Manufacturer: | Scratch |
Style: | Ring/Tube/Cone Fin, Upscale |
Long before I was buildin' rockets, a very small, tumble recovery rocket was introduced by Estes. Ya scallywag! It was t' 1/2A powered Astron Sprite. Avast, shiver me timbers, me proud beauty! T' those nay familiar with this rocket, I would like t' explain a very unique characteristic o' this design. Ya scallywag! 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. 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, durin' t' second launch o' me 4-inch airframe based Superscale Sprite, ya bilge rat, t' whistle was clearly heard by all those in attendance. Ya scallywag! Ya scallywag! As t' rocket arced over, ya bilge rat, even before t' ooh’s and aah’s had subsided, it was obvious that I had a major deployment problem…there was none! T' Sprite raced back t' earth, shiver me timbers, and a fact that I be previously unaware of, shiver me timbers, became perfectly clear. Begad! Begad! This amazin' rocket whistled comin' down, shiver me timbers, louder than when it was goin' up. In fact, it whistled right up until it impacted with t' rock-hard Pennsylvania soil at our Jones Farm launch site. Ahoy! Naturally, me fellow rocketeers were quick t' offer their condolences, arrr, but I was more amused by t' memory o' it whistlin' back t' Earth. Ya scallywag! I collected t' remains, matey, matey, includin' diggin' t' nosecone out o' t' ground, and went back t' me truck t' prep me next rocket.
My son, me bucko, Chris, almost immediately began urgin' me t' build another one. Aye aye! Due t' t' amount o' work that be involved in t' project, I be unwillin' t' commit t' such an ambitious undertaking. Over t' next twelve months or so, matey, I did acquire a piece o' 15-inch diameter cardboard drum, 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. Well, blow me down! 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, me bucko, that I planned on usin' t' turn a scale nosecone. 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. One weekend in February o' 2001, me bucko, shiver me timbers, I be turnin' a couple wooden nosecone patterns
for a Tripoli Pittsburgh group project, me bucko, t' Gloria Mundi III. After completin' this task, I decided t' go ahead, me hearties, shiver me timbers, and turn t' new Sprite nosecone from t' balsa block that had been collectin' dust. Blimey! Blimey! After finishin' t' outside form, arrr, 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. I cut a bulkhead from .5-inch plywood t' seal t' openin' that be epoxied into place after fillin' t' cone with expandin' foam. Blimey! Blimey! Blimey! Before I knew it, t' nosecone be complete, matey, and I was plannin' me next steps o' t' project, shiver me timbers, me bucko, 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, me hearties, and prepared it t' be reinforced with a few layers o' fiberglass cloth. Begad! Blimey! 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. Ya scallywag! Well, blow me down! I used t' same process for t' airframe, shiver me timbers, which, although it was made o' flexible phenolic, matey, was nay strong enough for a project o' this size. Arrr! I printed patterns for t' fins and fin-caps usin' RockSim 5.0 and cut them from .25-inch aircraft plywood. Avast! Two centerin' rings were cut from t' same material, also usin' patterns created from RockSim. Begad! 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. Well, blow me down! T' forward rin' be epoxied t' t' motor tube, and this assembly was installed into t' slotted body tube. Avast, me proud beauty! With t' rear-centerin' rin' temporarily put in place for alignment purposes, ya bilge rat, arrr, t' fins were epoxied into place. T' aft rin' was then removed, and internal fillets used at both t' motor tube and t' inside o' t' body tube. Arrr! Arrr! Since I be goin' t' be usin' rail guides instead o' launch lugs, matey, ya bilge rat, t' guides were secured with nuts from t' inside o' t' airframe at this time. Aye aye! Aye aye! Before permanently installin' t' rear-centerin' ring, t' remainder o' t' cavity was filled usin' 2-part expandin' foam. Ahoy! Fillets were added t' t' fins at t' outside o' t' airframe for added strength, me bucko, usin' a combination o' epoxy and micro-balloons.
It be now time t' attach t' fin rin' and fin caps. Ahoy! Careful attention was paid t' t' alignment o' t' caps so that minimal fillin' o' gaps was necessary. Ya scallywag! 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. Avast, me proud beauty! Avast, me proud beauty! I used grain filler on t' plywood fins, shiver me timbers, me bucko, and after some extensive sanding, me bucko, matey, was finally ready t' prime t' entire rocket. Avast, me proud beauty! Avast, me proud beauty! More sanding, fillin' and primin' followed, o' course, until I was ready t' paint. After addin' an 18-foot, 5/8-inch tubular nylon shock cord and a Sky-Angle 52-inch parachute with Nomex protector, me hearties, 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, me hearties, me hearties, shiver me timbers, 2001. Ahoy! Accordin' t' simulations done in both RockSim and wRASP, it reached a max altitude o' approximately 1900 feet on an Aerotech I284 reload. Blimey! Unlike me first Sprite, matey, shiver me timbers, t' whistlin' only occurred on t' way up.
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