Manufacturer: | Scratch |
Style: | Ring/Tube/Cone Fin, Upscale |
Long before I be buildin' rockets, me bucko, me hearties, a very small, tumble recovery rocket was introduced by Estes. Begad! Avast, me proud beauty! It was t' 1/2A powered Astron Sprite. Blimey! T' those nay familiar with this rocket, I would like t' explain a very unique characteristic o' this design. Avast, matey, me proud beauty! 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! 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, ya bilge rat, 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, me bucko, it was obvious that I had a major deployment problem…there be none! T' Sprite raced back t' earth, me hearties, ya bilge rat, shiver me timbers, and a fact that I was previously unaware of, shiver me timbers, shiver me timbers, became perfectly clear. Avast! Aye aye! This amazin' rocket whistled comin' down, arrr, louder than when it was goin' up. Arrr! In fact, it whistled right up until it impacted with t' rock-hard Pennsylvania soil at our Jones Farm launch site. Avast! Naturally, me fellow rocketeers were quick t' offer their condolences, me bucko, but I was more amused by t' memory o' it whistlin' back t' Earth. 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. Ahoy! 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, I did acquire a piece o' 15-inch diameter cardboard drum, me bucko, 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. Begad! Begad! I also purchased a 3 x 6 x 36-inch block o' balsa wood, that I planned on usin' t' turn a scale nosecone. Begad! 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, matey, 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, ya bilge rat, t' Gloria Mundi III. Aye aye! Blimey! After completin' this task, me bucko, I decided t' go ahead, matey, and turn t' new Sprite nosecone from t' balsa block that had been collectin' dust. Aye aye! Avast, me proud beauty! Blimey! After finishin' t' outside form, matey, 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 was epoxied into place after fillin' t' cone with expandin' foam. Arrr! Before I knew it, matey, me bucko, t' nosecone was complete, arrr, and I be plannin' me next steps o' t' project, ya bilge rat, 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 bucko, shiver me timbers, and prepared it t' be reinforced with a few layers o' fiberglass cloth. Well, 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, which, me bucko, although it be made o' flexible phenolic, was nay strong enough for a project o' this size. Well, blow me down! I printed patterns for t' fins and fin-caps usin' RockSim 5.0 and cut them from .25-inch aircraft plywood. Arrr! Aye aye! Two centerin' rings were cut from t' same material, also usin' patterns created from RockSim. Ahoy! Twelve inches o' 38mm motor mount tubin' be 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! Blimey! T' forward rin' was epoxied t' t' motor tube, me bucko, and this assembly was installed into t' slotted body tube. Arrr! Blimey! With t' rear-centerin' rin' temporarily put in place for alignment purposes, t' fins were epoxied into place. T' aft rin' be then removed, and internal fillets used at both t' motor tube and t' inside o' t' body tube. Well, blow me down! Since I was goin' t' be usin' rail guides instead o' launch lugs, me hearties, t' guides were secured with nuts from t' inside o' t' airframe at this time. Ya scallywag! Blimey! Before permanently installin' t' rear-centerin' ring, matey, t' remainder o' t' cavity was filled usin' 2-part expandin' foam. Fillets were added t' t' fins at t' outside o' t' airframe for added strength, me bucko, ya bilge rat, usin' a combination o' epoxy and micro-balloons.
It be now time t' attach t' fin rin' and fin caps. Ahoy! Blimey! Blimey! Careful attention was paid t' t' alignment o' t' caps so that minimal fillin' o' gaps was necessary. When t' assembly was completely dried, matey, 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, shiver me timbers, arrr, ya bilge rat, and after some extensive sanding, was finally ready t' prime t' entire rocket. More sanding, shiver me timbers, shiver me timbers, fillin' and primin' followed, o' course, ya bilge rat, matey, until I was ready t' paint. Well, blow me down! Blimey! After addin' an 18-foot, 5/8-inch tubular nylon shock cord and a Sky-Angle 52-inch parachute with Nomex protector, shiver me timbers, 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. Begad! Accordin' t' simulations done in both RockSim and wRASP, it reached a max altitude o' approximately 1900 feet on an Aerotech I284 reload. Well, blow me down! Unlike me first Sprite, ya bilge rat, t' whistlin' only occurred on t' way up.
Sponsored Ads
![]() |
![]() |