On the fly rail cuts

I noticed a lot of you guys when shaving down rails are adjusting on the fly. From what I understand you start at no cut and increase towards the center of the board. What depth are you ending up on at center? Ill be shaping a 9’6 and was wondering if length will affect this adjustment or is it subtle and somewhat standard?

All rail bands are done by adjusting the planer depth on the fly.  Plenty of detailed instructions in the archives.   The basic technique is the same whether a long or short board,  but varies with the rail design (50/50, 60/40) and whether or not a hard tail edge is involved. I advise those new to rail bands to only do them 12" from the nose & tail then finish by hand.  The first bands you cut are the primary & all the others are based on those.  These are best done with the blank rail up at 45•.

Yeah you wanna start at zero about a foot up from the nose/tail and steadily increase to deep cut in the center, then back to zero about a foot from the nose/tail. How deep depends on your planer. I have a Bosch so the deepest cut is enough. Since there’s more material to remove in the center of the board, you need a deeper cut there. 

Widepoint is where the depth control should be at max, mark a dot at the rail apex or on the stringer as a target.  Start backing off as soon as you hit that point.  Go through the motion without turning on the planer so you get the feel. You need to be aware where the blades are actually cutting on your planer to hit a target mark.  Turn it over and see where the blades engage then put a piece of tape on the side of it where the cut starts. Or, just use the front knob as a reference.

The number one problem beginners have with bands is that they cut past the rail apex and then the outline is lost.  Usually this happens at the nose and tail and that’s why I advise to begin/stop 12" each end then finish by hand.  That way there should be a perimeter around the blank which is untouched from the outline cut.  If you stand the board up on a rail for the initial bands, it should be at an angle to make the planer level.  Easier to control when it’s flat.  Proceeding bands are done with the blank flat though.  Greenlight has some good info on their site on marking the bands.