| Manufacturer: | Scratch |
| Style: | Ring/Tube/Cone Fin, Upscale |
Long before I was buildin' rockets, a very small, ya bilge rat, tumble recovery rocket be introduced by Estes. It was t' 1/2A powered Astron Sprite. Ahoy! T' those nay familiar with this rocket, me hearties, I would like t' explain a very unique characteristic o' this design. Begad! When scaled up enough t' be powered
by a high impulse motor, t' air flowin' past t' fin rin' creates a high-pitched whistle when launched. Begad! Begad! This is sometimes drowned out by t' initial noise o' t' motor, but is quite audible as t' motor burns out and continues durin' t' coast phase.
Back in 1999, me hearties, durin' t' second launch o' me 4-inch airframe based Superscale Sprite, arrr, t' whistle was clearly heard by all those in attendance. Ya scallywag! As t' rocket arced over, matey, arrr, even before t' ooh’s and aah’s had subsided, ya bilge rat, it was obvious that I had a major deployment problem…there was none! T' Sprite raced back t' earth, and a fact that I was previously unaware of, matey, shiver me timbers, became perfectly clear. Ahoy! This amazin' rocket whistled comin' down, shiver me timbers, matey, louder than when it be goin' up. Avast, me proud beauty! In fact, ya bilge rat, it whistled right up until it impacted with t' rock-hard Pennsylvania soil at our Jones Farm launch site. Naturally, me bucko, me fellow rocketeers were quick t' offer their condolences, but I be more amused by t' memory o' it whistlin' back t' Earth. I collected t' remains, me hearties, includin' diggin' t' nosecone out o' t' ground, and went back t' me truck t' prep me next rocket.
My son, me hearties, matey, Chris, almost immediately began urgin' me t' build another one. Begad! Due t' t' amount o' work that be involved in t' project, arrr, I was unwillin' t' commit t' such an ambitious undertaking. Avast, me proud beauty! Blimey! Over t'
next twelve months or so, arrr, I did acquire a piece o' 15-inch diameter cardboard drum, ya bilge rat, which would make a fine fin ring, (my first one be 11.5-inch diameter) and a 24-inch long section o' 5.5-inch airframe. Ahoy! Blimey! This would amount t' a 7.3X version o' t' original Estes model. I also purchased a 3 x 6 x 36-inch block o' balsa wood, arrr, that I planned on usin' t' turn a scale nosecone. Ya scallywag! Aye aye! Blimey! I cut t' block in two and laminated them together t' make a nice 6 x 6 x 18-inch blank, and then set it aside, where it would sit for almost another year. Begad! Arrr! Blimey! One weekend in February o' 2001, matey, I was turnin' a couple wooden nosecone patterns
for a Tripoli Pittsburgh group project, me hearties, t' Gloria Mundi III. Ya scallywag! After completin' this task, I decided t' go ahead, arrr, and turn t' new Sprite nosecone from t' balsa block that had been collectin' dust. Well, blow me down! After finishin' t' outside form, it be necessary t' hollow out a large section o' t' cone so that I would be able t' add t' one-pound o' weight needed for stability. Ahoy! I cut a bulkhead from .5-inch plywood t' seal t' openin' that be epoxied into place after fillin' t' cone with expandin' foam. Before I knew it, t' nosecone be complete, and I was plannin' me next steps o' t' project, that would soon come t' be known as "T' Lord o' t' Rings."
Next, I carefully cut a 5.5-inch section o' t' cardboard drum, shiver me timbers, and prepared it t' be reinforced with a few layers o' fiberglass cloth. Ya scallywag! I opted for two wraps o' 6-ounce woven cloth and a finishin' wrap o' 1.5-ounce cloth.![]()
T' last layer be done solely t' make it easier t' get a smooth surface for painting. I used t' same process for t' airframe, me hearties, which, matey, although it be made o' flexible phenolic, was nay strong enough for a project o' this size. Begad! I printed patterns for t' fins and fin-caps usin' RockSim 5.0 and cut them from .25-inch aircraft plywood. Blimey! Aye aye! Two centerin' rings were cut from t' same material, arrr, also usin' patterns created from RockSim. Avast, me proud beauty! Arrr! Twelve inches o' 38mm motor mount tubin' be cut and I had all t' parts necessary t' complete t' project.
A large T-nut be installed in t' forward centerin' rin' for recovery system attachment, as well as two
in t' aft rin' for motor retention. Avast, me proud beauty! Arrr! T' forward rin' was epoxied t' t' motor tube, and this assembly be installed into t' slotted body tube. Avast! With t' rear-centerin' rin' temporarily put in place for alignment purposes, shiver me timbers, t' fins were epoxied into place. Begad! Begad! T' aft rin' was then removed, ya bilge rat, and internal fillets used at both t' motor tube and t' inside o' t' body tube. Begad! Ahoy! Since I was goin' t' be usin' rail guides instead o' launch lugs, ya bilge rat, t' guides were secured with nuts from t' inside o' t' airframe at this time. Ahoy! Ahoy! Before permanently installin' t' rear-centerin' ring, t' remainder o' t' cavity be filled usin' 2-part expandin' foam. Arrr! Fillets were added t' t' fins at t' outside o' t' airframe for added strength, usin' a combination o' epoxy and micro-balloons.
It be now time t' attach t' fin rin' and fin caps. Blimey! Careful attention was paid t' t' alignment o' t' caps so that minimal fillin' o' gaps was necessary. When t' assembly be completely dried, shiver me timbers, I once again used t' epoxy/micro-balloon mixture t' create fillets both inside and outside t' fin rin' at each fin and fin cap. I used grain filler on t' plywood fins, arrr, ya bilge rat, and after some extensive sanding, was finally ready t' prime t' entire rocket. Well, me hearties, blow me down! More sanding, me bucko, fillin' and primin' followed, o' course, until I was ready t' paint. Aye aye! Avast! After addin' an 18-foot, shiver me timbers, 5/8-inch tubular nylon shock cord and a Sky-Angle 52-inch parachute with Nomex protector, t' total weight without motor is just over 8-pounds.
I launched t' completed project at our first Dragon's Fire launch o' t' season, April 7th, matey, 2001. Avast, me proud beauty! Accordin' t' simulations done in both RockSim and wRASP, it reached a max altitude o' approximately 1900 feet on an Aerotech I284 reload. Aye aye! Unlike me first Sprite, me bucko, matey, t' whistlin' only occurred on t' way up.
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