Round Britain for the RNLI Blog

Whilst at sea from Padstow to Milsford Haven I encountered something I haven’t seen before… a large ground swell.

It was quite wierd… the sea was not at all big. It was choppy and difficult to plane but the waves were no more than 0.5m and not a problem at all. However, there was a swell comprising of very long interval waves with very shallow sides, that rolled in from the west to east, like ghosts.. They were so long interval that if I didn’t actually look left or right I would not have noticed them at all as the boat just raised up and down over them without any noticable movement at all. It was clear that these were ground swell waves that were coming in off the Atlantic, possibly all the way from America. They didn’t affect me but I could imaging them creating quite a big wave when hitting the North Cornwall coast… no wonder that North Cornwall is famous for its surfing. I would imagine that they could turn very nasty though in any wind especially wind against or if entering a harbour.

Apparently, this swell is normally present in the Bristol channel and West Cornwall and is often there even on calm, smooth days.

Low pressure is not far awqay again and with the jetstream again being east to west over the UK there is again a bit of a block of the normally prevailing westerly passage of systems. So again this makes for a bit of an unpredictable situation.

Basically… the prospects of a departure tomorrow are not very good. The inshore waters forecast are giving F4-5 occasionally F6-7 and a sea state of Moderate to rough, occasionally very rough. My little boat doesn’t do very rough, or rough, and even struggles a bit with moderate so it looks like a no go tomorrow. But, as always, the final decision won’t be until tomorrow morning and I shall update the web site at about 7am.

Looks like a bit of a delay is likely.

Collecting outside Tesco Milford Haven (with their permission BTW) saw a half full bucket and I would like to thank everyone that stopped to chat or dropped some pennies into the bucket. It is why I am doing the trip and it was an absolute pleasure to be there.

It hasn’t been counted yet but from the weight I would imagine it is in the £250 bracket.

Thank you.

In my case it is the prop that is on the engine!

For the first 3 legs I used a 21" pitch propeller. For those that don’t know what that means it means that when the propeller rotates one full rotation the it moves forward through the water 21". In reality that isn’t quite true as there is slip and other aspects that make it slightly less than that but it is a gauge that tells you how coarse or fine the propeller is. Finer pitch propellers, that is propellers that have lower numbers and move less through the water for a full turn, are better at acceleration and less good at top speed (like a low gear in a car) and coarser pitches, higher numbers, are better at top speed and less good at acceleration.

I did some fuel runs prior to departure that suggested that the better prop for this trip would be a coarser one so I fitted the coarser of the two I have… the 21". As it is turning out, this may not be the best choice. I am finding that the sea is much more lumpy than when I did the tests and that is meaning that I am having to slow down and speed up much more than on the test which was done at a steady speed. For speeding up I need a lower pitch propeller and so I have changed it over today to the 19" one I have as a spare. The 21" will now become the spare.

I will see how it goes and report back when I get in to Pwllheli.