Web Site Reviews [47]

The Ultimate Directory of Kayaking Links – Ken Winter has amassed a massive mass of links for every conceivable facet of sea kayaking, and there is simply no better collection of up-to-date and relevant kayak links to be found on the net.

We’re quite possibly doing this column a huge disservice advertising this page because once you have it you’ll never need to read this column again! Neverthless it’s well worth checking out. But make sure you have a coffee… you’ll be busy for hours and hours.

The Weather Co – Outstanding Australian site that provides a myriad of up-to-date information on weather around the country.

Easily navigable and with more information than the poor, old Editor can understand, it contains information on seasonal outlooks, rainfall information, wave and swell charts, forecast models, TWC charts, coastal waters forecasts… the lists go on and on.

Beats the BOM site hands down – an absolute must-visit for all kayakers before they paddle.

Sea Kayaking Frequently Asked Questions – One of the most comprehensive FAQ lists available. Amassed from the rec.boats.paddle newsgroup, this FAQ covers virtually every question you could want to ask about sea kayaking.

Everything from buying a boat to hypothermia to kayak history is well covered here, but most importantly there is an extensive section on folding kayaks.

Enough said… visit it today.

Attack of the Killer Ray [47]

By Trevor Gardner

The stingray is ubiquitous in most areas of Australia where sea kayakers lurk.

Stingrays inhabit tropical to temperate water, from open sea to many kilometres upstream in brackish water. There are Whiprays, Giant Stingrays, Butterfly Rays, Eagle Rays, Round Stingrays, Cow-nose Rays, Mantas, Freshwater Stingrays and River Rays.

Stingray

Stingrays are bottom dwellers, so that their flat body is often submerged in sand and only detectable by an eye or two, a piece of tail or the spiracles (water intakes) showing above the elevated disk or mud. Usually shallow water creatures they have been found in tropical waters at 30 to 60 metres. At up to 2 metres across and 4 metres long, a 2 ton ray is an impressive creature. Manta often jump out of the water and have occasionally damaged fishing boats. Stingrays feed on a variety of shellfish, molluscs, crustaceans and worms. The one or more spines are used for defence.

The stingray is non-aggressive, but is capable of protecting itself. Treading on the dorsal surface by mistake or swimming too close above a ray can result in a reflex upward and forward swing of the tail. The injuries can be either a sword like lacerations or penetrating injuries with the serrated spine. Serious injury can either be from the physical trauma of a vital body part, from the venom of the spine or both. In the USA 1,500 stingray injuries are reported annually.

I regularly see small and medium stingrays in 30 to 60 cm of water in the Port Hacking estuary system south of Sydney. On one occasion I disturbed a 1 metre ray in 60 cm of water by paddling over its back. I have subsequently pondered whether the stingray spine is capable of penetrating the hull of sea kayak. Probably a good selling point for kevlar over fibreglass hulls; ‘This hull is ISO certified stingray resistant’.

The paper below was recently published in the Medical Journal of Australia and has been edited and reproduced with permission of the author. The case history makes an interesting and dramatic read of the most severe consequences of a stingray misadventure. The discussion highlights some of the sequelae associated with a stingray spine injury and is followed by the current management principles of a stingray injury. The literature indicates that disabling sequelae can persist for more than a year due to incomplete initial wound management. Specifically, failure to adequately image the injury (x-ray or ultrasound) and debride the wound of spine and integument remnants.

Reference

Dangerous Marine Creatures – Field Guide for Medical Treatment, Carl Edmonds MD, 1995, Best Publishing Company

 

Survivor of Stingray Injury to The Heart

Beatrix Weiss MBBS FRACS & Hugh Wolfenden MBBS FRACS (from MJA 2001; 175: 33-34)

Injuries to the extremities from stingray barbs are not uncommon along the Australian seaboard. Cardiac injuries from Stingray barbs are rare, even worldwide, and all but one have been fatal. We report a survivor of a cardiac injury caused by a stingray barb. Penetration of a body cavity by a stingray barb requires early surgical referral and management.

Australian coastal waters contain many species of stingrays, and injuries to the extremities caused by the barb or barbs on a stingray’s tail are not uncommon. These wounds are painful, and may develop necrosis and secondary infection. Penetration of a body cavity by a stingray barb may cause major morbidity and even death, particularly with cardiac injury, and requires early surgical referral and management.

Clinical Record

A 33 year old man was snorkeling at Coogee, a popular Sydney swimming beach, when he was noticed to be in distress. He was rescued by lifeguards, and found to be unconscious, not breathing, and had an increased heart rate (150 beats/min). After a short period of expired air resuscitation performed on the beach, he regained consciousness and said he had been struck by the tail of a stingray. He complained of difficulty breathing and severe, left-sided chest pain where the tail had struck.

