Semroc Wac Corporal Build, Part 5, Fin Shaping C

After doing the taper from the root edge - 

Start the leading and trailing edge tapers.

I've again marked the first high point with pencil.

Round off the sides to an rounded taper. The center area is the high point.

On the left is the root edge view, 

on the right is the leading and outside edge view.

The black ink remains for now. 

Each fin took 35 minutes to shape up to this point.

Here's all three, the shaping done.

The fin on the left has had the remaining ink sanded down with 400 grit.  

The edges are lightly rounded with 400 grit. Keep the root edge square.

Semroc Wac Corporal Build, Part 4, Fin Shaping B

Start by sanding the taper from the wide root edge to the thin outside edge. Concentrate on getting the outside edge thin - you don't have to taper the full face yet.

On the right you can see the taper cutting into the black inked edge.

Continue until you get the thin outside edge to about .05" thick.

It's a compromise. You want the outside edge thin while still keeping it strong enough to survive a hard landing.

To show where we're at now, I pencil shaded the fin face down the high point sand line.

Now sand down that face joining the two different widths - a smooth flat face from the root edge to the thinner outside edge.

Semroc Wac Corporal Build, Part 3, Fin Shaping A

The kit includes a cardstock marking guide to mark the centerline of the fins. It is supposed to be half the thickness of the 3/16" thick balsa.

Set the fin into the cardstock piece and trace around the top edge of the fin. On the right, the pencil line wasn't perfectly centered.

The instructions say you could use a marker to draw this centerline - NEVER use ink when making model rockets! The ink can bleed through the finish paint.

Instead of a hard to see simple centerline, I mark a high contrast edge. 

You can use ink - IF the balsa wood is sealed and be sanded off later.

Sealing the wood stops the ink from soaking in.

I seal the edges with a wipe of super glue. This also strengthens a thin fin edge.

Drip the CA glue onto a Q-tip and wipe the glue onto the side edges - but NOT the root edge. The root edge is left  unsealed as it is glued to the body tube.

After the CA glue seal, 

Mark the sides of the fin with a wide point marker.

Don't apply ink to the root edge.

Semroc Wac Corporal Build, Part 2, Parts

Apparently I started this build and got sidetracked. One of the centering rings is glued onto the motor mount tube. 

Outside the glue tab of the tail cone cardstock has been trimmed off.

The tunnel shaping has been started.

A name decal is included but there were no name markings on the real rocket, except for round numbers.

The parachute is one of the newer Semroc multi-sized chutes. You can cut a 12", 18" of 24" chute from the sheet. 

The fins are 3/16" thick! To form them you are supplied a cardstock centerline template. More on this later.

I'm not a big fan of the cut launch lugs. The laser cut lugs are always burnt brown and the ends uneven.

I like conical nose cones - 

But for some reason, conical nose cones always get banged up and dented after a few launches.

Semroc Wac Corporal Build, Part 1, Fin Shape

Here's how Estes shaped the WAC Corporal fins in the 1960s.

The tapered sides are incorrect and the tips of the fins have sharp corners.

I doubt there were many available pictures and scale data available then.

This picture implies the fin taper shown above.

The Peter Always drawing shows the taper from the wide root edge to the thinned outside edge.

Note the fin corners are rounded off.

From the Semroc instructions, 

The fin taper matches the front view above.

The root edge profile shows the correct shape of the fin, the widest point at the center.

Semroc Wac Corporal Build, Background

The WAC Corporal was the first sounding rocket developed in the United States and the first vehicle to achieve hypersonic speeds. These were the first missiles launched at White Sands.

For more information: CLICK HERE

I don't remember buying this kit!

This was one of Semroc's "Deci-Scale" models, 1/10th the size of the original rocket.

This is advertised as a semi scale model. 

The real Wac Corporal was 12" in diameter. The kit body tube is a Centuri Series 11 at 1.17" diameter.

The kit has a cardstock boat tail. 

12" parachute recovery.

If you were flying rockets in the 1960's you probably had an Estes Wac Corporal. It seems this was the first "scale" model produced by  Estes.

The Estes version was built around a BT-20 and was only 11.8" tall.

A long launch lug was hidden under some balsa strips making the tunnel.

This smaller model didn't include a boat tail. Two lead disks were screw eyed into the nose cone for 1/4 oz. of nose weight.

To see the original ESTES instructions: CLICK HERE

Splatter Paint?

Anytime I've done drywall repair I use this texture paint.

It sprays with random splatters and helps to hide uneven drywall patches.

Mentioned in earlier rocket builds - flat paint can help hide rough surfaces.

It always reminds me of a bad can of Rusto 2X Gloss White. Note the can says "orange peel". 

Not recommended as a model rocket finish.  

Why would I bring this up on a rocket building blog?

Building model rockets has given me confidence, taught me project planning and patience. Filling, sanding to surface, priming and paint. 

I would think hobbyists can read a ruler better than most!

I removed a large mirror from my master bathroom. Because I work alone and it was heavy, the mirror was cut into thirds. Look close - that diamond wheel on my ancient Dremel tool is red hot!

Here's the nearly finished project - 

Drywall repair, measuring, leveling and centering

the mirrors. I still have to mask off the mirrors and paint the frames a light gray.

Masking - more modeling techniques!