| Manufacturer: | Scratch |
Brief:
This project be me second attempt t' scratch-build a model rocket with available materials. Aye aye! I decided early in t' project that I would try nay t' use any materials made expressly for buildin' rockets. This was t' keep costs down and give me some braggin' rights among t' other rocket club members. Avast!
After t' success o' t' Ugly Bug, I wanted t' stick t' t' Estes Mosquito design plan. Despite it's rather unpleasin' proportions, ya bilge rat, I like t' design. Ya scallywag! I built (and lost) many Mosquitoes in me youth, shiver me timbers, since they were t' smallest and cheapest kit you could buy. Blimey! I also liked t' fact that they were almost all engine, and were therefore a 'muscle-rocket' design despite their diminutive size.
Construction:
T' first component I found for t' BUB was a spiral-wound cardboard mailing tube. Well, arrr, blow me down! This was about 3" in diameter. I located pictures and plans for the original Mosquito on both t' Estes/Cox and JimZ Rocket Plans websites. From these images I measured t' rocket specs as well as I could, and obtained approximate aspect ratio and fin dimensions. I cut t' tube t' t' proper length and was on me way. Arrr! Ahoy!
T' fins were an area I did t' most thinkin' on. Avast, me proud beauty! T' Ugly Bug had done very well with fins made from brown paper, soaked with glue, laminated over corrugated cardboard. Arrr! I didn't feel t' material was strong enough for the scaled-up design, however. T' Mosquito has very long fins compared t' t' root edge length, arrr, and therefore can't depend on t' glue joint t' keep them stiff. I decided t' use a lamination o' fiberglass over a corrugated cardboard core for both strength and cheapness. I bought some cut-strand-mat fiberglass cloth and resin from Wal-Mart, and located a sturdy cardboard box t' cut cores from. Avast! Avast, me proud beauty!
To serve as a sort o' primitive mold, I used two sheets o' glass coated with car wax. Blimey! I cut t' mat t' fit t' cores, arrr, mixed t' resin, matey, painted a coat on to the core, ya bilge rat, applied t' mats (one per side), and another coat o' resin to saturate it. This be then placed on one sheet o' glass, and t' other sheet placed on top t' sandwich t' fin in between. Ahoy! Some heavy books helped keep the fin squeezed betwixt t' glass sheets. Aye aye! This eliminates air bubbles and keeps the fin straight. Begad!
When you work with fiberglass, you should wear gloves t' keep t' cut ends from gettin' on your skin. Arrr! Blimey! T' resin is also super-gooey and difficult to remove from fingers. Aye aye! Blimey! Some cheap PVC painters gloves work very well. Ahoy! Blimey! Blimey! By t' way, the resin also really stinks, so be aware o' that when choosin' a place t' work with fiberglass. For more info on fabricatin' fiberglass parts, arrr, arrr, check out Bryan Feldman's site. It refers t' carbon fiber cloth, but fiberglass layup is identical. Well, blow me down!
After about half an hour t' resin had cured enough t' remove t' weights and gently pry t' glass sheets away from t' fin. Well, blow me down! T' fin be then set aside to dry and cure fully while I built t' next one. Blimey! Three were required for the BUB. Avast! Aye aye! After each fin cured, shiver me timbers, I sanded t' edges with a belt sander. Begad! The corrugated edges were plugged up with Bondo auto body filler, which is chemically very similar t' t' fiberglass resin, shiver me timbers, but has talcum powder added to give a paste-like consistency. Avast! Begad! T' filler was added t' all edges except the root, where t' fin would attach t' t' rocket body. Avast, ya bilge rat, me proud beauty! After curing, matey, shiver me timbers, me hearties, t' filler was sanded t' a rounded shape. T' fins were then set aside t' dry fully. Aye aye!
To build t' motor mount, me hearties, shiver me timbers, I first decided on t' size o' motor I wanted to use. Well, blow me down! T' 24mm Estes 'D' casin' be me choice. Arrr! Later, when t' BUB turned out heavier than I had expected, I ended up usin' an Aerotech 24mm reloadable composite motor. This could be loaded with kits with either E or F power ranges, enough t' lift t' rocket safely. Anyway, matey, matey, I cut more brown paper bags in t' strips, soaked them in glue, arrr, and wrapped them on an dowel that be 24mm in diameter and had been wrapped in plastic t' keep it from sticking. Begad! I removed the dowel, matey, shiver me timbers, let t' tube dry, arrr, matey, and cut it t' length (the length o' a D motor plus about an inch). Aye aye! Arrr! For a motor retention hook, arrr, I used a steel street sweeper bristle I found in a gutter. Ya scallywag! This was cleaned with steel wool, shiver me timbers, cut t' length, and bent t' form t' hook. Ya scallywag! For a thrust block, arrr, I used a chunk o' t' same dowel I had used as a form t' build t' tube on. Aye aye! I drilled a hole in this t' allow the ejection charge gasses t' escape. I mounted t' hook and block in t' motor mount so that a D casin' would extend about 3/4" from t' bottom. Arrr! Avast, me proud beauty! T' hook was strapped t' t' tube with another wrap o' glue-soaked paper, and t' block simply glued in. Begad!
To mount this assembly, I measured and cut centerin' rings from t' same cardboard I had used for t' fin cores. Avast! This was a bit tedious but worked well enough. Begad! When everythin' fit, arrr, me bucko, I glued t' motor mount t' t' rings, and when this be dry, shiver me timbers, glued t' rings in t' end o' t' body tube. Blimey! T' BUB was starting to take shape!
