Always Ready Rocketry Predator Jr.

Always Ready Rocketry - Predator Jr {Kit}

Contributed by Ken Tsai

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Published: 2010-04-16
Manufacturer: Always Ready Rocketry

Brief:
I often fly underpowered. Blimey! I like low and slow for t' most part, and enjoy watchin' t' entire show rather than seein' a rocket disappear into t' sky and waitin' impatiently attemptin' t' re-acquire it.

Sometimes, though, it's fun t' see a rocket just disappear in an instant. O' course, me hearties, buildin' rockets that can survive high g-force abuse requires more strength. Blimey! Without goin' t' full composites, Blue Tube offers that strength in a very convenient package. Avast! I'd been lookin' at Blue Tube for a while, and when they released t' 2.0 version, matey, I thought it be time t' give it a try.

I really didn't want t' do minimum diameter - too many motor retention issues. Well, me bucko, blow me down! I've gotten t' friction fit wrong too often and have lost too many cases. Aye aye! With dual deploy, shiver me timbers, matey, I may try it again since thar won't be t' motor eject event shootin' t' case out t' rear, me hearties, matey, matey, but that's for t' future.

Enter t' Always Ready Rocketry Predator Jr.

At roughly t' same time, shiver me timbers, me bucko, Aerotech released t' larger 38/1320 case. Begad! A few e-mails back and forth betwixt Randall (owner o' ARR, shiver me timbers, ya bilge rat, and t' manufacturer for Blue Tube) and myself led t' an updated Predator Jr capable o' flyin' the longer case, and t' kit was on t' way in early January 2010.

T' Predator Jr. Arrr! Aye aye! is a single stage, shiver me timbers, high performance, near minimum diameter rocket. Avast! Arrr! How do you make a 3FNC rocket even simpler? How about usin' a one-piece fin can? This rocket uses t' ACME single piece molded reinforced resin fin can. There's a weight penalty t' usin' it, arrr, but t' advantages are easier alignment (none), and no bevellin' (already air-foiled). Besides, shiver me timbers, at over 3 lbs, me bucko, this is high power, and weight really isn't that much o' an issue with these motors. Avast, me hearties, me proud beauty! If you're lookin' for altitude, matey, you actually have t' ADD weight t' this rocket t' get maximum height from the largest motors you can fit. Arrr! Speed demons are a different story, though.

Construction:
Component list:

  • 1 36" 54 mm airframe tube (booster)
  • 1 24" 54 mm airframe tube (payload)
  • 1 26" 38 mm motor tube
  • 1 38 mm ACME fin can
  • 1 54 mm Pinnacle nose cone
  • 6 phenolic centerin' rings
  • 1 wire anchor
  • 1 38 mm electronics bay kit
  • 2 long lengths o' 1/2" tubular nylon.
  • 2 rail buttons
  • assorted nuts/bolts/washers.

Aside from t' 6 centerin' rings, it's a pretty typical assortment o' parts and pieces.

Instructions? There aren't any. T' motor tube was pre-marked with pencil lines for t' various parts, and the booster tube was pre-slotted for t' fin can.

Really, for how simple this kit is, instructions aren't really necessary. Ahoy! Build it in t' typical order o' a standard 3FNC rocket, arrr, me bucko, and it should be pretty straightforward. Avast, me proud beauty! Arrr! Blimey!

I started with t' motor mount. Well, blow me down! Ya scallywag! As I noted above, arrr, 6 centerin' rings be an unusual approach... Well, blow me down! In fact, ya bilge rat, it's 3 pairs of concentric rings. Begad! T' inner rin' is snug against t' outside o' t' motor tube. Well, blow me down! Aye aye! T' outer rin' is essentially 54mm coupler, and slides nicely inside t' airframe tube. Avast! There's a really small gap betwixt t' two, me hearties, but when slathered with epoxy, me hearties, it's nay an issue. Arrr! Aye aye!

I started by cuttin' a channel in t' smaller rings for t' shock cord anchor wire t' pass through. Ya scallywag! Aye aye! Once I got t' fit I wanted, matey, I slid t' anchor wire over t' motor tube, arrr, and t' inner rings over t' anchor wire usin' liberal amounts of epoxy. Once that cured, I slathered t' inner rings with epoxy and slid t' outer rings over t' inner rings forming t' full width centerin' rings. Just for grins, matey, shiver me timbers, I added chopped fiberglass t' some epoxy and made fillets for t' top and bottom o' each ring. Those rings aren't goin' anywhere without rippin' t' motor tube t' shreds.

