The above post is almost correct, the shear webs need to be bonded to the upper and lower spars. Contacting the ribs is not as important as keeping the upper and lower spars from flexing. Carry the shear webs out at least three ribs from the tip. It makes little sense to carry them out all the way to the tip, as there is little to no shear force applied there. Grain needs to run perpendicular to the spars, as indicated above.

Vince