Estes Honest John, #7240 Build, Part 7, Fin Shaping

If you've never sanded wedge shaped scale fins before, don't start with the kit fins!
Cut some extra fins out of 3/16" thick balsa and practice on those! Trust me, you won't get the technique right on your first attempt.

The leading and trailing edges shouldn't be shaped to a knife edge. This makes them very weak and they won't last through the first rough landing.
The instructions recommend sanding to a 1/32" thickness.
I start by sanding that 1/32" edge width first.

The inset picture shows the contrast of the black ink width.

I use my left thumb as a guide to help keep the block sanding in a straight line.

These fins (and Nike style fins) are thicker at the root edge and thinner at the smaller outside tip edge.

Notice the pencil line to the left of the center. You will be sanding over the center to the lower half of the fin.
When you sand the lower half that (penciled) line will be raised back to the center and the small outer tip edge will end up thinner.

At the top and bottom you can see the middle layer of the fin showing after the outside layer was sanded down.
The inset picture shows the diamond shape of the outer tip edge.

Each fin took me one hour to shape. If you don't have the patience, don't tackle the shaping. Simply round the leading and trailing edges and it'll still be recognized as an Honest John.