Estes Teros Upscale, Part 11, Four Fin Gluing

After the fin lines were drawn, the gluing area was sanded down with 220 on a block. This was to rough up the surface for a good glue bond.
It's easy to get control over how much is sanded off with the Easy Touch block.
The pencil alignment lines were redrawn.

TIP: It's a good idea to check the 90 degree angle of the root edge and trailing edge against a true corner.
I used CD box.
The inset picture shows how the root edge was a bit long at the bottom right side.
If the fin isn't true the rocket will wobble when standing up.
The bottom of the root edge was sanded until the root and trailing edges were at 90 degrees.

TIP: Here's one way to visually align four fin models.
Look over the top making sure the fin on the other side is in line with the fin closest to you.

The fourth fin isn't glued yet. On a four fin model the up and down position of the last fin can decides if the model will wobble.

Turn the rocket over and set it on the three fins already glued on.
(Note the tape wrap at the top. This is a good reference for getting the leading edge tips in line.)
TIP: Glue the fourth fin on making sure the trailing edges are all touching the flat table top. Make very small slides up or down the root edge pencil line until all four fin trailing edges sit flat and are even.
This extra alignment step only applies to four fin models. Three fin models stand flat without any extra work.