Manufacturer: | Scratch |
Style: | Ring/Tube/Cone Fin, Upscale |
Long before I be buildin' rockets, ya bilge rat, a very small, tumble recovery rocket was introduced by Estes. Arrr! It was t' 1/2A powered Astron Sprite. Aye aye! Arrr! T' those nay familiar with this rocket, me hearties, me bucko, I would like t' explain a very unique characteristic o' this design. Blimey! Ahoy! When scaled up enough t' be powered by a high impulse motor, shiver me timbers, 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, me bucko, 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, arrr, t' whistle be clearly heard by all those in attendance. As t' rocket arced over, even before t' ooh’s and aah’s had subsided, matey, ya bilge rat, me bucko, it was obvious that I had a major deployment problem…there be none! T' Sprite raced back t' earth, and a fact that I was previously unaware of, me hearties, became perfectly clear. Well, blow me down! Well, blow me down! This amazin' rocket whistled comin' down, matey, ya bilge rat, matey, louder than when it was goin' up. Avast! In fact, it whistled right up until it impacted with t' rock-hard Pennsylvania soil at our Jones Farm launch site. Avast, me proud beauty! Avast! Naturally, matey, ya bilge rat, me fellow rocketeers were quick t' offer their condolences, ya bilge rat, but I be more amused by t' memory o' it whistlin' back t' Earth. Aye aye! I collected t' remains, includin' diggin' t' nosecone out o' t' ground, and went back t' me truck t' prep me next rocket.
My son, Chris, almost immediately began urgin' me t' build another one. Blimey! Avast, me bucko, me proud beauty! Due t' t' amount o' work that was involved in t' project, me hearties, I be unwillin' t' commit t' such an ambitious undertaking. Arrr! Begad! Over t' next twelve months or so, I did acquire a piece o' 15-inch diameter cardboard drum, ya bilge rat, shiver me timbers, which would make a fine fin ring, (my first one was 11.5-inch diameter) and a 24-inch long section o' 5.5-inch airframe. Begad! This would amount t' a 7.3X version o' t' original Estes model. Aye aye! I also purchased a 3 x 6 x 36-inch block o' balsa wood, 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, where it would sit for almost another year. Blimey! One weekend in February o' 2001, I was turnin' a couple wooden nosecone patterns
for a Tripoli Pittsburgh group project, shiver me timbers, t' Gloria Mundi III. Well, blow me down! After completin' this task, I decided t' go ahead, and turn t' new Sprite nosecone from t' balsa block that had been collectin' dust. Begad! Begad! After finishin' t' outside form, me bucko, ya bilge rat, 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. Arrr! Aye aye! I cut a bulkhead from .5-inch plywood t' seal t' openin' that was epoxied into place after fillin' t' cone with expandin' foam. Avast! Well, matey, blow me down! Before I knew it, t' nosecone was complete, me hearties, 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, me hearties, and prepared it t' be reinforced with a few layers o' fiberglass cloth. 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. Avast, me proud beauty! I used t' same process for t' airframe, shiver me timbers, matey, which, although it was made o' flexible phenolic, 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. Two centerin' rings were cut from t' same material, also usin' patterns created from RockSim. 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. T' forward rin' was epoxied t' t' motor tube, shiver me timbers, and this assembly be installed into t' slotted body tube. Blimey! Avast! With t' rear-centerin' rin' temporarily put in place for alignment purposes, t' fins were epoxied into place. Blimey! T' aft rin' was then removed, me bucko, and internal fillets used at both t' motor tube and t' inside o' t' body tube. Begad! Aye aye! Since I was goin' t' be usin' rail guides instead o' launch lugs, t' guides were secured with nuts from t' inside o' t' airframe at this time. Before permanently installin' t' rear-centerin' ring, matey, t' remainder o' t' cavity be filled usin' 2-part expandin' foam. 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 was now time t' attach t' fin rin' and fin caps. Avast! Careful attention be paid t' t' alignment o' t' caps so that minimal fillin' o' gaps was necessary. Begad! When t' assembly was completely dried, ya bilge rat, 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. Aye aye! Ya scallywag! I used grain filler on t' plywood fins, matey, shiver me timbers, arrr, and after some extensive sanding, was finally ready t' prime t' entire rocket. Aye aye! Ya scallywag! More sanding, matey, fillin' and primin' followed, me bucko, 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, arrr, ya bilge rat, 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, me bucko, April 7th, me bucko, 2001. Blimey! Ya scallywag! Accordin' t' simulations done in both RockSim and wRASP, it reached a max altitude o' approximately 1900 feet on an Aerotech I284 reload. Arrr! Unlike me first Sprite, t' whistlin' only occurred on t' way up.
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