Cardboard Creation Chaos!

Our assignment was to pick and item and recreate it on a large scale using only carpenter's glue and cardboard. I seen a shell and knew immediately I wanted to it and that it would be so easy. I started out by layering shell shaped cardboard that progressed in size. I then planed on peeling of the paper on the cardboard so I could use the grooves as the shells ridges. My bubble was burst when I was told it would not be to scale.

My next idea was yo use craft paper and fold it like a fan to get my desired ridges of the shell and have them more to size. Unfortunately the paper would not bend properly for the upper part of shell that folds over.

Idea number three was to fold the corners of one end in then fold the rest down. After that I wanted to trim the other end to round it out. You guessed it, that didn't work the way  I thought it would.

Attempt number four. To make arches and gradually get smaller, then add ridges after. Might work but I was having trouble transitioning to the next size, plus I am running out of time.

Now I need to decide if this last idea is going to work or i should move onto another. *sighs* I did however find out I don't have to make it hollow.