: Don't give up. When you find it the light will go on. My theory is that you
: are trying to plane a concave area.... an area the plane will span and not
: hit with the blade. (Sounds like what you said) You can follow any number
: of types of advise given before, but also try this.. Instead of planing
: with the plane sides parallel to the direction of planing, put it
: diagonally as much as you can. This will effectively shorten the contact
: area of the planes sole and get the blade closer to the wood.

: To check it, just lay the plane on the wood and crouch down and look at what
: is happening .... Is there a gap? Or, is the blade touching the wood.
: Observe as much as you can and you will find the problem. - Scott

And see if it works on a normal flat board.