NOOZ
Like any good kayak site, we need a blog to keep you all up to date o our adventures in whitewater medium, and that's what the Nooz is all about!
| OC-1 Freestyle Design Theory | ||
Freestyle OC-1 Design Theory Designing a Freestyle open boat- the dirty work. There's a fundamental difference between kayaks (or even C-1's) and canoes. Canoes fill with water, kayaks don't. This simple fact has far reaching implications for the design considerations of freestyle boats, but before I get into that, a bit on the history and how I came up with these theories.  Competing at team trials in 2006 in a SpanishFly In 2006, I decided to train to make the US Freestyle Team in C-1. I spent most of the summer on the Ottawa training in C-1 on the various waves the river has to offer. I also brought my Spanishfly along for kicks, and to mix it up a bit when things got monotonous. When team trials rolled around, I missed the team in C-1 by one spot and a narrow point differece, but had also decided to compete in OC-1, to be another person in the class. No one else showed up, and I made the team by default. Suddenly, I was faced with the issue of finding an open boat I wanted to paddle on Buseater the next spring. I looked around, tried a few boats, but none of the boats seemed quite right to me. The CU Fly and the Salsa both seemed to have the issue that the ends were hard to keep up when the boat was full of water- making it hard to do more than one move, and hard to paddle back up the eddy- or down river. I wanted something that would be decent all around and that could do more than one move on the wave. I decided to design my own boat, based on a shortened Spanishfly. The first version of the boat, dubbed the "Blackfly" was pretty unstable, slow and a bit too chunky in the ends, but I learned a lot from it, and won a bronze medal a the 2007 Worlds. In 2009, I reworked the boat a good bit, and made a boat I'm very happy with. This boat carried me to the top of the podium at the 2009 World Championships. The experience I've had in designing (and continuing to design) the Blackfly is the basis for the evolution of my design theories.  Blackfly Version 1 The simple fact that a Canoe can take on water changes the game a good bit when compared to kayaks. The predominate design paradigm for whitewater kayaks for the past decade or more is the "beachball with fins." A fat, buoyant, retentive center, with slicy ends that are easy to pull through the water. Overall, this is all the model for freestyle canoes, but with one problem. In a canoe, the part in the middle- the retentive bit of the kayak- is the part that fills up with water. Not only does this mean you lose the buoyancy of the middle of the boat, but you also increase the weight. For competition, you need to be able to fit a minimum of 40 liters of water in the boat when you're in it- that's about 85lbs, but since it's hard to get the boat foamed out exactly right, it's not unreasonable to figure it could be 100lbs extra. So for a 150lbs paddler, you need the buoyant volume equivalent to that of what a 250lbs paddler would want- plus the volume occupied by the water. The numbers are a bit fuzzy, but a quick review of manufacturer's specs for kayaks shows it works out that you want something like 1/3 of a gallon volume for every pound of paddler weight for a kayak. In the case of the canoe with a 150lbs paddler, and 100lbs of water, you'd want about 80-some gallons of buoyancy- plus another 10 gallons of volume to fit in the water. These numbers are a bit fuzzy and fudged, and I've never measured the actual volume on the Blackfly, so don't take them for gospel truth, but It should become apparent why adding a turret to kayak hull to meet the regulations isn't the best option.  Blackfly version 2 The issue becomes how to distribute the volume, and quite a few other design considerations fall out of this. The first is width- volume is the product of 3 dimensions, and increasing width will increase the volume of the boat without increasing the cross-sectional area that needs to be pulled through the water on any number of the freestyle moves. Increasing the width also means more stability- so you can sit on a higher saddle and have more leverage to throw around the extra volume- and the extra weight of the water- without falling over or having to do a lot of bracing. It also means the boat will have a bigger planing surface- which is also necessary to support the extra weight of the water on a wave. This is another area where the kayak conversion boats are a bit lacking. Big planing surfaces are needed, but need to be balanced with the ability to edge the boat. My theory is that lengthening the planing surface helps, and having the widest part from the middle of the boat forward, with a narrower stern, as this is the part engaged in the water during most surfing.  Hull view of Blackfly2 Another way to help distribute the volume is to take the "beachball with fins" and stretch out the beachball. Essentially, the goal is to split the buoyant center, and move it out, and add the "canoe part" (the bit that fills with water) to the middle. Since there's a good bit of foam outfitting-saddle, bulkhead, ankleblocks, etc, in the middle, you don't need to increase the length of the center section all that much. As with many aspects of boat design, the key is to find a balance between enough volume to keep the boat retentive, and too much to make it hard to throw around.  Blunting Blackfly 2.1 on the Black River Beyond volume, there are other issues that also need to be address with consideration for the extra weight of a water-filled boat. Rocker profile is one. One of the reasons I started with a modified Spanishfly is because even when completely full, the ends of the boat are still above water, because the boat has a lot of rocker. This makes it very forgiving to paddle. In a C-1 or OC-1, the range and magnitude of the paddlers weight throw are greatly increased over the K-1, whether intentionally, or inadvertently. This means that it's easier to get the ends of the boat underwater when you want to, but also means that sometimes they'll catch when you're just paddling forward aggressively. An accidentally caught end on an eddy line or in a hole is most often the end of your ride. By increasing the amount of rocker over what might seem "normal" this can be avoided, but it's a balance between so much that it makes the boat slow and hard to initiate the ends, and too little, so the ends are underwater when you don't want them to me. The final point I'll bring up is edges. Don't be afraid to go aggressive, but also keep forgiving in mind. Many of the OC-1 boats in the past have focused too much on keeping the edges extremely forgiving, at the cost of actually allowing the edge to release from the water. Forgiving is certainly important, as a caught edge in a boat full of water can generate a lot of momentum off the wave and be hard to recover from, but forgiving and loose are not mutually exclusive.  Sanding the plug, prepping to build a mold Obviously, I've left out a lot of the finer points of boat design, and the trick is to get everything into a suitable balance. But this is the theory I've been working with for the past 3 years, and so far it has served me pretty well.  Competing at the 2009 World Championships |
||
|
Content Management Powered by CuteNews