When paramedics arrived he was cyanosed, with a systolic blood pressure of 75 mmHg (usually 110 to 140) and sinus tachycardia (heart rate 150 beats/min), but with normal level of consciousness. He was given fluid resuscitation on the way to hospital with no improvement in blood pressure.

On arrival at the emergency department, he remained in cardiogenic shock with a low blood pressure and high heart rate, hypothermia (temperature of 31C), poor peripheral perfusion and central cyanosis. He had a 2 cm laceration over the lower left chest next to the sternum. His Glasgow coma score (level of consciousness; 15 normal, 3 dead) had deteriorated to 10. He was intubated and manually ventilated. Invasive monitoring catheters were inserted and cardiac support commenced with adrenaline.

Echocardiography revealed a cardiac tamponade, fluid trapped in the sac around the heart causing restriction to cardiac function. A needle drainage was performed and 150 ml of blood was aspirated from the pericardial sac. This resulted in prompt restoration of blood pressure to 170/80 mmHg, and reduction in heart rate to 100 beats/min.

Because of the possibility of foreign material in the pericardial space and the known necrotic effects of stingray venom, the patient was transferred to the operating theatre, where the chest was opened the pericardial space and left pleural cavity were explored. A puncture wound that had spontaneously sealed over was found in one of the coronary arteries. There was no injury to the cardiac muscle. No foreign material was found. The area was copiously irrigated to remove all potential venom. Intravenous antibiotics were commenced and continued for five days.

His recovery was uncomplicated. He was discharged home on the sixth day after the operation and was well at the two month follow up.

Discussion

Stingrays are the largest of the venomous fish, and there are many species in the Australian coastal waters. The tail of the stingray carries at least one barb or spine that may be up to 37 cm long. The barbs are cartilaginous and retroserrate, and covered by a film of venom and mucous contained within an integumentary sheath. Two longitudinal ventrolateral grooves contain venom secreting glands. Stingrays usually lie in the sand on the seabed. When disturbed by pressure over the dorsum of the body, the tail is thrust upward and forward, driving the barb in to the victim. Rupture of the integumentary sheath on penetration allows the venom to be released.

The venom contains toxic proteins. The effects of the venom may be local and/or systemic. Local effects include severe pain at the site of injury and tissue necrosis. Systemic effects include nausea, vomiting, salivation, sweating, respiratory depression, muscle fasciculation, convulsions, cramping abdominal pain, cardiac arrhythmia, myocardial ischaemia and, rarely, death. Many of the systemic effects have been documented only in patients with viscus penetration (gut), and not in those with peripheral stingray injuries.

Local venom effects are usually more troublesome in peripheral stab injuries, but if the barb pierces a vital organ or structure mechanical damage may be more dangerous then the venom effects.

Instances of serious, penetrating, non-cardiac injuries include collection of pus within the chest three days after netting a stingray and sustaining a barb injury to the chest; penetration of the liver; multiple bowel perforations; and laceration of a femoral artery, with death by exsanguination. Penetrating cardiac injuries have generally been fatal. In 1938, an adult women died after a stab wound to the heart by a stingray. The autopsy showed that the ventricles had been completely transfixed by the barb. An Australian soldier died in 1945 after a stab wound to the left heart, sustained while swimming in seawater baths near Melbourne, Victoria.

The current patient was fortunate to have a sustained an injury to the coronary artery rather than the heart muscle. The bleeding artery immediately washed the venom away, whereas injury to the heart muscle is difficult to debride and carries the risk of delayed necrosis and perforation (seen in a 12 year old boy in Queensland in 1989).

Current Management Principles For Stingray Injuries

  • Immersion of the affected part in hot water (about 45C) for at least 30 minutes for pain relief (relief is generally only effective while the affected part remains immersed).
  • X-ray of the affected body part to exclude the presence of cartilaginous barb remnants.
  • Local infiltration of local anaesthetic.
  • Systemic analgesia.
  • Careful wound examination, removal of foreign material, irrigation and debridement.
  • Heal by secondary intention (not closing the wound and allow to close from bottom up).
  • Antibiotic cover, broad spectrum.
  • Tetanus booster if required.
  • Early referral of confirmed or suspected penetrating injuries of chest or abdomen.

Secretary’s Report [47]

By Nick Gill

Almost another Rock ‘n’ Roll. I can’t say I was at the first one, but I’ve been going since 1993, missing only maybe one or two. At my first event I could roll already, but there, just off Patonga, I rolled in open salt water for the first time. Suddenly extreme lean turns held no fear! I remember vividly the feeling of achievement. The Rock ‘n’ Roll weekend can do that for paddlers, and many have had such experiences over the years.