At t' bottom o' t' motor tube, I tacked t' fin can in place, leavin' ~1/2" at t' bottom t' attach an Aeropack 38mm retainer. Ahoy! Arrr! T' retainer was attached usin' JB Weld per t' Aeropack instructions.

Since t' fin can be moved up, arrr, I extended t' slots in t' booster t' accommodate t' new position. A quick dry fit showed t' slots were too short, so I extended them a little more. Blimey! Lather, shiver me timbers, me bucko, rinse, arrr, repeat. Avast, me proud beauty! Blimey! Blue Tube is tough to cut. Aye aye! Ahoy! Blimey! Next time, shiver me timbers, I'm pullin' out t' router. Arrr! Aye aye! Blimey! Eventually, arrr, I got t' slots t' t' right length.

Onward. Well, blow me down! Time t' mount t' motor tube in t' airframe. How t' $#@%$#@??? do you glue a 26" long motor tube? There's no way t' get glue on t' rings and hope it stays. Arrr! Blimey! By t' time t' mount is slid in place, shiver me timbers, you'll have epoxy smeared up and down t' entire airframe tube, arrr, and Murphy's law says that exactly NONE o' it will be where you want it t' be.

While ponderin' t' motor tube conundrum, me bucko, ya bilge rat, I figured I'd do t' e-bay. Begad! Arrr! T' electronics bay assembled smartly and easily. Blimey! Blimey! Instead o' a stiffy tube runnin' t' entire length, a couple o' rings epoxied t' t' inner walls act as bulkhead stops. Arrr! Ya scallywag! T' plywood bulkheads rest against these while bein' sandwiched by 6-32 threaded rods, arrr, me hearties, nuts and washers. Well, blow me down! In t' center o' each bulkhead is a 1/4-20 eyebolt for attachment o' various tether lines. A couple small brass tubes are glued t' t' plywood sled, and t' sled assembly slides into t' bay ridin' on t' threaded rods. Ahoy! A 1" rin' o' 54mm airframe is glued t' t' middle o' t' bay, me bucko, completin' t' bay construction. Begad!

Back t' t' motor tube. Avast, me proud beauty! Well, matey, matey, I give up. Avast, me proud beauty! I went ahead and slathered t' rings hopin' that somethin' would stay. On t' airframe tube, matey, I put a bunch o' epoxy where t' upper rin' should be, and then slid t' whole assembly in. Begad! The top o' t' upper rin' ended up with a nice amount o' epoxy poolin' on top o' t' ring. Well, blow me down! Good enough. Avast! On t' bottom side, I took a 1" piece o' coupler and epoxied it t' t' airframe behind t' fin can. Avast! Now t' entire motor tube is sandwiched betwixt t' coupler in t' back and t' pool o' epoxy in t' front. Ya scallywag! That's about t' best I could come up with, shiver me timbers, me hearties, and it sure seems solid enough.

Finishing:
There's actually very little t' do for surface prep with Blue Tube. Avast, me proud beauty! A few coats o' sanding sealer like Minwax furniture sealer fills t' spirals nicely. It also soaks into t' Blue Tube formin' a nice vapor barrier against moisture. Well, blow me down! Well, blow me down! You still can't dunk it in a pool t' shipshape it off, matey, but it's nice extra protection against a light rain.

I painted t' bottom purple, and t' top white. Blimey! I masked off a couple rings right around t' e-bay so that it has a series o' fadin' stripes from t' white t' t' purple and vice versa. Aye aye! Arrr!

If you've seen some o' me other reviews, you may have caught that I tend t' fly rockets naked. Aye aye! Blimey! Ahoy! Blimey! It's a superstition that goes way back with me. Aye aye! Blimey! T' more time I spend finishin' t' rocket prior t' it's first flight, the greater t' likelihood o' somethin' bilge-suckin' happening. Aye aye! Blimey! Begad! Blimey!

