Streamer D Rocket Build, Part 2, Fins

Normally I wouldn't cut fins with scissors.
But this plywood is only 1/32" thick! It cuts easily if your scissors are sharp.

It was fairly easy to sand an airfoil in the fins. The interior color layers make a good depth gauge when sanding.
If you are inexperienced in airfoil sanding, cut out a few extras for practice.

I used 220 grit on my Great Planes Easy Sanding block.

The upper left corner was rounded off. No reason, I thought it looked sleeker. 

Here's a closeup of the airfoil.
The outside edge (to the left) is also tapered.

The side view shows the airfoil taper from the root edge.

Apogee Mini Condor Boost Glider Build, Part 6, Tail Gluing, Wing Airfoil

I did round the edges of the tail surfaces. Go light with the sandpaper, there isn't much balsa thickness.
The horizontal tail glued over a tab on the back of the boom. The fit was tight and once set in place was perfectly aligned.

The rudder is glued on one side of the boom with the back edges even.

The instructions say you can airfoil the wing for a better glide. I used my sanding block with 220 grit for initial shaping. After that, 400 grit was used to smooth the surface.


The inset picture shows the airfoil profile from the outside edge.


Here's how the dihedral support piece sits on the fuselage. The pre-set angle is molded into the bottom slot.
The forward end is to the right of the picture. The dihedral support piece is not glued in place yet, it is adjusted forward and back when doing test glides.

Estes Constellation Build Part 8, Fin Airfoil

I used the rounded side of my old sanding block with 400 grit to sand the recess at the rear trailing edge.
This seemed to be the best way to get a round concave shape.

Here's how that sanded recess looked after sanding.
You can see how the trailing edge tip remains thick and less likely to break off. I still have to sand a "knife edge" to the trailing edge.

With the fin held upside down,
On the left is looking directly at the root edge. The tip was rounded off.

On the right is the tapered trailing edge viewed from the rear of the fin.

Estes Constellation Build Part 7, Fin Airfoil

The old Estes instructions tell you to airfoil the fins. That rounded tip on the rear root edge could be a problem. Sand it down to a sharp taper and you run the risk of it easily breaking off.
The fin drawing in the instructions show a shading that suggests the shape penciled in at the right. This leaves the tip at the 3/32" thickness.

The end of the outside edge pod will be replaced so it was cut off now.

It's hard to see the trailing edge taper on the light balsa wood.
The leading and trailing edges were marked with an old, half dried out Sharpie pen.
You don't want a heavy black ink to soak into the balsa! In the end the black ink will be sanded off. Any remaining ink might show through the white paint.
When marking an edge like this, draw the line quickly allowing very little ink to color the balsa.

Apogee Heli-Roc Build Part 3 Airfoil Rotors and Fins

On the left is a before and after pic of the fin airfoil.

On the right is the rotor blade airfoil (one side flat or chambered) before and after.


The fins are smaller so the airfoil was sanded using a sanding block.

The rotor blade is 10 inches long so a consistent airfoil could be hard to do.
I used the emery board featured in an earlier post, HERE.

TIP: For support, place the trailing edge of the blade near the edge of a hardcover book. Set the emery board over the trailing edge at a slight angle on top of the balsa blade. Sand down the entire length of the rotor blade.