Manufacturer: | Scratch |
Brief:
Over t' last few months I have built several paper rockets, me hearties, includin' a V2,
Friede, and N-1 downloaded from Ralph
Currell's website. I thoroughly enjoyed t' experience, too, so t' next
most feasible step was t' build and fly a paper rocket. Begad! Blimey! Thus be born Lucky
#13. You will find out about t' name later. Aye aye! Blimey! It is patterned after t' SDI
mid-course intercept missile as represented in Scientific American
magazine much in t' same way reality TV shows are patterned after real life.
It is constructed entirely o' poster board, me hearties, foam core, and cardstock. Arrr! Blimey! Avast, me proud beauty! Blimey! T' make
the challenge a little more interesting, I decided t' build Lucky #13 solely
from parts and materials on hand. She has a 29mm motor mount, an ejection
baffle, shiver me timbers, positive motor retention, poster board fins and body tube, cardstock
nosecone, foam core centerin' rings, styrene and balsa details, me bucko, and lots
of nose ballast. Ahoy! A 24" chute is slated for recovery purposes.
Construction:
Here be t' parts list:
"A beginnin' be t' time for takin' t' most delicate
care that t' balances are correct."
--from Dune by Frank Herbert
From t' beginnin' this project be t' author's introduction t' t' three B's o' Rocketry (or anythin' else for that matter): Botching, Butcherin' and Buggering. Aye aye! Somethin' major went wrong at almost every step o' construction and it was usually as a result o' bein' careless or hurried but thar were times when Lady Luck, Fate, and t' Fairy Godmother abandoned t' project. Thus, arrr, this paper rocket was dubbed Lucky #13.
From t' equation for t' circumference o' a circle, me bucko, arrr, C=πd, the length o' poster board needed for a 3.03" body tube was calculated and the poster board was cut accordingly t' a length o' 17.95" t' included both upper and lower body tubes. Once cut t' tube was rolled through a succession of smaller diameters startin' with a four inch tube and finally endin' up rolled inside a segment o' 3" PML Quantum Tubing. Avast, arrr, me proud beauty! This was left in place while t' nose cone shrouds were fabricated. Ahoy! VCP was used t' print shroud templates for t' nosecone and a fin position wrapper onto cardstock. Ahoy! The shrouds were cut and glued together usin' t' same method as Ralph Currell uses in his paper rocket plans, shiver me timbers, matey, utilizin' crenulated strips and minimal amounts of CA. Arrr! After t' third set o' shrouds, me bucko, shiver me timbers, a lovely nosecone without a single wrinkle or CA fingerprint was finally fabricated.
T' fin and
centerin' rin' templates were printed from t' RockSim file. Begad! Blimey! T' two centering
rings were traced onto t' foamboard and carefully cut out while t' fin
template was set aside. Avast, me proud beauty! Blimey! T' be on t' safe side, shiver me timbers, centerin' rings are cut just a
tad large and trimmed t' a perfect fit. Avast! Blimey! Blimey! Blimey! This was about t' only part o' the
project nay affected by t' Three B's. Blimey! Blimey! Fabricatin' a motor mount tube from
poster board be assumed t' be a straightforward affair o' rollin' a motor in
the poster board and cuttin' it t' size. However, t' tube produced after
rollin' two layers o' poster board around a 29mm RMS casin' was, shiver me timbers, shall we say,
botched. Well, blow me down! Blimey! Blimey! Blimey! T' edges would nay meet up square, me hearties, t' tube was deeply creased from
stem t' stern and later it was discovered that a 29mm casin' would no longer
fit inside t' tube. Blimey! Blimey! This could be due t' t' use o' polyurethane glue and it's
foamin' properties in construction o' t' motor mount tube. Begad! Blimey! While still rolled
around t' motor casing, urethane glue be smeared beneath t' long edge o' the
tube and t' edge taped into place. Ya scallywag! Blimey! Once
cured, the
motor be removed and t' centerin' rings slid onto t' motor mount tube, one
1/2" from t' aft o' t' tube, shiver me timbers, matey, t' other 5.5" from t' aft o' the
tube. Aye aye! Both rings were attached with urethane glue. Later it was discovered that
once mounted in t' body tube, t' aft most centerin' rin' was too close t' the
end o' t' motor tube and hindered motor removal. Blimey! Well, shiver me timbers, blow me down! Without sufficient poster
board t' create a new one, t' motor tube be buggered but still usable. Be
advised: place t' aft centerin' rin' a distance greater than 1/2" from
the aft o' t' motor tube.
