Picture courtesy of Public Missiles

Brief:
The PML Phobos is a 2.15" HPR with payload section. I selected it because PML website indicated that is was capable of flying with a J350. This would allow me to use it for both for a TRA Level 1 certification as well as Level 2.

Construction:
The PML Phobos is a 2.15", 57” long HPR with payload section using the PML Quantum (smooth gray plastic) tubes. The Phobos has 3 triangular fins of .062” G-10 with through the body tube mounting to the motor tube. The kit comes with a pre-slotted body tube 34” long, a 12” long payload section and a plastic ogive nosecone. The kit comes with an 8" motor tube and two centering rings. It uses PML’s piston deployment system. The piston is basically a coupler tube and bulkhead attached to the motor mount by a 6’ long, 1” nylon strap and the parachute shock cord attaches to the piston’s D-ring.

Because I planned to fly a 14” long J350W, I changed to motor tube to a 15” long one with three centering rings. The middle centering ring was located just forward of the fin to motor tube attachment. The forward and middle centering were glued to the motor tube along the 1” heavy nylon strap for the piston. The forward centering ring has a slot in it that allows clearance for the nylon strap, which is glued to the side of the motor tube. The motor tube assembly was then glued into the body tube with thickened 30-minute epoxy.

The fins were glued in with thickened 30-minute epoxy with generous fillets on both the outside and inside of the body tube and on the fin to motor tube joint. It is a real challenge getting the internal fillets done with only about ¼” of clearance between the body and motor tubes. I used a bamboo skewer to dab the epoxy in trying not to get too much where the aft centering ring location.

I also glued aluminum circuit board standoffs that were about 1” long x 3/16” OD with #6 internal threads for a motor retention system at each of the body tube to fin junctions. I found the standoffs at a surplus electronics dealer.

Next step was gluing on the aft centering ring with 3 holes drilled in it for the #6 screws for the motor retention system.

The remainder of the kit was built stock. The piston required extensive sanding to get a smoothly sliding fit it the body tube. The body tubes, parachute and nose cone were first rate. The fins required some cleanup so that all were exactly the same. I thought the plywood in the bulkheads and centering rings were of only of okay quality due to some splitting of the wood.

My rocket came in a 35-oz or 3 oz heavier than listed. This was mostly likely due to the longer motor tube and larger amount than normal of epoxy on the fin fillets.

Finishing:
The Quantum tubes are very easy to paint since they are so smooth (no spiral line!).

Construction Rating: 5 out of 5

Flight:
PML recommends motor ranging from hotter F's to J350’s.

My first flight was a TRA level 1 certification flight using a 38 MM H123W-10 at San Diego’s Tripoli Ocotillo Test Range (500’ elevation, FAA waivers from 10,000’ to 12,500’). Perfect flight to about 2800’ landing 100 yards away.

The next flight was TRA level 2 using a J350W-14 with a Missile Works RRC altimeter recording altitude. Good flight with a little weather cocking in the wind to an altitude 6956’ on the RRC (PML says 6915’ with 15.6 second optimum delay) and drifted about ¾ mile way taking two of us about ½ hour to find.

Third flight was on an I161W-14 going about 4600’ up landing about ½ mile away.

A friend built a Phobos with similar modifications at the same time and has done his level 1 with a H123W and level 2 with J350W as well.

I have since modified mine for dual deployment and have flown it on an H123W-10 with perfect results.

Recovery:
The rocket has not sustained any damage other than minor paint chipping. The Quantum tubes and G-10 fins are tough. Landing area at Ocotillo Test Range is open desert with hard dirt and some rocks. The piston deployment system has worked well and no wadding is required. I have used about 0.6 grams (1/8 teaspoon) of black powder for the ejection charge with good results.

Flight Rating: 5 out of 5

Summary:
This is one tough rocket that can fly on a wide range of motors from F's to 700' to J350's to 7000'.

Overall Rating: 5 out of 5

Brief:

The PML Phobos is an easy to build single stage, single motor 3FNC MPR/HPR kit. It could be used for Level 1 certifications but I don't know if I would recommend it for that. You have a choice of either Quantum or phenolic tubing and 29mm or 38mm motor mount.

Construction:

I used 12 minute epoxy for the entire build. The build went without any major issues, however, I want to point out 4 potential "gotchas" when building a PML kit stock with the QT:

1. You must sand the QT near the fin slots so that the epoxy has something to "bite" into.
   
2. Same goes for where the launch lugs are attached.
   
3. When epoxying the the MMT tube, after epoxying on the piston strap, make sure that the strap is not in the way of the fin placement.
   
4. Sand the piston coupler so that you have a smooth (almost loose) travel in the QT. Patience & "elbow grease" is needed here as it might take a while to get the proper fit.

I did not make any serious modifications, but I did do the following outside the scope of the kit instructions:

1. Foamed the fin can with PML expanding foam. There is maybe 1/4" gap between the QT & MMT tubes. Rather than apply epoxy fillets in such a small space, it was easier & faster to dump the foam in and sand to shape.
   
2. Added rail buttons. I did not however drill them into the QT. Instead I built standoffs with popcicle sticks and mounted the rail button there (see railbutton.com for more information on doing this).
   
3. The aft centering ring was too small to add Kaplow clips or the PML retainer. I purchased and installed an AeroPack retainer and 38-29 motor adapter. (Overkill, I know!) Special note about the AeroPack retainer: I did a dry test fit. It was so snug that I was (and still am) unable to get it back off! That's not a bad thing though...

