like boards ridden with foot straps. Here this continuous rocker creates a flatter tail (same rocker height rise) and this generates a lot of pop.
The fin positions are also a bit further forward which increases the turning ability that is normally reduced with the continuous rocker, longer length and greater surface area in the tails.
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Rails
Another important feature in feel is the rail shape. Because of the forgiving nature of the flex, on my regular kiteboards I am able to use surfboard type rails, tucked with a sharp bottom edge to further increase the smoothness in carving turns. The sharp under edge still allows you to keep the board on it's edge when powered up. railsTowards the tail I reduce the tuck and sharpen the rail to give the board 'pop' off the tail for tricks and positive bite during turns. Rail shape is more important than you would think. It determines how the water is released from the board and this effects the feel as it cuts through the water. I have found that having a rounded tucked rail shape towards the middle of the board allows the board to release more water from the center of the board and not have the rail in the middle of the board grab the water too much. I prefer to have the grabbing towards the tail closer to your back foot position, that way you have more control of the board. So what happens as the entire rail is loaded up equally, more pressure is released by the slightly rounded rail near the middle and pressure is built up towards the tail.
Somewhere in between the tail and middle, there is a point where the water is released cleanly from the sharp edge and where the water wraps the rounded rail. This point moves according to the amount of pressure, speed and force being applied to the board and can be controlled by back foot pressure giving you full control of this point. If the rail shape is the same throughout the length of the board, what happens is the entire rail loads up evenly. rail boardsWhen the load builds up to a point where you can not hold it down, the pressure gets to great and it will just pop out of the water to release the pressure without warning. The board becomes unpredictable. Have you ever ridden a board that holds an edge great to a point then it just brakes loose? this could be the reason. As you are powered up riding, you should be able to feel when the board is loading up and adjust the back foot pressure to maintain a perfect trim angle enabling you to hold you edge effectively. Any thing that gives the rider more control is a big advantage.
On my Wake style boards, I pinch the rails a bit more so they are not as full. I can do this because of the added leverage gained by using bindings. The boards can now handle the power and less forgiving water release of sharper edged rails. There is some roundness to it in the middle, but it sharpens out towards the fins. Depending on the riders style, the amount of roundness and where it starts and stops is customized to best suit the rider.
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Bottom Shape
Regular kiteboard
I stick to o slight single concave that begins and ends under the foot position with a flat tail... Keeping with my focus in controlling flex, a flatter/shallow concave bottom is the most accommodating shape for this. The reason most channels or full concaves are incorporated into the bottom on boards is to increase the lift and to control the water release for control through the water. Most of the upward force on a kite board is achieved with the kite itself. Kite boards are edged and glided over the water, not plowed through the water like a wake board or water ski behind a power boat, so the forces involved are different. If I need more lift for personal preference or for heavier riders I can get this by increasing the width of the board by as little as 1 cm. without deteriorating the feel of the board as opposed to trapping water under the board with channels or deep concaves.
big airBut more importantly, deep concaves and channels greatly stiffen the bottom of the board. Try this, bend a playing card lengthwise. It bends easily.. Now put a concave in it or bend a couple channels into it length wise and now try to bend it as before. A lot stiffer now, and in fact, keep bending it and it will be stiff until it finally brakes losing it's shape and damaging the surface of the card.. Without a concave or channel you could probably bend the two tips together without destroying the surface of the playing card at all. Evenly distributed forces is the reason for this. So apart from not being able to control the flex, when a board with channels does flex, the forces are now unevenly distributed throughout the board requiring more glass to provide the strength needed. Result, more weight. Not good. As far as using channels and full concaves for control water release? This is done to restore the feel destroyed by the stiffness created by uneven bottom shapes in the first place. My concaves never run from tip to tip. The concave is in the middle of the board between the foot straps and I take it out towards the tips of the board where you do not need it. I found this is the best way to use concave and keep the flex properties of the board. That way I am also using the stiffening tendencies of the concave to help me stiffen the middle of the board as well as give the board the riding improvements of a concave.. With a simple bottom shape along with the control flex shaped into my boards, the more pressure (downward force) that is applied on the board the more the parabolic curve in the tips of the board bends, productively increasing the rocker line of the board. Then, when the pressure is off the board the rocker returns to the it's memorized shape. It's like having more rocker when you need it. Great feel.
