[max-peck]

You can still treat it as a standard Fast-90 attack.

Why?

Because the ship is constant helming along a base course.

See pic




The ship sails along the green path as you watch it. But you can treat it as following the base course (in red).

The 3.15 rule still applies.

Mark your two points to get the speed.




This will be the average speed he is making along his base course.

And set your AOB as if the ship was travelling along the base course (red line)

Finally, a rule of thumb if you are short of time.

Once a ship has started constant helmig, it will make about two thirds of the speed it was making before.
I use this quick rule of thumb a lot and hit most of the time

Finally: if weather permits use magnetic pistols, as you may be hitting him at an angle, and an impact pistol may bounce off.

Good luck