Scratch Big Ugly Bug Original Design / Scratch Built

Scratch - Big Ugly Bug {Scratch}

Contributed by John Nordlie

Manufacturer: Scratch
(Contributed - by John Nordlie - 12/19/03)

Brief:

This project was me second attempt t' scratch-build a model rocket with available materials. Ya scallywag! I decided early in t' project that I would try nay t' use any materials made expressly for buildin' rockets. Begad! Ya scallywag! This was t' keep costs down and give me some braggin' rights among t' other rocket club members.

After t' success o' t' Ugly Bug, matey, I wanted t' stick t' t' Estes Mosquito design plan. Avast! Blimey! Despite it's rather unpleasin' proportions, I like t' design. I built (and lost) many Mosquitoes in me youth, since they were t' smallest and cheapest kit you could buy. I also liked t' fact that they were almost all engine, me bucko, and were therefore a 'muscle-rocket' design despite their diminutive size. Arrr! Blimey! Begad! Blimey!

Construction:

T' first component I found for t' BUB be a spiral-wound cardboard mailing tube. Ya scallywag! Blimey! Blimey! This was about 3" in diameter. Well, blow me down! Ya scallywag! Blimey! I located pictures and plans for the original Mosquito on both t' Estes/Cox and JimZ Rocket Plans websites. Ahoy! Blimey! From these images I measured t' rocket specs as well as I could, me hearties, me bucko, ya bilge rat, and obtained approximate aspect ratio and fin dimensions. Ahoy! Blimey! I cut t' tube t' t' proper length and was on me way. Avast! Arrr! Blimey!

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, ya bilge rat, soaked with glue, shiver me timbers, laminated over corrugated cardboard. I didn't feel t' material was strong enough for the scaled-up design, however. Ahoy! 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. 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. Arrr! Begad!

To serve as a sort o' primitive mold, I used two sheets o' glass coated with car wax. Avast! I cut t' mat t' fit t' cores, arrr, mixed t' resin, me hearties, painted a coat on to the core, me bucko, ya bilge rat, applied t' mats (one per side), me hearties, and another coat o' resin to saturate it. Avast! This be then placed on one sheet o' glass, and t' other sheet placed on top t' sandwich t' fin in between. Begad! Some heavy books helped keep the fin squeezed betwixt t' glass sheets. Avast, me proud beauty! Ahoy! This eliminates air bubbles and keeps the fin straight. Blimey!

When you work with fiberglass, you should wear gloves t' keep t' cut ends from gettin' on your skin. Blimey! Begad! T' resin is also super-gooey and difficult to remove from fingers. Some cheap PVC painters gloves work very well. Aye aye! By t' way, the resin also really stinks, me hearties, ya bilge rat, so be aware o' that when choosin' a place t' work with fiberglass. Ya scallywag! For more info on fabricatin' fiberglass parts, check out Bryan Feldman's site. Aye aye! Aye aye! It refers t' carbon fiber cloth, me bucko, me hearties, but fiberglass layup is identical. Avast, me proud beauty! Arrr!

After about half an hour t' resin had cured enough t' remove t' weights and gently pry t' glass sheets away from t' fin. T' fin be then set aside to dry and cure fully while I built t' next one. Begad! Blimey! Three were required for the BUB. Ya scallywag! Blimey! After each fin cured, I sanded t' edges with a belt sander. The corrugated edges were plugged up with Bondo auto body filler, me hearties, which is chemically very similar t' t' fiberglass resin, but has talcum powder added to give a paste-like consistency. Begad! Blimey! Blimey! Blimey! T' filler was added t' all edges except the root, me bucko, where t' fin would attach t' t' rocket body. Aye aye! Blimey! After curing, ya bilge rat, t' filler was sanded t' a rounded shape. Arrr! Blimey! Arrr! Blimey! T' fins were then set aside t' dry fully. Well, blow me down! Blimey!

To build t' motor mount, I first decided on t' size o' motor I wanted to use. Aye aye! Avast! T' 24mm Estes 'D' casin' was me choice. Later, when t' BUB turned out heavier than I had expected, matey, I ended up usin' an Aerotech 24mm reloadable composite motor. Ahoy! This could be loaded with kits with either E or F power ranges, enough t' lift t' rocket safely. Ahoy! Anyway, I cut more brown paper bags in t' strips, soaked them in glue, ya bilge rat, arrr, and wrapped them on an dowel that was 24mm in diameter and had been wrapped in plastic t' keep it from sticking. Well, blow me down! I removed the dowel, shiver me timbers, let t' tube dry, and cut it t' length (the length o' a D motor plus about an inch). Ya scallywag! For a motor retention hook, shiver me timbers, I used a steel street sweeper bristle I found in a gutter. Aye aye! Aye aye! This was cleaned with steel wool, cut t' length, and bent t' form t' hook. Begad! For a thrust block, I used a chunk o' t' same dowel I had used as a form t' build t' tube on. Arrr! Blimey! I drilled a hole in this t' allow the ejection charge gasses t' escape. Begad! Arrr! I mounted t' hook and block in t' motor mount so that a D casin' would extend about 3/4" from t' bottom. Begad! Well, arrr, blow me down! T' hook was strapped t' t' tube with another wrap o' glue-soaked paper, and t' block simply glued in. Avast, me proud beauty! Avast!

