Spindrift
Latest updated Monday, February 5, 2024, 60 comments
Images | Particulars | More about | Background and history
Plans, Spindrift - 130 EUR
Purchase
My wood strip surfski has been brewing for a very long time. It started with the Sea Racer. As the name implies, it was designed as a very fast sea racer with long-distance touring capacity. I found the inspiration in Alaska and the plans were finalized during spring 2006.
But before I had my own Sea Racer launched I was asked to design surfskis: first out was Nordic Kayaks Fusion, the first in a long line of top skis. Then came Seabird Designs, for which I designed the Wave line of skis, followed by a new company, Axis (that sadly didn't survive), with a line of surfskis and surfski hybrids, and a thermoplastic surfski "Onwind" for Chinese Liker kayaks.
Now realizing the potential of surfskis I initialized a project of my own: a wooden surfski. The idea was, that with the inherent advantages of wood (lighter and stiffer), this ski would almost match the top elite skis while still be within reach of intermediate paddlers. The result is Spindrift.
Spindrift is available also as a two-person surfski: Spindrift.2
What a fabulous boat! I have done 5 races and have had 2 first-place wins, a second, and a fourth. Surprisingly have been able to come out in front of a number of paddlers that are 1/3 my age. [...] I can't take all of the credit for my success and have to thank you for a design that has exceeded my expectations. I am truly amazed at the speed/stability ratio. I know that given the dimensions of this surfski, it can't possibly be as fast as many of the elite-level boats on the market. The fact that it is fast for its length and beam can partially be attributed to its linear stability curve. I am able to apply full power in this boat and that is not always the case for me in "faster", tippier boats. [...] I have been in some reasonable-sized "bumps" and have occasionally had the bow dip under, but not too far. [...] The boat has attracted more attention than I ever imagined. The lines that you drew create a beautiful sight when they come to life in wood.
Ken Katz
18 km/h on my first outing in my Spindrift. Good conditions 6 m/s and 0,4 m waves. Then in November, I clocked 19,5 km/h. As a touring kayak in the summer, it is superb. I leave all sea kayak paddlers far behind and I can take a swim anytime. (my translation)
Camilla Persson
I´ve never paddled anything that fast and easily driven!
Assar Åhlander
It can be built with an under-the-hull rudder (the most efficient version) for racing/exercise or an aft-mounted rudder and hatches for touring. The dimensions are 608x48 cm and the length can be adjusted as usual during setup, with advice on the plans for hulls between 576 and 640 cm. The surfski hull is easy to build due to its clean, harmonious lines. The cockpit structure may seem complicated, but three different methods are indicated on the plans: strip, foam, or carbon/fiberglass – and the general shape is drawn as a good starting point for individual adjustments.
A shorter and wider version will be available later – in about six years... (just joking ;-)
I do not plan to include a top-level elite ski. Very few amateur builders would be able to match a professionally built elite ski tipping the scale at approx 10-11 kg – and those who would, won't need my plans anyway. If you want to compete in the surfski top worldwide circus, I suggest you buy a Nordic Kayaks Nitro or one of the other top skis.
Take a look at Ken Katz's photoblog showing the construction of his Spindrift.
Jose Francisco Yuste Ramirez has a lot of very instructive and inspirational photos from building his Spindrift. Here is a short video of Spindrift in Spanish waters.
Particulars
| Length¹ |
608/603 cm (overall/WL) |
| Beam |
48/44 cm (overall/WL) |
| Draft |
10 cm |
| Weight² |
16-19 kg |
| Displacement/volume⁶ |
110 kg/381 litre |
| Prismatic coefficient |
0.55 |
| Wetted surface |
2.05 m² |
| Intended use |
Racing, excercise and touring on open sea, lakes or rivers |
* These dimensions can be adapted to suit personal needs or wishes.
** Depending on type of wood, equipment, care with epoxy usage, sanding etc. etc.
*** The speed numbers are based on mathematical standard formulas (175 lb paddler + 30 lb carco weight) and corrected from the kayaks actual performance om trials, on tours and in races.
⁴ Calculated resistance in 4 and 5 knots (at nominal load capacity).
⁵ Initial stability and secondary stability on a subjective scale, where 1 is very tippy and 5 is very stable.
⁶ Displacement is kayak + paddler + load. Count off the kayak weight to get the load capacity.
Plans, Spindrift - 130 EUR
Purchase
Minimum window dimensions to get your kayak out from the workshop:
49x34cm
Why a surfski instead of a sea kayak?
There are of course good reasons for both. They do the same job and there is not much that cannot be done in both. But I guess that surfskis will take over some of the sea kayaks' home waters (perhaps we will declare rudder-dependant sea kayaks, multisport kayaks, and training kayaks endangered species in a few years). Surfskis are in a way a step forward in the kayak concept. The rationale may go like this:
Safety
The safety routines in a ski are easier to master than comparable routines in a sea kayak.