Why not run the concave throughout the length of the board?
There are a few reasons for this. If the concave runs the full length of the board, it means that the rocker running down the middle of the board is pretty much the same as the rocker running along the rail. This is not a big deal , but I found that by stopping the concave under the foot areas means the rocker down the middle of the board is different than the rocker towards the rail. How different? well due to the concave, if you lay a yard stick down the middle you will see that the middle has a flatter section (because of the concave) and the rocker towards the tips is has a more pronounced rocker curve. Rocker is defined as ' the amount of rise over a given distance.' But, the rate of change over a distance also effects the performance of the rocker. For example, a greater change over a smaller amount of distance, basically meaning more 'curve' effects the turning ability of a board dramatically. (even though the total rocker height at the tip is still the same) So by stopping the concave under the foot area I am actually increasing the rate of curve towards the tip of my boards without actually increasing the overall rocker height. Result? When you put pressure on the tail to make a turn, this increased rocker curve allows the board to be turned sharper and it really sticks without popping out during a turn.
Concaves running the entire length definitely improves the tracking ability of the board and softens the ride but only when riding in a straight line. Lots of top board makers are still using full concaves like Jimmy Lewis's dominatrix bottom, and I see even more production boards coming out with it. But from testing I found that in a turn when you increase pressure on the tail, the concave under the tail traps water (so to speak), increasing pressure under the tail of the board and results in the tail braking away prematurely and unpredictably. So when you try to make a sharp turn, you dig in and then it just brakes loose. With a flatter bottom near the tail, and the added benefit of the exaggerated curve in the rocker line towards the tail, pressure is released towards the rail of the board assisting in controlling the thrust of the board in a turn. With a full length concave, the pressure is forced out the back of the board without directional control of this pressure release. In hydro dynamics (and aero dynamics as well ) it is all about controlling pressure. Another point to consider, you have fins on the bottom of your board, and increasing pressure between the fins with concaves effects the performance of the fins. Fins basically work on the principal of pressure differentials on either side of a fin to function. Something more to think about. Also, the concave between the foot positions also help me to stiffen the mid section of the boards through design and not have to rely on adding more glass fiber in those areas as much. The flatter tails lend itself to allowing the tips to bend and not effect the middle of the board.
Flip Tips & Steps
You see flip tips and steps used quite a bit in the industry. These allows the rocker to be flattened and still have some tip scoop. Flattening the rocker makes a board plane earlier, faster and provides more lift. However, if the step height and angle is not right the performance of the board can actually be deteriorated. There are a lot of molded boards from main stream companies that try to put steps on the boards, but due to the molding process, the correct angle is very difficult to reproduce in the mold and the results are not good. (free tip...If you have one of these molded boards with a step, if the edge feels rounded with the touch of your finger, build up the edge with some epoxy filler to sharpen the edge. fliptipsThis promotes water separation and you will feel the increase in performance.) So, having this advantage of reducing wetted surface with a fine tuned rocker line can improve the performance of a boards. (for example, a 138cm board with a step 5cm from the tail of the board is actually riding on 128cm of board surface and the reduced drag is noticeable.) I first started putting this step and flip tip on the Player boards to improve it's chop/all terrain riding ability and keep the useable wetted surface down, but after a lot of testing some my team riders thought it had a 'catching' 'toe stumping' feel in the nose of the board. So with some tweaking of the rocker line and outline template I was able to remove the step and flip tip and still maintain the all terrain properties of this board. The board is shorter without loosing wind range despite it's slightly smaller size. I also realized what made a difference and one other reason why a well made stepped board worked so well was because the distance from you back foot to the edge of the step (where the water separates once plaining) was shorter than to the actual end of the board and that is what gives you that positive feeling like you are riding a board shorter than you really are. So by tuning the rocker, removing the step, shorting the board along with adjusting foot placement closer to the tail of the board, it allowed the trim angle to be increased resulting in not needing a flip tip to stop the nose from dipping under when riding in chop or waves. It all came together.
