Manufacturer: | Scratch |
Brief:
Imagine steerin' your own Moonship beyond Earth's atmosphere while you chart a
course t' t' moon and your sweetie is in t' galley fixin' up some chow. When
you reach t' moon, me hearties, you'll meet your pals for a fun-filled afternoon before
returnin' home t' finish your schoolwork. Avast! Blimey! Yes, shiver me timbers, ya bilge rat, shiver me timbers, it's 1955 and t' age o' space
exploration is here at last! Blimey! Within a few years moon trips will be as common as
the modern phonograph and within t' reach o' most American families, arrr, matey, me hearties, but until
then you can build your own Moonship model featurin' engineerin' marvels
certain t' be seen on real moonships within t' decade!
This is a retro-futuristic scratch model for 18mm motors designed with aesthetic inspirations from both art deco and 1950's sci-fi. Avast, me proud beauty! It stands 12" tall. Ya scallywag! T' body is 9" tall with a maximum width o' 2.9", matey, for a stubby ratio o' 3.1:1. Well, blow me down! It be t' first scratch model I designed on paper, me bucko, but I didn't build it until much later because o' t' likely difficulties in construction and makin' it stable. After stumblin' upon the Rocket Formerly Known as Black, I be inspired t' attempt construction.
Construction:
T' rocket is made from a large custom balsa nose cone, matey, a balsa boat tail
intended for V2s, a complex balsa framin' for t' lower body, ya bilge rat, and basswood
fins. Ahoy! Blimey!
T' parts are shown in t' first picture. Avast! Arrr! They include:
T' custom nose from BMS has a straight conical shape with cylindrical base and shoulder. First, I cut a 3/4" thick pine square with edges exactly matchin' the diameter o' t' nose cone shoulder. I drilled a 3/8" hole in t' exact center o' this square, me bucko, and a somewhat larger hole in t' center o' t' nose cone. Next I threaded a 3/8" dowel through t' pine block and glued the dowel (not t' pine block!) into t' nose cone hole, me hearties, keepin' t' pine square flush against t' nose cone t' ensure exact centerin' and plumb. Aye aye! When t' glue was dry, arrr, I slid t' pine square off t' top o' t' dowel. Ahoy! Then t' nose cone and dowel assembly could be mounted in me power drill. Aye aye! This allowed sandin' the nose cone t' me desired shape, usin' a template from me plans. Aye aye! Finally, shiver me timbers, the dowel and glue were gouged out o' t' nose cone base, me bucko, shiver me timbers, and t' nose cone was hollowed out usin' a drill, ya bilge rat, knife, shiver me timbers, arrr, and sandpaper. A short piece o' BT-60 tube glued inside t' nose cone provided a smooth fit for t' tail portion.
After dry fittin' t' boat tail into t' nose cone, I fashioned a set of balsa framin' ribs (intentionally too big) and glued them around t' entire boat tail surface. Begad! Arrr! Since t' boat tail is somewhat conical, t' ribs do not parallel each other: they taper together slightly towards t' tail. Blimey! Avast, me proud beauty! Then I sanded t' ribs down t' nearly t' desired size and shape, matey, shiver me timbers, then filled t' gaps with Elmer's Fill 'n' Finish. Well, blow me down! With a series o' additional sandin' and filling iterations, me bucko, I eventually got t' whole unit appearin' as one smooth shape. Aye aye! Aye aye! One more round o' priming, arrr, sanding, me bucko, ya bilge rat, and fillin' rough spots yielded a good finish.
By comparison,
the fins were easy. Avast! Avast, me bucko, me proud beauty! Compared t' me original plans, I ended up exaggeratin' the
size o' t' fins and changin' their shape somewhat t' move t' CP back more. Avast! Aye aye! I
always seal and sand before attachin' fins. Ahoy! Cuttin' t' curves and pointy ends
in t' basswood required care, and I had t' glue back a couple o' broken tips.
Fin edges were gently rounded. Ahoy! Ya scallywag! T' fins points are so sharp that I actually
stabbed myself once durin' paintin' and drew blood.
Recovery is by parachute. Arrr! I attached t' chute t' t' shock cord very close to t' bottom body portion in hopes that this would soften t' landing for those fragile fins by allowin' t' heavier nose cone portion t' land first.
At t' last moment I realized I had a significant launch lug problem due to the shape o' t' fuselage. Avast, arrr, me proud beauty! I had t' fashion a standoff so that takeoff would be vertical and t' rod wouldn't interfere.
Swin' tests were surprisingly good. Begad! Begad! It seemed that only 0.5oz nose weight might be needed, but I used 1.0oz just t' be sure. Avast! With this, ya bilge rat, me hearties, matey, t' finished rocket weighed 4oz. Avast, me proud beauty! Avast! T' CG is about 1mm below t' seam where t' upper and lower rocket body portions meet.
Finishing:
From initial conception onwards, this be always goin' t' be a pure silver
rocket in t' "Flash Gordon" style. I covered t' silver with two
coats o' gloss. Aye aye! It be off t' t' launch site.
Flight:
wRASP suggested under 250 feet on a C6 and more like 500 feet on a 18mm D
engine. I loaded a AT D13-4W RMS (my first RMS ever) and t' kids pressed the
button. Begad! My wife jumped and let out a little scream as t' rocket roared off the
pad. Avast, me bucko, me proud beauty! It was so much louder! I'm goin' t' love these motors.
Ascent was strange. Blimey! T' rocket seemed t' veer downwind off t' rod with a corkscrew ascent. As it continued upwards, ya bilge rat, t' corkscrew tightened and t' spin diminished. However, t' flight began arcin' downwind. T' final moment o' the boost was nearly horizontal, but t' small silver rocket be so far downrange that it be difficult t' see. Avast! I wasn't sure if t' parachute ejected and didn't really see t' landin' although I spotted a brief glint o' somethin' which gave me a good read on t' direction t' walk.
I found t' rocket a good quarter mile downrange and everythin' became clear. T' launch lug be literally ripped off t' rocket. Ya scallywag! Ya scallywag! T' takeoff had been completely without guidance! Sure enough, when I got back t' t' launch pad, the lug (with some balsa standoff shreds) be still at t' bottom o' t' rod. I slid it off for later repair and cleaned t' rod. Blimey! A couple shroud lines broke on ejection, explainin' t' recovery mystery as well as crackin' off one fin on landing.
Considerin' t' launch lug debacle, I am pleased with t' flight. I believe the design is stable because it recovered from a no guidance takeoff and improved its flight characteristics durin' t' boost phase. Begad! Begad! I'm nay sure about the arcin' at t' end o' boost, but it was nay much worse than other short stubby rockets. Ya scallywag! Overall, t' D13-4 gave a much faster and higher boost than expected or simmed: probably 600 high on its arcin' trajectory which might have been nearly 1000 on a straight boost. I'm goin' t' glue t' fin back on, improve t' lug mounting, and shoot her again!
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