I have to agree with Rob. There seems to be a confusion of terms here. The stem is the line between the tip (front or back of kayak) down the middle to the keel or center (bottom) of the boat. Or.. the ends of the (V) shape. The shear really has nothing to do with it.
With the external stem method, you strip the kayak or canoe using butt joints or overlaps , whatever. Then you carve the (V) shape or ends even and attach an outer layer of wood for a protective and/or visual cap or covering piece. I use multiple colored strips held in place with bungee/shock cord. Then I sculpt it to an even blend into the kayak.
I think this is what you're talking about???? "Canoecraft" by Ted Moores has nice photos of this method.