As we all know we had problems last year. That wasn’t the Club’s proudest moment, but it has made this year an interesting one to be on the committee. We have had to deal with the aftermath, re-evaluate our procedures, and decide how we will run Rock ‘n’ Roll this year. I think we have come up with an approach that recognises the growth of the event, which will maintain the fun and which will attend to safety as well. I think the Club has responded well to the situation. On top of this has been the new AC Award structure and considerable thinking as to how to position the Club for this. To a large extent actually implementing the Club approach to this is probably next year’s main task for the new committee. That committee will also have the task of assessing our approach to this year’s Rock ‘n’ Roll weekend.

It’s been good fun, and I have always enjoyed meeting up with other committee members. Being involved with a group trying to manage a Club engaged in a relatively high-risk sport has been a learning experience to say the least! Each year produces new situations to deal with and demands adjusting our procedures. The Club is in constant evolution as we strive to maintain a focus on paddling and trips, whilst ensuring safety and risk management are not ignored. I can recall when the trip grading system, first put together by Gary Edmond, was introduced. At the time it was about the only management tool the Club had. It’s been tweaked a few times now, and we now also have various policies, a trip leader’s briefing guide, waiver forms, improved insurance, a trip leader’s course and a strong group of instructors.

I won’t be there next year. I am pulling the pin after two years on the committee. Much of the job of Secretary/Treasurer is characterised by routine compared to other positions. However, as a committee member you are also involved in other issues to do with Club management, and can expand your involvement as you wish.

So yes, the Secretary/Treasurer position is open. Consider putting yourself forward for the position. The work involved is consistent but not onerous. If you are interested or want more information, email me or phone me on (02) 4226 2647.

As for more mundane matters: membership has edged to just over 200. We remain down on the level of 250 in 2000, but it’s still healthy. Club finances are in reasonable shape, although we still have this magazine to pay for this year. We are also spending more than previously on the Rock ‘n’ Roll weekend. The small fee we are charging for attendance will hopefully cover our expanded costs.

Thanks to the efforts of Wollongong member Andrew McPhail, we also have a new batch of Club stickers. These are available for $2 when you rejoin and they’ll be available at the Rock ‘n’ Roll weekend.

Speaking of rejoining, do yourself and the Club a favour and renew your membership by post before the Rock ‘n’ Roll. You’ll save yourself and the organisers some work on the weekend. There is a copy of the membership form in this magazine – get it off to me today.

We have also been attending to the matter of proficiency assessments. Due to some problems in past with administration of the awards and in instructor certification, some proficiency assessments have not actually been formally confirmed. These problems came to light at the beginning of the year as I attempted to process proficiency assessments from Rock ‘n’ Roll 2000. The administration of the award scheme is being centralised to a greater extent and this has exposed shortcomings in the existing system. Shortly before fronting up for our instructor assessments, Rob Mercer and I discovered that, as far as Australian Canoeing was concerned, we didn’t have the proficiency award, a prerequisite for the instructor award! We thought we had it under our belts some years ago. Fortunately for us, this was resolved in conjunction with Australian Canoeing.

We have gone through our database and provided Australian Canoeing with a list of members whom we believe have the proficiency award. If you believe you have the proficiency award and you have an older certificate, for example, a small green one from the Australian Canoe Federation, get in touch with Australian Canoeing in Sydney and check your status. They have been most helpful when such certificates have been produced and have accepted the award and issued certificates (at no charge) even if you were not registered on their database as having proficiency. If you sat for proficiency in late 2000 or in 2001, you should have received your certificate by now. Unfortunately there were some hiccups in the process. These have now been resolved by the Club and Australian Canoeing. We apologise for the delay.

Kayak Sailing [47]

The Aerodynamics Of Sails And The Implications On Performance And Stability Of Kayaks

Mladen Milidragovic

The aim of this article is to turn the attention of sailing minded kayakers and canoeists (and sailors in general as well) to certain irrefutable, scientific facts about the aerodynamic efficiency of sails; to give them a starting point for their own research of this utterly important matter; and to convince them that a well designed sail guarantees pleasant and safe sailing without the need of transforming their light craft into trimarans.

Upwind sails are devices for generating horizontal aerodynamic force. In aviation terms this force is known as the Lift force and the name of the generator of the aerodynamic lift is the Wing. Common names for such devices are airfoils and airprofiles and they work on the same principle called the Bernoulli principle.

Essentially, the generated lift force is a result of different pressures on the lower and upper sides of a wing, or the windward and leeward sides of a sail. The Bernoulli principle (1738) states that the pressure depends on the speed of a fluid – the lower the speed the higher the pressure, and vice versa. Wings are designed (by nature and then by humans) in such a way that their upper surface is cambered (airflow wise), thus longer than the lower surface. As a result, the airspeed above the wing is higher than below the wing, the pressure below the wing is higher than above it, and this pressure difference is what keeps birds and non-powered aircraft (paragliders, hang gliders, sailplanes) as well as subsonic and supersonic planes in the air.

