Brief:
Scratch built 38mm, apogee only recovery, through the wall G10 fins with a 3" OD phenolic airframe specifically built to take Pro38 G motors.

Construction:

• 1 - 20" long by 3" OD phenolic body tube
• 3 - G10 fins with fin tabs
• 1 - 3"OD x 12" PML nosecone
• 2 - 5mm plywood centering rings
• 1 - eyehook with nuts
• 1 - 38mm slimline motor retainer
• 1 - 3" bulkplate with eyehook for forward recovery mount point.
• 4oz lead shot for nose weight
• 15' of 1/2" tubular nylon
• 1 - 20" SkyAngle parachute

I had some left over components for this rocket. So it was only a matter of fleshing out the details using RockSim before construction could start. I was not going to reinforce the body tube as I wanted to be sure that it would fly on the single grain Pro38 motors. This meant that construction followed the usual process with the exception that I slotted the airframe all the way down (i.e. I mounted the fins on the motor mount externally to the airframe and then slotted the whole fin/motor assembly back into the airframe).

As always I used my Dremel to profile the fins but that was really all that was needed on the base materials.

All gluing was done using 1 hour epoxy. Fillets were applied to the airframe (after fitting the fin/motor assembly back into the airframe) using 1 hour epoxy and microballons (this gives a nice smooth fillet).

The construction was completed very quickly and before long I was ready to apply wood filler to fill the spirals. Once dry I sanded down the airframe and sprayed it using grey Holts Filler Primer paint.

A couple of paint/sand cycles left me with a nice smooth primed rocket. The color scheme consisted of a white rocket with red fins and upper section.

Picture by Bob Arnott

A G50 decal (still to do) will finish it off.

Flight:
The rocket was built for Pro38 G's so I started with a G79 Smokey Sam which boosted perfectly to an estimated 1500 feet (RockSim). The parachute deployed at apogee and due to its small size brought the rocket down quite fast. With no damage I was ready for a second flight on a Pro38 G66 (US reload). As before it boosted nicely with an apogee deployment and nearby recovery. Again no damage and I look forward to many more flights.

Summary:
PROs: Your basic 3FNC rocket is just so easy to build. If you keep it stock (i.e. no layups etc..) you can finish one in a couple of days.

CONs: The cost of the motor retention is always a bit of a sore point. I just don't trust DIY methods of retaining expensive motor hardware.