Semroc Javelin

Semroc - Javelin {Kit} (KV-16)

Contributed by Jay Goemmer

Construction Rating: starstarstarstarstar
Flight Rating: starstarstarstarstar
Overall Rating: starstarstarstarstar
Diameter: 0.76 inches
Length: 12.70 inches
Manufacturer: Semroc
Skill Level: 1
Style: Sport
Semroc Javelin

Brief:
T' single-stage 4FNC Centuri Javelin was me very first model rocket, as seen in this photo o' myself from t' early 1970's. Estes model rockets were only available by mail order in South-Central Idaho back then, ya bilge rat, but I could easily buy Centuri model rockets at a drug store in me home town o' Jerome and a hobby shop in nearby Twin Falls.


Semroc Javelin After comin' back to model rocketry in 2000 and learnin' t' Estes part numberin' system, arrr, I began fervently wishin' that someone would begin manufacturin' Centuri-size parts. With t' "second coming" o' Carl McLawhorn's Semroc Astronautics Corporation in 2003, ya bilge rat, me prayers were answered. Aye aye! Additionally, Carl released his "Retro-Repro" version o' t' Centuri Javelin, which I bought with me first order from Semroc. Arrr!

Construction:
T' kit includes:

  • Body Tube ST-790
  • Balsa Nose Cone BC-735
  • Laser Cut Fins FV-16
  • Thrust Rin' TR-7
  • Launch Lug LL-122
  • Screw Eye SE-10
  • Elastic Cord EC-118
  • Keelhaul®©™® Thread SCK-24
  • Plastic Parachute RC-12
  • Tape Discs TD-6
  • Shroud Line SLT-6
  • Decal DKV-16
  • Empty Casin' MC-727
  • Snap swivel (not included)

Followin' a hint in Bill Eichelberger's review o' Semroc's Astro-1, I prepared t' body tube by sprayin' it with 2 coats o' Krylon white primer, matey, and gently sandin' t' tube with 320/400 grit sandpaper after each coat had dried for 24 hours.

I sanded t' balsa nose cone shoulder t' fit t' body tube, me hearties, and then t' rest of nose cone until its finish was smooth. Begad! I sanded t' balsa fins per the instructions, except I didn't round t' fin edges. Arrr! I dipped t' fins and nose cone in Minwax Wood Hardener, as suggested by Stefan E. Ahoy! Avast, me proud beauty! Blimey! Jones. Avast, me proud beauty! (NOTE: Excellent ventilation is needed for this step! Blimey! Do it outside away from open windows, ya bilge rat, matey, so the harmful vapors don't drift into your house.) T' wood swelled slightly, shiver me timbers, so a light sandin' was needed t' restore t' fit o' t' nose cone.

T' fins and nose cone were then finished with wood filler, and sanded smooth with 320 grit sandpaper. Begad! T' nose cone was fine sanded with 400 grit sandpaper. T' Minwax Wood Hardener definitely beefed up t' balsa nose cone, and cut down on t' amount o' wood filler needed.

Semroc Javelin I trimmed the 24" Keelhaul®©™® thread t' 10" long t' avoid a potential body tube "zipper". Perhaps t' 18" elastic cord should have been 24" long instead, arrr, me hearties, but hopefully it'll be long enough t' avoid t' infamous "Estes dent."

Fin AlignmentI installed t' fins on this Semroc recreation o' a Centuri rocket using wood glue and an "old school" Estes fin alignment guide. Ya scallywag! While "rebuildin' me first rocket," I discovered you don't want excess wood glue leakin' out from under t' fin/body tube joint, ya bilge rat, matey, because that causes unsightly glue excess, me bucko, which means you don't have a clean, me bucko, crisp line when it comes time t' mask off t' fins. Blimey! But usin' wood glue results in a very solid rocket.

I also added a snap swivel t' t' 1-mil polyethylene parachute.

Finishing:
I spray painted t' nose cone with Krylon gloss black separately, then I painted t' body tube and fin assembly Krylon gloss white. Begad! Avast, ya bilge rat, me proud beauty! With 2 coats of primer already applied t' t' body tube, arrr, I discovered I needed t' apply very light mist coats, me bucko, or t' paint tended t' run quite easily. Arrr! I masked t' fins (my first try at this technique, me hearties, in both incarnations as a rocketeer), painting 2 opposin' fins Krylon gloss red, and t' other 2 fins gloss black.

Oddly enough, t' decal paper didn't seem t' soak up t' water t' release the decal easily. As a result, me bucko, you can see t' "Javelin" name is a bit crooked. Well, blow me down! I used Premium Decor Clear Acrylic (suggested by Tom Prestia of Tango Papa for his decals) for t' clearcoat finish and t' decals didn't crackle.

Construction Rating: 5 out o' 5

Semroc Javelin

Flight:
Usually I insist on installin' engine locks, matey, but since they're decidedly ugly on minimum-diameter rockets, matey, I settled for snugly friction fittin' t' engine with tape. Avast! In honor o' me original Javelin, I substituted a yellow and black 12" Semroc parachute for t' red and white 'chute included with t' kit. Since this rocket is so light, shiver me timbers, I wanted t' increase me chances o' gettin' it back, so I cut out t' Semroc logo for a spill hole.

