Originally Posted by CPMcGraw

Well, it's most certainly not the 18" version...

I just took a quick measurement of my one copy of that cone, and found it to be 3.75". Next, I measured the outline given for the fins, and found the overhang to be about 1/2" past the rear edge of the tube (this is going to be a fudge-figure, not exactly accurate...).

Now, taking the catalog measurement for the completed rocket as reasonably accurate, since I don't have any way to confirm it or deny it, the length is 15.40". Subtracting 3.75", I get 11.65"; subtracting out the fin overhang as just a hair over 0.5" gives me a more-likely figure of 11.125" for the body tube.

I hope someone can get a better scan of the fin, and an accurate measurement of the tube. The shape in the plan set doesn't fully match the shape drawn in the plans on page 2. I've found that Estes usually drew these reference images pretty close to being accurate, although smaller than full-size. When I enlarged that image, the shapes were not the same. Close, but no pickle.