James Stevens answers your Questions of Seamanship. This issue - when is the best time to leave port when faced with a strong tidal stream and overfalls?
George and Jill keep their Contessa 26, Martingale, at Largs on the Clyde Estuary. She’s a tough little boat – long keeled, over 40 years old, well looked after and well kitted out.
Unfortunately, their intentions to venture further afield beyond the Clyde are frequently thwarted by lack of time and the weather.
This year, they plan to go to Northern Ireland and visit friends at Ballycastle. The distance from the Mull of Kintyre to Northern Ireland is only about 11 miles but in between is the North Channel where the tidal stream, on the day they have chosen, runs at a maximum of 4 knots.
This can create a rough sea, especially wind against tide, and there can be some nasty overfalls south of the Mull of Kintyre. Sturdy though Martingale is, they don’t want to push her too hard.
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They are currently at Campbelltown. In the morning, the wind forecast is SW 5, which means they can’t lay Ballycastle on one tack from Mull of Kintyre, and while Martingale is fine in this wind in the shelter of the estuary, George is anxious about venturing into the open sea.
Jill reckons it’s possible. The tidal stream in the channel runs south-east until 1200.
What would your plan be?
It makes sense to get across the channel into the less of the Northern Ireland coast s soon as possible before the stream starts getting too strong.
Timing is critical: they should arrive at the southern end of the Mull of Kintyre at the end of the south-east going tidal stream, leave Sanda Island and the overfalls well to starboard and then sail close-hauled on starboard tack.
Within an hour, the tide will have turned and Martingale will be favourably lee bowed by the tide.
Given there is such a strong favourable tide, I would crack off the wind slightly and go for boat speed. This would get the yacht out of the rough weather.
Keep on eye out for ships entering the TSS. Once on the NI side, hug the weather shore in the calmer water to Ballycastle.
Setting off on port tack seems the most direct and simplest route but it keeps the boat in rough water and would include the corner of the TSS where the boat would have to tack to keep her course as close to 90 degrees to the traffic as possible.
Again the tide isn’t an option; Martingale would be almost stationary over the ground.