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REV 2.4 - Fri Apr 6 09:00:44 2012

Madcow
DX3
24338 El Toro Rd #E-134
Laguna Woods, CA 92637
(949) 547-8847
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SPECS: 44.5" x 2.6" - 17.0 oz
ROCKSIM FILE: Right Click to Download
SpaceCAD FILE: MISSING - please submit here
REC'D MOTORS: F20-4, F40-4, F50-6, G40-7, G64-7, G80-7

Rating
(Contributed - by Mike Caplinger [Who's Who Page] - 01/28/09)

DX3Brief:
The DX3 is a fairly simple 2.6" diameter 3FNC mid-power rocket with a large payload section.

Construction:
The kit is complete, with a pre-slotted body tube, a payload tube, plastic nose cone, 3 laser-cut 1/8" plywood fins, 29mm 8" cardboard MMT, plywood centering rings, a cardboard coupler with plywood bulkhead, a Nomex chute protector, a Kevlar/Nylon shock cord (total length about 8 feet), eyebolt and washers, 1/4" launch lugs, and a 24" nylon parachute. All tubes are heavy-duty cardboard.

This was my first MPR build and being of the balsa generation of LPR, I wanted to avoid the plastic-fins route.

The kit quality was excellent and I had little trouble dry-fitting everything. I basically followed the instructions, with the exception that (per the excellent review of the Madcow Cowabunga on EMRR) I left the aft centering ring off so I could put internal fillets on the fins and MMT, and I used 30-minute epoxy for the centering rings (which is a pain if you're an impatient builder like me; I'm sure 5-minute would have been fine.)

I also bought the Madcow motor retention kit, which is a metal plate that attaches to the aft centering ring with two 6-32 cap screws into brass inserts. The only gotcha for me was that the inserts are quite close to the ID of the centering ring and I had trouble drilling and screwing them in without breaking through the plywood. I also found it hard to thread them straight in. But with some epoxy I didn't have any problem.

I thought about building this zipperless by drilling some holes in the coupler bulkhead and attaching the coupler to the lower body tube, but decided to not get fancy this time around. (Minor issue with the instructions: they say to attach the shock cord to the nose cone, but of course it goes to the eyebolt in the coupler.)

Fillet Retainer

The biggest problem I had was that the coupler required a fair bit of sanding to get a proper fit into the body tube and even then it's still pretty snug.

The instructions also didn't say anything about how to attach the NC to the payload section, so I friction-fitted it with masking tape.

Split

Finishing:
Finishing used two coats of watered Elmer's Wood Filler with 220 grit sanding on the fins, then one coat of Rustoleum Painter's Touch white primer, 400 grit dry sanding, and then a coat of Painter's Touch Deep Blue on the lower and Gloss White on the upper. I left the NC bare; Madcow recommends multiple coats of plastic primer on the NC, but I was lazy.

Note that the vendor site gives a weight of 15 oz but mine ended up at 18.2 oz and RockSIM estimates around 17 oz.

Construction Rating: 4 ½ out of 5

LaunchFlight:
Though the smallest recommended motor was an F20, the first flight was on a fairly small field, so I went with an E30-4T, which simmed to about 500 feet. The Madcow 24-29mm adapter was used; this has a thrust ring front and back, and a 24mm Madcow retainer was used on the DX3.

Like other Madcow models, the DX3 uses a Nomex chute protector so no wadding is needed. It's easy to get everything above the Kevlar portion of the shock cord wrapped up in the protector.

The first flight was straight and went to about the expected altitude, though the NC came off the payload section at ejection and fell free (no damage landing on packed sand); there were some blue paint marks on the white payload section, so the sections hit each other at some point (7' of shock cord may not be enough given the large and fairly heavy forward section.)

Recovery:
The chute deployed normally and the descent rate was about right, maybe a little fast, but that kept it on the field better.

In a total of four flights, all on E30-4T, the NC came off twice despite progressively more tape, and there was a small dent in the bottom edge of the tube from the landing (since the fins are above the end of the body tube, the tube ends up taking the landing impact.)

Recovery Recovery

Flight Rating: 4 out of 5

Summary:
The kit quality is extremely good and I enjoyed the build. I'm looking forward to trying larger motors. With the large payload section you could imagine building this for dual-deployment easily.

The biggest con is that you really need to make sure that the NC is well-attached to the payload section. Since the NC is pretty heavy (over four ounces) friction-fitting may not be effective. Removable rivets or rivet nuts would probably work well.

A longer shock cord might lessen the deployment forces.

Overall Rating: 4 ½ out of 5

Other:
You may want to strengthen the bottom of the body tube with a doubler and some epoxy since it'll bear the burden of impact.

