Always test fit pieces before gluing them. Always.

That v-shaped piece of wood is the dihedral brace (I think that's what it's called). It's meant to put a slight angle into the wings. Chances are, you needed to sand the brace a bit to get the wings to sit flush against each other. If that epoxy has dried and there's a sizeable gap, someone else with more building experience will have to tell you how to fix it.

Again, always test fit your pieces.