Cupped Bottom Blanks

What technique do you guys use to remove the cupped bottom from some blanks (or to remove roll from other blanks too)? Crosscutting the bottoms with the planer has worked the best for me so far, but stringer blow outs are always on my mind. Any tips would be appreciated.

this method works both ways. to flatten a concave bottom I cut the length of the blank along the stringer with a shallow cut and then work my way out to the rails with a deeper cut each time.the reverse of this will flatten out roll.

Might be a crap blank? Big heavy block with very rough grit, as wide as blank

“Big heavy block with very rough grit, as wide as blank” Ditto! I use a 6" wide decking board. I use contact cement to glue 1/2" backpacker foam and 36 to 50 grit sandpaper to it.

I’ve noticed that most of the “R” blanks have a pre concave bottom. Rather than start at center, try banding the rail edge down to clean foam and then move towards the center. Many of the modern longboard blanks have a flat or concave bottom, if I am not doing a down rail, I band the bottom before getting into the shape and wind up with some roll in an otherwise flat bottomed board

Jim nailed it as usual.I do it before templating.The rail band is real shallow say 2 to 3 inches in from the rail and 1/4 or less down.

Do any of you ever leave the “cup” or pre-concave in the bottom if your going for a single concave or single to double?