Estes USS Enterprise #1275, Part 6, Internal Support Ring

The internal support ring  (RT-99D, 3.7" diameter)

has to fit over the "hump" in the primary hull bottom disk. 

Cut the template using a straightedge on the straight lines an scissors on the curves. 

The template doesn't go all the way around the support ring. 

Mark the cutaway crescents with pencil.

Cut the crescents out with a sharp knife.

Here's how the cuts are placed on the ring, directly on opposite sides.

A dry fit in the lower hull disk. Note they do not contact the hump when centered on the disk.

I'm not gluing the ring in place yet.