Wake Style Boards
I use different bottom shapes on the wake style boards. Because efficiency is not as important I can use different designs to help control speed and pop. For normal wake riding looking for big pop and and controllable hard high speed landings the v bottom with double concave works great. v-bottomTo solve the problem of hard landing and high speed control I introduced a modified 'V' bottom with slight concave that washes out under the foot positions. I realized that I did not have the option of just increasing the flex to soften the landings because of the stiffening problem mentioned above. So I went in the other direction. I made the board stiffer. This way I have full control of the rocker profile and this gives me a fixed design platform to now find a way to design a bottom shape that dispenses the energy on landing. So I was looking for a bottom that will separate the water and control the release of energy. Also, the stiffer middle means the board will not distort ( negative bend) on high impact landings reducing the 'cupping' effect. Boards with large single concaves serves to trap water underneath. Works great if you want to get more lift/efficiency from a narrower board but not to good if you are trying to release energy on flat hard landings on wider boards.. But generally these binding boards are wide enough to not have to worry about being efficient, so totally efficiency is not reduced.
So I decided to use a 'V' concept which has been used for a long time to control speed in the marine world. ( for example: deep V in power boats) So the center line down the middle of the board is lower than the rail so it parts the water outwards. I have used a small Concave from the lowest part of the 'V' outward towards the rail, so when the board is on it's edge, you still have the dampening and edging effect of a concave. I used a rounded 'V' instead of a sharp 'V' to make it smother transitioning from rail to rail, similar to the 'V' on a surfboard bottom. Also, it is more forgiving on the sliders than a sharp 'V' which has a tendency to wear and damage the board. Consistent with my other bottom shapes, I have taken out the 'V' / concave underneath the feet position and transition to a flat bottom towards the tips. This makes for predictable feeling and clean water release off the tail.bottom This modified 'V' is carried through the boards top and bottom in the mid section of the board. It also has longer 'one love handles' on the deck. Doing it this way keeps the volume distribution consistent and assists in controlling the stiffness because of it's cross sectional shape. Looking at the side profile of the rail, there is a flattish section in the middle which creates more wetted surface when edging to improve tracking. Down the center of the board the profile is a continuous curve which provides really positive control. The rails are rounded in the middle to reduce grabbing. Makes riding blind and high speed landings easier and more controllable. For Wake Style boards to be used on sliders the 'V' becomes a problem because once on the rail, having the 'v' down the middle actually makes it difficult to keep the board balanced. Because of the high point of the 'v', it actually pushed you off one side or another of the rail and my test riders did not like the.
So to make a board that is slider friendly, I am using the same THUG template but I use a completely flat bottom. The result is positive control on the sliders and rails for the rider.... The rocker line was changed a bit to make the landings as forgiving as the 'v' bottom boards and teh size increased to increase the POP!
