How high are …..

….. the waves?

We’re still battling our way across the Bay of Biscay, with about another 100 nm (nautical miles) to go before we round the most northwesterly tip of Spain when the weather should start to improve.We currently have a bit of a force 8 lull (!) before the weather worsens overnight – but hopefully that should see the end of it, if, we can get to Spain before the next weather system rolls in.

Our transit as been significantly slowed by the weather with the wind and the sea on the starboard bow slowing us to under 3 kn at times.

The RRS James Cook is fitted with a radar system that measures the direction, height and period of the waves. The image above is the wave map for 360 degrees around the Cook, which is in the centre. The average wave height is currently over 6m, that’s nearly 20 feet.

The view from the stern working deck, which is not too high above sea level, should give you some idea what it feels like to be on the Cook at the moment.

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The waves are above the photo taker’s head.

Work continues, though, getting all the equipment ready for a full systems test in 3-4 days time when the seas get significantly calmer than they are now. We are heading to 200 nm to the west of the Canary Islands, where it should not only be calmer, but it should also be a lot warmer. The hardier amongst us have already broken out the shorts in anticipation.

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Currently, work is concentrated on cabling up each airgun (the silver cylinders hanging from the yellow tow “beams”) and running those cables into the lab where the shot firing control computer is set-up. Once wired we can “click” each airgun and make sure its firing system works, before we supply high pressure air to them for a “pop” test in the water, to ensure each airgun seals when its vents are supposed to be closed between fires.

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Running cables, especially quite large diameter ones like these, through is ship’s bulkheads (walls) and deckheads (ceilings) is a nightmare because the cables have to be run through special ports built into the steelwork, which then also have to be baffled with fire retardant material in case of a fire, to stop the fire moving between compartments.

The above image shows a number of the cables running through a bulkhead and into the lab. The slack will be wound into tidy loops and the ends attached to the junction box, which is, itself, attached to the back of the control computer – or gun controller as it is called.

The gun controller controls the fire time of each airgun in the seismic source – there will be a maximum of 13 – and displays the output on the screen.

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We will be firing seismic shots at two different rates – or intervals – for the two types of seismic acquisition we will be undertaking; 20 s for the reflection type and 60 s for the refraction type.

And finally – we don’t need scientific technology to tell is how much the vessel is moving currently – the baubles on the Christmas tree in the mess are doing quite a good job, as is the tree itself, and we have had to resort to wedging that in with chairs to stop it falling over!

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