The same process develops when a sail is set under a proper angle of incidence to the wind. If the sail is vertical, the resulting force will be horizontal and not necessarily parallel to the vessel’s longitudinal axis – depending on the angle between the axis and the sail. The vessel’s keel and rudder actually decompose the total aerodynamic force into its driving (parallel to the axis) and heeling (perpendicular to it) components. The ratio between these components should obviously be as high as possible and this is what makes a sailboat design a piece of art.

Sails that are too small cannot produce sufficient driving force. Large sail areas produce excessive heeling which in turn necessitates a wider hull and a heavier ballast to make the vessel more stable and safe, and its sailing rig as vertical as possible to avoid dissipation of the aerodynamic force as well.

Unfortunately, heavier hulls with a more wetted surface are slower, need larger sails… and the story goes on.

Traditionally, the problem of sailboat stability has been treated at the level of the hull. Light craft (kayaks and canoes), by their nature, are very light and narrow/streamlined. No ballasts, no wide beams, no righting arms to counter heeling forces – and they cannot even be balanced by the crew. Outriggers seem to be the only solution.

But let us move from this low level and go higher, to the root of the problem – to the sails again.

The above-mentioned Drive/Heel ratio (D/H) is variable and depends on the point of sailing. However, there is a characteristic value for each sail that clearly determines the D/H ratio at a given point of sailing, and it is called (borrowed from the aviation terminology again) the Lift/Drag ratio (L/D).

This ratio goes from 5:1 in modest sails to 10:1 in America’s Cup sail rigs.

Now comes the strange part: the L/D ratio in wings of some sailplanes goes up to 50:1! Why is this so?

Wings are designed according to the science of aerodynamics and numerous catalogues (NACA, Goetingen, RAF, Wortmann, Eppler, Quabeck, Clark, etc) with hundreds of efficient wing sections, each of them described by their amount of camber, the thickness, the position of maximum thickness, the leading edge radius and the coefficients of lift and drag.

Wings of non-powered, low speed aircraft (could be compared to sail rigs) have very high aspect ratios (the ratio between the span and the average chord of the wing) of up to 40:1 that significantly reduce the induced drag.

On the contrary, a traditional single ply sail rig doesn’t have any ‘aerodynamic’ thickness and its leading edge (mast, even a ‘wing’ mast) is disproportionately thicker than the foil itself, creating a lot of turbulence just behind it.

The position of maximum camber is much further aft from its leading edge, their aspect ratios being usually between 4:1 and 6:1. Such a sail generates much smaller aerodynamic lift force (small coefficient of lift) per unit of sail area than an ‘ideal’ sail and needs to be much larger than the ideal one in order to produce the same driving force (from now on I’ll call an ‘ideal’ sail a wing sail because there is simply no such design that is better than a design of the wing). A larger sail in turn increases the friction drag component. Because it is single ply, it must be trimmed closer to the centreline (the angle of attack of the wind has to be bigger to avoid ‘luffing’) which increases the form drag. We can see that all of the aspects of drag are inevitably higher for a conventional sail than for a wing sail – so is their sum total. The aerodynamic drag is usually thought to be a nuisance that only decreases the speed of moving through a surrounding fluid, but for sailboats it is also responsible for the heeling momentum (see Figures 1 and 2).

Figure 1 – a conventional rig

Figure 2 – a wing sail

This is something very important that somehow eludes most designers and sailors (including specialists from WUMTIA – Wolfson Unit for Marine Technologies and Industrial Aerodynamics in Southampton, UK), in spite of their customary familiarity with the name and work of CA (Tony) Marchaj, who in his Sailing Theory and Practice wrote, “We can conclude immediately from either pair of these equations that the drag not only lowers the driving force FR, but also increases the harmful healing force FH.”

The total aerodynamic force FT, as a vector, is determined by its magnitude and direction. Ideally, this direction would be the same as that of the vessel (even theoretically impossible, except at a certain broad reaching angle) – practically, the force is being rotated back toward the stern and the major factors that contribute to this are: the angle of attack at which the sail works, the positions of maximum camber and thickness, and the total drag. A wing sail is absolutely superior to a conventional sail in all of these points and its total force direction is much closer to the bow. It should be beared in mind that the drive force FD is the total force FT times the cosine of an angle between the FT and the centreline (ideally, when this angle is zero, FD=FT; in the same time the heeling force FH, which is FT times the sine of this angle, would be zero). It is no wonder that some authors claim that the driving force FD of a wing sail is 250% larger than that of a conventional sail, with twice the smaller heeling force FH. Yet, America’s Cup design teams “toil over hot computers to get that extra hundredth of a knot”.

One might ask why a boat wouldn’t simply be rigged with a wing instead of a Bermudian sail if it is that superior?