- Reentering the cockpit from the sea is a straightforward and quite simple procedure (at least in surfskis with some level of stability) that takes a couple of seconds and is done the same way in all conditions. Since it is very quick there is less risk of getting cold or tired, and there is no water to pump out – it drains as soon as you start paddling (but, of course, a well-designed sea kayak and a bomb-proof roll is even better!).
- A surfski is basically a simpler craft with fewer components that can break or malfunction, and the few needed are within reach in the cockpit (the pedal setup and the drain).
- A surfski is an efficient craft; faster and lighter – but it is not just about speed. Just as important is conserving energy on long distances, touring or racing, about having the strength to deal with a headwind or current at the end of the day.
- A surfski is controllable in conditions where a sea kayak is hard to control. The reason is efficient steering: solid pedals and big efficient rudders (never thought I would actually say that ;-). But an elliptical rudder two or three feet from the stern on a highly maneuverable hull is far more efficient than an aft-mounted rudder on a sea kayak and the solid and precise pedal control with no flex is much better than on most sea kayaks – and the direction stability needed in a sea kayak will compromise maneuverability to a degree.
Fun to paddle
A surfski is exciting on the water. In addition to all what most sea kayaks can do, the surfski offers downwind runs in rough seas with amazing surf under full control and at speeds well above what even a very fast kayak can achieve - or to play in the breaking waves in the same way board surfers do.
Simple to use
The surfski invites a minimalistic approach: fewer gadgets to buy, pack and unpack during trips, and less upkeep. That means less weight, better performance, and quicker launchings. Of course, those paddlers used to filling up their sea kayaks for trips will perhaps not like roughing it out in a surfski.
Excercise
A surfski is a formidable exercise and training craft. A trip in a sea kayak is of course as efficient as a workout (provided you do not lean against the backband and use your arms only) but the simplicity is a bonus: a light surfski on the shoulder, paddle and PFD in the hand, launch and away you go...
Sea racer vs surfski?
What is the real difference between the Sea Racer and the Spindrift? Or in general – what separates surfskis from sea kayaks or multisport kayaks?
Well, it turns out the only sure sign is the cockpit configuration. In everything else there are lots of crossover crafts floating around, defying categorization: sea kayaks with surfski maneuverability and surfski with the calm movements of sea kayaks and all kinds of hull configurations.
Modern Surfskis were from the start developed to run off the wind on large swell reaching extreme speeds, and to surf the wavefronts in control. To keep the position and direction on those waves, extreme maneuverability was needed. To control the craft, precise steering and a large rudder were necessary. The stem was high to avoid diving in the gigantic waves of the native waters in Hawaii, South Africa, California, Australia – while the stern often became little more than a long tail with a rudder. The fore part was deep and narrow moving the lateral center forward to balance the large rudder, while the aft part was wide and shallow to prevent the stern from submerging at speeds close to or above hull speed. Surfskis became elite tools for tough oceans races. But eventually, the market evolved to include also crafts more suited to "normal" paddlers with touring ambitions.
Sea kayaks, on the other hand, evolved towards strong tracking, rather than maneuverability. The designers sacrificed some maneuverability for comfort on long passages – in automotive terms, they have the soft somewhat imprecise steering with a healthy margin for errors of a family car, rather than the precise and attention-demanding direct steering of a race car. Of course, some of the control is lost in the process. Have you tried to surf a steep wave diagonally in a sea kayak, you will know what I am talking about. But lately, we have seen a lot of sea kayaks with almost surfski-like maneuverability and control.
A look at the lines of the Sea Racer and Spindrift reveals these differences. The Sea Racer hull is more symmetric, with LCB, LCF, and CLA quite close to the center, indicating a hull that moves smoothly and predictably in the water (LCB = Longitudinal Center of Buoyancy = the centroid of the underwater volume of the boat expressed as a longitudinal location. LCF = Longitudinal Center of Flotation = center of the waterplane, the "seesaw" pivot of the craft. CLA = the geometric center of the lateral plane). The seat is located slightly aft of the center, providing controllability without being overly dependent on the rudder (mildly understeering in automotive terms). The rocker is not very accentuated, which improves tracking. The kayak deck with cockpit rim/spraydeck keeps water out, allowing for a lower and less wind-sensitive profile. For the same reason, the freeboard amidships can be lower, to allow a lower and less tiring paddle stroke on touring.
In the surfski, the CLA is moved forward to balance the large rudder. The seat position slightly forward of the LCB is the key to the efficient and precise steering on wavefronts – in automotive terms, the ski is slightly oversteered in low speeds, but becomes neutral in higher speeds since the longitudinal position of the hull's center of turning is related to speed.
Note that the Sea Racer is not a typical sea kayak – it was influenced by surfskis from the start.
