Estes Constellation Build Part 9, Fin Pod Gluing

Each fin will be individually fitted.
Draw a line on the side of the pod side that will be glued to the fin.
Mark the outside edge of the fin with a "1" and the matching pod "1".

Match the edges of the pod and the outside curved edge of the fin. Lightly trace around the side of the pod.
(While not shown well in this picture, the tip of the pod should be even with the leading edge of the fin.)

Carefully cut off the pod recess.

After a bit of shaping checking against a bright light, the pods fits pretty well.

Glue fillets filled in the seams.
The fillets go from narrow at the tip to wide in the rear, the same shape as the teardrop shaped pod.

Estes Constellation, Part 8, Airfoiling The Fins

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.

You could also use some 220 grit sandpaper wrapped around a 24mm engine casing for the round contour.

With the trailing edge facing up - 

Here's how that sanded recess looked after sanding.
You can see how the trailing root edge tip remains thick and less likely to break off. I still have to sand a "knife edge" to the remaining 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, Part 7, Shaping The Fins

The reissue Estes kit has you round just the leading edge of the fins. 

I'm showing an earlier Semroc build that follows the original Estes instructions where the fins are airfoiled. This is difficult because of the sharp tip at the rear of the root edge. 

This post shows one way to airfoil the fin and still keep that extended tip strong.

   

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.

Estes Constellation, Part 6, Fin Tip Pods

Both sides of the dowel pod were sanded flat to match the thickness of the three layer kit fins.
The flattened side edges were rounded again.

The dowel pod was set on the fin edge matching up the top, bottom and sides.
A fine pencil line was drawn around the side.

The fin pod was cut off just outside the line for shaping.
Sandpaper wrapped around a pen barrel to smooth the curve and fit the pod sides.

Here's a good fit of the dowel pod in the fin recess.

Estes Constellation, Part 5, Fin Tip Pods

After the front is shaped, the dowel is cut to length.

The rear of the teardrop pod is carved and sanded smooth.

Here's a finished pod next to one of the three laminate balsa pieces.

Each dowel pod carving took 25 minutes to make.

Note: After the pod was made I checked the dowel thickness against the three layers of 3/32" thick balsa.
While the dowel is round, the 3 layer kit pod was more oval shaped.
If this is to work, the sides of the dowel would be flattened then re-rounded.

Estes Constellation, Part 4, Fin Tip Pods

I was never happy with the way my fin tip "pods" came out.
Trying to form a teardrop pod at the end of an airfoiled fin is hard enough. Trying to form the pod out of three laminated pieces of balsa makes it even harder.
This time I wanted to make the fin and pods separately. Making the pods from a dowel will make a stronger fin tip assembly.

The widest part of the pod is 3/8". I pulled some 3/8' dowel from the spare parts box.

The taper starts and cut off points were marked around the dowel.

The dowel isn't cut to length yet. Shape the top first.

A center dot was made at the top. This is the point you carve towards.
Chip carve and continually check to be sure you are carving towards the center.

After carving to shape, it was rotated and smoothed on 100 grit on a block.

The front end is done, checked against the original balsa piece profile.

Estes Constellation, Part 3, Engine Mount & Kevlar Upgrade

Onto the forward centering ring - 
I'll be using some 150 lb. Kevlar in addition to a longer replacement shock cord.
The forward centering ring was notched with the side of a small rectangular file. The Kevlar will loop through this notch. 

The old instructions have you glue the rings even with both ends of the engine mount tube. This would put the upper ring just past the top of the engine hook. I'd rather have the ring overlap the upper bend of the engine hook.

A slight notch was cut into the low end of the upper ring, directly opposite the Kevlar notch.
The inset shows a wire used to keep the Kevlar notch clear of any glue.

There isn't much space between the BT-20 mount tube and the BT-50 tube. With such little clearance the Kevlar isn't knotted. A knot could show as a bump outside the BT-50 tube.

The Kevlar tail was wrapped three times around.
To glue it in place, pull the wrap tight then slide the Kevlar away from the forward ring.
Apply a glue fillet around the forward ring joint and let it set up for a few minutes.
When the glue is partially dry, slide the Kevlar wrap into the glue ring.

After the fillets dry, trim off the excess Kevlar tail.

Here's the finished, upgraded engine mount ready for installation.