There are at least two reasons that make this difficult. First of all, one can always tell which side of a wing is the upper side and which is the lower side (except for some special purpose symmetrical wings). On the contrary, sailboats tack and gybe, receiving the wind from either the port or starboard side. That means that a wing sail has to be adjustable (i.e. flexible) in order to provide an asymmetrical aerodynamic shape on either tack.

Secondly, a wing sail has to be light, much lighter than aircraft wings.

Increasing the weight aloft can easily annul the aerodynamic superiority of a wing sail, or even render it unusable.

For instance, the US patents No 3, 332 and 383 mechanically solved variability of a wing sail camber, but such a sail (small size, as for kayaks) would probably weigh hundreds of kilos and a ripple would be enough to flip it over.

The search for a soft, light, simple and foldable wing sail has not been fruitful until recently. Now there are a couple of designs that fulfil the requirements mentioned above. Between the two sailcloth panels there is either a lateral or a longitudinal light structure that maintains the thickness of the sail while giving it a near optimum asymmetrical aerodynamic shape, depending on which side of the sail is being exposed to the wind. Details about technical/structural solutions for these sails would go beyond the scope of this article.

Now a few words on downwind sailing: if traditional upwind sails are conventional, traditional downwind sails are pre-conventional. That is how sailing started and how upwind sails were derived from downwind sails. Downwind sails as we know them work on a different, much simpler principle than Bernoulli’s one. The resistance of a large sail area spread out before the wind (basically the form drag) is much higher than the resistance between a hull underneath and the water. The end result is running before the wind.

There is an interesting development here. An airfoil under a proper angle of attack to the wind (10-20 degrees, Bernoulli effect) will produce an aerodynamic force roughly twice the resistance force produced when the same airfoil is placed at a right angle to the wind (conventional downwind sailing). Why isn’t this effect utilized in downwind sailing?

First, rigging wires (stays) don’t allow booms to travel beyond 90 degrees – at this point the boom would hit a stay.

Secondly, long and heavy booms, if they could pass the beam point when they rotate toward the bow (like freestanding 360 degrees rotational masts), could be difficult to haul back. Freestanding (unstayed) masts have been a reality for some time, thanks to technological advancements (the Team Philips catamaran, the British entry in the Jules Verne Around the World Trophy, had two freestanding masts over 40 m high!). Combined with wing sails, they bring sailing to a quite amazing perspective.

Figure 3 – a wing sail downwind

Wing sails do not care which direction the wind is blowing from. When in neutral position, a wing sail will align with the wind, like a flag. When set under a proper angle of attack, it will start producing an aerodynamic force (see Figure 3). It is only up to a sailor to use this force for propelling the sailing vessel in a preferred direction.

The only difference between upwind and downwind sailing from this standpoint is that the aerodynamic drag slows down upwind sailing and speeds up downwind sailing – yet the sailor might easily be unaware of this effect.

Even tacking and ‘gybing’ are substantially identical operations.

Stayed rigs on large boats and yachts still have some merits, but kayaks and canoes are actually much easier to rig with freestanding rigs than with stayed rigs both technically and practically, either on shore or in the water.

Happy sailing!

Mladen can be contacted at:
Wing Sails Co (Canada)
phone/fax: + 1 604 669 0757
www.wingsails.com

Rogue Waves [47]

Ooh Aah Big Motion In The Ocean

By Richard Birdsey

Intrigued by an article on rogue waves in a recent New Scientist magazine I found out a bit more about the myths, science and reality of this awesome ocean phenomenon. Stories of giant waves taking ships and their crews have been around since ancient times. Many of these legends are being revealed as fact as modern oceanography, marine engineering and complex computer models build up a more realistic picture of these mountains of water.

We often hear about the results (sometimes tragic) of rogue or ‘freak’ natural events but what exactly is a ‘rogue’ wave?

‘Rogue’ is a generic term given to an unusually large wave appearing in a smaller set of waves. Trip reports often talk about the biggest wave (or set of waves) seen that day arriving during a beach launch or exit, damaging boats and threatening life and limb. These waves could be called ‘rogues’. However, the waves I’m talking about are truly monsters. Wave heights (trough to crest) of 17 metres to heights over 30 metres (11 storeys high) are common. When you consider these monster waves may be interspersed among a background of 5 to 7 metre high waves you can start to understand the forces at play. Mariners have accurately measured a few rogue waves, usually by watch officers triangulating wave crests against parts of the vessel. Marine radar, satellite instruments and wave buoys now provide most of the information on rogue waves.

Some of the characteristics of rogue waves are:

  • they are greater than twice the size of the ‘significant wave heights’ of surrounding waves,
  • they are often deep water waves,
  • they may be associated with a very deep trough and other uncommonly large waves moving in a set or ‘train’,
  • they often come unexpectedly from directions other than prevailing wind and waves,
  • they probably last only a short time or distance (minutes or a few hundred metres), and
  • they are unpredictable – though they do occur more frequently in some places in the world.

