WATCHET TO CARDIFF AND RETURN
To make Cardiff from Watchet, sailing across the tide and aiming to be on the final approach before the change of tide, it is important to leave Watchet as soon as practicable after the gate opens. As I will demonstrate, even an hour after the gate means missing the tide on the final run in to Cardiff and can add significantly to the passage time.
1. WATCHET TO CARDIFF -
This I believe is the best passage. I have shown a passage when local high water is 11.15, leaving Watchet at 0900 with an ETA at Cardiff lock for 1300.
The inbound lock operates on the hour and half hour and the Call Sign is "Barrage Control" on channel 18.
On the illustration below the blue line is the course, the red arrows indicate the tidal offsets and the green arrows the course to steer.
2. WATCHET TO CARDIFF -
In this example local HW is 0810, leaving Watchet at 0600 with and ETA at Cardiff lock for 1000 or 1030.
As can be seen the tide turns by the time you reach Lavernock Cardinal which is why the ETA is rather imprecise.
I have allowed for a boat speed of about 4kn through the water. Any more is a bonus and will allow for reaching Lavernock before the tide turns with commensurate benefits for the run in for Outer Wrack
3.Watchet to Cardiff Spring Tide example 2
In this example local HW is 0815, leaving Watchet at 0700 with and ETA at Cardiff lock for 1400
This illustration shows the effect of leaving just an hour later which can add two or more hours to the journey.
CARDIFF TO WATCHET
I have shown two examples. The first is a passage aiming to make Watchet on the ebb tide and arrive about two hours after HW. This is the quicker passage and relies on fighting the tide for half way and then picking up the ebb for the run into Watchet. There is little margin of error in this passage and any mishaps or miscalculations could cause you to miss the gate! However, I have done it many times and not missed yet!!
Cardiff to Watchet 2
This is a longer sail but is pleasant if the weather is fine. The idea is to leave Cardiff on the ebb, a couple of hours before low water and make the best of the tide to about Breaksea, then go across the channel and pick up the flood into Watchet. There is a far greater margin of safety since the aim is to reach Watchet as the gate opens. I have often found that I have to slow down on the run from Minehead Bluff so as not to arrive too early.