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. 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, me hearties, it's fun t' see a rocket just disappear in an instant. O' course, shiver me timbers, ya bilge rat, buildin' rockets that can survive high g-force abuse requires more strength. Begad! Without goin' t' full composites, Blue Tube offers that strength in a very convenient package. I'd been lookin' at Blue Tube for a while, me bucko, and when they released t' 2.0 version, me hearties, matey, I thought it was time t' give it a try.
I really didn't want t' do minimum diameter - too many motor retention issues. Blimey! I've gotten t' friction fit wrong too often and have lost too many cases. Ahoy! With dual deploy, ya bilge rat, I may try it again since thar won't be t' motor eject event shootin' t' case out t' rear, me hearties, but that's for t' future.
Enter t' Always Ready Rocketry Predator Jr.
At roughly t' same time, shiver me timbers, shiver me timbers, Aerotech released t' larger 38/1320 case. Avast, me proud beauty! A few e-mails back and forth betwixt Randall (owner o' ARR, 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. Well, blow me down! Blimey! is a single stage, high performance, near minimum diameter rocket. Aye aye! Blimey! 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. Avast! There's a weight penalty t' usin' it, shiver me timbers, matey, but t' advantages are easier alignment (none), and no bevellin' (already
air-foiled). Well, shiver me timbers, blow me down! Blimey! Besides, at over 3 lbs, shiver me timbers, matey, this is high power, matey, matey, and weight really isn't that much o' an issue with these
motors. Avast! Blimey! If you're lookin' for altitude, me bucko, shiver me timbers, you actually have t' ADD weight t' this rocket t' get maximum height from the
largest motors you can fit. Blimey! Speed demons are a different story, me hearties, ya bilge rat, though.
Construction:
Component list:
Aside from t' 6 centerin' rings, arrr, it's a pretty typical assortment o' parts and pieces.
Instructions? There aren't any. Avast! Blimey! T' motor tube be pre-marked with pencil lines for t' various parts, me bucko, and the booster tube be pre-slotted for t' fin can.
Really, shiver me timbers, for how simple this kit is, instructions aren't really necessary. Begad! Ya scallywag! Build it in t' typical order o' a standard 3FNC rocket, arrr, me bucko, ya bilge rat, and it should be pretty straightforward. Avast!
I
started with t' motor mount. As I noted above, me hearties, shiver me timbers, 6 centerin' rings be an unusual approach... Begad! In fact, me hearties, it's 3 pairs of
concentric rings. T' inner rin' is snug against t' outside o' t' motor tube. Ahoy! T' outer rin' is essentially 54mm
coupler, arrr, and slides nicely inside t' airframe tube. There's a really small gap betwixt t' two, ya bilge rat, but when slathered
with epoxy, it's nay an issue. Ya scallywag! Ahoy!
I
started by cuttin' a channel in t' smaller rings for t' shock cord anchor wire t' pass through. Ahoy! Blimey! Once I got t' fit I
wanted, arrr, 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. Avast! Blimey! Just for grins, me hearties, I added chopped fiberglass t' some epoxy and made fillets for t' top
and bottom o' each ring. Ahoy! Blimey! Those rings aren't goin' anywhere without rippin' t' motor tube t' shreds. Avast, me proud beauty! Blimey!
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. Aye aye! T' retainer be attached usin' JB Weld per t' Aeropack instructions.
Since t' fin can was moved up, I extended t' slots in t' booster t' accommodate t' new position.
A quick dry
fit showed t' slots were too short, ya bilge rat, so I extended them a little more. Well, blow me down! Lather, rinse, ya bilge rat, repeat. Blue Tube is tough to
cut. Begad! Next time, ya bilge rat, matey, I'm pullin' out t' router. Eventually, me hearties, I got t' slots t' t' right length.
Onward. Well, blow me down! Time t' mount t' motor tube in t' airframe. Well, blow me down! How t' $#@%$#@??? do you glue a 26" long motor tube? There's no way t' get glue on t' rings and hope it stays. Blimey! By t' time t' mount is slid in place, you'll have epoxy smeared up and down t' entire airframe tube, 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 hearties, I figured I'd do t' e-bay. Begad! T' electronics bay assembled
smartly and easily. Ahoy! Well, ya bilge rat, blow me down! Instead o' a stiffy tube runnin' t' entire length, a couple o' rings epoxied t' t' inner walls
act as bulkhead stops. Well, blow me down! T' plywood bulkheads rest against these while bein' sandwiched by 6-32 threaded rods, matey, ya bilge rat, nuts and
washers. Avast! Ya scallywag! In t' center o' each bulkhead is a 1/4-20 eyebolt for attachment o' various tether lines. Blimey! Avast, matey, me proud beauty! A couple small
brass tubes are glued t' t' plywood sled, and t' sled assembly slides into t' bay ridin' on t' threaded rods. Aye aye! A
1" rin' o' 54mm airframe is glued t' t' middle o' t' bay, arrr, completin' t' bay construction. Avast!