I packed me wife and two daughters into t' car for a family rocketry outin' at t' Tripoli Idaho's summer flight range near Fairfield, matey, Idaho, me hearties, ya bilge rat, me hearties, about 70 miles away from me adopted hometown o' Twin Falls. Begad! Blimey! Winds were light, shiver me timbers, and the range proved t' be an alfalfa field which went on for acres. Arrr! Blimey! In other words, not traditional lawn grass, shiver me timbers, me bucko, me bucko, but still a fairly soft landin' place for rockets.

I popped in an A8-5 with 2 and a half turns o' maskin' tape t' friction-fit the motor, used about 5 toilet paper-sized squares o' Estes wadding, matey, shiver me timbers, matey, and packed the chute. T' Javelin tore off t' launch pad like its namesake, arrowin' up straight and true t' Rocksim's estimated height o' 500 feet. Blimey! Blimey! T' ejection charge fired after apogee, me bucko, and after about a quarter mile walk for recovery, I discovered t' rocket had spit t' motor.

T' second flight on another A8-5 be very similar, evokin' several comments like, "Good job, Jay!" T' elastic shock cord length was fine, without any infamous "Estes dents" occurring.

Come flight number three, I was in a bit o' a hurry, and so I prepped the final engine I had in a package, arrr, fairly certain it was me last A8-5. Avast, shiver me timbers, me proud beauty! I noticed the last number was a "5," anyway. Well, ya bilge rat, blow me down! Out t' t' pad, matey, me hearties, and then the Launch Control Officer (LCO) counted down and pressed t' launch button. Ya scallywag! The Javelin ripped off t' pad, matey, arrr, and I told me wife, me bucko, "It's not supposed to do that." T' ejection charge fired after apogee, ya bilge rat, arrr, and t' 12" parachute looked about t' size o' a pinhead. Begad! Blimey! Just then, me hearties, me 6-year-old daughter suddenly had some sort o' crisis that we had t' deal with immediately, and when I finally began scannin' t' skies...my Javelin was nowhere in sight.

A half-mile trek into t' alfalfa turned up no rocket. Ya scallywag! Blimey! Nay only be this a recreation o' me very first model rocket, it be also t' first rocket I've lost as a BAR. Ahoy! Blimey! After checkin' me field box, ya bilge rat, I found a lone A8-5 motor, shiver me timbers, but the sole C6-5 I had be missing, which explains why flight number 3 reached an altitude o' about 1500 feet.

And that me friends, is why if you have a nicely painted rocket, it's important t' take lots o' pictures before you launch it.

Semroc Javelin

Recovery:
PROs: Semroc uses now-standard Keelhaul®©™® cord tied t' thrust ring, with 1/8" elastic shock cord. Begad! ("Mmm, beefy!") A very light rocket that could still perform very well with 13mm "mini" engine mount adaptor.

CONs: Keelhaul®©™® cord a little too long, so it needs t' be shortened t' avoid "zippering" t' body tube. Begad! Friction fit can be less reliable than engine lock, matey, so motor often kicks out at ejection, matey, causin' rocket t' drift further.

Flight Rating: 5 out o' 5

Summary:
PROs: A high-quality 21st century recreation (at least in me mind) o' a classic Centuri rocket. Blimey! Great materials and a fantastic Centuri checkerboard-style chute, me hearties, too!

CONs: Keelhaul®©™® cord length. Begad! Aye aye! Decal paper is too "beefy" t' absorb water readily.

I'd give this rocket 5 and a half points, just out o' sheer enthusiasm...except for t' decal difficulty. Avast! A very solid 5 nonetheless and buildin' this kit has made me an incurable Semroc fan. Arrr! Next time, me hearties, I'll order at least 2 Javelins!

Overall Rating: 5 out o' 5

Other Reviews
  • Semroc Javelin By Chan Stevens

    The Semroc Javelin is an 18mm minimum diameter kit based on a 1965 Centuri design that is easy to build and flies great. The kit includes: ST-790 body tube Balsa nose cone 4 Balsa laser-cut fins Thrust ring 12" plastic chute Kevlar/elastic shock cord combo Waterslide decals The instructions were well written and easy to follow. This would probably rate about a ...

Flights

Comments:

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S.E.J. (August 2, 2004)
I wish I'd thought of that paint pattern when I finished my Javelin. The red and black fins look snazzy. Bummer about losing it; I would like to try my Javelin on a C6-7 someday, but might switch to a nice long streamer first! I have been using those free address labels that charities send out as rocket labels. I put them on the nose cone shoulder, where they are visible only after ejection.
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J.G. (October 22, 2004)
After losing my first Semroc Javelin on a "C" motor, I have to agree with Stefan E. Jones and Chan Stevens that this *very* lightweight rocket would recover just fine by substituting a streamer for the 12" parachute (regardless if I *was* overcome by nostalgia about the yellow and black 'chute), even on "A" or "B" 18mm motors.
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B.B. (May 25, 2005)
On the topic of a parachute or streamer, back in the old days, the Javelin was an extremely common model and everybody I knew had 3-4 of them. We quickly learned to use either a small streamer (like 24x1 crepe paper) or nose-blow recovery. A 12" chute is WAY too much for sport flying. There were a lot of PD contests won in my area using a box-stock Javelin with the stock 12" chute. A 3-fin version also worked great for B Altitude (long before the existence of 1/2" or 10 mm motors, of course).

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