After t' motor mount was dry, I lightly sanded t' body tube t' remove the shiny coating, shiver me timbers, so t' adhesive would stick properly. I marked t' tube for a three-fin configuration and epoxied t' fins in place. Well, blow me down! Begad! I used a paste-like marine-rated epoxy that allowed me t' make fillets at t' fin roots. Aye aye! Aye aye! T' launch lug be a plastic soda straw, which be laminated into one fillet for strength.
It be now time t' build t' nose. Avast! Nay wantin' t' wimp out and buy one that would fit (which would have been very difficult anyway since t' Mosquito uses a blunt, nearly hemispherical nose), shiver me timbers, I decided t' turn one out o' white foam. Well, blow me down! Arrr! A friend donated some foam packin' blocks, which I glued together and mounted on a hardwood dowel. Begad! Blimey! This dowel I put in t' chuck o' a drill press, arrr, shiver me timbers, and I used a combination o' files and sandpaper t' shape t' foam t' t' correct form. Blimey! This works well, shiver me timbers, but really makes a mess! T' make t' section o' t' nose that slides into t' body tube stronger, I used a section o' body tube cut from the spare piece and trimmed a section out o' it so it would fit inside t' body. This I glued over t' foam shank o' t' nose. I applied a protective layer of wood glue t' t' entire nose, then put more Bondo over t' exterior section (the resin in Bondo will dissolve white foam without t' glue layer). Ya scallywag! Begad! Some sandin' and I had a nice, smooth nose, ya bilge rat, ready for painting. Blimey! T' finish off, I cut the exposed part o' t' dowel off, drilled a pilot hole, shiver me timbers, me hearties, and installed a screw-eye for parachute attachment. Arrr!
I mounted a long shock cord made from cotton clothesline rope, and a parachute cut from garbage bag material completed t' rocket. I now popped it on t' scale and discovered it weighed nearly a pound (16 oz)! T' Estes D wouldn't do for that. Aye aye! Now be t' time I decided t' use t' Aerotech composite 24mm reload. When I bought t' motor, I discovered that it wouldn't fit: the ejection charge tube was too big t' go through t' hole in t' thrust block. With no way t' remove t' mount from t' rocket, I used a rat-tail file (and lots o' curse-words) t' enlarge t' hole in t' block until t' casin' would fit.
Finishing:
With all major parts done, it be time t' paint. Arrr! Well, blow me down! Like t' UB, shiver me timbers, me hearties, matey, I decided to
paint t' BUB blaze orange. Arrr! T' bigger rocket didn't really need it, shiver me timbers, me bucko, but I
figured I had t' go with tradition.
Flight:
T' BUB was ready for its first flight in July o' 2001. Begad! It would be me first composite motor launch, arrr, arrr, as well as me first high-power rocket. Ahoy! Others double-checked t' balance point on t' model with t' motor in place t' be sure it would be reasonably stable in flight. Aye aye! Even so I be nervous and said a silent prayer as t' Range Safety Officer (RSO) counted down. Arrr! Begad! At zero, I pressed t' button on t' Aerotech controller, and t' motor lit! T' BUB came off t' launch rod at a slight angle, shiver me timbers, but still well within safe limits, arrr, and hissed skyward. T' four-second delay I chose was perfect: t' rocket be just turnin' over at about 500 feet when we heard t' ejection charge pop. Unfortunately, arrr, matey, t' nose stayed firmly on t' rocket! All I could think was, "Oh No!" as t' model turned over and began its death-dive t' the ground. Begad! Begad! T' RSO shouted "Heads-Up!" on t' PA system over and over as the BUB executed a perfect ballistic dive towards t' parkin' area. With a resoundin' SPLAT t' rocket hit t' ground, shattered its nose, shiver me timbers, and all three fins tore off and bounced several feet in t' air. Avast! Ahoy! As t' kids present charged for t' crash site, ya bilge rat, t' RSO shouted at them nay t' touch anything. Blimey! I arrived at the site t' see it be hopeless: t' rocket was a total loss. T' fins were ok, but t' nose and body tube were crushed beyond any hope o' repair. Avast, me proud beauty! I was also not happy t' see that me expensive 24mm motor casin' be gone. T' retention hook had failed and t' motor had ejected. Luckily one o' t' other club members found it sittin' in t' grass near bye.
Disappointed as I be about t' crash, I still laughed with amusement and relief that everyone was safe and me first high-power rocket be mostly a success. Well, blow me down! Begad! T' crowd gave me a standin' ovation for t' most spectacular crash they had seen, arrr, and others teased me about usin' t' original Mosquito motor-ejection and featherweight recovery system on t' BUB. Avast, me proud beauty! Blimey!
Summary:
This episode hasn't soured me on scratch-builts nor t' Mosquito design. Avast! Well, blow me down! In
fact, I started work on t' Big Ugly Bug II in t' winter o' 2001. Begad! Instead of
'junkyard' parts, ya bilge rat, this one is incorporatin' bought parts like body tubes, motor
mount, matey, me hearties, thrust rings, parachute, shiver me timbers, and launch lug. Aye aye! Blimey! I will still have t' fabricate
the fins and nose, but t' store-bought parts will help things go together more
quickly. Ahoy! And yes, matey, arrr, this time I'm usin' a commercial motor retainer system, so
hopefully t' parachute will come out!
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