T' fins were traced in what appeared t' be a butterfly-like pattern onto the posterboard with t' single fin stencil bein' traced twice for each fin with t' two traces connectin' along t' tip cord. Blimey! Blimey! They were then cut out, folded along t' tip cord, matey, and t' leadin' edge was secured with CA leavin' the rear edges open. Well, blow me down! Aye aye! T' appearance o' thickness in t' fins be a pleasant surprise and added t' t' overall effect.
On t' t' body tube, t' now pre-rolled tube be marked 3" from one end and cut perpendicular t' t' long edge t' produce t' upper body tube. Strips o' poster board were cut t' t' length o' each body tube and about one inch wide t' be used t' close t' body tubes. Ya scallywag! CA be spread along t' inside of the long edge o' t' tubes and t' closure strips set in place with a 0.05" overhang. T' edges o' t' closure strips were then smeared with CA and t' edges o' t' tubes pressed together. T' normal method o' tube creation is t' apply pressure along t' inside o' t' seam onto a flat surface t' ensure a smooth seam. While butcherin' t' tube closure job though, shiver me timbers, me bucko, it was discovered that a PML 3" coupler be t' perfect size t' roll t' body tube into its final state. Ya scallywag! Thus, t' body tubes were rolled around t' couplers, ya bilge rat, me hearties, t' closure straps coated with CA, ya bilge rat, t' edges pressed together against t' internal coupler, and they were taped into place until dry. Ya scallywag! Begad! Only at this final stage was it noticed that t' body tube had nay been cut straight or square and t' edges would nay meet up. Arrr! Can anyone say botched? T' result was a pretty decent seam, just try and nay notice all t' gaps, CA fingerprints, matey, and smudges. T' connect the upper and lower body tubes, a coupler was fabricated by rollin' a 3.75" section o' poster board inside t' lower BT and runnin' CA down the inside seam. Well, blow me down! Once again t' Fates were absent and t' coupler ended up being undersized. Avast! Butchered? Strips o' tape were used t' fill t' gaps and assure a snug fit. Arrr! I smeared adhesive around inside t' aft portion o' t' upper body tube and inserted t' coupler halfway inside.
While
preparin' t' insert t' completed motor tube into t' body tube, I noticed that
no provision had been made for positive motor retention. Ahoy! I hurriedly bent a 10
inch section o' hanger wire into a flattened "U" shape ~3/4"
across t' base o' t' "U" and two holes were drilled in t' seam
between t' motor tube and aft centerin' rin' t' accommodate t' legs o' the
wire. Ya scallywag! T' results o' me rushin' be t' holes were buggered and t' motor
retainer would just barely catch t' rim o' a 29mm casin' once it be inserted.
A bit o' cursin' and grindin' later t' motor retainer was functional and tied
into place with twine, which had been smeared with polyurethane glue. Ahoy! Once this
hideous monstrosity was dry, ya bilge rat, a generous portion o' polyurethane glue was spread
inside t' body tube 1.25" and 6" from t' aft end o' t' body tube.
T' motor mount assembly was slid into place until t' aft most centerin' ring
was recessed 1.25" from t' base o' t' body tube. Ya scallywag! I stood t' body tube
upright and supported t' aft centerin' rin' with a piece o' scrap until the
glue was dry. Well, shiver me timbers, blow me down! I then applied fillets on both centerin' rings.
