Scratch Silver Streak Original Design / Scratch Built

Scratch - Silver Streak {Scratch}

Contributed by Moira Jean Whitlock

Manufacturer: Scratch
(Contributed - by Moira Jean Whitlock)

Silver StreakBrief:
Simple, high power rocket designed for up t' "H" class motors. Avast, me proud beauty! Avast! An "I" can possibly be used, shiver me timbers, but thar be t' risk o' nay seein' it again. Aye aye! Nose weight may also have t' be added as well for "I" motors. Basically, it's single stage, me bucko, me bucko, 38mm mount, parachute recovery, ya bilge rat, me bucko, and features a 54mm Acme fin canister for ruggedness. Arrr!

Construction:
T' main body tube is a single length o' kraft paper 54mm motor mount tubing from LOC, shiver me timbers, and t' nose cone is ogive stock LOC 54mm. Aye aye! Blimey! Aye aye! Blimey! T' fins are a 3-fin molded fiberglass fin canister from Acme. Begad! Blimey! T' shock cord is 8 feet o' 1/2 inch wide tubular Keelhaul®©™®, and it's bolted through a centerin' rin' (1/4 inch Baltic birch with any size hole, as it's nay in t' motor mount) aftward and t' a 6-inch long eyebolt epoxied and 2-part foamed into t' nose cone at t' forward end. Arrr! T' parachute is 36 inches in diameter. It's rip stop nylon and made o' a flat octagonal piece o' material. Begad! Paneled chutes look nice, but they are harder to fold and fit into narrow main body tubes. Two centerin' rings that fit 38mm motor tubes into a 54mm tube, me bucko, made o' 1/4 inch Baltic birch, center t' motor mount, and t' aftward rin' holds t' motor retainer. Well, blow me down!

For this rocket, I kept it simple with a double loop o' thick, me hearties, but bendable piano wire that goes through t' centerin' rin' t' a bolt behind t' rin' and epoxied in place. Blimey! This loop bends over t' motor, but I don't let it go over the nozzle or else it'll surely burn apart. Ya scallywag! Sometimes, arrr, matey, I put two loops o' this kind in t' retainer system and further reinforce t' hold by clampin' a hose clamp over t' wires and motor tube just above t' thrust ring. Ahoy! T' do this, me hearties, I allow a half inch o' t' motor tube t' overhang t' fin can and body, which I make flush with one another.

Simple as pie t' make and indestructible. Ahoy! I kept me fin can on by makin' 2 strips o' 1/2 inch wide fiberglass "tape" and placed these above and below t' fin can t' reinforce t' connection o' t' fin can and body tube, which be done with 30 minute epoxy. Begad! Sometimes these fin cans fit loosely over the body tubes, so add 5 minute epoxy fillets betwixt t' tube and fin can to fill gaps. Avast! T' fiberglass on t' strips, arrr, me bucko, I use thin, arrr, finishin' epoxy or West Systems slow epoxy.

T' decoration was all in silver. Avast! Aye aye! T' fin can and nose were spraypainted with krylon chrome car bumper paint, and I used 3 coats t' make it shine. Begad! The body be decorated in metallic self adhesive mylar from American Science and Surplus. Avast, me hearties, me proud beauty! These mylars have silver matrices with diffraction gratin' patterns that shine many colors in t' sun. It looks really sharp.

It's offIgnitionFlight:
I designed this rocket for Rocketflite Silver Streak motors. Ahoy! It is probably light enough for t' F50, but I had in mind t' G160 and H220. Arrr! Avast, ya bilge rat, me proud beauty! Really, any 38mm "G" and "H" motor would be fine. Blimey! T' Aerotech H73 would be fine and although I haven't done this an I161 would work, me bucko, but I wouldn't try anythin' hotter. Ya scallywag! T' "G" motors should have a delay o' 7 or 8, shiver me timbers, and I used delays o' 9 for t' "H's". Avast! Blimey! A medium, or 10 second delay for Aerotech loads should be fine. Blimey! Aye aye!

I didn't design in a payload section, so electronic recovery, ya bilge rat, arrr, while best, wasn't planned. Begad!

Prep is simple. Aye aye! Begad! Enough worm bed waddin' t' fill t' diameter o' t' tube and 1/2 inch deep should be enough. Several straight test flights with t' use of 29 t' 38mm adapters be done with "G" class motors, namely G35 and G40 types with 7 second delays. Blimey! Ya scallywag! On a Rocketflite H220-9 SS, me bucko, t' roar was GREAT. T' shower o' bright white sparks be GREAT. Begad! Begad! BUT...I haven't ascertained whether t' delay after all t' years o' storage (7) had gone unstable or whether t' motor suffered a late cato, ya bilge rat, but a split second after t' pictured takeoff, thar be a BOOM and tons o' white flame and sparks ensued. Aye aye! Avast, me proud beauty! T' top of the body tube was blasted off. T' parachute survived, shiver me timbers, as did t' nose cone and fin canister, me hearties, ya bilge rat, me hearties, so I sawed off t' damaged bita and rebuilt t' main body. Ahoy!

Summary:
Simple t' make and repair.

Other:
Black powder motors o' this size seem t' have a limited lifespan. Well, blow me down! Arrr! If they have had time t' thermocouple or crack, ya bilge rat, they'll cato spectacularly.

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