It depends of the area and of the duration of the trip.

There is 3 sources of tidal current: Tidal current tables (ATT), Tidal
current charts and tidal currents shown in the sea charts.

If you only know the time of HW and LW, you can assume that the curve
of the tidal current will look a bit like a sinus curve.
Generally there is a period of relatively weak currents around HW and
LW and the current will run faster halfway between HW and LW.

If the trip is expected to take 9 hours it would best to leave around
6.30
so you can sail in two periods of slack (weak currents) and one period
of favourable current.
If the trip is expected to take 3 hours, if you leave around 9.30 you
should be able to sail the whole trip in favourable current.

I'm sure Donald or some of the others who sail in areas of strong
tides could elaborate further, but they probably think that you need
the mental exercise of figuring it out yourself.

Peter S/Y Anicula

"Scott Vernon" skrev i en meddelelse
...
I found some current charts for some areas, they give slack, max
ebb,
and max flow. this I understand.
For other areas I find only the H & L tide chart. I want to make
max
use of the tide (ebb). Say H is at 0800 and L is at 1400. is it
simply
a matter of shoving off at 0800 and 'ride the out going tide till
1400?
TIA

Scotty