At this stage, I’m going to cheat and ignore conical shoulders and conical boat-tails, simply because many model rockets don’t have them. (For those that do, you’ll need to look up the full formulae for them).

I’m going to move on to the fins. Most fin shapes can be simplified to an “idealized” shape that has four straight edges, with the root and tip parallel. When reducing a fin shape to an idealized shape, it is important for the area of the idealized shape to be very close to the area of the actual fin. Examples are shown below.

Incorrect                        Correct

There are two examples of “idealized” fin shapes at left. The one at far left is incorrectly idealized because area has been added that wasn’t present in the original fin. The one at right is correct because the area of the idealized fin approximates to that of the original fin.

Shown at left are other examples of idealized fin shapes. Note that the area of the idealized fin approximates closely to that of the original fin.

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