Cathedral Rock

It was a stunning morning at Cathedral Rock, Nr Lorne, Vic today, with super clean waves and clear blue skies.

The swell was around 4-6ft, it packed quite a punch and I managed to end up on the rocks a couple of times fortunately without injury, its interesting to experience how much more power is in a 3ft wave versus 4ft and then again from 4ft to 6ft , on the way back we had a discussion about how much this factor increases since it is definitely not linear!

So after some research and some basic assumptions, it goes something like this:

Today at 4-6 ft which peak to trough is around 2-4 metres

significant period 15 sec

Assuming an average depth of 3 metres and an efficiency of 40%

we get a wave that is moving at around 5.4 m/s (20 km/h)

If these factors remain constant then this gives a net power of

2.7 KW or 2700 N/m/s at 1 metre

10.8 KW or 10800 N/m/s at 2 metres

43.4 KW or 43400 N/m/s at 4 metres

In reality we would also get depth variation with wave size and therefore an increase in velocity as the wave increases in size.

But in everyday terms this is a compressive force of approximately 4.5 tonnes at 4 metres which is pretty incredible but what is more incredible is that the force increase is so rapid, more than 4 times the power of a wave at 2 metres and 16 times more powerful than a wave at 1 metre.

The fields were beautiful :-).