Scratch 2x Big Bertha Upscale

Scratch - 2x Big Bertha {Scratch}

Contributed by David Fergus

Manufacturer: Scratch
Style: Upscale

2x Big BerthaBrief:
This is a scratch 2X upscale o' a popular Estes kit. Blimey! Ahoy! It features a 3 inch diameter body and PML components (except t' nose cone, which was turned on a lathe out o' solid pine). Begad! Ahoy! It weighs 3.5 pounds and is 45 inches tall.

Construction:
2x Big Bertha A 36" long, arrr, 3" diameter quantum body tube be ordered with fin slots custom cut for .062" G-10 fins. T' G-10 fins were ordered custom from PML and cost $8.50 each. They were up-scaled from t' Estes kit fin pattern with through-the-wall tabs for mountin' t' a 38mm motor mount tube. Avast, me proud beauty! A 3" piston assembly, shiver me timbers, 1/4 inch brass launch lug (10" long, also upscale), and an 18" 38mm motor mount tube with three centerin' rings was also ordered from PML. Begad! All o' these components were obtained within two weeks o' placin' t' order. Motor retention was accomplished by epoxyin' two pieces o' threaded rod t' t' motor mount tube. Blimey! Standard PML construction techniques were employed t' build t' rocket includin' internal fin fillets and piston strap attachment t' t' upper motor mount tube. Ya scallywag! T' nose cone be turned out o' pine on a lathe. Begad! A search was conducted on t' internet for a suitable 3 inch nose cone, but t' only one found was too expensive. Arrr! Aye aye! I decided t' apply me knowledge from 9th grade shop (when I made a lamp out o' light and dark mahogany by gluin' 1x4 together) t' make me own solid pine nose cone. Ahoy! Blimey! I used pine because I wanted t' make sure it would be stable on BIG engines. T' finished nose cone ended up weighin' 12 oz. Avast, me proud beauty! by itself.

2x Big Bertha

Finishing:
2x Big Bertha I sprayed a coat o' grey Krylon sandable primer, then followed with two coats o' Krylon gloss black. Ya scallywag! I still need some upscale decals.

Flight:
This be me level 1 cert rocket, so I used t' chute from me PML 'lil Luner Express and about 25 feet o' shock cord, loaded an H123W with a medium delay, and let it rip. Begad! Rocksim predicted about 1200 feet and that looked about right.

Recovery:
It ejected at apogee, and drifted down for a soft landin' on t' sod. It returned in triumph for a successful certification flight.

Summary:
A fun time be had by all. Ya scallywag! Begad! My thanks t' Leland Cheng for loanin' me a motor case and sellin' me a motor, Alan Estenson for bein' me certification observer, shiver me timbers, and Tripoli chapter 45 for hostin' t' launch.

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