SR-72 Darkbird (Apogee)

The Apogee SR-72 Darkbird is a replica of the US stealth plane. This kit was given to me by my wonderful wife on my 43rd birthday, her first rocketry gift to me. Since the kit is being discontinued this year, it's a great choice. 14" as compared to the 19" version from Estes, I plan to build both!

This version is a boost glider, kicking it's entire motor assembly at apogee and gliding back to earth, the motor mount will have a streamer recovery.

Length: 14" (35.6 cm)
Diameter: 0.736" (18 mm)
Weight: 1.05 oz (30 g)
Recovery: Glider. (Engine pod comes down on via a streamer)
Recommended Engines: 1/2A3-2T, A3-4T, A10-3T

CLICK ON ANY PICTURE below to see a larger image.


Here are all the parts all accounted for. The kit is marked $12.95 in the cover art, but they sell it for $15.41 on their web site. I thought that was pretty weird.

I have the Scissor Wing Transport in my build pile, this boost glider will be a great warm-up. Here we go.


Die cut balsa fins. Sanded both sides before removing. A LOT of pieces in this one.

The main fins are created by joining 3 smaller pieces. I was concerned about alignment, so I used a metal straight-edge to glue against. Worked well.

The preforming on the main fins is complete and the 3 exterior BTs marked for fin attachments.


Here you can see the first fin attached and I immediately didn't like the frailty of what I saw.

I decided midstream to paper all the fins to smooth the finish and strengthen the fins. Here you can see the adhesive cutouts for the fin already attached and two other fins already papered.

Here are all the smaller fins papered next to the granite plates I used to weight them down to set the paper.


OK, the main fins are papered and attached, filleted with CyA glue. Strong now. Looking good.

The outer jets attached and straight with CyA and filleted.

The kit comes with a template for creating my own canopy (I'll get to that later). It also includes a template for weird angles the outer fins have to be attached.

I used the template to get the outer horizontal jet fins attached and angled up at the correct position. Filleted with CyA.

The special aileron template guide has all the measurements needed on a single template to do all the angle fin assemblies. I glued the template to cardstock to make it easier to use. Here I'm using it insure the top fin is angled in properly.


The motor mount goes the full length of the Darkbird. You can see the high-visibility mylar streamer attached in the middle and a cool "collar" in the rear which will serve to center the mmt in place AND hold the ailerons in the down position for launch.

Here, I've attached the jet nacelle cones and assembled the canopy shroud.

Here it is all put together minus the final piece, the aileron flaps.

At this point I refilleted over the CyA with white glue for a cleaner look and additional strength.

...and here is the bird with ailerons added. Hmm, what's wrong with the picture??? Nothing, as long as I WANTED my bird to nose dive at high speed!

I installed the ailerons to the bottom of the rear flap instead of to the top. Didn't even notice I was holding the bird upside down until after the CyA had set completely. (*sigh*)


I was getting ready to saw off the ailerons and find new hinge material when I remembered I had debonder for CyA glue. What the hey, can't hurt.

Soaked the fin-hinge piece in debonder using a Qtip to control it.

20 minutes later, they slipped off smoothly. A little cleanup and I repapered the underside of the wing to correct the mess you see here.

No pic, but reattaching the ailerons on the top was straighforward.

The trick I use to properly align multi-piece launch lugs is very simple. Make sure the line you're gluing on runs the length of the BT. Next, slip a dowel inside the LL and position it correctly on the BT. Drop a dab of CyA and it sets in 10 seconds. Repeat for second LL.

Immediately fillet with white glue. All done.


The ailerons are back on now in the perfect position. I've precolored the entire assembly of ailerons, aileron stops and even the edges of the fins where they all meet. This is in case I have trouble with the paint later, the pieces started already black.

Using needlenose pliers, dipped the raw edge in a pool of CyA and positioned for 10 seconds to set them. Repeat for the other four pieces.

Here are all the aileron stops installed and they already have a tendency to lift to the proper position even without the rubber bands. I'll use the bands during flight just to be sure.

This shows the tail assembly with the MMT installed, so you can see how it will be during launch. The MMT holds the ailerons in the flat position.

Here she is all repaired and assembly complete, ready to paint. I've removed the MMT and will hand paint the portion of the tail that will be visible.

more to come...

more to come...