(Contributed - by Michael Veno)
Picture courtesy of Public Missiles
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.
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 nosecone. The kit comes with an 8" motor tube
and two centering rings. It uses PMLs 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 pistons 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
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
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
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.
The Quantum tubes are very easy to paint since they are so smooth (no spiral
out of 5
PML recommends motor ranging from hotter F's to J350s.
My first flight was a TRA level 1 certification flight using a 38 MM
H123W-10 at San Diegos Tripoli Ocotillo Test Range (500 ,
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.
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.
out of 5
This is one tough rocket that can fly on a wide range of motors from F's to
700' to J350's to 7000'.
out of 5
(Contributed - by Lance Alligood - 07/01/04)
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.
I bought the kit direct from PML with the Quantum tubing (QT) and 38mm motor
mount. My goal in picking the Phobos was that it was going to be easy to build,
a stable design, and that I could fly it on a G before attempting my Level 1
certification with it.
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:
- You must sand the QT near the fin slots so that the epoxy has something to
- Same goes for where the launch lugs are attached.
- 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.
- 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:
- 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.
- Added rail buttons. I did not however drill them into the QT. Instead I
built standoffs with popcicle sticks and mounted the there (see
railbutton.com for more information on doing this).
- 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...
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.
out of 5
I did 2 test flights on G motors. First was a single use G40-7W. I built up
a good tape , 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
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 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.
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.
out of 5
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!
out of 5
(Contributed - by Aaron Stanley - 04/20/05)
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.
The Phobos kit contains all the parts necessary to build a flying mid/high
- 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.
The finish was super easy. Just sand it and paint it.
out of 5
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.
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.
½ out of 5
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
½ out of 5