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GUEST's OPINION:
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SPECIFIC ROCKET TIP:
11/09 - "I drilled a small hole in the ring next to the eyebolt and ran a nylon cord from the eyebolt through the ring and tied on to the nose cone. (I added a second eyebolt to the nosecone.) This is a backup to the friction fit to ensure I don't lose the nosecone and allows me to access the upper tube to add payloads later if desired. This paid off on my L1 cert as the nose cone separated but stayed with the rocket due to the nylon cord. I would not have had a successful L1 if the nose cone had fully separated." (T.J.B. )

[Enter Flight Log]
Date Name Motor Ejection/
Altitude
Wind Notes
11-21-2009 Tim Bookwalter AT RMS H128-M Just Before 5-10 mph winds Event: Club Launch
- L1 Cert Flight. Perfect Launch. Rocksim predicted 1900 feet adjusted for actual weight with eject just before, but I think actual was ~100-200 feet higher. Very long walk to recover, but in open farm field with no damage. Cert Flight: L1
01-25-2009 Mike Caplinger AT SU E30-4 Just Past (1-2sec) 5-10 mph winds - Nose cone detached at ejection, no damage
01-25-2009 Mike Caplinger AT SU E30-4 Apogee - NC Up 5-10 mph winds -
01-25-2009 Mike Caplinger AT SU E30-4 Apogee - NC Down 5-10 mph winds - Lost NC at ejection again.
01-25-2009 Mike Caplinger AT SU E30-4 Apogee - Perfect 5-10 mph winds -
02-15-2009 Mike Caplinger AT EconoJet F27-4 Just Past (1-2sec) 0-5 mph winds -
02-15-2009 Mike Caplinger AT EconoJet F20-4 Apogee - NC Down 0-5 mph winds -
02-15-2009 Mike Caplinger AT EconoJet F23-4 Apogee - NC Down 0-5 mph winds -
02-15-2009 Mike Caplinger AT EconoJet F27-4 Apogee - NC Down 0-5 mph winds - Four good flights; needs longer shock cord.
02-28-2009 Mike Caplinger AT EconoJet F20-4 Apogee - Perfect 0-5 mph winds - Doubled shock cord length.
02-28-2009 Mike Caplinger AT EconoJet F23-4 Apogee - Perfect 0-5 mph winds -
04-04-2009 Mike Caplinger AT SU G79-7 Apogee - Perfect
(1822 ft)
5-10 mph winds Event: Plaster City
- Long walk for recovery and some rash from chute dragging.
04-04-2009 Mike Caplinger AT RMS H128-10 Apogee - Perfect
(2536 ft)
5-10 mph winds Event: Plaster City
- Nice motor if you have a large launch site!
09-13-2009 Mike Caplinger AT EconoJet F20-4 Very Early
(503 ft)
5-10 mph winds Event: Fiesta Island
- 1-2 second early ejection; 4-second delay was perfect in simulation, so this batch of motors appears to be funky.
09-26-2009 Mike Caplinger AT RMS F40-7 Just Past (1-2sec)
(976 ft)
0-5 mph winds Flight PictureEvent: Fiesta Island
- Good flight, landed on the flight line.
10-02-2009 Mike Caplinger AT RMS G64-7 Just Past (1-2sec)
(1777 ft)
0-5 mph winds Event: Plaster City
- Chute partially tangled, no damage.
10-03-2009 Mike Caplinger AT RMS G64-7 Just Past (1-2sec)
(1774 ft)
0-5 mph winds Flight PictureEvent: Plaster City
- Last flight of a good rocketry weekend.
11-06-2009 Mike Caplinger Ces RLD I180-Altim Apogee - Perfect
(4130 ft)
0-5 mph winds - First dual-deploy flight for glassed DX3 with 38mm MMT.
11-07-2009 Mike Caplinger Ces RLD H123-11 Didn't See 0-5 mph winds - Glassed DX3 -- One of 21 Skidmark rockets launched at dusk for PB8. Found by a quad rider well east of the launch site.
12-27-2009 Mike Caplinger Ces RLD G69-7 Apogee - Perfect
(840 ft)
0-5 mph winds Flight PictureEvent: Fiesta Island
- Glass DX3, dual deploy with main at 500 feet. Indicated altitude seems low, RRC2 altimeter may be damaged from last crash.
12-27-2009 Mike Caplinger AT SU G79-7 Apogee - Perfect
(658 ft)
0-5 mph winds Flight PictureEvent: Fiesta Island
- Glass DX3, dual deploy with main at 500 feet. Altitude seems low. Came within 20 feet of landing in the bay.
01-02-2010 Mike Caplinger Ces RLD I170-14 Apogee - Perfect
(4432 ft)
0-5 mph winds Flight PictureEvent: Plaster City
- Corkscrewed on the way up; good dual deploy.
02-14-2010 Mike Caplinger Ces RLD G115-8 Just Past (1-2sec)
(1345 ft)
0-5 mph winds Flight PictureEvent: Fiesta Island
- Glass DX3, dual-deploy main at 500 feet; worked well. About as high as I'll ever fly at Fiesta!
05-01-2010 Mike Caplinger CES RLD I195-13 Just Past (1-2sec)
(4644 ft)
5-10 mph winds Flight PictureEvent: Plaster City
- Dual-deploy with motor ejection. Didn't see the deployment, but it was spotted by a friend (thanks Jim) and landed near the road tothe south. Not a good weekend for close recoveries!
06-12-2010 Mike Caplinger Ces RLD I540-15 Apogee - NC Down
(5872 ft)
10+ mph winds Flight PictureEvent: LDRS29
- First machbusting flight for the Glass DX3. Recovered practically at the south edge of the lakebed despite dual deploy.
10-16-2010 Mike Caplinger AT RMS F40-7 Apogee - NC Down
(911 ft)
Calm Flight PictureEvent: Fiesta Island
- Nice flight.
11-05-2010 Mike Caplinger Ces RLD G54-9 Just Past (1-2sec)
(2480 ft)
Calm Flight PictureEvent: Plaster Blaster 9
- Stock DX3 on CTI Pro29. Faster liftoff than I was expecting; chute shroud lines wound up, but no damage.

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