Hi Gabriele
I will try and describe this as best I can. If it comes out as garbage I will then take a photo for you.
There are two ways to grind a curve onto a blade. The first is just do it freehand at a grinder. Since the surface is going to be chewed up (although this can be chewed up neatly!), the blade shape is less critical. So just get as close a curve as you can. Of course, the grind angle is between 25 - 30 degrees as with all plane blades.
The second method is the one I prefer since it produces a clean, smooth curve. Cut a piece of hardwood the same size as the blade. At the end of this piece, shape the curve you want to grind. Now, since you are using a Stanley blade, which has a groove down the centre, bolt the two together. What you are going to do is use the curve on the hardwood as a template for the blade. The curve runs up against the edge of the grinder rest, and the blade (bolted to the top) is extended until it contacts the grinder wheel at approximately 25 degrees. You then turn the blade against the wheel using the curve of the hardwood template as a guide.
Once you have ground the curve (either fashion), it is necessary to hone the blade (sandpaper, waterstones, etc). It is not necessary to hone as high a grit as other plane blades as you asre not trying for a smooth finish. A 1200 waterstone is adequate, although I would prefer to go to at least 4000 myself.
Let me know if this is an adequate description.
Regards from Perth
Derek