If there actually isn't a weather vane, it is easy to make using the Complex Profile Tool.
Do you want a rooster, a duck, or a horsie?
Perhaps you want a weather vane like the one foretelling the tornado disaster in last week's Despicable Housemarms where the sun shines from the North in the scene. And it is the Northern Hemisphere! AAAArgh! Like no one would notice! Such amateurs! But a great tornado! They must have rented every wind machine in Hollywood for that!
Make a complex profile guidefill shaped like the animal and the arrow and then use the beam tool in the perpendicular direction. You make a shallow extrusion equal to the casting depth.
Then another one perpendicular without the animal.
Dwight Atkinson