# Allowance for tidal streams 3

To allow for set and drift of the tide firstly we will apply the tidal set of 115 True degrees from point A.
We place the parrallel ruler on the 115 degree line on the compass rose and then transfer to point A and draw a line.
Using the dividers we span 2.3 nautical miles on the lattitude scale. Then we place one leg of the dividers on point A and the other leg in the direction of the tidal set and we mark this point with C.
Mark this line with 3 arrowheads in the direction of the set and drift – this marks the tidal effect.
Now open your dividers to the boats speed of 8 knots.
Place one leg of the dividers on point C and mark the point where the other leg crosses the track at D
Draw a line connecting the points C to D. We mark this line with one arrow head as this is the course to steer
Now we transfer the parrallel ruler to the compass rose and read off the course. The True course to steer to point B is therfore 027 degrees.
This course is required to offset the effects of the set and drift of the tide over a one hour period
Do not forget to convert your course to steer from a true course to a compass course!