So How do These Monster Waves Form?

There are a number of factors that generate waves. Underwater seismic movements and other natural phenomena can generate huge waves (called tsunamis), but most waves are generated by wind. Atmospheric variations in air pressure force air down, displacing surface water. As the wind moves laterally across the surface of the water along a pressure gradient it drags or pushes the water with it. These two air movements, vertical and lateral (or ‘shearing’) dump energy into the water. The particles of water don’t actually move much, but the wind-generated energy is transmitted through the water, sometimes at many hundreds of kilometres an hour. As wave height is determined by wind speed, wind duration and fetch (the distance the wind blows uninterrupted over the sea surface) it would be logical to assume that a big wind blowing constantly over a big stretch of water (say the Pacific Ocean) would produce monster waves. Generally in open waters a wave 1.86 times the significant wave height can be expected every 1,000 waves or so. But any resulting big waves would be toppled by winds at about 70 knots and 100 knots of wind would flatten them, so a train of rogue-sized waves couldn’t form. Wave physics is a vastly complex area and I’m not going to weigh into it here.

Some different types of waves are outlined below. “Significant wave height” is the average height of the highest one-third of waves measured by an observer over a period of time.

Deep-water waves (or ‘short waves’)
waves whose length (measured from crest-to-crest or trough-to-trough) is less than the water depth. These waves include wind-generated waves travelling across the open ocean.
Shallow-water waves (or ‘long waves’)
where the length of the wave is greater than the depth of the water. These are wind generated waves that move into shallow coastal waters, tsunamis, and tide waves generated by the interaction of the sun and moons’ gravitational fields.
Capillary waves
rounded and V-shaped wind-generated waves smoothed out and destroyed by the ocean’s surface tension. They have wavelengths less than 11.7 cm.
Sea waves
ocean waves driven to their maximum height by the wind. As the waves move away from the area they are generated in they smooth out into longer (‘swell’) waves.
Tsunamis
are waves generated by underwater seismic movements and shallow-water waves with wave lengths of 160 km or more. Comes from a Japanese word tsu meaning ‘harbour’ and nami meaning ‘wave’. They travel at 500 km/h and are vastly destructive when they come ashore.

The answer probably lies in a complex interaction between wind, current and topography of the seabed. Mechanisms that could generate rogue waves include:

  • Constructive interference. Waves move from their point of generation in sets or ‘trains’. Constructive interference suggests that several different wave trains travelling roughly in the same direction meet at some point and build on top of each other. The energy in the wave trains builds and adds on to the other resulting in a set of large waves, and one huge wave, embedded in the train. This wave will only last a short time as the different trains disentangle themselves and move in their own direction.
  • Focusing of wave energy. As kayakers know, when strong wind-generated waves run into a current going in the opposite direction then dangerous standing waves can form. A rising seabed will further concentrate energy in the currents. This hypothesis suggests that the energy contained in the waves smashing into the counter current can build and accumulate over time, forming huge waves. These waves are thought to be longer-lived than those developed by the constructive interference mechanism.
  • Normal wave height distribution. Wave heights are distributed (like most things) along a bell-shaped curve. Some waves are tiny (occurring at one end of the curve), most occur in the middle of the ‘bell’ and some extremely large waves are generated at the other end of the bell. At sea, most of the waves you encounter are in the middle of the bell (i.e. these are the most common waves) and there is a very low probability of meeting an extremely large wave. But if you do – tough luck. This is the ‘wrong place at the wrong time’ principle.

Whichever of these mechanisms is true (they probably all are in different situations), it is obvious that big seas, big winds and strong currents all are factors in generating monster waves. These factors determine why rogue waves are more commonly associated with some parts of the world. It is of little surprise that these ‘hot-spots’ are some of the most dangerous waterways known. The Agulhas current off the tip of South Africa, the Kuro Shio current off Japan and the Gulf Stream are places where deep ocean paddles are definitely not recommended.

However, the New Scientist article points out two problems with this picture. Firstly, rogue waves are commonly found in places such as the North Sea where there are relatively few fast flowing currents and constructive interference can’t entirely explain their frequency. The second and more pressing problem is that rogue waves appear to be much more common than the bell shaped curve suggests. Complex computer models that attempt to simulate wave patterns also predict that monster waves should be extremely rare. The problem is that studies observing real-life wave patterns (such as those using radar) show that monster waves can occur in some places as frequently as one per week.

Scientists are realising that rogue waves are not as predictable as first thought. Many of the computer models assume linear and predictable outcomes from variables (wind velocity, sea state, wind direction, etc) fed into the model’s algorithms. Scientists now think the sea is more ‘chaotic’ and that chaos theory needs to be introduced into these models. You will probably have heard the chaos adage about how the flap of a butterfly’s wing in Brazil causes a hurricane in Canada. Similar principles are being applied to wave models (e.g. a puff of wind off Cape Horn causes a rogue wave in Japan). How these theories work is far beyond the scope of this article and my ability to explain them. More interesting is how this research is being applied to make the sea a safer place to live, work and play.