The station drawings show that the surfski is wider and higher than the Sea Racer. But the difference in volume and load capacity is not as large as it might seem – the higher Cp of the Sea Racer means that the volume is more evenly distributed along the hull, while the surfski has more volume concentrated midships. This suggests that the Sea Racer should be slightly faster on flat water, but the surfski should win in waves.
The shape of the sections looks quite different. In the Sea Racer, I wanted to optimize the initial stability in what is a very narrow craft (43 cm), with the chines also enhancing steering control when the hull is leaned (a way to keep rudder turbulence to a minimum). For the wider surfski, I chose to minimize friction with elliptical sections below the waterline.
Software and the design process
The sectional shape is also to a degree influenced by different calculation algorithms. The Sea Racer was developed using Bearboat by Robert Livingstone for the hydrodynamic calculations. The main advantage of this is that the underbody defining vectors hang from the waterline and the keel, which makes it possible for the software to minimize the wetted surface for every set of design parameters chosen. It saves a lot of time fine-tuning the hull to low friction but also means that the bottom and freeboard are two independent sets of curves, meeting at the waterline. On certain kinds of hulls, this complicates getting a smooth natural curve from the sheer to the keel.
For the surfski, I used Ross Leidy's KayakFoundry, forked from Bearboat, but with one important difference: the vectors hang from the sheer and the keel. That means better overall control of the lines (including deck shape and stem and stern) compared to Bearboat, but the disadvantage is that you have to work the wetted surface manually based on experience and through repeated iterations followed by checking the calculations. One further disadvantage is that KayakFoundry is just for Windows. I have to run it virtualized in Parallels on my iMac – it works, but a bit slower than native Mac applications (it takes a lot of memory to run two separate OS).
Both applications are easy to use and do an excellent job at their level, but the downside of the simplicity is the many limitations in what can be achieved (not a problem for the amateur builder, who would solve those issues in the construction phase rather than on the computer anyway). Therefore I use them for a quick zooming in on the hull shape I want, along with all the hydrodynamical data I need – getting within 95% of the final design in a surprisingly short time and with adequate accuracy. From there I transfer the lines to Illustrator for the final manual fine-tuning, including both functional tweaking and the visual layout of lines and surfaces – which always takes a lot more time than the first 95% in the design software!
That may seem a tedious way to design a kayak, but the alternative – professional ship CAD design systems are very expensive and bloated with features of which I would use a small percentage (I do not need to know what happens to the ship's stability when 600 tons of crude oil sloshes around in a half-empty tank, nor at which parameters the risk of propeller cavitation becomes an issue ;-) and would take hundreds of hours training for me to master.
Spindrift
The surfski is named Spindrift – an apt name for a craft with an appetite for wind and waves.
Surfski history
The surfski history is linked with surfboards rather than with kayaks. One common starting point is two brothers in Australia, Harry och Jack McLaren, using a kind of paddleboard a hundred years ago in the breakers around the oyster beds the family-owned at Port Macquarie, New South Wales. From the descriptions, these were ancestors of today's surfboards and SUPs rather than what we now mean with surfski. But surfski was the common name then.
Sometimes mid-century the rescue organizations in Australia found out that these “surfskis” were more efficient than the rowboats with a crew of 5 that were used to save swimmers swept out to sea by the currents. They were simpler, cheaper, and faster, and 1946 surfskis were officially accepted as rescue crafts – then flat surfboards, far from the surfskis of today.
What now is known as surfskis developed in competitions between rescue teams on different beaches during the 50s. The early paddleboards were heavy skin-on-frame designs, but they soon evolved to longer and narrower hulls – still paddled standing up as SUP:s.
At the Melbourne Olympics 1956, athletes from other countries saw the surfboards and were impressed – and the surfski paddlers discovered the efficiency and power when sitting down with a kayak paddle. In the US and South Africa, the next steps in the development of the modern surfski were taken.
In South Africa, the skin-on-frame was exchanged for foam-filled fiberglass hulls with a cockpit and the main focus was distance competitions. In Australia, the sport came to focus on sprint in strictly regulated fiberglass surfskis.
On Hawaii, this evolution took off a little later and, very interestingly without any rules regarding the hulls. The developing environment was the toughest possible: formidable Pacific swell and fast-moving currents around the islands. Molokai Race became the most important event to evaluate new designs and ideas. Also very interesting is that the fastest time ever on Molokai is from 1997 with an older, shorter, and heavier Hawaiian ski and a standard flat paddle (Dean Gardiner). That is just one indication that today's surfskis at 6,5 meters may be longer than necessary – and the reason may be that a couple of very big and strong competitors dominated the sport for some time, tricking the manufacturers to increase the length. They could make good use of the long hulls in spite of the increased friction. But can we?
I believe that the top surfskis of tomorrow will be perhaps 5% shorter.
