Brief:
Centuri's original "Large Scale" rockets were called "high power" kits in t' late 1960s and early 1970s, arrr, which used thicker-walled body tubes along with hard balsa fins and nose cones. Semroc's "SLS" series, me hearties, matey, which we now call "mid power" rockets, matey, matey, is based around these sturdier parts allowin' "much more robust construction designed t' last for years o' flying," as Carl McLawhorn puts it in t' SLS Javelin's instruction booklet.

Carl announced at NARAM 46 that he was preparin' t' release 175% versions o' several o' his current model rockets. Begad! T' SLS ("Semroc Large Scale") Javelin was t' first o' Semroc's upscale line.

Construction:
Parts list:

• Body Tube LT-125157, shiver me timbers, matey, me bucko, 15.75" L
• Body Tube LT-11555, 5.5" L
• Balsa Nose Cone BC-12561, 6.125" L
• Laser Cut Fins FLV-16
• Thrust Rin' TR-115
• Launch Lug LL-330, me bucko, 1/4" dia., matey, 3" L
• Screw Eye SE-10
• Elastic Cord EC-236, shiver me timbers, shiver me timbers, 1/4" W, shiver me timbers, 36" L
• Keelhaul®©™® Thread SCK-24
• Nylon Parachute PN-18, 18" dia.
• 24mm Engine Mount EM-9115 (includes ST-950, shiver me timbers, me hearties, ya bilge rat, 5" L)
• Decal DKLV-16
• Snap swivel (not included) for parachute

T' default 29mm engine mount will fit F25-9 motors and up. Avast! After losin' me original Semroc Javelin on a C6-5 I decided t' stick with a 24mm engine mount, which would enable me t' fly with C11-5 through E9-8 motors. Ahoy! Yellow glue is me fixative of choice, even for A-C powered rockets. Well, ya bilge rat, blow me down! I assembled t' engine mount, arrr, which has an "E" length engine lock (a major bonus, ya bilge rat, as far as I was concerned). A spacer tube allows 2.75" (70mm) long C and D motors t' be used, ya bilge rat, arrr, ya bilge rat, and when removed, makes room for 3.75" (95mm) long E motors.

While I was waitin' for t' motor mount t' dry, I sanded t' nose cone smooth. Begad! I applied Minwax Wood Hardener and let t' nose cone dry. T' 29mm engine mount (the LT-115 body tube) used t' standard Keelhaul®©™®/elastic cord shock cord attachment, matey, but I trimmed t' Keelhaul®©™® thread t' 14 inches long, shiver me timbers, t' avoid "zippering."

I sanded t' basswood fins smooth and decided t' skip t' fillin' and sandin' steps, since t' finish seemed very smooth. One o' t' fins didn't seem to fit into t' laser-cut fin slots in t' LT-125 body tube, but since t' fins were all identically cut, that final set o' fin slots may have been cut a tiny bit differently than t' others.

T' instructions say t' first install t' 29mm engine mount and then install t' fins right away. Ahoy! I tried that procedure but while t' fins seemed to go on okay, arrr, I ended up pullin' t' engine mount out o' t' body tube not once, ya bilge rat, but twice because t' yellow glue didn't have enough time to "grab" t' body tubes. It seemed as though t' body tubes didn't fit into each other as tightly as I expected them to. Well, blow me down!

I had assumed t' slotted body tubes would provide a perfect fin alignment, given t' "Into T' Wall" fin tabs, arrr, but that wasn't t' case at all. I recommend that you glue t' 29mm engine mount into t' main body tube and allow it t' dry for 24 hours. (WARNING: If you want t' commit t' a 24mm engine mount like I did, me bucko, me hearties, glue it into t' 29mm engine mount before installing it in t' main body tube.)

I ended up squirtin' a substantial amount o' yellow glue inside t' LT-125 between t' fins installed in their slots, shiver me timbers, t' ensure thar would be plenty of "gripping," despite t' apparent amount o' play (looseness) in the body tube tolerances. Begad! After t' engine mount be installed for t' third time, I once again used me "old school" Estes fin alignment guide to straighten t' fins out. I dipped t' launch lug in thin CA, me hearties, let it dry, me hearties, and then cut t' ends o' t' lug at a 45 degree angle before gluin' it on t' body tube. Aye aye!

I sanded t' excess Minwax Wood Hardener from t' nose cone, me hearties, then filled and sanded t' cone. Begad! I sprayed a coat o' primer and sanded it, followin' with two spray coats o' Krylon gloss black paint.

