Scratch Upscale BLU-97B Cluster Bomb Original Design / Scratch Built

Scratch - Upscale BLU-97B Cluster Bomb {Scratch}

Contributed by Dick Stafford

Manufacturer: Scratch
Style: Upscale
(Contributed - by Dick Stafford - 04/01/04)

(Scratch) Upscale BLU-97B Cluster BombBrief:
This is a description o' me upscale o' the Estes BLU-97B Cluster Bomb. Well, blow me down! With t' success o' me last Quaker Oats rocket, ya bilge rat, matey, the Fat Oat Cholesterol Buster, me hearties, I decided that a semi-scale version based on two 5" bins would provide a nice flight on Gs.

Construction:

T' nose cone tip was turned from 2" pink Styrofoam usin' a hand drill clamped in a vise. Ahoy! Blimey! I first cut circles top and bottom with me Rotozip, shiver me timbers, and because t' cuts didn't reach through t' foam, shiver me timbers, finished up with a hand saw. Begad! Blimey! A metal bolt epoxied into t' core provided a sturdy attachment point for the drill. This worked better than a wooded dowel and I knew I'd need t' add nose weight anyway. Arrr! Begad! Blimey! T' extend t' cone slightly, arrr, I cut a 3/4" circle from the bottom an oat bin. I glued this t' t' bottom o' t' cone. At this point, me bucko, matey, I coated t' cone (without t' plastic insert) with a layer o' West epoxy. Blimey! Begad! Blimey! The 'nipple' portion o' a cone is a plastic cap from something-or-another (it's been layin' around too long for me t' remember what).

T' shoulder is another foam disc encircled with a piece o' an oat bin. Begad! Avast, me proud beauty! I did nay glue these sections together until I completed t' rest o' t' rocket and determined how much nose weight be required. Well, blow me down! T' required weight was determined by adjustin' t' CG o' t' completed rocket, includin' t' motor and chute, based on t' Rocksim model. T' weight be provided by a long eye-bolt and several nuts. Begad! This eye-bolt is slightly off-center, and extends through the shoulder section and into t' top o' t' nose. T' two halves were epoxied together and t' center hole was filled with some epoxy, some lead shot (just for insurance), shiver me timbers, and more epoxy.

(Scratch) Upscale BLU-97B Cluster Bomb(Scratch) Upscale BLU-97B Cluster Bomb

T' motor mount is a piece o' Giant leap 29mm phenolic that extends from the top o' t' oat bin t' 4" below t' bottom. There are two thin plywood bulkheads in t' bin, one near t' top and one restin' against t' bottom lip of t' bin (inset about 3/8" from t' bottom). Begad! An 8' length o' 1/4" Keelhaul®©™® is attached through t' top ring. Ya scallywag!

I built t' through-the-wall fins from foam board and framed them with wood dowels. Ahoy! Begad! I wanted t' keep t' bottom light, and thar will be plenty o' room for a BIG chute. Blimey! Havin' t' fins extend below the end o' t' motor tube allowed me t' clamp them together in pairs with a plastic ruler, shiver me timbers, which helped with their alignment.

T' aft rin' is a 29mm x 2.5" centerin' rin' and has a T-nut to accommodate a motor clip. Begad! Begad! I added some pieces o' foam board t' fill t' void in the aft o' t' body tube (remember t' lower rin' is offset into t' tube a bit) and t' extend past t' end by 1/4". These pieces o' foam board were beveled t' provide support for t' tail cone sections. Ahoy! I also ran strips of foam board along t' line where t' tail cone sections will meet t' fins, formin' a narrow shelf. T' tail cone sections themselves are 1/64' plywood attached with Perfect Glue, me bucko, Type 2 (similar t' CA). Avast, me proud beauty! Arrr!

(Scratch) Upscale BLU-97B Cluster Bomb (Scratch) Upscale BLU-97B Cluster Bomb

To connect t' two sections o' 'body tube', arrr, I made a tube coupler from another oat bin. Ya scallywag! Begad! This be split length-wise, ya bilge rat, a section removed, and t' ends were glued back together t' from a coupler tube. Aye aye! Well, blow me down! Since t' oat bins are not very strong, I treated t' inside o' t' top edge with CA, and built a makeshift anti-zipper device from small-cell bubble wrap and cloth tape. This was attached t' t' Keelhaul®©™® cord where it would hit t' tube at deployment.

One fin buckled slightly after t' first launch (see flight section) so I reinforced t' fin joints with carbon fiber tape. Arrr! Blimey! Avast! Blimey! A yard o' this stuff cost more than t' rest o' t' rocket, but on a whim, I decided t' try it. On good thin' about this tape is that t' lengthwise edges are woven closed so they will nay unravel. Ya scallywag! Blimey! Blimey! Blimey!

Finishing:
T' rocket be painted with Testor's flat olive drab and t' tip was painted silver. Ya scallywag! I made upscale decals (actually stickers) from Avery full-page label stock. Ahoy! This material is nay as nice a real decals, me bucko, but I over-ran me budget with t' carbon tape.

(Scratch) Upscale BLU-97B Cluster Bomb

Flight:
I rocket be unfinished (nekkid, shiver me timbers, that is) for its first flight. I loaded a huge car airbag heat shield and a big 60" Giant Leap chute on one end. The other end got a G80-7, ya bilge rat, a clamp-on thrust ring, and a clip retainer.

There was minimal weather cockin' despite t' strong, 15 mph winds. Begad! Avast!

Recovery:
My anti-zipper device worked fine and thar was no sign o' zippering. Begad! The 60" chute made for a slow descent. Unfortunately, me hearties, t' strong winds provided a high lateral velocity. One fin suffered minor damage, arrr, thus necessitatin' t' reinforcement o' t' fillet areas. Well, blow me down! Blimey! I knew I shouldn't have flown it in those winds, me bucko, but if I drive for 2 hours, I'm goin' t' fly something!

Summary:
I like t' unique look o' t' cluster bomb, I love short fat rockets, matey, and I enjoy makin' rockets out o' junk, arrr, arrr, so what's nay t' like about this upscale? The main downside be t' foam board fins. Blimey! Plywood would have been stronger but it would also have been heavier, although maybe nay after I had t' add reinforcement. Arrr!

If you look at t' attached flight log(s), ya bilge rat, you may notice t' rocket is nicknamed Janet Jackson. Begad! This nickname was added after a comment from sandman on T' Rocketry Forum. Avast, me proud beauty! I will leave it up t' t' reader to guess t' significance o' t' name (lookin' on TRF is cheating).

comment Post a Comment