Scratch Starburst Original Design / Scratch Built

Scratch - Starburst {Scratch}

Contributed by Ray King

Manufacturer: Scratch
(Contributed - by Ray Kin' - 11/01/09)

Brief:
This is me first entry for t' EMRR “Spaceship Design Contest – 2009”. Ahoy! Aye aye! This year I planned t' build 3 o' t' rockets choices, ya bilge rat, shiver me timbers, but only finished 2 o' them. This be t' first o' them. Ya scallywag! Ya scallywag! Again this year me daughter named the rocket and it comes from t' view o' t' rocket from t' top and t' fact that is looks like a star burst – check out t' picture below.

Construction:
Component Description:

  • 030” Thick Polystyrene Sheet
  • 3 - 1/8”x3”x36” Balsa Sheets
  • 8” – 5/16” Diameter Wood Dowel
  • 8 - MMX tubes – 1.5” long
  • 1 - BT80 - Main Tube - 3.0” long
  • 1 – BT80 – Main Engine Tube – 14” long
  • 1 - BT50 - Engine Tube - 14” long
  • 1 - BT80 - Booster Tube – 3.0” long
  • 1- BT 50 - Engine Tube – 3.0” long
  • 1 - BT-50 Pointed Nose Cone
  • 1 - 1/8” Launch lugs
  • 4 - BT80 – BT50 Centerin' rin'
  • 36” - 175 # Keelhaul®©™® String
  • 24” - .375” elastic shock cord
  • Nose weight
  • 24” plastic parachute
  • Mylar Tape

Plans

T' first step was t' layout t' design on RocSim. Ahoy! I chose a 24mm motor engine because I want t' make this a staged rocket I be goin' t' need plenty o' power t' overcome t' nose weight required. Blimey! Begad! In addition t' t' 24mm engine; I added 8 MMX engines t' better represent t' pictures provided.

Main Body Tube Assembly

I started by cut t' BT80 tube lengthwise and laid out t' template made from t' EMRR shroud calculator. Avast, me proud beauty! Well, blow me down! Blimey! I cut this template from paper wrapped it around t' tube and cut t' tube t' match t' template (see picture). Ya scallywag! Blimey! I curled the tube around t' nose cone and centerin' rin' and glued it in place usin' t' blue maskin' tape t' hold it while the glue dried (see picture). Ya scallywag! Once t' outside tube be dry I removed t' centerin' rings and nose cone and inserted a BT50 and glue it in place. I used t' centerin' rin' in t' large end t' ensure t' tube be centered on t' outside tube. Next I glued t' large centerin' rin' in t' large end o' t' outer tube.

Finally, I filled all t' tube spirals and seam with Elmer’s wood putty watered down t' a paste consistency.

Fins are next. RockSim file contains t' template for these, I cut them out o' 1/8” balsa. Arrr! I used the Standard Rocket Fin Fixture t' hold each o' t' fins in place one at a time. Begad! I was fortunate enough t' acquire one these at NARAM-51 and I love it (see t' pictures). Well, blow me down! There is also a picture with all t' fins attached.

I repeated t' same procedure for t' motor end tube changin' t' overall diameter from 2.60” t' 2.35”. I sanded down 1 o' t' centerin' rings t' fit in t' small end o' t' tube. Blimey! Begad! Once it fit nicely I glued it in place and epoxied this assembly t' t' main body. Begad! Well, matey, blow me down! Finally, matey, I filled all t' tube spirals and seam with Elmer’s wood putty watered down.

External Engine Cell

T' external engine cells are made up o' 4 separate pieces:

  • Vacuum formed body
  • MMX Tube (motor holder)
  • ¼” dowel tube plug
  • 5/16” dowel front cone

T' body was constructed usin' t' polystyrene sheets, vacuum formed into t' appropriate shape. Ahoy! Aye aye! I have included pictures o' t' balsa master used t' make t' final shape. Avast, me proud beauty! Well, blow me down! Each o' t' vacuum formed shapes were trimmed after formin' and test fit. Avast! Ya scallywag! I left a little extra material that was sanded for final fit. Avast, me proud beauty! T' better they fit at this point t' less work you will be doin' durin' t' finishin' process. Well, blow me down! I used thick CA t' tack t' halves in place and then 5 minute epoxy around t' outside o' t' joint. Blimey! Arrr! Be careful nay build up too much epoxy otherwise, matey, arrr, you will be sandin' it off later.