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Speed
Let's talk about the speed of a board and how it affects performance. Depending on your style of riding the speed of the board can be very important. This has changed over the years with the development and improvements of the kites. Earlier kites were not as forgiving and did not fly as fast nor turn as well as the newer kites. So you did not want a board that was too fast because you would keep catching up with the kite and causing the lines to become slack creating 'off' and 'on' power. So the kite would power up, pull you forward, accelerating you towards the kite causing the lines to go slack, you slow down because of slack lines and it starts all over again. That is why early board design had lots of continuous rocker (remember the pickle fork). That continuous 'banana' rocker (as I have heard it been called ) was to keep you relatively slow to keep constant tension on the lines giving you much more control of the kite and hence your board skills improved. Wake board still have this type of rocker to keep the pull as constant as they can behind a boat. Recently, the kites are super fast, efficient and controllable, so the speed of the board can be increased to make use of the new improved kites. I promised myself when I started making boards that I will always use the newest kites on the market because I realized that it was important to match board speed to the current kite trends. (expensive for me, but worth it for board design)
What does this extra board speed do for you? With faster more controllable kites, it allows you to have better control of your line tension which is a must for the new style of unhooked tricks. When you unhook to do handle passes etc, you do not want to be dragged behind while your kite feels like it is pulling your arms off. You want to be able to turn towards your kite, keep your speed up to reduce the pull on the bar forcing the kite towards the back in the window a bit, complete the maneuver or jump unhooked, then after you complete the maneuver you can re-edge your board to load up the line tension for another trick. More control of your kite. And having more control of you kite can only be a good thing.
The speed of the board is controlled with the rocker line. Flatter is generally faster, but you do not just want a flat board because a flatter rocker also kills the turning and tracking ability. So like everything else in board design, a compromise is sort. I believe with my combination of a concave to flat undersurface, fine tuned into the overall rocker line I have achieve a perfect compromise.
shaping
Length Vs. Width
The width of the board has a more profound effect on the plaining surface rather than the length. So, I vary the width to suit the rider and different performance requirements. Many think that you need a longer board in light air... not so. Width will do the trick. That is why snow shoes are short and wide. To increase the usable surface area. Same thing with a kite board.
With the continued improvements in kite design making them easier to handle power and the current riding style trend of low powered up riding, I think you will see kiteboard lengths settle down around 130cm to 135cm in length for regular kiteboards and up to around 140cm (but much wider) for wake style boards using bindings. . Generally you can go a wider with bindings because you have more control of your edge. For wake style boards, it is all about how much POWER can you handle when it comes to bindings boards.
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Outline/Profile
The outline of a board lends itself to the overall performance of the board ( I think second in order of importance behind rocker) Things to consider are 'parallel lines' of the board, where the major bend is and how it tapers towards the tips and the shape of the tips.
It is all about load and load distribution. As far as the tip outline, squaring off the tail allows you to load up the tail of the board which is better for more pop but can become less forgiving. By less forgiving I mean that overloading the tail can result in the tail braking loose in tight turns for example (but this can be remedied with proper fin placement and rocker line.).
Rounded tails are more forgiving, but may give up some bite and pop. I generally use squarer tips on most of my boards but I pay attention to other elements to maximize the turning ability.. Most of the riders riding my boards know what they are doing and want a more loose lively board.
Rail outline is another consideration. If the rails are more parallel, the boards rail is loaded up more evenly along the length of the board and this is great for edging in flatter water. In flatter water, there is less risk of overloading the rail that causes the board to pop out of the water unpredictably. So more parallel rails are best suited for wake style in flatter water. In choppy water or for riding waves, having a curvier rail outline handles chop a lot better by allowing you to control the loading of the rail. So, generally speaking, the curvier the outline of a board is, the better it is for choppier conditions and wave riding, and a square'er more parallel the outline is, the better suited it is for flat water, wake board style riding.
Conclusion
Board designing is not a defined equation, it is a combination of all the things I have mentioned above and more. It all has to work together in synergy. There is a lot of high tech 'know how' in terms of the materials used and construction technique used, but just like surfboard making, there is still a big part of personal feel by the shaper that has to go into the shaping and making of a great kiteboard . The shaper is still a big part of the process to get the 'great feel' of a custom board that has not been able to be reproduced by machines in a factory. This is where knowledge, creativity and skill meet to make art.
I am continually seeking for feedback and will change any belief I have in my goal to make better boards. This page will always be continually updated as I find out more and more about kiteboard design and keep up with current developments in kiting as I progress as a board builder. Currently I think 'feel' continues to be a big part in the design of a kiteboard that is being overlooked and I will continue to develop my designs in this area. 'Predictable Feel' is what allows you as a rider to really get dialed into your equipment and take your riding to another level.
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