This mirror system works well, but it does require a good cleaning after every flight.  The black powder ejection charge leaves a residue on the mirror each time because as the midsection airframe begins to separate from the booster, the first opening that develops is the hole for the lens at the mirror mount.  Some of the ejection charge gases pass through this hole.  The camera lens itself is protected at all  times and does not get coated with any residue.  The mirror is easily cleaned with isopropyl alcohol.

The process starts by drilling a one-inch diameter hole in the airframe.  Here the midsection airframe is mated with the booster section and the two are taped securely together.  The hole being drilled goes through the outer airframe body tube, as well as the coupler tubing at the top of the booster.  The camera will ultimately be mounted inside that coupler tube.

A nice clean lens hole.  I decided not to add any clear plexiglass over the hole.  It is simply left open.

The mirror itself was cut to shape by experimenting with a larger piece of mirror glass and adding black tape to it until the smallest possible shape was found that still gave the camera a full field of view.  The mirror was then cut to that shape (a triangle with the top clipped off.)  Some double sided tape was then applied to the back of the mirror and the mirror was mounted onto a T-bevel tool. 

The T-bevel tool allowed me to experiment with different angles between the mirror and the camera lens.  You can just barely see the camera lens looking out the hole in the booster coupler.  One edge of the T-bevel tool is held firmly against the coupler and the other end can be adjusted to get the optimum view.  This was all done while the camcorder was connected to an external TV to allow me to see what it sees. In the end, I settled on a 48 degree angle.  It gave a nice view down the side of the rocket without filling too much of the frame with the rocket itself.

After determining the best angle, the T-bevel was placed along the side of a 2.5" x 2.5" x 6" solid wood block and the angle was marked on the wood with a pencil.

Next step was to cut the wood block at the indicated angle.

The bottom surface of the wood block was then marked with a arc that matched the radius of the body tube. I then sanded it on the end of a table mounted belt sander.  The end of my belt sander had a nice radius but it was slightly different than what was needed to match the body tubing. However, it was very easy to rotate the wood block around into different positions as the belt sander arced the bottom of it to match the radius I wanted. 

This is a small piece of 1/16" thick G10 fiberglass that is slightly smaller in size then the mirror end of the wood block.  It will serve as a base plate for mounting the mirror.  It will also make it possible to easily replace the mirror should it become damaged. Two holes have been drilled in it to mount this base plate to the wood block.

These are #4-40 threaded brass inserts that can be screwed into the wood block and allow #4-40 x 0.25" machine screws to be used to hold the G10 base plate to the wood block.

Here we see the brass inserts after they were installed into the surface of the wood block that will hold the mirror.

The mirror was attached to the G10 base plate with a piece of double sided carpet tape.  The base plate is held in place with two small #4-40 x 0.25" socket head machine screws.

The block and mirror can now be aligned with the lens hole to double check the camera's view.

The mirror was then removed from the wood block and the back side of the block was cut at an angle to begin the process of streamlining it. 

The left and right sides of the block were also cut at angles so that the forward end of the block was smaller and more streamlined.

The sharp corners on the top two edges of the block were then sanded down to create a nice radius.  This completed the fabrication of the block itself.  Now we have to mount it on the airframe.

To proceed with the next phase, I used a scrap piece of body tubing that was the same diameter as the Starfire body tube.  A small one-inch diameter hole (simulated lens hole) and a straight line for alignment of the block were drawn on the body tube.   On top of that, I taped down a piece of wax paper and placed the wood block on top of the wax paper.  The wax paper will prevent the epoxy in the fiberglass shroud from sticking to this body tube.  Once the shroud has been built and is cured, it can be lifted off the was paper and trimmed to final size before epoxying it onto the Starfire body tube.

The mirror shroud will be made out of a combination of fiberglass and Kevlar cloth.  This is the fiberglass I chose.  It is 9oz weight and is flexible in both directions to make it easy to contour around the shape of the wood block and body tube. 

The Kevlar cloth is from Thermostatic Industries, Inc.  It is the lightest weight cloth they sell.  Their part number for it is 8K-60  which I think means it is 8 oz/sqyd. It is 0.026" thick.  Many other material properties and specifications for it are available right here.

Top view showing where some of the fiberglass has been put in place behind the Kevlar strip.  These first few strips of fiberglass cloth were used to build up the height on the back side of the wood block to match the height of the Kevlar. 

Side view showing that more strips of fiberglass have been added over the top of the whole thing. The fiberglass even overhangs the edges of the Kevlar but will be trimmed back once the epoxy has cured.

Once the epoxy has cured the whole thing can be lifted off the wax paper.

Here I have placed the mirror hood onto a body tube and laid out a temporary piece of wire (yellow) around the outer periphery of it.  This allowed me to play with the shape of the wire until I was happy with it.  I wanted it to be symmetrical and to give plenty of undersurface for bonding the whole thing to the Starfire body tube.  

Once I was happy with the shape of the wire, I marked around it with a felt tip Sharpie pen.  The piece was then trimmed along that line.

The completed mirror hood after trimming away the excess fiberglass.

Another test fit over the lens hole on the actual Starfire body tube.

Looking into the mirror hood during the test fit.  The mirror is mounted in place.  The overhanging edges of the Kevlar cloth are easy to see here.  You can also see how the whole thing conforms to the shape of the body tube.

Top view.

Next step was to rough up the bottom of the mirror hood with some 60 grit or 100 grit sand paper.  This was done to help give the epoxy something to bite into when it is epoxied onto the surface of the body tube.

West System epoxy was then applied over the entire bottom side of the mirror hood and then the unit was placed onto the Starfire body tube and held down with plenty of blue masking tape.  The inside edges of the Kevlar were also filleted with epoxy where they meet the body tube.

Once the epoxy had cured the blue tape was removed.

Side view.

Once the mirror hood was bonded to the body tube, it was time to start sanding.  All the rough edges and rough surfaces were smoothed out.  Wet sanding with water and wet-or-dry sandpaper works very well.  It avoids loading-up the sand paper with dust.

Squeeze out only enough that can be used in 5-10 minutes and mix in a very small dab of hardener.  It will cure in about 3-15 minutes depending on how much hardener you add.

Icing as applied but before being sanded.

"Icing" after sanding.  The edges of the mirror hood are now nicely blended into the natural curvature of the tubing.

Side view.  You can also see where some Icing was used to fill the fiberglass overlap seem along the side of the body tube.

At this point the tube has been painted and the mirror is installed inside the holder. 

Side view of the mid-section airframe tubing with the mirror hood on the left side.   This completes this part of the project!

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