Bull Pup 12D (Estes)

I didn't start documenting my rockets with pictures until this one was built.  Too bad, it was a solid build, IMO.

However, I did document the repair job below after it's 3rd flight. Click on any of the pics to blow them up for more detail.

Length: 15.6 in. (39.6 cm)
Diameter: 1.33 in. (33.8 mm)
Weight: 1.8 oz. (51 g)
Recovery: 12 in. (30 cm) Parachute
Fins: Die cut balsa
Max. Altitude: 675 ft. (206 m)
Recommended Engines: A8-3, B4-4, B6-4, C6-5

Length: 5.25 in. (13.3 cm)
Diameter: 1.0 in. (25.4 mm)
Weight: 0.74 oz. (21.2 g)
Recovery: Streamer
Fins: Plastic molded
Max. Altitude: 700 ft. (213 m)
Recommended Engines: 1/4A3-3T, 1/2A3-4T, A3-4T, A10-3T

Length: 4.5 in. (11.4 cm)
Diameter: 0.54 in. (13.7 mm)
Weight.: 0.094 oz. (2.7 g)
Recovery: Featherweight
Fins: Die cut balsa
Max. Altitude: 750 ft. (260 m)
Recommended Engines: 1/4A3-3T, 1/2A3-4T, A3-4T, A10-3T

Rockets built/repaired the week of 10-15-05
220 Swift, Bull Pup 12D, Mini Meanie

CLICK ON ANY PICTURE below to see a larger image.


This flight took place on 10/7/2005.

I had already flown an A engine and B engine, decided to go for it with a C6-3.

This was one of the better timed launch pics of the day. Click the photo for an enlarged image. Note the spare engine I used to offset the rocket from the launchpad...it's blasting off toward the camera.

This baby REALLY took off. When the ejection charge popped, even from this far away I heard something *crack* and thought I saw the nose cone fly free.

When the rocket landed, it turned out the sound was the nose cone slamming into the body and snapping off one of the main fins.

So, the damage is pretty severe. Main fin gone to jet-stream. The parachute completely disentegrated, so I'm assuming this little missile was REALLY moving when the chute deployed, destroying the chute and slamming the nose cone back into the BT.

So, the shock cord worked. Hehe.

With no way to refillet the fins without messing up the paint job and decals, I opted to strengthen the replacement fin by going through-the-wall. I went back to the instructions and noted where the centering rings (CRs) should be and cut into the tub inside the rings. I widened the hole to the proper width and used my knife to find the actual edges of the CRs.

I scraped off the paint forward and aft of the slot where the fin would need to attach to the outer portion of the tube.

Using the template in the instructions, I created a new fin with the added tab on the bottom for the through-the-wall attachment. I made the tab a little too long so I could adjust the fit.

This was the last rocket I built before I learned about airfoils, so the fins will remain square on all edges. It was screaming fast anyway, so no harm done.

I dry fitted the fin and kept sanding the tab edges until it snugged up perfect on all sides.

CA glue was used on the surface and I dropped a large (LARGE) glob of wood glue into the slot to coat the motor mount.

I attached the fin and inverted the assembly. The loose wood glue crawled back up the fin and filleted the fin to the underside of the body tube. This technique attached that fin to THREE separate surfaces, BT outside, BT inside and MMT Strong...

Thought I'd try a technique I read in The Rocketry Forum for painting. I used tin foil to lightly protective wrap the whole rocket, then tore open a hole at my needed spot.and taped around that area. Only the fin was left exposed.

I used three coats of white primer, sanded, then 2 coats of white gloss.


This is how cheap I am. I didn't have any black paint, I didn't want to mask the whole rocket for those tiny little slots anyway. So I cut black squares from the ESTES packaging card and split the paper layers apart. I then glued the thin glossy paper layer to the rocket in the right position.

Hehe, it looks PERFECT. A few coats of gloss and we're done.

I now use a snap-swivel assembly on all my rockets making the parachute and shock cord assemblies interchangeable in the field, so I am tripling the length of the shock cord to make it harder for the nose cone to hit the body so easily in flight. I'll just use a parachute from another rocket for each flight.