The impact these waves have on maritime commerce and industry is huge. Inquiries into maritime disasters are increasingly looking at the possible involvement of rogue waves. Analysis of a number of ship sinkings suggests rogue waves may rip off the ship’s hatches, causing fatal down flooding into the main hold, which then rolls or pitch poles the ship or breaks its back. In any case the wave would come from nowhere and the end would be violent and fast.

Research is being applied to avoid these disasters on three main fronts. First, oceanographic studies and computer models are being combined to try to develop a system to predict when and where rogue waves may form. This will eventually enable maritime authorities to provide an early-warning system for ships and platforms.

Research is also being used in trials to program marine radar systems to identify rogue waves. Land-based radar or satellites might eventually be able to track rogue waves. Similarly, radar on ships can be programmed with calculations used in the models to identify an approaching wave and warn the ship, similar to laser systems used in aircraft to detect wind shear.

Finally, marine architects and engineers are looking at the design of ships, platforms, ports and other structures to gauge their susceptibility to damage from very large waves. Inquiries into the sinking of a number of container and cargo ships have recommended stronger hatches be installed to prevent flooding of the main hold. Complex designs and structures susceptible to wave damage are also being looked at. Drilling rigs may need to be made higher and stronger.

At any rate, the chance of us running into a ‘real’ rogue wave is pretty small. And I’m glad of it!

Some Resources

The 2001 Rock’n’Roll Weekend [47]

What Are You Waiting For?

Yes folks, it’s official! The NSWSKC’s 10th annual Rock ‘n’ Roll weekend is a reality and is steaming its way towards sunny Batemans Bay. Drop everything and make sure you’re there on 24 November 2001 for the three-day extravaganza of the Club year.

Many of you will recall that future Rock ‘n’ Roll weekends were considered a no go earlier this year following the incidents at Rock ‘n’ Roll 2000. But since then the committee and several hard-working members have met on an increasingly regular basis, and from those meetings the new and improved Rock ‘n’ Roll weekend was born.

The structure and the operation of the weekend has changed dramatically with a lot more organisation behind the scenes, which does mean a few rules for participants, but in general the increased levels of organisation will be mostly transparent to attendees, and a good weekend will still be had by all.

The focus of the weekend is socialising off the water and various kayaking skills on the water. Activities include;

  • Basic rolling tuition
  • Advanced rolling tuition
  • Rolling demonstrations
  • A rolling competition
  • Support strokes tuition
  • Self rescue tuition
  • Assisted rescue tuition
  • Towing tuition
  • A handicap kayak race
  • A wooden boat workshop
  • A kayak sails workshop
  • A forward paddling clinic
  • Grade 2 day trips
  • Grade 3 day trips
  • A buying your first sea kayak session
  • A sea kayak fit-out and safety gear session

In addition to these activities a number of kayak retailers will be setting up during the weekend to exhibit and demonstrate their wares for the benefit of members.

There is also excellent Saturday evening entertainment from the Australian Navy at Creswell who will be demonstrating the Navy’s latest personal survival equipment followed by a slide presentation on Navy survival and training. Plus more excellent Saturday evening entertainment from the National Parks and Wildlife Service who will be presenting information on coastal parks and sea kayaking.

On Sunday evening a number of members will be presenting slides, including Andrew McAuley who is presenting his recent trip through Cape York and Torres Strait (see page 34 of this issue).

And of course, the NSWSKC AGM will be held on the Saturday evening as usual, for the election of officials and reporting of Club activities and other matters.

Important Information

Many of you will recall that we couldn’t account for numerous paddlers last year who had left without advising the organisers. To alleviate this problem at future Rock ‘n’ Roll weekends all attendees will be required to register (whether you are camping, staying in a cabin or just coming for one day), and all attendees will be issued with a waterproof ID card for the weekend which lists who you are and how long you’re staying. Without the ID you won’t be joining in any activities so you won’t be having any fun.

This ID card will be cable-tied to your PFD for safety and security, so bring your PFD with you to the Rock ‘n’ Roll HQ (Cabin C1) when you arrive. There will be a refundable $20 security deposit for the ID card which will help remind you to return to the Rock ‘n’ Roll HQ before you leave. And if you don’t return the ID card before you leave, you’ll lose your $20 as well as hearing untold grief from the Rock’n’Roll Coordinator.

After you arrive you will need to sign up for the various activities in which you wish to participate. This will be easily done at the Rock ‘n’ Roll HQ and it allows us to organise enough instructors and volunteers for each activity as well as allowing us to account for everyone as they come on and off the water.

