Public Missiles Cirrus

Public Missiles - Cirrus {Kit}

Contributed by David Fergus

Manufacturer: Public Missiles
Rating
(Contributed - by David W. Fergus)

Rocket PicBrief:
This is a rocket designed t' fly t' extreme altitude if desired. Aye aye! Blimey! It has a 1.6" diameter and is 44" tall with a payload bay and solid resin nose cone. Begad! Blimey! It can be flown with 38mm motors; or 29mm motors with an adapter. Everythin' that normally comes with a PML phenolic kit is provided includin' a piston ejection system, parachute, and fiberglass fins. Begad! A 29/38 adapter is not provided, nor are any motor retention or nose cone retention methods or parts provided. Begad! Begad! Blimey! Since this rocket can conceivably go very fast and high, shiver me timbers, one item not normally provided with PML kits but provided with this one is fiberglass cloth for stronger fin attachment. Begad! Blimey! T' finished weight o' t' rocket with a simple phenolic adapter and all retention hardware is 21oz. Avast! Begad! Blimey! without a motor. Ya scallywag! Aye aye! Blimey!

Prize Notification/Delivery:
This kit be provided as a prize from a periodic random drawin' sponsored by EMRR, matey, and donated by Rocket Silo. Blimey! Ahoy! Upon notification that I was t' winner, Rocket Silo very smartly responded, me hearties, ya bilge rat, and had PML drop ship t' kit directly to my home. Avast! I received it within a few days. Arrr! I thank them profusely for their rapid response and generosity. Aye aye! Begad! I would nay have chosen this kit myself because I be intimidated by t' high altitude design (the fields in Minnesota do not support real long walks). Ya scallywag! Avast! However, ya bilge rat, it stretched me t' learn how t' fiberglass for t' first time, gave me me first high power payload rocket (now I will have to buy an altimeter), me bucko, and by necessity led me t' find a source o' high quality motor retention for all me rockets. Ahoy! Begad!

Construction:
Construction o' this rocket is very straightforward as is typical with PML kits. Begad! T' method for fiberglassin' t' fin area be described adequately, and I experienced no problems. Avast, shiver me timbers, me proud beauty! However, me bucko, arrr, I had t' wait t' do this step till after I had designed, shiver me timbers, purchased, me bucko, ya bilge rat, and installed motor retention hardware. Begad!

TailSince this is a minimum diameter rocket, t' usual engine retention methods o' blind nuts and clips can nay be installed. Ahoy! Avast! I decided t' try two different methods, with this rocket bein' a test bed for both. Avast, me proud beauty! One method would be t' epoxy a piece o' small threaded rod t' t' outside of t' body tube, ya bilge rat, ya bilge rat, ya bilge rat, and use a nut and washer t' retain either a 29/38mm adapter or a 38mm motor case. Well, blow me down! T' fiberglass would then be applied over t' top o' this threaded rod for extra strength. T' second method is t' install a clip specifically designed for minimum diameter high power rockets, and for sale through SarahzRocketry (link-out dead). Arrr! Blimey! I highly recommend this hardware, me bucko, as it is designed t' exactly fit this application. Well, blow me down! T' only problem I encountered was that t' 29/38mm adapter I purchased had a longer than standard thrust ring. Avast, me proud beauty! Arrr! So the brass clip that retained a 38mm motor case would nay fit over t' thrust rin' o' t' adapter. Begad! Arrr! I wrote SarahzRocketry, me bucko, explained t' problem, and they were gracious enough t' make a second brass clip that exactly fit over t' end of me adapter. Blimey! Arrr! T' MD-1 hardware normally includes a brass retainer clip sized for standard RMS motors, a stainless steel machine screw, arrr, a threaded mounting flange and installation instructions. Blimey! Avast, me proud beauty! T' web site also has detailed installation instructions with lots o' pictures. They probably had t' make toolin' capable o' makin' this second custom brass clip, so if others buy this kit and also buy t' adapter I did, it should be easy t' include both brass clips at t' same time if you ask. Arrr! T' adapter was purchased from Red Arrow Hobbies in Michigan over t' Internet. I purchased this particular adapter because it be $8.00 and included both a thrust rin' and motor retention.

