Madcow Rocketry - Super DX3 {Kit}

Contributed by Mike Caplinger

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Diameter: 4.00 inches
Manufacturer: Madcow Rocketry
Style: Sport

Madcow Rocketry Super DX3

Brief:
The Super DX3 is a 4" 38mm version of the Madcow DX3. It's a 3FNC with a large payload section.

Construction:
The kit includes a pre-slotted body tube, a payload tube, plastic nose cone, 3 laser-cut 1/4" plywood fins, 38mm x 18" cardboard MMT, 1/4" plywood centering rings, a cardboard coupler with plywood bulkhead, a Nomex chute protector, a 12-foot tubular nylon shock cord, eye bolts and washers, Delrin rail buttons, and a 36" nylon parachute. All tubes are heavy-duty cardboard.

The kit went together smoothly. I again left the aft centering ring off so I could add internal fillets to the MMT-fin joint.

There was a slight mismatch between the nose cone and tube diameters and the coupler was fairly loose. Otherwise the part fit was excellent.

The instructions for installing the rail buttons were a bit unclear as I had not used them before, but a visit to railbuttons.com quickly cleared up my questions. I drilled holes for the buttons but waited until after painting the install them so I wouldn't have to mask them. However, if I had it to do over, I'd mask the area the buttons epoxy to (sanding the paint off was a bit tricky).

Madcow Rocketry Super DX3 For motor retention, I used a PML PMR-29/38. While I put the inserts in prior to gluing the aft centering ring in, which the PMR instructions strongly suggest you not do, I used a drill press and a hand drill to put them in very carefully. Still, I managed to get the plywood layers to split at one place, so I think this is the last insert-in-plywood system I'll be using--from now on I'll either use T-nuts or something like the Aero Pack retainer. If you want to use a ring-and-insert system though, the two-screw Madcow system is probably easier to install and otherwise as good as PML's.

I used four removable plastic rivets from PML to hold the NC to the payload tube.

I thought seriously about building it zipperless, but decided that with the extra volume to pressurize in that configuration, and what seems like a small amount of BP in the typical Aerotech G motor (less than a gram) I'd be better off with the standard setup.

Finishing:
Finishing used two coats of diluted Elmer's Wood Filler with 220 grit sanding on the fins, then one coat of Rustoleum Painter's Touch gray primer (two on the NC), 400 grit dry sanding, and then a coat of Painter's Touch Deep Blue on the lower and Gloss White on the upper and nose cone. Paint and primer adhere rather poorly to the NC plastic, but it came out OK. (I still can't get gloss white on with no runs though.)

I didn't fill the tube spirals but slightly regretted it, since they are relatively deep.

Construction Rating: 4 out of 5

Flight:
For the first flight, I used a G79-4W with a PMR 29-to-38 adapter. After some continuity problems and one spit igniter, the motor boosted the Super DX3 to about 500 feet as simulated. Under calm conditions the boost was straight up.

Like other Madcow models, the Super DX3 uses a Nomex chute protector so no wadding is needed. A small part of the tubular nylon shock cord is exposed below the chute protector; Madcow sells an optional Nomex protector for this also.

I attached the shock cord to the centering ring eye bolt with a quicklink in case the cord got damaged.

Recovery:
Recovery was perfect. I was a little concerned that the 36" chute would be too small for the rocket, but the descent rate was just about right. No damage landing on packed sand. The shock cord was very slightly scorched in a couple of places near the bottom, but should be fine for many flights.

Launch Recovery

Flight Rating: 4 out of 5

Summary:
The Super DX3 is a good-sized kit if you want to fly near the high end of what the FAA now defines as a "model rocket" (1500 grams). It performs well on a G but will probably really excel with H and I motors. I plan to fly it for my Level 1 cert as soon as I can.

Overall Rating: 4 out of 5

Flights

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