We have had to introduce a fee for registration which is required to cover such items as our Waterways Aquatic Licence, general administration, communications gear for the weekend, ID production … the list goes on and on so we’re sure you won’t begrudge us this small fee.

The registration fee is based on a sliding scale, primarily to encourage all attendees to pre-register. If you register prior to the weekend the charge is $10 per person. If you turn up on the weekend without pre-registering, you’ll be paying $20 per person.

Pre-registration is recommended as we need to produce a laminated ID card for each attendee and to do this on the spot for every member will cause l-o-n-g delays. When you pre-register, you not only save $10, but when you arrive at Rock ‘n’ Roll all you have to do is show up at the Rock ‘n’ Roll HQ, collect your ID card and you’ll be quickly out the door.

Registration is required for both members and non-members. Non-members will need to become members (for insurance purposes), and can either take out a full membership, at $50 per annum, or take out a short-term 6-month membership for $25. Please note there will be no kayaks available for hire during the weekend.

The weekend is being held at the Glenhaven Caravan Village at Batemans Bay, and is again a three-day weekend, from Saturday 24 to Monday 26 November 2001.

Glenhaven Caravan Village has both camping and cabin facilities, and members who wish to use a cabin for the weekend should contact the Caravan Village direct. Cabins are limited, so early contact is recommended. Campers can go straight to Rock ‘n’ Roll HQ where they will be directed to the camping grounds.

Please note that no naked flames are permitted, so bring appropriate cooking gear (there will be BBQs available for use by members).

There is a Reply Paid envelope included with this issue of the magazine which makes it easy for you to get your registration forms and membership renewal forms back to us in plenty of time.

Have we forgotten to tell you anything? We hope not, but if you have any questions or want any further details prior to the event, contact the Editor today on 1300 36 8111 or email the Editor.

In a Nutshell, Everything You Need to Know & Do…

  • Rock ‘n’ Roll 2001, 24-26 November 2001, is being held at the Glenhaven Caravan Village – 51 Beach Road, Batemans Bay NSW 2536.
  • Cabin C1 at the Caravan Village is Rock ‘n’ Roll 2001 headquarters and is open from the Friday evening. Everything you want will be here – registration, activity information, First Aid, the Rock ‘n’ Roll 2001 Coordinator, etc.
  • The Rock ‘n’ Roll 2001 Coordinator for the weekend is Ian Phillips (the intrepid Editor). Want to know something? Got a problem? Have spare wine? See Ian.
  • Pre-register today – you’ll save yourself $10.00 and plenty of time when you arrive.
  • When you arrive, see the Caravan Village office and they’ll direct you to Cabin C1. If you’re planning to stay in a cabin you should organise this directly with the Caravan Village – call them on (02) 4472 4541.
  • Collect your Rock ‘n’ Roll 2001 ID card at Cabin C1 (bring your PFD) and from there you can sign up for whatever activity you want.
  • Visit the camping grounds and marquee area where all the people and retailers will be and where all the activity begins. Have a good time.
  • Visit Rock ‘n’ Roll 2001 headquarters before you leave to return your ID card and collect your security deposit.

Product Reviews [47]

Adapt-A-Cap

It always happens this way. As soon as you’re unable to do something, you find the perfect accessory for the job. And so, as soon as the Editor was unable to kayak, he found the perfect kayaking hat.

Adapt-a-cap

The editorial staff’s newest best friends from Adapt-A-Cap have just sent through a range of caps for us to put through the patented Editorial Testing Machine, and the Editor has been so impressed that he’s been wearing the hat ever since (Mrs Editor isn’t too happy about him wearing it in bed either).

Now don’t scoff and say that wearing it around the office isn’t real testing – we’ve trampled it, squashed it, squeezed it, stretched it and even placed it in a musty Feathercraft for a week and it’s still come up roses (just not smelling like roses). Seriously though, the specialist staff at the editorial office did take the hats kayaking many times, and they performed so well that they were quickly stuffed into personal gear bags and never seen again. Looks like the Editor will have to send a cheque off to Adapt-A-Cap pretty swiftly.

But anyway, back to the caps…

Adapt-a-cap

They’re very lightweight, made from a UV-stable knitted fabric (cotton Lycra blend or micro mesh is available depending on specification) and come in an assortment of colours ranging from deep blue to burgundy to olive to white, fluoro yellow, fluoro orange and even Aus-Cam (which has been a huge hit around the office here).

The large non-reflective visor is superb for kayaking, and the caps have a built-in sweatband made of some high-tech looking stuff which has proved far better than the towelling you get in many hats.

The neck shield is fabulous and has been really well designed so that you can wear it in all sorts of configurations – you can cover everything or almost nothing … fantastically versatile.

They are priced from $29.00 each, so phone Adapt-A-Cap today on (02) 6454 1241 or email them.