Having stopped for his picnic and explored a little, Tom reckons he might set off at 1400hrs BST. The tidal diamond shows a tidal stream of between 0.4 knots when he starts, increasing to 1.0 knots north and east until 0230hrs BST on the 18th. By then the wind may be veering to the south- west. Sea conditions will be very calm, making it a gentler journey than the outward trip. Tom will take off some of the extra clothing he wore for the trip out, stow it securely in the boat and make sure everything is stowed correctly.
In the afternoon, with the forecasted fresher breeze, Tom decides to reef, estimating that his boat speed will still be about 4 knots. He will be reaching and running into the harbour, assisted by the flood tide, so his speed over the ground should be 4 knots plus tide of 1.0 knots = 5.0 knots SOG with little leeway.