Downscale A-20 Demon Build Part 3 Fins

This is the cereal box cardboard used for the interior of the 3-ply fins.

The printed side should be roughed up for best adhesion. You only have to hit the printed side with some 220 grit sandpaper. I don't sand deep, just scratch it up a bit to remove some of the printing.

Be sure you dust off the surface before gluing on the fin overlays.

Before cutting out the fins score the fold lines. In the picture, I'm using just the tip of a butter knife, just making a line indent. (Use a straitedge for a true line, the straitedge is not in the picture so you can see the indent line itself.) The tip of a butter knife is not sharp or serrated. All you want to do is "push" a straight indent line into the cardstock.

Many kit instructions will have you cut halfway through the cardstock with a sharp knife. This is unnecessary.

For most models, this step will give you a very sharp fold line without the worry of cutting too deep or through the cardstock.

After making all fin center lines, cut out the fins oversize. Use scissors and cut a little larger than the outside the printed area.

Now the center lines can be folded over using the indent line you made and burnished flat with the back end of a Sharpie pen.