There are a lot of centering rings with all the motor mount adapters. I usually sand off the laser cut burn marks from the flat faces of the...

The inside of the interior ring can be roughed up before epoxying to the engine mount tube. I used one of my diamond files.  On the right si...

The aluminum motor retainer is epoxied onto the rear of the motor mount tube. The shock cord is tied to the nose cone shoulder loop. The nyl...

I also had to cut free the die-cut centering rings. On the right -  You can see the compression wrinkles from the die cut process. On the le...

I used 220 grit to roughen up the inside are of the engine retainer ring. I'm always tempted to apply epoxy to the inside of the plastic...

With the fins in place,  The third centering ring is dropped in and pressed down onto the rear of the fins tabs. I applied some wood glue to...

Here's the finished nose cone with the upper tunnel ends filled and painted. I was happy with the results. Note the position of the tunn...

Look at Step 1 of the ASSEMBLE ENGINE MOUNT on page 4. It says to mark the tube at 8 1/8" from the top. GOTCHA:   At the lower right, i...

TIP: Parachute Fix The kit parachute had the start of a tear that was outside of the tape disk. This tear could spread and rip through the ...

The instructions show tube type plastic cement. I used brush-on liquid cement. The fin can halves were pressed together dry. The inte...

The black paint was scraped off the low end to glue on the engine retaining rings. (I really should have masked off the gluing areas!) I...

The fin detail "guns" are slid in place and glued at the ends. Check the exposed ends to make sure that the rear end of the re...

Here's the Boosted Bertha before decals. Orange overall, one white fin on the booster, one white fin on the second stage. Tha...

In a comment from Boosted Bertha build Post #2, Openroad asked: "I’m curious about how the engine retainer holds up on the sustainer -...

Estes has had many Big Bertha variations over the years, now a two stager! I've seen a few two stage Bertha flights on the for...