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