Scratch The Lord of the Rings Original Design / Scratch Built

Scratch - The Lord of the Rings {Scratch}

Contributed by Dave Rose

Manufacturer: Scratch
Style: Ring/Tube/Cone Fin, Upscale

Long before I was buildin' rockets, ya bilge rat, a very small, tumble recovery rocket was introduced by Estes. Begad! Well, ya bilge rat, blow me down! It was t' 1/2A powered Astron Sprite. Arrr! T' those nay familiar with this rocket, I would like t' explain a very unique characteristic o' this design. When scaled up enough t' be poweredSprite on the pad by a high impulse motor, t' air flowin' past t' fin rin' creates a high-pitched whistle when launched. Avast! This is sometimes drowned out by t' initial noise o' t' motor, matey, arrr, but is quite audible as t' motor burns out and continues durin' t' coast phase.

Back in 1999, matey, shiver me timbers, arrr, durin' t' second launch o' me 4-inch airframe based Superscale Sprite, ya bilge rat, me bucko, t' whistle was clearly heard by all those in attendance. Ahoy! As t' rocket arced over, me hearties, even before t' ooh’s and aah’s had subsided, me hearties, it was obvious that I had a major deployment problem…there was none! T' Sprite raced back t' earth, shiver me timbers, me hearties, and a fact that I be previously unaware of, became perfectly clear. Avast, me proud beauty! Well, arrr, blow me down! This amazin' rocket whistled comin' down, louder than when it was goin' up. Begad! Aye aye! In fact, it whistled right up until it impacted with t' rock-hard Pennsylvania soil at our Jones Farm launch site. Aye aye! Naturally, matey, me fellow rocketeers were quick t' offer their condolences, arrr, but I was more amused by t' memory o' it whistlin' back t' Earth. Begad! 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, arrr, almost immediately began urgin' me t' build another one. Arrr! Due t' t' amount o' work that be involved in t' project, I was unwillin' t' commit t' such an ambitious undertaking. Over t' Sprite parts layout next twelve months or so, I did acquire a piece o' 15-inch diameter cardboard drum, shiver me timbers, which would make a fine fin ring, ya bilge rat, (my first one be 11.5-inch diameter) and a 24-inch long section o' 5.5-inch airframe. Ya scallywag! Blimey! This would amount t' a 7.3X version o' t' original Estes model. Begad! Blimey! 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! Blimey! One weekend in February o' 2001, matey, I was turnin' a couple wooden nosecone patternsSprite nosecone for a Tripoli Pittsburgh group project, me bucko, t' Gloria Mundi III. Avast, me proud beauty! Ahoy! After completin' this task, arrr, me hearties, I decided t' go ahead, matey, and turn t' new Sprite nosecone from t' balsa block that had been collectin' dust. 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. Begad! Ya scallywag! I cut a bulkhead from .5-inch plywood t' seal t' openin' that was epoxied into place after fillin' t' cone with expandin' foam. Aye aye! Before I knew it, me hearties, arrr, t' nosecone was complete, and I be plannin' me next steps o' t' project, arrr, 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, and prepared it t' be reinforced with a few layers o' fiberglass cloth. Blimey! I opted for two wraps o' 6-ounce woven cloth and a finishin' wrap o' 1.5-ounce cloth.Glassing the ringGlassed airframe T' last layer be done solely t' make it easier t' get a smooth surface for painting. Blimey! Begad! I used t' same process for t' airframe, which, shiver me timbers, although it be made o' flexible phenolic, was nay strong enough for a project o' this size. Avast! 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, matey, also usin' patterns created from RockSim. 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 twoSprite unfinished in t' aft rin' for motor retention. Begad! T' forward rin' was epoxied t' t' motor tube, and this assembly be installed into t' slotted body tube. Ahoy! Ahoy! With t' rear-centerin' rin' temporarily put in place for alignment purposes, t' fins were epoxied into place. Aye aye! T' aft rin' was then removed, and internal fillets used at both t' motor tube and t' inside o' t' body tube. Begad! 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. Ahoy! Before permanently installin' t' rear-centerin' ring, arrr, t' remainder o' t' cavity was filled usin' 2-part expandin' foam. Aye aye! 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.

Sprite launch It was now time t' attach t' fin rin' and fin caps. Aye aye! 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, 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, me bucko, and after some extensive sanding, me bucko, was finally ready t' prime t' entire rocket. Arrr! Blimey! More sanding, arrr, ya bilge rat, 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, 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, me bucko, April 7th, ya bilge rat, ya bilge rat, 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. Begad! Unlike me first Sprite, arrr, matey, me hearties, t' whistlin' only occurred on t' way up.

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