Scratch Thunder'ceptor Original Design / Scratch Built

Scratch - Thunder'ceptor {Scratch}

Contributed by March Briner

Manufacturer: Scratch
(by March Briner)

Scratch Thunder'CeptorBrief:
Long and skinny, single stage, arrr, ya bilge rat, high-power rocket [though it appears t' be multi-stage]. Arrr! Over 12 feet tall. Ya scallywag! Recovers under 44" chute.

Construction:
This project started in me mind's eye in 1991, me bucko, though construction never started until late 1992. Blimey! In all, me bucko, thar was 80 inches o' 3.1" LOC airframe, 60 inches o' 2.26" LOC airframe [not countin' a 30 inch long 54mm motor tube], 16 fins, shiver me timbers, me bucko, 2 transitions made from epoxy-glassed posterboard, arrr, me hearties, me hearties, and about 24 feet o' 3/4" braided shock cord.

T' first pieces o' t' rocket came from a Caliber ISP kit. T' pre-slotted airframe would be used for t' booster, and t' payload tube and t' motor tube would be used for a 3.1-2.26 transition about halfway up t' rocket. Avast! The centerin' rings were used t' anchor t' protrudin' 2.26 tube t' t' 3.1 tube. T' bulkhead assembly be put in t' other end o' t' 3.1 tube as per usual. Begad!

One inch was taken off t' root edge o' t' Caliber fins, and attached to the upper section. Well, blow me down! Blimey! T' other pieces, me bucko, ya bilge rat, more airframe, me hearties, shock cord, matey, plywood fin stock, me hearties, etc., me hearties, came together. Begad! Blimey!

At t' time, matey, I was in high school and was enrolled in a wood shop class, so I had easy access t' machinery t' cut and shape t' fins. Begad! Cuttin' and shaping the fins took, arrr, in all, almost 25 hours. Aye aye! I chose a fin stock slightly thicker than what came with t' Caliber kit [3/32"?]. Avast, me proud beauty!

T' first set o' fins [from t' bottom] were rhomboid, matey, me bucko, 3 inches wide and 4 inches long. Ahoy! For added effect, arrr, I glued an 8 inch length o' Estes BT-5 t' the tip edge. Well, blow me down! Begad! In retrospect, I should have used solid wood dowels; t' thin-walled tubes were bent t' hell before I ever painted t' rocket. Blimey! These fins were mounted through t' wall through t' existin' slots.

T' next set o' fins were 3 inch squares mounted through t' wall. Well, ya bilge rat, blow me down! A new set o' slots were made for them. Begad! Blimey! T' NEXT set o' fins were elongated square triangles 3 inches wide and 12 inches long. Arrr! They were surface mounted. Filletin' all o' these fins took nearly three sets o' 15 minute epoxy.

Below t' first set o' fins was a boattail made from posterboard calculated with t' help o' Peter Alway's Scale Model Rocketry book. Begad! Well, blow me down! Two o' these were made; one for t' boattail, and one for t' upper transition. Begad! Both were given a liberal epoxy glaze almost 1/8 inch thick. Ya scallywag!

T' motor mount tube be 30 inches long and was held in place with 3 centerin' rings. Begad! Blimey! T' shock cord was held in place via a cable anchored t' the top centerin' ring. Arrr!

Given that thar were 12 thick plywood fins at t' back end, shiver me timbers, I'd probably have t' put some ballast at t' front end. I filled a 2.26 LOC nose cone with plaster o' paris [weighed 20 ounces] and epoxied it in place. Avast, ya bilge rat, me proud beauty! Doin' a swing test on a 12 foot rocket is nay as easy as it looks. Avast, me proud beauty! Avast! It turned out that the plaster filled nose cone be makin' more problems than it solved. Ahoy! Begad! I later replaced it with an empty cone. Blimey!

Finishing:

T' paint scheme be simple; white airframe, black nose and fins. Ahoy! Well, me hearties, blow me down! Painting it took more cans o' Krylon than I anticipated. But eventually, it was finished. Begad! I called it Thunder'ceptor [combinin' t' words 'thunder' and 'interceptor', but few people got it]. Ahoy!

Scratch Thunder'CeptorFlight:
T' first flight be at a Connecticut Tripoli launch in Morris, CT on 28 February 1993. Ya scallywag! Ahoy! T' motor o' choice was an AeroTech I210 [single use]. I packed the chutes with plenty o' baby powder, shoved in some wadding, ya bilge rat, and prepped the motor with maskin' tape [friction fit and thrust ring]. Settin' it up on the pad brought a few realities t' light. Avast, me proud beauty! T' rocket was almost top-heavy even for a 1/2 inch rod [this was before I replaced t' plaster-filled nose cone]. Well, blow me down! Begad! It flew straight and true t' a little over 1000 feet. Begad!

Future flights were made at Battle Park launches in 1993 and 1994, ya bilge rat, and at LDRS 1996, ya bilge rat, me bucko, all on full or nearly full impulse I motors. 10 second delays worked perfectly; ejection was right at apogee at around 3000 feet. Begad! After t' first two flights, it started corkscrewin' a bit. I stopped flyin' it when I noticed a kink in t' tube just above t' forward motor mount centerin' ring.

Summary:
T' rocket was definitely an attention-getter, which was somethin' in t' back of me mind as I built it. Avast, arrr, me proud beauty! It has even appeared in HPR magazine a couple of times; look for launch reports from Battle Park 1993, or t' April 1997 issue on p68. Arrr! Ya scallywag! I enjoyed buildin' it; it gave me somethin' t' do durin' t' cold winter months. T' only thin' I might have done different be reinforce the tubin' more and had it disassemble into smaller pieces [transportin' it 7 hours to Battle Park be nay easy].

comment Post a Comment