Think before you Leap!!!

River Kayaking with Plastic and Kevlar Reinforced Sea Kayaks – Safety Hazards


Some safety hazards that kayakers need to be aware of before venturing onto rivers in kayaks “not fit for purpose”.

Never underestimate the power of flowing water even at a low speed. One cubic meter of water weighs one tonne, so if you or your kayak gets pinned against an obstacle it may be extremely difficult to escape.

Three cases I have personal knowledge of are:

#1 A group of kayakers were paddling down the Wye River near Hereford in the UK. The river was placid and slow flowing and while waiting for the group to catch up, a paddler was facing upstream watching the others approach. She drifted sideways into one of the bridge pillars and capsized with the cockpit facing upstream. In a matter of moments the spray skirt was popped inwards by the water, the kayak flooded and the water pressure from the “slow” current folded the plastic kayak around the pillar trapping the kayaker’s legs. Despite the efforts of others on the trip they were unable to pull her clear and she drowned. (general river grading is 1/6)

#2 In South Africa, another incident involved a member of our club who went on a camping trip with some mates down a flooding river. After paddling into a large rapid he did not reach the pool at the bottom. His mates waited a while then walked up the bank to see where he was. He was stuck in the centre of the river with the nose of his kayak wedged under a rock. Some of the guys went up to the top of the rapid and swam down to him, but the power of the current had forced the kayak under the rock and crushed/imploded the top deck trapping his legs and they were unable to release him.

Over the next hour the river level rose and covered him resulting in him drowning. Later, after the river receded, a helicopter was used to retrieve the kayak and his body. The force of the water had folded the boat upwards at the cockpit breaking both his legs. (estimated grading under flood conditions, 4/6)

This paddler was experienced and had done many trips through big rapids.

In both these cased the kayaks used were plastic and generally referred to as white water kayaks and failed under widely varying conditions. The difference of these kayaks from extreme white water kayaks (also plastic) is the bracing around the cockpit area as well as vertical foam to brace the top decks (front and rear) from imploding when under a crushing force.

#3 Also in South Africa the third case was a long distance river racing Kevlar kayak (similar to K1 or K2 flat water sprint kayaks). This race was a 30km river race with up to grade 4/6 rapids. The paddler capsized in a rapid and the kayak broached sideways with the cockpit upstream, then wedged against a rock – the spray skirt popped in – water flooded the kayak and wrapped it around the rock. The Kevlar top deck folded inwards trapping one of the paddler’s feet against the foot rest. Fortunately there were onlookers who swam out and released him. (As a consequence of this and other similar incidents the S A Kayak Federation advised manufacturers to make cockpits out of glass fibre with no Kevlar or similar reinforcement as these do not tear when the kayak structure fails creating the hazard outlined above).

 

OBSERVATIONS

There is an expectation by kayak users that plastics (used for kayaks) and composites e.g. Kevlar and Carbon Fibre will eliminate the risk of failing under extreme conditions. (The silver bullet?)

However, although they are very strong under tensile forces they are not as good when exposed to compression forces. When kayaks do not have suitably designed bracing at the point of contact between kayak and the obstacle they have encountered they may well fail on the compression point as seen above.

 Although designs and materials used for sea kayaks are adequate for open water and can stand some extreme conditions of waves and the odd abuse of head on collisions with rocks and sand banks etc., when one is wanting performance under difficult conditions (water force due to water density, current and immoveable obstacles, sometimes not perceived as seen in the examples above) one should ensure the kayak is designed for the purpose.

One sea kayak that comes to mind is the old Puffin which had a cockpit pod which looked as though it would be a lot more resistant to folding under an extreme condition. (One would need to verify this with the manufacturer.)

Other hazards, relevant to New Zealand rivers, that also come to mind are currents flowing through exposed tree roots, flood debris, fences, weirs and other manmade structures and of course the infamous overhanging tree branches.

Flood conditions are definitely not a time to be paddling down river unless you consider yourself skilled and competent.

What now?

The purpose of these observations is to create awareness of some of the hazards and initiate dialogue within the club (being at present almost exclusively a sea kayaking fraternity) about the implications of participating in river kayaking.

I strongly recommend that anyone wishing to paddle rivers should seek the advice of experienced and competent river kayakers.

<pPhilip Noble