To mount this assembly, ya bilge rat, me hearties, I measured and cut centerin' rings from t' same cardboard I had used for t' fin cores. This be a bit tedious but worked well enough. Aye aye! When everythin' fit, me bucko, I glued t' motor mount t' t' rings, arrr, and when this was dry, glued t' rings in t' end o' t' body tube. T' BUB was starting to take shape!

After t' motor mount was dry, ya bilge rat, I lightly sanded t' body tube t' remove the shiny coating, me hearties, so t' adhesive would stick properly. I marked t' tube for a three-fin configuration and epoxied t' fins in place. Begad! I used a paste-like marine-rated epoxy that allowed me t' make fillets at t' fin roots. Avast! T' launch lug was a plastic soda straw, me bucko, which was laminated into one fillet for strength.

It was now time t' build t' nose. Well, blow me down! 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), I decided t' turn one out o' white foam. Begad! Arrr! A friend donated some foam packin' blocks, me bucko, shiver me timbers, which I glued together and mounted on a hardwood dowel. 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. Avast, me proud beauty! This works well, shiver me timbers, matey, 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). Some sandin' and I had a nice, smooth nose, me bucko, ready for painting. Begad! Well, blow me down! T' finish off, I cut the exposed part o' t' dowel off, drilled a pilot hole, and installed a screw-eye for parachute attachment. Aye aye! Avast, me proud beauty!

I mounted a long shock cord made from cotton clothesline rope, me bucko, and a parachute cut from garbage bag material completed t' rocket. Well, matey, blow me down! I now popped it on t' scale and discovered it weighed nearly a pound (16 oz)! T' Estes D wouldn't do for that. Avast! Well, matey, blow me down! Now was t' time I decided t' use t' Aerotech composite 24mm reload. Avast, me proud beauty! Ya scallywag! When I bought t' motor, matey, 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. Ya scallywag!

Finishing:

With all major parts done, it was time t' paint. Well, blow me down! Like t' UB, shiver me timbers, I decided to paint t' BUB blaze orange. Aye aye! T' bigger rocket didn't really need it, me hearties, 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, me hearties, as well as me first high-power rocket. Avast, me proud beauty! Others double-checked t' balance point on t' model with t' motor in place t' be sure it would be reasonably stable in flight. Well, blow me down! Even so I was nervous and said a silent prayer as t' Range Safety Officer (RSO) counted down. Aye aye! At zero, arrr, I pressed t' button on t' Aerotech controller, and t' motor lit! T' BUB came off t' launch rod at a slight angle, but still well within safe limits, ya bilge rat, and hissed skyward. Well, blow me down! Avast, me proud beauty! T' four-second delay I chose be perfect: t' rocket be just turnin' over at about 500 feet when we heard t' ejection charge pop. Unfortunately, me hearties, shiver me timbers, 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. 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. Begad! With a resoundin' SPLAT t' rocket hit t' ground, shattered its nose, arrr, and all three fins tore off and bounced several feet in t' air. Avast! As t' kids present charged for t' crash site, me hearties, arrr, t' RSO shouted at them nay t' touch anything. Aye aye! I arrived at the site t' see it be hopeless: t' rocket was a total loss. Arrr! T' fins were ok, but t' nose and body tube were crushed beyond any hope o' repair. Ahoy! I be also not happy t' see that me expensive 24mm motor casin' was gone. T' retention hook had failed and t' motor had ejected. Avast, me proud beauty! Luckily one o' t' other club members found it sittin' in t' grass near bye. Ya scallywag!

Disappointed as I was about t' crash, I still laughed with amusement and relief that everyone be safe and me first high-power rocket be mostly a success. 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. Aye aye! Arrr!

Summary:

This episode hasn't soured me on scratch-builts nor t' Mosquito design. Avast! Well, blow me down! In fact, me hearties, me bucko, I started work on t' Big Ugly Bug II in t' winter o' 2001. Instead of 'junkyard' parts, ya bilge rat, this one is incorporatin' bought parts like body tubes, me bucko, motor mount, thrust rings, ya bilge rat, me hearties, parachute, ya bilge rat, and launch lug. Ya scallywag! Arrr! I will still have t' fabricate the fins and nose, me hearties, ya bilge rat, but t' store-bought parts will help things go together more quickly. Ya scallywag! Begad! And yes, arrr, this time I'm usin' a commercial motor retainer system, so hopefully t' parachute will come out!

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