Finishing:

Many people have touted the ease of finishing the PML QT and you can count me among the satisfied customers. It is indeed easy to work with. Scuff the entire rocket with 220 grit, prime with Krylon primer, sand with 320 or 400, spray with Krylon gloss colors. Where the different colors meet on my paint scheme, I covered them with 1/4" wide chrome automotive pinstriping. The chrome pinstriping has great reflectivity (my main goal) but lacks the stretchy characteristics of typical pinstriping. I did not have any notable problems with the finishing process.

Construction Rating: 5 out of 5

Flight:

I did 2 test flights on G motors. First was a single use G40-7W. I built up a good tape thrust ring, loaded the motor up in the AeroPack 38-29 adapter, slid everything into the motor mount,and screwed down the retainer cap. I had a lot of jitters for this being the largest rocket I'd ever built and launched at the time but it lifted off without a hitch. Estimated altitude of 1100ft but the delay was a good 3 seconds too long. I had a rapidly sinking feeling in my stomach as the rocket plummetted from the sky, however, it did (finally) eject at about 400 feet. No zipper or any other damage whatsoever. I couldn't believe it!

Second flight was a couple of months later on an EconoJet G35-4W. Altitude was slightly lower (~1000ft) but ejection was right at apogee. Perfect flight all the way around.

My club was finally able to have a vendor onsite at a launch for the third flight of my Phobos. I prepped a Pro38 2-grain H153, shaving 3 seconds off the delay (for a total delay of 10 seconds). Preparation was even easier this time because I didn't need to add a masking tape thrust ring and/or use the motor adapter--just slide in the motor and screw on the cap. What blew my socks off though is that the Phobos lifted off with significantly greater velocity! It darn near disappeared in the sky... Some of the more experienced fliers in my club estimated that it was well over a half-mile up! It was fairly windy that day so it did drift on the way down. After a 45 minute search, I finally stumbled upon it and everything was intact! I'd just become certified Level 1.

Recovery:

Pistons are a technology that people either love or hate. I have had nothing but success with my Phobos and particularly enjoy that I don't need to use any wadding. Cleaning out the body tube at least every other flight and always making sure that the piston fits loosely are the key points to remember. If I ever build another PML kit, and it's quite likely, I would build it stock with the piston again.

The stock chute is a PML 30" with spill hole. Drifting isn't too bad and the descent rate is fairly quick. According to PML's parachute FAQ, the Phobos it towards the heavy end of recommended weights for their 30" chute, which explains my quick descents. And it's a good thing that I launch at sites where it's all but guaranteed a soft, grassy landing! However, if I were launching at a site with hard surfaces, I wouldn't think twice to swap it out for a larger chute. The kit is durable and would probably sustain a reasonable impact with very little if any damage though thanks to the high quality parts in the kit.

Flight Rating: 5 out of 5

Summary:

With the 38mm MMT, I have a wide range of 29mm & 38mm motors to chose from since the Phobos will fly on as little as a G, really performs with an H, and probably can wish it good-bye on an I. (According to RockSim, a Phobos with phenolic tubing & fiberglassed could break Mach on as little as a I435T.) Despite that flexibility of motor choices and the nearly perfect results I've had, in hindsight I don't know if I would recommend it as a good kit to cert Level 1 on. I would instead recommend a kit with a larger diameter so that the cert flight would be "slow and low". After you get that certification though, you sure could let 'er rip with the Phobos!

Overall Rating: 5 out of 5

Brief:
The Public Missiles, Ltd. Phobos is one of the great, easy to build mid and high power rockets out there you can buy. This rocket can be launched on any where from a F40 all the way up to a J570 if you get it with the 38mm motor mount. This is probably the best rocket to use for your Level 1 cert attempt, which I used it for. The only down side to this kit is you have to clean out the main airframe after every two flights due to the ejection charge.

Construction:
The Phobos kit contains all the parts necessary to build a flying mid/high power rocket:

• 1 pre-slotted main airframe
• 1 payload airframe
• 1 airframe coupler tube
• 1 coupler bulkplate
• 1 coupler hardware set, consisting of:

• 1 Eyebolt
• 1 Washer
• 2 Nuts

• 1 nose cone
• 3 G10 fins
• 1 piston ejection kit, consisting of:

• 1 piston tube
• 1 slotted bulkplate
• 1 piston strap
• 1 D-ring

• 1 parachute
• 1 motor mount tube
• 1 airframe to MMT centering ring
• 1 notched airframe to MMT centering ring
• 1 shock cord
• 2 launch lugs
• 1 decal sheet
• 1 instruction sheet

The construction of this rocket went together like any other high power rocket. The only problem I ran into was trying to get the strap for the piston ejection system through the notched centering ring.

Finishing:
The finish was super easy. Just sand it and paint it.

Construction Rating: 5 out of 5

Flight:
First flight was on a F40-4W. It was a perfect flight to about 300 feet except the motor casing kicked. (I did find the motor.)

Second flight was successful on a H165R-M for my NAR Level 1 certification.

Third flight was with a G64-7W. Yet another perfect flight and perfect recovery except it hit a person's truck and broke a fin off.

The fourth flight was a H180W-M. WOW! Out of sight! I almost lost it but I was able to regain sight of it as it came back down on with a tangled parachute. It landed hard but with no damage.

Recovery:
The recoveries are good but a little too fast for my liking. The only thing I would change about the recovery is up grade to a 48 inch parachute instead of a 36 inch parachute.

Flight Rating: 4 ½ out of 5

Summary:
The main PROs of this kit are:

• Easy to build
• Easy to finish
• Great for flying on G and H motors

The cons are:

• Hard to put the piston strap through the notched centering ring
• Falls to fast with a 36 inch parachute

Overall Rating: 4 ½ out of 5