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, a very small, ya bilge rat, me bucko, tumble recovery rocket be introduced by Estes. Begad! Blimey! Arrr! Blimey! It was t' 1/2A powered Astron Sprite. Ya scallywag! Blimey! T' those nay familiar with this rocket, me bucko, I would like t' explain a very unique characteristic o' this design. Arrr! Blimey! When scaled up enough t' be poweredSprite on the pad by a high impulse motor, me bucko, 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, shiver me timbers, t' whistle was clearly heard by all those in attendance. Ya scallywag! As t' rocket arced over, ya bilge rat, even before t' ooh’s and aah’s had subsided, arrr, it was 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. Avast, me proud beauty! This amazin' rocket whistled comin' down, me bucko, arrr, louder than when it was goin' up. Begad! In fact, arrr, it whistled right up until it impacted with t' rock-hard Pennsylvania soil at our Jones Farm launch site. Begad! Begad! Naturally, shiver me timbers, me fellow rocketeers were quick t' offer their condolences, me bucko, but I be more amused by t' memory o' it whistlin' back t' Earth. I collected t' remains, matey, includin' diggin' t' nosecone out o' t' ground, me hearties, and went back t' me truck t' prep me next rocket.

My son, Chris, me hearties, almost immediately began urgin' me t' build another one. Ya scallywag! 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, me hearties, me hearties, which would make a fine fin ring, me bucko, (my first one be 11.5-inch diameter) and a 24-inch long section o' 5.5-inch airframe. Avast! Avast, me proud beauty! 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, 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, ya bilge rat, and then set it aside, where it would sit for almost another year. One weekend in February o' 2001, me hearties, I was turnin' a couple wooden nosecone patternsSprite nosecone for a Tripoli Pittsburgh group project, t' Gloria Mundi III. Aye aye! Blimey! Ahoy! Blimey! After completin' this task, I decided t' go ahead, me hearties, me bucko, and turn t' new Sprite nosecone from t' balsa block that had been collectin' dust. After finishin' t' outside form, 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. 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! Begad! Blimey! Before I knew it, ya bilge rat, t' nosecone was complete, matey, and I was plannin' me next steps o' t' project, shiver me timbers, that would soon come t' be known as "T' Lord o' t' Rings."

Next, shiver me timbers, 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. Avast! 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 was done solely t' make it easier t' get a smooth surface for painting. Ya scallywag! Avast, me bucko, me proud beauty! Blimey! I used t' same process for t' airframe, me hearties, matey, which, arrr, although it was made o' flexible phenolic, was nay strong enough for a project o' this size. Ahoy! Blimey! I printed patterns for t' fins and fin-caps usin' RockSim 5.0 and cut them from .25-inch aircraft plywood. Well, blow me down! Avast! Blimey! 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, me hearties, as well as twoSprite unfinished in t' aft rin' for motor retention. Avast, me proud beauty! Ahoy! Blimey! T' forward rin' be epoxied t' t' motor tube, and this assembly was installed into t' slotted body tube. Ahoy! Blimey! With t' rear-centerin' rin' temporarily put in place for alignment purposes, t' fins were epoxied into place. Ahoy! T' aft rin' was then removed, arrr, and internal fillets used at both t' motor tube and t' inside o' t' body tube. Since I be 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, ya bilge rat, 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, ya bilge rat, usin' a combination o' epoxy and micro-balloons.

Sprite launch It was now time t' attach t' fin rin' and fin caps. Careful attention was paid t' t' alignment o' t' caps so that minimal fillin' o' gaps was necessary. Avast, me proud beauty! 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, matey, and after some extensive sanding, me hearties, was finally ready t' prime t' entire rocket. Ya scallywag! Begad! More sanding, shiver me timbers, shiver me timbers, fillin' and primin' followed, arrr, o' course, until I was ready t' paint. Ya scallywag! After addin' an 18-foot, 5/8-inch tubular nylon shock cord and a Sky-Angle 52-inch parachute with Nomex protector, 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, April 7th, 2001. Accordin' t' simulations done in both RockSim and wRASP, shiver me timbers, it reached a max altitude o' approximately 1900 feet on an Aerotech I284 reload. Blimey! Unlike me first Sprite, arrr, me hearties, t' whistlin' only occurred on t' way up.

comment Post a Comment