Public Missiles Pterodactyl

Public Missiles - Pterodactyl

Contributed by Joel Simon

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar
Overall Rating: starstarstarstarstar_border
Manufacturer: Public Missiles

[Rocket Pic]Brief: Single-staged HPR rocket, built for Level 2 certification. Piston-deployed parachute recovery. No payload capability in kit form.

Construction: The parts were all there and in excellent condition. The Pterodactyl is actually a fairly basic HPR kit, except for the fins. So the parts consisted of main airframe, six G10 fin components, motor tube, 3 centering rings, nose cone, and piston assembly.

Instructions were surprisingly good; complete and accurate. Construction gave me very few "huh?" moments. Fit of all parts was dead on.

The kit does contain one massive 'gotcha', and one 'I wish I'd thought of this before I bought this !@#$! kit factor. Both involve the fins: one in construction, one in finishing.

Each fin is two-piece. The main section (rear) is a conventional double-swept design that has a tab extending through the airframe slot to the motor tube. The front section is a design accent which extends along the airframe and dwindles to a point. This section is only tabbed in its rear, about 1/3 of its length. The two sections fit together perfectly; PML really did a nice job. BUT...Getting them perfectly aligned so that they look like one fin is a real challenge. and while you're obsessing about that, you'll find that the untabbed part of the forward fin (the point) is warping. I ended up having to tape the front part of the forward fins down, so that they'd epoxy on straight.

The kit doesn't come with any method of motor retention. I bought an Aero-pac retaining ring set before beginning construction.

Finishing: When you've got the fins all glued on and the fillets cured, you'll learn that you've just committed yourself to sanding more than 18' (that's feet, not inches) of fin fillets. That's right, the fins extend more than half the rocket's length, and there are three of them, which makes six of the longest damn epoxy fillets you've ever seen. If you're like me, you'll soon wonder why this rocket looked so good in the catalogue. I did it by hand. My doctor says that with therapy I might someday resume a nearly normal life.

I also didn't consider before-hand how one goes about painting a rocket that's half as big as a car. I ended up building an impromptu paint booth in my garage (plastic stapled to roof trusses). It's not my best paint job. Next time I find an auto painter.

Construction Rating: 4 out of 5

[Rocket Launch]Flight: My rocket, which I built for my L2 certification, launched on a K550.

The rocket preps very easily. The piston needs to move smoothly but not sloppily in the airframe. No wadding is needed. I got rid of the elastic band that came with the kit and used 1/4" bungee. The parachute is more than twice as big as I'm used to, so I had to clear off my prep table to fold it.

The Aero-pac retention system I built on the rocket makes motor retention as simple as imaginable. Just slide the motor in and spin the ring on.

All those fins provide a rocket with barely one-caliber stability. I didn't add any nose weight, and I spent a lot of time thinking about that while waiting for my turn to launch. Even at 6.5', this is a very squat-looking rocket. But it flew straight and true. I loved it!

Recovery: Parachute, PML kits come with elastic bands which they insist are adequate and which I always discard. Maybe I'm paranoid. I used 1/4" bungee, and with all the separations I've watched at ROC launches lately I'm moving to Kevlar®.

The 6' parachute brings the rocket down too quickly for playa clay. It's probably just right for a softer, smaller field. I notice that even PML has come out and said that they'll spec a bigger chute in kits purchased for desert landings, but they did this after I bought my Pterodactyl. The nose cone (fiberglass) weighs 2.5 pounds. Next time I'll bring it down with its own 30" chute and let the main airframe have the 78" chute.

Flight Rating: 5 out of 5

Summary: This is not a beginner's kit, because of the fin construction. Because the rocket is so heavy and the phenolic is so brittle, you have to be VERY careful about bouncing it off the floor. Ask me how I know.

If I were doing it again, I'd make two modification; I'd stretch it with enough payload space for an altimeter (may still do this) and I'd get custom centering rings that would let me cluster 29mm motors with the central 54mm. (then I'd add nose weight). This is a great rocket for guys who like big heavy birds that look fantastic in flight but don't go out of sight.

Overall Rating: 4 out of 5

Other Reviews
  • Public Missiles Pterodactyl By Frank DeBrouwer

    (by Frank De Brouwer - 12/20/02) Note: This is a slightly condensed version of all the information that Frank has produced for his Level 3 project. Visit the Tripoli Netherlands site (look under Projecten) to read the additional information and enjoy additional pictures. I decided to fly a Level 3 rocket at ALRS 1 in Switzerland on the 24th and 25th of March 2000. After contact ...

Flights

comment Post a Comment