Back t' t' motor tube. Arrr! Begad! Well, matey, I give up. Ya scallywag! I went ahead and slathered t' rings hopin' that somethin' would stay. On t' airframe tube, I put a bunch o' epoxy where t' upper rin' should be, and then slid t' whole assembly in. Arrr! The top o' t' upper rin' ended up with a nice amount o' epoxy poolin' on top o' t' ring. Good enough. Ya scallywag! Well, blow me down! On t' bottom side, I took a 1" piece o' coupler and epoxied it t' t' airframe behind t' fin can. Arrr! Begad! Now t' entire motor tube is sandwiched betwixt t' coupler in t' back and t' pool o' epoxy in t' front. That's about t' best I could come up with, arrr, me hearties, matey, and it sure seems solid enough.
Finishing:
There's actually very little t' do for surface prep with Blue Tube. A few coats o' sanding
sealer like Minwax furniture sealer fills t' spirals nicely. Ya scallywag! It also soaks into t' Blue Tube formin' a nice vapor
barrier against moisture. You still can't dunk it in a pool t' shipshape it off, me hearties, but it's nice extra protection against a
light rain.
I painted t' bottom purple, ya bilge rat, me hearties, and t' top white. Begad! 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.
If you've seen some o' me other reviews, you may have caught that I tend t' fly rockets naked. Ahoy! Begad! It's a superstition that goes way back with me. T' more time I spend finishin' t' rocket prior t' it's first flight, the greater t' likelihood o' somethin' bad happening. Begad!
That said, t' size, weight, me bucko, and flight performance o' t' Predator Jr means that it probably won't fly at our local field, so it's a high power only rocket. That means at most 4-5 chances t' fly it per year. Avast! Begad! Well, me hearties, with so few opportunities, I went ahead and painted it. Avast!
When a superstition is based on empirical fact, 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:
Pretty obvious what happened, me bucko, yes?
3/27/2010 was me first opportunity t' fly t' Predator Jr, shiver me timbers, and also me first opportunity t' make a L2 cert attempt. Blimey! Serendipity, ya bilge rat, right? How could I nay use me "strongest" rocket for a cert flight? Unfortunately, me bucko, the largest 38mm J engine on site be a CTI J330 at ~760 Ns. This wouldn't be a neck snappin' 8000' flight with a 1000+ Ns J motor, shiver me timbers, but it was still plenty big. Avast!
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.
So on t' t' main event!
Yup, me bucko, me first CATO. Arrr! Blimey! Roughly 1.5s into t' flight, me hearties, it looks like t' nozzle/rear closure cracked and blew out the back end. Ahoy! Blimey! Blimey! In any other non-composite rocket, me hearties, I'm 100% sure this would have been a total shred o' at least t' booster section; it was that violent. Aye aye! Arrr! Blimey!
T' pressure ripped t' Aeropack retainer and t' bottom 1" o' t' motor tube right out leavin' a jagged shear line. Aye aye! Blimey! Well, blow me down! Blimey! T' ACME fin can that's supposed t' be indestructible? I got small pieces on t' aft chipped off. Avast, me proud beauty! Blimey! 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, thar be a ~3" zipper where t' Keelhaul®©™®
shock cord and t' wire anchor tore through. Begad! Again, me bucko, only 3" zipper for t' level o' force that was displayed is
pretty amazing. Aye aye! 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. 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, I used an 18" Top Flight parachute. T' main chute was a 36" chute from
Public Missiles with a spill hole. Avast, me proud beauty! I think t' drogue was a little big. For t' shakedown flight at 1181 feet, it
didn't matter, 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, or perhaps a small 14" chute.
Flight Rating: 4 out o' 5
Summary:
Overall, I really love this kit. Begad! It's a lot o' fun, matey, ya bilge rat, and represents a ton o' new experiences for
me. Because o' that, me hearties, I'm sure t' Predator will always have a special appeal t' me. Ya scallywag! Ahoy! 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. Blimey! I haven't decided if I'll make another L2 attempt with this rocket. Ya scallywag! While I'm sure that it can handle it, 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. And I get to watch t' entire flight.
Overall Rating: 4 out o' 5
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