Manufacturer: | Scratch |
Style: | Ring/Tube/Cone Fin, Upscale |
Long before I be buildin' rockets, shiver me timbers, a very small, me hearties, tumble recovery rocket was introduced by Estes. Avast, me proud beauty! It was t' 1/2A powered Astron Sprite. Avast! T' those nay familiar with this rocket, I would like t' explain a very unique characteristic o' this design. Well, blow me down! 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. Aye aye! This is sometimes drowned out by t' initial noise o' t' motor, arrr, but is quite audible as t' motor burns out and continues durin' t' coast phase.
Back in 1999, durin' t' second launch o' me 4-inch airframe based Superscale Sprite, t' whistle be clearly heard by all those in attendance. Avast, me proud beauty! As t' rocket arced over, arrr, matey, even before t' ooh’s and aah’s had subsided, it be 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, became perfectly clear. Well, blow me down! Arrr! This amazin' rocket whistled comin' down, louder than when it be goin' up. In fact, it whistled right up until it impacted with t' rock-hard Pennsylvania soil at our Jones Farm launch site. Naturally, me hearties, me fellow rocketeers were quick t' offer their condolences, but I was more amused by t' memory o' it whistlin' back t' Earth. Ya scallywag! Avast! I collected t' remains, ya bilge rat, arrr, includin' diggin' t' nosecone out o' t' ground, arrr, and went back t' me truck t' prep me next rocket.
My son, Chris, ya bilge rat, almost immediately began urgin' me t' build another one. Aye aye! Due t' t' amount o' work that was involved in t' project, I was unwillin' t' commit t' such an ambitious undertaking. Avast! Blimey! Over t' next twelve months or so, I did acquire a piece o' 15-inch diameter cardboard drum, arrr, which would make a fine fin ring, arrr, (my first one be 11.5-inch diameter) and a 24-inch long section o' 5.5-inch airframe. This would amount t' a 7.3X version o' t' original Estes model. Ahoy! Ahoy! Blimey! I also purchased a 3 x 6 x 36-inch block o' balsa wood, ya bilge rat, that I planned on usin' t' turn a scale nosecone. 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, me hearties, where it would sit for almost another year. Ya scallywag! Blimey! One weekend in February o' 2001, me bucko, I be turnin' a couple wooden nosecone patterns
for a Tripoli Pittsburgh group project, t' Gloria Mundi III. Blimey! Blimey! After completin' this task, arrr, I decided t' go ahead, me hearties, and turn t' new Sprite nosecone from t' balsa block that had been collectin' dust. Arrr! Arrr! Blimey! After finishin' t' outside form, it was 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. Blimey! Blimey! I cut a bulkhead from .5-inch plywood t' seal t' openin' that was epoxied into place after fillin' t' cone with expandin' foam. Blimey! Before I knew it, arrr, 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, ya bilge rat, arrr, I carefully cut a 5.5-inch section o' t' cardboard drum, arrr, and prepared it t' be reinforced with a few layers o' fiberglass cloth. Ahoy! Well, matey, blow me down! I opted for two wraps o' 6-ounce woven cloth and a finishin' wrap o' 1.5-ounce cloth. T' last layer was done solely t' make it easier t' get a smooth surface for painting. I used t' same process for t' airframe, arrr, matey, which, although it was made o' flexible phenolic, matey, was nay strong enough for a project o' this size. Ya scallywag! I printed patterns for t' fins and fin-caps usin' RockSim 5.0 and cut them from .25-inch aircraft plywood. Avast, me proud beauty! Two centerin' rings were cut from t' same material, also usin' patterns created from RockSim. Aye aye! Twelve inches o' 38mm motor mount tubin' was cut and I had all t' parts necessary t' complete t' project.
A large T-nut was installed in t' forward centerin' rin' for recovery system attachment, as well as two in t' aft rin' for motor retention. Begad! T' forward rin' was epoxied t' t' motor tube, ya bilge rat, shiver me timbers, arrr, and this assembly was installed into t' slotted body tube. Avast, me proud beauty! Begad! With t' rear-centerin' rin' temporarily put in place for alignment purposes, shiver me timbers, t' fins were epoxied into place. Arrr! T' aft rin' was then removed, matey, and internal fillets used at both t' motor tube and t' inside o' t' body tube. Avast! Since I was goin' t' be usin' rail guides instead o' launch lugs, ya bilge rat, me hearties, t' guides were secured with nuts from t' inside o' t' airframe at this time. Blimey! Before permanently installin' t' rear-centerin' ring, t' remainder o' t' cavity was filled usin' 2-part expandin' foam. Blimey! Fillets were added t' t' fins at t' outside o' t' airframe for added strength, usin' a combination o' epoxy and micro-balloons.
It was now time t' attach t' fin rin' and fin caps. Careful attention be paid t' t' alignment o' t' caps so that minimal fillin' o' gaps was necessary. When t' assembly was completely dried, 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, ya bilge rat, me hearties, and after some extensive sanding, shiver me timbers, was finally ready t' prime t' entire rocket. More sanding, me hearties, fillin' and primin' followed, me bucko, o' course, matey, until I was ready t' paint. Begad! After addin' an 18-foot, 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, arrr, April 7th, 2001. Accordin' t' simulations done in both RockSim and wRASP, it reached a max altitude o' approximately 1900 feet on an Aerotech I284 reload. Unlike me first Sprite, t' whistlin' only occurred on t' way up.
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