Does anyone have an equation to calulate travel time?

[Mush Martin]

How about using a ruler on the mapscreen to measure
out the necessary eight or twelve nautical miles, then
use your waypoint to angle into the intercept set
your speed to arrive at the end of the Hour Line
in 45 mins ask your navigator how long to get there
at current speed.
presto.

(times and distance may very some limtations apply void where prohibited
by maritime law)