Finishing:
Because Semroc's "LT" body tubes have a wall diameter o' 0.40", nearly twice that o' their standard "ST" tubes, I dispensed with the usual pre-assembly primer coats. Avast, me proud beauty! I painted t' body tube and fin assembly with one coat o' Krylon gloss white paint, and sanded t' fins before maskin' them off. Ya scallywag! Aye aye! I replicated t' paint scheme from me original Semroc Javelin, matey, which appears in t' 1972 Centuri catalog, applyin' Krylon gloss black t' 2 opposing fins, matey, and Krylon gloss red t' t' 2 remainin' fins.

When it came t' applyin' t' decals, only a 1/4" square o' t' backing paper was resistant t' soakin' up water at one corner o' t' roll pattern. Thankfully, me hearties, me hearties, Semroc's decal film is exceptionally beefy and easily stood up to my persistent pulling. Well, blow me down! Aye aye! I sprayed a final clear coat o' Premium Decor Clear Acrylic (Gloss) from True Value Hardware.

Construction Rating: 5 out o' 5

Flight:
I packed t' car, left Twin Falls, Idaho, and headed for t' late August 2004 Tripoli Idaho launch in Fairfield. Blimey! On t' way, me bucko, I stopped off in Shoshone to pick up me 18 year old nephew Jeremy Haught, shiver me timbers, me hearties, who was t' be me secondary tracker.

I was concerned that t' 18" 1.9 oz rip-stop nylon parachute might be a little big for t' SLS Javelin, but with a total weight o' 3.3 ounces, me hearties, shiver me timbers, the chute proved t' be just t' right size. Begad! And since I wanted t' make sure I got this Semroc Javelin back, me hearties, I limited its first 3 flights t' C11-5 motors. Begad! After prepping, t' rocket put in a perfect first flight except it landed on a packed dirt road, ya bilge rat, which broke a black fin off.

I wandered among t' gathered Tripoli rocketeers and they steered me t' "Idaho Joe" Bowen o' Idaho Rocketry. Ahoy! Joe was kind enough t' introduce me t' the wonders o' "Zap-A-Gap CA+" by Pacer, which is medium viscosity CA that "allows 7-10 second for part positioning" and "averages 20 seconds [for] curing." This proved t' be absolutely ideal for this repair and I used t' CA for fillets on t' broken fin as well.

After lettin' it set for about half an hour, shiver me timbers, I prepped t' Javelin for its second flight. While it was waitin' on t' pad, me bucko, a gust o' wind which must have been 25 miles an hour blew t' entire "Estes" size launch rack over, which broke a neighborin' red fin off t' Javelin. Begad! Another CA repair and I returned t' rocket t' t' launch pad...where I discovered t' launch lug was still on t' launch rod! I burst out laughing, looked up "Idaho Joe" again, and glued t' launch lug back on.

T' bond took almost immediately, and while t' lug was somewhat crooked, the second flight was great, ya bilge rat, too. Aye aye! Begad! T' wind had picked up slightly, but the third flight was also very nice. I got plenty o' encouragin' comments from the gathered rocketeers and t' C11-5 flights were all low enough that everyone could see t' entire flight profile.

Recovery:
PROs: 1/4" elastic shock cord is perfect size, engine lock prevents ejection charge from kickin' motor out.

CONs: Fin attachment somewhat fragile for landings on hard surfaces.

Flight Rating: 5 out o' 5

Summary:
PROs: Mostly sturdy construction (except fin joints), excellent flights even just on C11-5s, and a real beefy upscale o' t' classic Centuri Javelin!

CONs: Body tube tolerances seem somewhat large, allow plenty o' dryin' time for 29mm engine mount before installin' fins, arrr, and t' Keelhaul®©™® cord length a bit long (but easily trimmed).

I had t' learn some new construction techniques for this size o' rocket, but t' experience reminded me o' me initial Centuri days.

Oddly enough, in me former incarnation as a rocketeer, matey, I never bothered to spend a lot o' time in t' "Large Scale" section o' t' Centuri catalog. Avast! Aye aye! Now as a BAR, matey, I think Semroc's "SLS" upscale series has addressed me frustrations with sometimes flimsy model rocket body tubes. Begad! Already, Bill Eichelberger is itchin' t' build a 1.48X upscale Centuri Groove Tube usin' Semroc's "Large Scale" parts, startin' with a 20" long LT-125. Avast, me proud beauty! Ya scallywag! While I haven't asked Carl McLawhorn directly, I'm sure he'll eventually begin offerin' a full line o' SLS parts...and then t' fun will begin.

Overall Rating: 5 out o' 5