Depends on your emulsion (I use Autotype 8000, dual cure) and your mesh colour, and of course the sun/UV intensity, BUT
white mesh - 45 seconds
yellow mesh - 80 seconds
As you get into the summer, and assuming the ozone layer is pretty well shot, the times will decrease. Get a piece of nice film with fine lines and dots on it, use it in the corner as a tester - if the lines go or close in, you are over exposed - this assuming you have compressed the film completely to the emulsion - adjust on your next exposure.