Tangency between mirrored surfaces

 From:  mcdrury
Hi all,

Just wondering if there is a explanation to rectify to the problem I seem to be having?
How can I remove any ridges that are formed by the mirroring of two curved surfaces? Is there a way to create tangency with the other surface?

I'm basically drawing one half of an aircraft fuselage and when I mirror it I end up with a ridge running along the top and along the bottom.