Do you still lee bow after a wind shift?

Question:

Jackie is returning to the West Country from a visit to southern Ireland with her teenage son and daughter on board her 11m cruising yacht, Altair.

She is intending to visit the Isles of Scilly on the way back. Her current position is about 75 miles from the islands which bear 140° True.

The wind is Force 4 on the nose, not ideal for family sailing but they are looking forward to a few days’ rest on arrival.

The tidal streams in the Celtic Sea are quite weak, 0.5 knots, but stronger near the islands.

All three of the family are competent helms and can steer effectively.

They have windvane steering, so standing a watch is not too onerous.

Credit: Maxine Heath

Jackie has been tacking to lee bow the tidal streams, and is presently on starboard tack.

Her calculations, based on the velocity made good and tacking through 90°, show that they should be arriving in about 18 hours at 0900.

At this time, the tidal stream will be south-west going at 1 knot until mid day.

The Shipping Forecast for area Fastnet is for a southeasterly 4-5, veering southerly .

Should Jackie continue to lee bow the tide or should she change her strategy having obtained the forecast?

The crew are all very anxious to get ashore so would appreciate it if an efficient plan was agreed on.

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Answer:

The wind is forecast to veer to the south and possibly freshen later which means 12 hours from the time of issue.

Jackie should go about on to port tack and head towards the windshift.

She should work her way close-hauled to the south-southwest to make best use of the predicted wind veer in the final part of the trip, when she tacks back on to starboard.

James Stevens, author of the Yachtmaster Handbook, spent 10 of his 23 years at the RYA as Training Manager and Yachtmaster Chief Examiner

If the wind freshens to Force 5 later, it would be more comfortable to be in a position where the starboard tack course towards the destination is slightly free, say 50° to the wind rather than close hauled at 45°.

The final few hours will be lee-bowing the tidal stream so the heading needs to be a little uptide of the destination.

Receiving the forecast on passage by longwave transmission or satellite communication is helpful in this situation.

The predicted veer, if used intelligently, can shorten the passage time and improve the comfort of the passage to windward.

On the other hand if the yacht tacks away from the windshift, in this case to port of the rhumb line, it will end up down wind of the destination with a tedious beat instead of a free wind.

Some sophisticated navigation programmes will give the answer to this problem but most chart plotters are better at illustrating the past rather than the future, so working out the time to tack takes some calculation, which is hard work at the end of a long passage – but makes it shorter

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