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This page describes my construction of an Estes model rocket called "The Shadow". This kit was modified from a single-engine model (24mm diameter motor mount (MMT)) to a cluster model. Four 18mm diameter MMTs were installed around the 24mm MMT. An additional modification consisted of an internal baffle system to eliminate the need for recovery wadding. Here are some pictures taken during the early stages of construction: Cluster & lower part of stuffer tube, lower body tube, upper stuffer tube, upper body tube, nose cone

Here are some close-ups of the stuffer tube and cluster mount:
 

This is the bottom section of the stuffer tube. A 24mm MMT is contained within the stuffer tube. Four 18mm MMTs are glued to the side of the stuffer tube and a centering ring is glued just above these smaller MMTs. The outer MMTs have no engine retention clips and are held in (theoretically) by friction created by wrapping masking tape around the engines.

 

Here's a "reverse angle" shot of the bottom section of the stuffer tube. In this picture, one can see the 3/8" (10mm) holes in the centering ring at the top of the 18mm MMTs. The 3/8" (10mm) holes in the sides of the stuffer tube above the cluster engine mount allow the ejection charges from the outer engines to enter the stuffer tube (there are 4 holes). The next centering ring confines the gases and also adds rigidity to the airframe just above the main fins.

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This picture shows the two pieces of the stuffer tube before assembly. In this picture, the lower section (containing the MMTs) is shown above the upper section. One will note the additional holes (also 3/8" (10mm)) in the top of the lower section and the bottom of the upper section (there are 4 holes in each). These holes, along with a "block" in the tube connector make up the entire baffle. They force the exhaust gases to take an indirect path, and block any bits of ejection powder from striking the recovery system.

 

This picture also shows the two pieces of the stuffer tube before assembly (lower section is on the left). In this picture, the "block" in the tube connector is visible. This is nothing more that the cardboard punch-out from the center of one of the centering rings. It is held in place with a fair amount of yellow (wood) glue on both sides.

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Here are some photos of the completed rocket:
 

The body is almost 48" (over 1200mm) long and the fin span is almost 11" (280mm). Finishing was performed as follows: thinned Elmer's Wood Filler was applied to the balsa fins and body tube seams and sanded; two coats of Painter's Touch (PT) Gray Primer, sanded after each; one coat of PT SemiGloss White on the area to be painted silver; and one coat each of PT SemiGloss Black and PT Silver Metallic. Each coat was made up of 2 to 3 light coats a few minutes apart. Stock decals were applied per the box picture.

 

Here is the aft end after two launches. The first launch was on a single D12-3 with apogee at about 200 feet (60m). Expended engines with tape over the top ends were used to plug the outer MMT holes. The second launch was on one C6-3 (in a 18mm to 24mm adapter), two B6-4s and two A8-3s. WRASP said about 300 feet (90m), but the delay on the As was only about 1 to 1.5 seconds (about 2 seconds after ignition) so it didn't go much over 200 feet (60m).

 

Prepped for the second launch with a center C6-3 in a 18mm to 24mm adapter, two B6-4s and two A8-3s. Note that none of the leads are twisted. I built a new controller with five pairs of clips, individual switches to check each ignitor's continuity independently, and a connection for a car battery (540 cold cranking amps sure "crank" the ignitors!). Remember, the outer MMTs have no engine retention clips and the engines are held in by friction created by wrapping masking tape around the engines. This was the first launch after finishing. The initial launch was done "in the tan" to test the baffle.

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What was that? Oh, I remember, the outer engines are held in place by friction created by wrapping masking tape around the engines. NOT! The two A8-3 engines popped-out on the second launch, but not before pushing out just the nose cone. Anyone want to play lawn darts from 200 feet? Thank goodness the ground was soft. The body tube took a good 2" (50mm) core sample and did a minor crimp (5/8" (16mm) by 3" (75mm)).

 

Look at those streaks on the side of the body tube from the grass and topsoil. For as flimsy as Estes' BT-80 is, it was a miracle that there was no other crimping or buckling anywhere else. I was expecting a major buckle above the fins but the tube is still straight and strong. The stuffer tube in this kit is not standard BT-50, but rather, the thicker wall (1" (25mm) O.D.) material. This appears to add a tremendous amount of rigidity to the model.

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This page was created on December 15, 1998, and last updated on December 24, 2002.