Retention Retention

Nose ConeT' other problem I encountered be nose cone retention. Avast, me proud beauty! Blimey! After irreplaceably losin' t' original nose cone off my vintage Estes SAROS several years ago because it was nay firmly enough attached to t' payload tube, I am particularly sensitive t' this issue. Begad! Normally, with a hollow plastic nose cone, this would nay be difficult. T' PML instructions say "Now install t' nose cone atop t' rocket and secure it in place usin' small screws or rivets.", arrr, me hearties, which would be easy t' do with a hollow nose cone. Ya scallywag! Avast! Blimey! However, shiver me timbers, this nose cone is solid resin, and you wouldn't want to trust screw holes tapped in t' relatively soft resin t' stand up t' repeated launches and recovery. So I found some small 4mm machine screws and compatible steel nuts at Home Depot. Holdin' t' nose cone firmly in t' payload tube, I drilled two 5/32" holes through t' phenolic body tube into t' nose cone shoulder about 1/2" deep. These two holes are about 5/8" back from the front o' t' tube. Usin' t' 5/32" holes as pilot holes, ya bilge rat, I then carefully drilled two 5/16" holes 1/4" deep into t' nose cone shoulder after I removed it from t' body tube. Caution must be exercised with this step because steel bits dig deep fast into resin. Avast, me proud beauty! I goofed and went too deep t' first time and had t' rotate 90 degrees and try again. Avast! Ahoy! Blimey! I CA'd and then epoxied t' nuts into those holes. Blimey! Blimey! I used t' machine screws t' simultaneously keep glue out o' t' threads o' t' nut and keep t' nuts lined up vertically, but also bein' careful t' nay permanently glue t' screws into t' nuts. This was a dicey operation as I kept turnin' t' screws in and out o' t' nuts until the glue had cured.

Launch LugOne other minor deviation from t' kit was to elevate t' brass launch lug off t' rocket body by use o' a wooden popsicle stick. Avast! Ahoy! I did this so that launch rod friction would nay mar t' finish or otherwise rub against t' body durin' takeoff. Begad! Begad! I used a little leftover fiberglass cloth t' cover t' front and back o' t' popsicle stick, arrr, and used plenty o' epoxy t' fillet t' sides o' t' assembly. Arrr! It took quite a bit of epoxy and putty, shiver me timbers, but it looks nice and streamlined, yet raised off t' body some. Aye aye!

Finishing:
Since this rocket apparently only comes with phenolic tube rather than t' new quantum tube, matey, finishin' involves quite a bit o' work with putty t' fill in the spiral grooves. Arrr! T' body tube is essentially 38mm engine mount tubing. Blimey! The transition t' t' fin area that had fiberglass also required quite a bit of sandin' and fillin' t' smooth it out as much as possible. T' 20 minute finishin' epoxy used on top o' t' fiberglass as recommended by the instructions is quite a bit easier t' sand than regular 30 minute epoxy. Aye aye! A coat of primer revealed spots requirin' more putty, ya bilge rat, and t' final paint coat was Krylon teal, which goes well with t' dark blue and red decal.

Construction Rating: 4 out o' 5

Flight:
T' first flight be with a 29mm F40-4W reload. T' rocket flew straight up to about 1000 feet, shiver me timbers, and deployed t' cute at apogee. Begad! T' second and third flights were also hot, arrr, straight and normal with an F and a G. Begad!

Recovery:
At t' time o' t' first flight, me hearties, I did nay have t' brass clip from SarahzRocketry and only had t' single threaded rod and nut t' retain the adapter/motor casing. Arrr! T' small threaded rod was nay hefty enough and bent out of t' way t' allow t' adapter and motor t' eject out t' back when the ejection charge fired. Avast, me proud beauty! Fortunately, thar was enough gas pressure buildup to also eject t' parachute. Begad! T' adapter and RMS casin' were found by a spectator, and returned promptly. T' lesson here is if you can bend a threaded rod with your fingers, it is nay strong enough t' retain a motor. Blimey! T' other lesson is to use t' hardware obtained from SarahzRocketry. Avast! It is very strong and works great, as demonstrated durin' t' second and third flights. Aye aye! T' parachute is a little small for a 21-oz. rocket, but I am sure that PML downsized a little out of concern about how high it would be comin' down from if used with an H or bigger engine. Well, me bucko, blow me down!

Flight Rating: 5 out o' 5

Summary:
PRO: Strong PML materials and design. T' solid resin nose cone provides plenty of CG shift forward for bigger motors. Avast! Aye aye! CON: No provision for motor and nose cone retention. Ahoy! 29/38 adapter nay included. Arrr! Avast, me proud beauty!