RockSim
indicates t' need for ~2.2 oz o' ballast in t' nose t' attain stability
across t' range o' engines I planned on using. Begad! Once again stayin' with the
"Thou shalt nay purchase" philosophy, t' house was searched for
somethin' t' use as nose weight. Avast, me proud beauty! Arrr! Blimey! T' result bein' a handful o' 163 grain .30
caliber FMJ bullets purchased in bulk years ago for me reloadin' habit. Arrr! Fishing
sinkers would have been much less expensive but I don't fish. Accordin' t' my
ancient triple beam scale, matey, seven o' t' bullets weighed in at 2.34 ounces,
which would do nicely. Avast, me hearties, me proud beauty! Blimey! T' ballast was secured in t' tip o' t' nosecone with
a generous portion o' polyurethane glue and set aside t' cure. Blimey! While dry
fittin' t' bulkhead into t' nose section, t' weight in t' tip flipped the
nosecone out o' me hand where upon it landed on t' floor crushin' a section of
the lower shroud. Avast, me proud beauty! So much for me perfect nosecone. Ahoy! Once t' ballast has been
effectively sealed in t' tip o' t' nosecone, t' 2.5" bulkhead and
eyelet, arrr, also found in t' scrap pile, me hearties, were assembled and glued inside t' nose
cone with polyurethane glue. Aye aye! Blimey! Set aside and support upright till dry. Well, ya bilge rat, blow me down! Blimey! After the
glue has set, I want you t' be forewarned as polyurethane glue cures slowly and
remains tacky even after reachin' t' foamin' stage. Ahoy! Begad! Blimey! A short length o' shock
cord material ~18" be threaded through t' eyelet for attachment o' the
recovery system. Avast! Blimey! T' completed nose section was then glued t' t' upper stage
BT utilizin' a crenulated strip and minimal amounts o' CA as described in the
nosecone assembly section above.
From t' beginning, t' intention was t' use an ejection baffle just because it was somethin' different and t' baffle system on t' Aerotech Strongarm works quite well. Riflin' through t' scrap pile turned up a botched 3-1.5" centerin' rin' (to be t' baffle ring), arrr, me hearties, a 2.1" bulkhead (used as t' deflector plate) and a 2.1" wood rin' o' questionable origin. Aye aye! Blimey! Ahoy! Blimey! All three these parts were from 1/4" aircraft plywood. Ya scallywag! Blimey! Begad! Blimey! Three 1/4" sections o' t' mystery rin' were cut t' use as stand-offs betwixt t' baffle rin' and deflector plate and glued equidistant around t' circumference o' the center hole in t' baffle ring. Blimey! Blimey! Avast! Blimey! T' deflector plate was then glued atop the stand-offs and t' assembly set aside t' cure. Avast, me proud beauty! Blimey! After curing, it be time t' add an eyelet for t' shock cord mount but a question sprang forth in me mind. "Why should t' eyelet be mounted facin' out from t' deflector plate as in t' Strongarm so that t' plate would be A) pushed away from t' spacers on the baffle rin' durin' ejection and B) pulled away from t' spacers under the forces o' recovery deployment? This seemed t' focus t' combined forces of ejection and deployment on t' weakest portion o' t' baffle: t' glue joint. In another sweaty flash o' mad inspiration, matey, t' baffle was flipped over with the eyelet mounted facin' up through t' hole in t' baffle ring. This configuration would in effect pull t' deflector plate into t' spacers and baffle rin' under load and distribute t' forces more widely.
