Public Missiles Phobos

Public Missiles - Phobos

Contributed by Lance Alligood

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

Brief:

T' PML Phobos is an easy t' build single stage, ya bilge rat, ya bilge rat, single motor 3FNC MPR/HPR kit. Avast, me proud beauty! It could be used for Level 1 certifications but I don't know if I would recommend it for that. Blimey! Blimey! You have a choice o' either Quantum or phenolic tubin' and 29mm or 38mm motor mount.

Construction:

I bought t' kit direct from PML with t' Quantum tubin' (QT) and 38mm motor mount. Well, blow me down! My goal in pickin' t' Phobos was that it was goin' t' be easy t' build, a stable design, and that I could fly it on a G before attemptin' me Level 1 certification with it.

I used 12 minute epoxy for t' entire build. Avast, me proud beauty! Avast! T' build went without any major issues, however, I want t' point out 4 potential "gotchas" when buildin' a PML kit stock with t' QT:

  1. You must sand t' QT near t' fin slots so that t' epoxy has somethin' t' "bite" into.
  2. Same goes for where t' launch lugs are attached.
  3. When epoxyin' t' t' MMT tube, after epoxyin' on t' piston strap, make sure that t' strap is nay in t' way o' t' fin placement.
  4. Sand t' piston coupler so that you have a smooth (almost loose) travel in t' QT. Avast, me proud beauty! Arrr! Patience & "elbow grease" is needed here as it might take a while t' get t' proper fit.

I did nay make any serious modifications, me bucko, me bucko, but I did do t' followin' outside t' scope o' t' kit instructions:

  1. Foamed t' fin can with PML expandin' foam. There is maybe 1/4" gap betwixt t' QT & MMT tubes. Well, blow me down! Rather than apply epoxy fillets in such a small space, ya bilge rat, it be easier & faster t' dump t' foam in and sand t' shape.
  2. Added rail buttons. Aye aye! I did nay however drill them into t' QT. Ya scallywag! Instead I built standoffs with popcicle sticks and mounted t' rail button thar (see railbutton.com for more information on doin' this).
  3. T' aft centerin' rin' be too small t' add Kaplow clips or t' PML retainer. Begad! I purchased and installed an AeroPack retainer and 38-29 motor adapter. Avast! Arrr! (Overkill, me hearties, I know!) Special note about t' AeroPack retainer: I did a dry test fit. Avast, me proud beauty! Blimey! It be so snug that I was (and still am) unable t' get it back off! That's nay a bad thin' though...

Finishing:

Many people have touted t' ease o' finishin' t' PML QT and you can count me among t' satisfied customers. Aye aye! It is indeed easy t' work with. Avast, me proud beauty! Scuff t' entire rocket with 220 grit, arrr, prime with Krylon primer, sand with 320 or 400, spray with Krylon gloss colors. Where t' different colors meet on me paint scheme, arrr, I covered them with 1/4" wide chrome automotive pinstriping. Begad! Begad! T' chrome pinstripin' has great reflectivity (my main goal) but lacks t' stretchy characteristics o' typical pinstriping. Begad! I did nay have any notable problems with t' finishin' process.

Construction Rating: 5 out o' 5

Flight:

I did 2 test flights on G motors. Begad! Blimey! Aye aye! Blimey! First be a single use G40-7W. Ya scallywag! Blimey! I built up a good tape thrust ring, me bucko, ya bilge rat, loaded t' motor up in t' AeroPack 38-29 adapter, slid everythin' into t' motor mount,and screwed down t' retainer cap. I had a lot o' jitters for this bein' t' largest rocket I'd ever built and launched at t' time but it lifted off without a hitch. Estimated altitude o' 1100ft but t' delay was a good 3 seconds too long. Avast! Blimey! I had a rapidly sinkin' feelin' in me stomach as t' rocket plummetted from t' sky, shiver me timbers, however, it did (finally) eject at about 400 feet. No zipper or any other damage whatsoever. Blimey! Blimey! I couldn't believe it!

Second flight was a couple o' months later on an EconoJet G35-4W. Blimey! Altitude was slightly lower (~1000ft) but ejection be right at apogee. Begad! Perfect flight all t' way around.

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

Recovery:

Pistons are a technology that people either love or hate. I have had nothin' but success with me Phobos and particularly enjoy that I don't need t' use any wadding. Cleanin' out t' body tube at least every other flight and always makin' sure that t' piston fits loosely are t' key points t' remember. If I ever build another PML kit, and it's quite likely, I would build it stock with t' piston again.

T' stock chute is a PML 30" with spill hole. Ahoy! Blimey! Driftin' isn't too bad and t' descent rate is fairly quick. Blimey! Accordin' t' PML's parachute FAQ, me hearties, shiver me timbers, t' Phobos it towards t' heavy end o' recommended weights for their 30" chute, arrr, which explains me quick descents. And it's a good thin' that I launch at sites where it's all but guaranteed a soft, shiver me timbers, grassy landing! However, if I were launchin' at a site with hard surfaces, me hearties, I wouldn't think twice t' swap it out for a larger chute. Blimey! T' kit is durable and would probably sustain a reasonable impact with very little if any damage though thanks t' t' high quality parts in t' kit.

Flight Rating: 5 out o' 5

Summary:

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

Overall Rating: 5 out o' 5

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  • Public Missiles Phobos By Brian Kain

    ( Contributed - by Brian Kain - 10/15/00) Brief: I shortened the span of the fins to 2.25". Used 1/4" graphite tubing for launch lugs. Modifications: I took the three (3) fins and put them in my flat jaw vice, making sure to keep them all straight and lined up. Then with my dremel tool and a carbon cutting wheel, I cut all 3 fins at once. Then kept them in the vice ...

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    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 ...

Flights

Comments:

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K.B. (June 1, 2000)
This was my first high power rocket and I thought it was great. The parts fit together easily and the instructions were easy to follow. I have since flown it many times. The motors I have used are G40-4, G80-7, H70-10 (for level one cert.), several H180-10, and one super long burn H45 (38mm). This rocket is nearly indestructible because of the Quantum tubes and G-10 fins. It has landed on concrete with just minor scratches. In addition, it had a G80 CATO at lift off and I just had to replace the 38/29 motor adapter. There are a few things I wish I would have done during the building of this rocket: extended motor mount, Kevlar recovery straps, an additional bulkhead on the piston (so its not as likely to zipper), and the Aeropack motor retainer. With those few mods I believe that this rocket would last forever barring some error in deployment. The review was very accurate.
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R.D. (October 1, 2000)
Great first HPR. Easy to assemble. Be sure if you order the 38mm upgrade (comes 29mm standard) That the fins sent are for the 38mm and not the 29mm.
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L.A. (October 31, 2003)
PML Phobos is an EXCELLENT first HPR although I wouldn't necessarily recommend it for a Level 1 certification flight. Design is comfortably over-stable but the smallish diameter allows for a LOT of altitude when used with a Pro38 H153 (be prepared for long recovery walks with one too). The Quantum Tubing is a cinch to finish--no spirals--& is very tolerant of early/late ejections, meaning little chance of zippering. I would recommend a larger chute than the 30 incher that comes with the kit if you are launching anywhere but a soft, grassy location...it comes down quick. Also with the 38mm MMT, only choices for motor retention on the Phobos are masking tape (cheap & sometimes unreliable) or a Slimline/Aero Pack retainer (expensive & overkill) because of the narrow centering rings.

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