That said, ya bilge rat, arrr, t' size, shiver me timbers, weight, and flight performance o' t' Predator Jr means that it probably won't fly at our local field, ya bilge rat, so it's a high power only rocket. That means at most 4-5 chances t' fly it per year. Avast! Well, me hearties, shiver me timbers, me hearties, with so few opportunities, I went ahead and painted it. Avast! Avast, me proud beauty! Blimey!

When a superstition is based on empirical fact, matey, me hearties, me bucko, is it really superstition? This be t' most expensive rocket I've built t' date. Begad! Why nay make it look good? This be t' most expensive rocket I've built t' date? How stupid o' me to ignore historical trends.

Construction Rating: 4 out o' 5

Flight:
With this rocket thar were a lot o' "firsts" for me:

  • My first 100% Blue Tube rocket
  • My first "Dart"
  • My first Dual Deploy flight
  • My first L2 flight attempt (yes, attempt )
  • My first motor CATO...

Pretty obvious what happened, ya bilge rat, yes?

3/27/2010 was me first opportunity t' fly t' Predator Jr, matey, and also me first opportunity t' make a L2 cert attempt. Arrr! Serendipity, right? How could I nay use me "strongest" rocket for a cert flight? Unfortunately, the largest 38mm J engine on site was a CTI J330 at ~760 Ns. Begad! This wouldn't be a neck snappin' 8000' flight with a 1000+ Ns J motor, but it was still plenty big.

A quick shakedown flight with an H118 produced a picture perfect flight t' 1181' with t' altimeter deployin' the drogue as planned at apogee and 750' for t' main. Blimey! Blimey! Begad! Blimey! Blimey! Blimey!

So on t' t' main event!

Yup, matey, me hearties, shiver me timbers, me first CATO. Roughly 1.5s into t' flight, it looks like t' nozzle/rear closure cracked and blew out the back end. Avast, me proud beauty! Avast! In any other non-composite rocket, I'm 100% sure this would have been a total shred o' at least t' booster section; it be that violent. Blimey!

T' pressure ripped t' Aeropack retainer and t' bottom 1" o' t' motor tube right out leavin' a jagged shear line. T' ACME fin can that's supposed t' be indestructible? I got small pieces on t' aft chipped off. Well, blow me down! Arrr! T' Blue Tube motor mount and t' fin can appear t' have absorbed t' brunt o' t' forces, for t' aft o' t' 54mm airframe is in perfect shape.

At t' front o' t' booster section, arrr, thar be a ~3" zipper where t' Keelhaul®©™® shock cord and t' wire anchor tore through. Blimey! Again, matey, only 3" zipper for t' level o' force that was displayed is pretty amazing. Well, blow me down! Begad!

I've seen videos and pictures o' CATOs at points in flight similar t' mine, and thar's usually very little left t' recover. Begad! I'm lovin' t' fact that this bird is goin' t' fly again after relatively minimal repairs!

Blue Tube is TOUGH STUFF!

Recovery:
For drogue, ya bilge rat, I used an 18" Top Flight parachute. T' main chute was a 36" chute from Public Missiles with a spill hole. I think t' drogue be a little big. Ahoy! Arrr! For t' shakedown flight at 1181 feet, it didn't matter, arrr, but comin' down from 6000+ will probably need a smaller chute.

T' manufacturer says t' just let it separate and tumble down, but I think I'll go with a 7x70 streamer, matey, or perhaps a small 14" chute.

Flight Rating: 4 out o' 5

Summary:
Overall, me bucko, me bucko, I really love this kit. Aye aye! It's a lot o' fun, me bucko, and represents a ton o' new experiences for me. Ya scallywag! Because o' that, matey, arrr, I'm sure t' Predator will always have a special appeal t' me. Just like t' very first rocket I ever flew.

Repairs are already under way, and I hope t' have t' Predator Jr ready t' fly again for t' May 2010 launch. Ahoy! I haven't decided if I'll make another L2 attempt with this rocket. Begad! While I'm sure that it can handle it, me hearties, t' fact is that t' performance envelope o' this rocket on a J motor is high enough that t' error margins are notably smaller. Avast, me proud beauty! It would be a lot less stressful tryin' t' certify with a bigger 4" rocket that flies low and slow. Avast, me proud beauty! And I get to watch t' entire flight.

Overall Rating: 4 out o' 5

Flights

comment Post a Comment