Public Missiles Miranda

Public Missiles - Miranda

Contributed by Mark Weitemeyer

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Published: 2011-01-01
Manufacturer: Public Missiles

Courtesty of PMLBrief:
The PML Miranda is probably intended to be a second HPR kit, but this was my first HPR kit. (Picture is courtesy of Public Missiles)

Construction:
The PML Miranda is a single stage 3" rocket with a 12" payload section. This kit comes with PML's Kwik Switch system allowing you to use up to 54mm motors and spend more money than you really should. Not that this will stop you.

The instructions were easy enough to follow for me, but I enjoy building things and have "engineer tendencies" - I like to over-build things. Therefore - I fiber-glassed the nylon strap to the motor tube and added a third centering ring to the motor tube as well, forming a fin can. Before I even really knew what that was... I suppose I did TOO much research on the web and read too many horror stories about epoxy not sticking to Quantum tubing. Well, as long as you follow the directions, there will be no trouble at all. I roughed up the Quantum tubing with 80 grit sandpaper and used 30 minute epoxy everywhere. I suppose a K motor might tear things up, but I feel good about everything up to that. One thing the instructions left out, is to drill 1/8" vent holes to help the function of the piston system.

Finishing:
I'm not sure what to say about finishing except that I hate to do it. This rocket flew primer-only for it's first flight, and has been painted 1 1/2 times since then: I changed my mind about the payload section and repainted it. I used the Rustoleum product line for this rocket. I used Krylon on my second and it's going to be Krylon from here on out! That said - I'm glad this was PML's Quantum tubing and that I didn't have to fill any grooves!

Construction Rating: 4 out of 5

Flight:
Well, I'll have to extrapolate from a data set of one (flight) here, but I used an Aerotech H124J SU motor and I have a TRA level 1 to show for it. My conservative paranoia led me to purchase PML's retention system and so I had no trouble at all with keeping the motor firmly in the rocket at ejection. Other than some mild weather-cocking as it left the rod, the rocket flew extremely straight to (according to the eyes of our TRA prefect) somewhere around 1500 feet. Since I can't find RockSim data for this motor, I can't even try to confirm it. It DID take quite a while to come down, though.

Recovery:
All the recovery items used were exactly what PML provided in the kit. The piston system in place of wadding, tubular nylon shock cord, and a 36" rip-stop nylon parachute. Everything about the recovery system went together very easily and worked very well. The rocket recovered with almost no damage. The phenolic piston tubing had a crack in it upon post flight inspection. It was easily repairable, but it has me wondering how to prevent it as it happened to a friend's PML Io as well. I'm not sure if the paint would have scratched because it flew almost naked. (I was told that pretty rockets crash) On first inspection, I thought that the nylon strap for the piston had been burned slightly by the ejection charge, but I now think that what I am noticing is black powder residue. Still, my next kit got a Nomex protector for the cord and so will everything else I build.

Flight Rating: 4 out of 5

Summary:

Overall Rating: 4 out of 5

Flights

Comments:

avatar
G.S. (May 1, 2001)
I have an idea for strengthening your piston (and any other coupler as well. Currently, I am building a PML Tethys. After I installed the bulkhead and used a generous amount of epoxy on both sides (mixed liberally with Kevlar pulp and milled fiberglass), I took .7 oz Kevlar matting and laminated to the INSIDE of the piston. In theory, it should strengthen the piston and keep it from cracking. I'll see when it flies in a couple of weeks how effective it is. As for the piston strap, if you replace that nylon strap with tubular Kevlar, you have no worries about heat damage. Kevlar just does not burn!

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