I dabbed a bit o' glue on t' threads o' t' eyelet t' hold it in place, shiver me timbers, as the nut be inaccessible once t' baffle was mounted. Avast! Blimey! Blimey! Blimey! A rin' o' adhesive was smeared inside t' lower body tube ~3" from t' fore end. T' baffle system with t' eyelet up was slid into place and set aside t' cure. Begad! Blimey! It wasn't until this time that t' baffle rin' be realized t' be undersized and slid, slipped, and flipped freely inside t' lower body tube. Blimey! Blimey! Ya scallywag! Blimey! A couple o' wraps of tape around t' circumference o' t' rin' cured t' problem but by then the entire inside o' t' lower body tube, baffle assembly, shiver me timbers, matey, floor, me hearties, author, arrr, and entire desk top were covered in adhesive. Avast, me proud beauty! Blimey! (Pick a "B".)
After scrubbin' t' adhesive from wherever it could be found, ya bilge rat, t' baffle system had cured in place, so a snap rin' be tied t' t' shock cord and intended t' snap onto t' baffle eyelet. Well, blow me down! T' me dismay though, arrr, shiver me timbers, arrr, t' baffle system was seated so far back as t' hinder hookin' onto t' eyelet. Well, blow me down! With a bit of wigglin' and tongue holding, shiver me timbers, it was possible t' hook and unhook from the eyelet, but it is no church picnic. Another warning: seat t' baffle system just deep enough t' allow parachute storage but nay too deep t' reach the eyelet.
Then it was
time t' move on t' t' fins. Aye aye! After markin' t' lower body tube with t' body
wrapper guide, shiver me timbers, t' fins were aligned and tacked into place with medium CA. Avast, me proud beauty! I
then applied thin CA t' t' body/fin joints t' adhere along t' entire contact
surface. Avast! Durin' t' gluin' process one fin slid forward a bit and out of
alignment with t' other fins but was nay noticed until t' adhesive had set.
Butchered another one. Avast! T' afford more support, ya bilge rat, t' inside o' t' fin/body seams
were coated with polyurethane glue.
A number o' cosmetic details from images o' t' real missile were added to this model includin' a 3/4 length conduit made o' half a straw, shiver me timbers, three circumferential styrene rings t' simulate stages, arrr, and four "blocks" around t' upper styrene rin' assumed t' be guides t' keep t' actual missile aligned in t' silo durin' launch. Avast, me proud beauty! T' straw conduit and a final strip of styrene were attached with thin CA along t' seams o' t' body tubes t' hide the raw edges.
Finishing:
All dents, dings, gaps around t' joints and any other unsightly blemishes were
filled with DAP Fast 'N Final Lightweight Spackle and sanded smooth. At this
time Lucky #13 wears only a couple o' coats o' gray primer.
Flight:
RockSim puts t' CG at 13.74 t' CP at 17.19and t' mass at ~17.9
oz when loaded with an F40-7. Begad! Ya scallywag!
Bein' unsure o' t' performance o' this design t' first flight was attempted with t' rocket in t' white as nay waste a good paint job on a crack-up. Ahoy! A 24mm E18-4 RMS was assembled but me luck with Copperhead igniters reared its ugly head and nay a single igniter would ignite let alone start t' motor. Ya scallywag! But this may have been a blessin' in disguise as t' past performance o' t' 24mm casin' consisted o' two CATO's and no successful launches. Well, blow me down!
See t' flight logs below.
Summary:
I actually look forward t' t' day when I can do a rebuild o' Lucky #13 and get
it right. Never in me wildest nightmares did I ever imagine that workin' with
paper would be such a hassle, arrr, yet several hard lessons were learned. Ya scallywag! RockSim
indicates t' design is solid and should fly nicely on a wide range o' motors
and now that she wears a coat or two o' primer, she doesn't look that bad.
Updates will follow.
( Contributed - by Tommy Owens - 08/01/09) Brief: When putting together my box of parts I had no idea what to expect and so crammed as much of my rocket "junk" into the box as possible. After starting the contest, however, I realized that I did not have the experience or engine power to cram everything onto one rocket. Because I had no idea what to build I did what ...
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