I understand PML's philosophy on nay providin' motor retention with their kits as many modelers have many different preferred methods and hardware. However, me bucko, this is a minimum diameter rocket and most modelers' preferred methods and hardware are nay appropriate on this rocket anyway. Blimey! Begad! Blimey! Since this is a rocket that will nay normally be flown with a 38mm motor unless someone regularly launches at large recovery areas, I feel that PML should also include an adapter with t' kit. I STRONGLY urge PML t' include a simple 29/38 adapter (like t' one I bought) and minimum diameter retention hardware for both a 38mm motor and a 29/38mm adapter. Blimey! Blimey! In fact, arrr, they should subcontract this to SarahzRocketry, shiver me timbers, where I obtained t' hardware used on this kit. Ahoy! Since this is the only rocket made by PML (that I know of) that has a solid nose cone on a payload section, me hearties, me bucko, I also urge PML t' include a method for nose cone retention, as normal nose cone retention methods are nay applicable either. Avast! Begad! Blimey! T' rocket itself is a great addition t' me fleet. Blimey! Aye aye! Blimey! It flies well, arrr, shiver me timbers, and t' payload bay is large enough for an RRC altimeter.

Overall Rating: 4 out o' 5

Other Reviews
  • Public Missiles Cirrus By Greg Briden

    ( Contributed - by Greg Briden - 11/01/02) Brief: Minimum diameter, high altitude rocket. Construction: Two main phenolic body tubes, piston ejection, solid resin nose cone. This was my first HP rocket, which I used for my L1 cert. I do not recommend this rocket for any first time HP builders, and it is a less favorable cert. Let me explain; For one, its hard to find motor ...

Flights

Comments:

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B.Q.B. (September 25, 2001)
Nice review. I certified Level 1 with a Cirrus Dart this last weekend at the ROC club launch at Lucerne Valley, California. I used an Aerotech H128 and the performance of this kit is really spectacular. I recommend it highly. As far as construction goes, I modified the kit to incorporate secure motor retention. I did this by first notching the aft, root edges of the G10 fins. After the fins were affixed to the airframe using think Cya, I epoxied drywall anchors in the space created between the airframe and fin at the aft, root edge. These drywall anchors are plastic with a metal screw and are roughly triangular in shape. Next, I epoxied some 1/4" basswood triangle stock to the base of the fins to provide some more structure for the fin attachment joint. Lastly, I glassed the fins from tip to tip over the basswood and drywall anchor. Because the drywall anchor in at the base of the fin and inline with the fin, there is no aerodynamic drag with this type of motor retention. Also, I have three metal screws holding the motor in place. After I retrieved my Cirrus Dart from its certification flight, it was obvious that the nose cone/payload assembly slammed back into the main airframe on ejection causing a large crack in the payload airframe. As a result, the nose cone was almost lost on descent. The crack was surprising in that I had glassed the entire airframe including the payload section with 6 Oz. cloth, so it must have taken a helluva knock. Next time, I will replace the stock black elastic shock cord with 10 to 15 feet of 9/16" tubular nylon. I'm fairly certain the relatively short elastic cord caused the midair collision. I was lucky I got all the parts back and the rocket was still flyable! As stated previously, this is a great kit to get started in HPR and incorporates many of the building materials and techniques needed to go on to larger rockets. A 38mm to 29mm motor adapter would be a welcome addition to this kit.
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A.D.W. of PML (October 4, 2001)
The reason we provide no motor retention for this kit and recommend friction fitting is that the Cirrus Dart is intended to be a super-high-performance 38mm altitude bird, and any positive motor retention method would add drag to the rocket, reducing altitude. We also mention in the instructions that some people may not wish to mount the launch lugs. Again, this is a drag-producer, and most people with this kit are going for ultimate altitude and use a tower launcher. So, no positive motor retention is by design, not an omission. Friction fitting with masking tape works great, and adds no drag. Regarding no 29/38mm motor adapter, that is available separately as it is for any of our kits that come with a 38mm MMT. To include a 29/38mm adapter with every Cirrus would add cost to the kit for the parts, and many users would not need/want the adapter. So, we keep the kit cost to the minimum and offer the adapter separately. (No offense intended to the reviewer, just wanted to point out why we do what we do with this kit).

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