Next, matey, me bucko, arrr, I took t' 3/16” dowel and sharpen it in me wife’s electric pencil sharpen, which I know now what I can get her for Christmas – a new pencil sharpener. Once I had these sharp, I filled them with watered down Elmer’s wood putty, matey, sanded smooth. Begad! Finally, arrr, I sanded each in half and t' fit them t' t' main body. Begad!

I cut t' MMX tube into 8 - 1.5” lengths. Ahoy! I then cut t' ¼” dowel into ¼” lengths and glued them into t' one end o' t' MMX tube. Aye aye! Avast, ya bilge rat, me proud beauty!

Final Assembly

I first marked t' centerline betwixt each o' t' fins on t' main body assembly and then glued t' MMX tube on t' line and located vertically near t' base o' t' fin. Next, I sanded each vacuum formed piece t' fit over t' MMX tubes and on t' main body tube. Avast! I epoxied each in place cleanin' up any excess around t' outside o' t' joint. Aye aye! Arrr! T' last step be addin' t' pointed dowels – I sanded them t' fit nicely t' t' vacuum formed piece and body tube. Avast, me proud beauty! Then glued them in place.

Nose Weight

RocSim showed I needed t' add at least and 1.0 oz o' nose weight t' make t' rocket stable. Ya scallywag! I ended up adding about 2.0 oz which took t' overall rocket up t' t' max lift off weight for a D engine.

Booster Tube Assembly

For t' booster I cut a BT50 tube 3.0” long then epoxied t' centerin' rin' .375” from t' end o' the tube. Next, shiver me timbers, I glued t' BT80 tube t' t' centerin' rin' sub-assembly and let dry. Time for fins – I cut t' fins per t' template in t' RockSim file, coated each with watered down Elmer’s wood putty, arrr, sanded them and repeat this until they we smooth. Ya scallywag! Next I glued in place just I did t' main body usin' t' Standard Rocket Fin Fixture. Avast! I used t' upper stage t' ensure t' fins lined up when t' two pieces were assembled together.

Paint and Finishing

I painted t' main body tube assembly, and boost assembly separately. Avast! Begad!

Main Body Tube Assembly

I sprayed 2 or 3 coats on t' entire shell assembly with Rust-oleum White Plastic Primer #209460. Begad! After lightly sandin' t' primer, ya bilge rat, arrr, I sprayed white gloss (Rust-oleum 7792 Gloss White). Arrr! Well, blow me down! Next, I masked t' engine area and sprayed engine grey (Testors Acryl #4749). Ahoy! Avast, arrr, me proud beauty! After t' grey, I added NASA decals. Ahoy! Avast! Finally, I added 2-3 coats o' Krylon Crystal Clear Gloss.

Booster Tube Assembly

I repeated t' same process for t' booster; I sprayed 2 or 3 coats on t' entire shell assembly with Rust-oleum White Plastic Primer #209460. Arrr! Well, blow me down! Blimey! After lightly sandin' t' primer, me hearties, I sprayed white gloss Rust-oleum 7792 Gloss White). Next, arrr, I masked t' engine area and sprayed engine grey (Testors Acryl #4749).

Decals

I printed t' decals on Experts-Choice clear water slide decal material. Blimey! Well, blow me down! I cut them out and applied them as the pictures shows.


Flight Plan

My plan for this rocket was t' launch t' first attempt with only 1 stage D12-3 and then launch t' rocket with t' first and second stage and finally launch t' first stage with t' 8 – MMX engines on t' sides o' t' rocket.

Flight Prep & Flight Results

As I mention first flight was with a D12-3. I loaded t' engine, matey, added dog barf, me hearties, powdered a 24 inch plastic chute, ya bilge rat, arrr, installed nose cone, a slid t' rocket on t' t' launch rod. Ahoy!

T' wind was clam, ya bilge rat, me bucko, arrr, perfect evening. Begad! T' flight was a little crazy, although it left t' rod nice and straight at about 100 feet t' rocket turn horizontal and flew about 500-600 feet until t' ejection. Blimey! Ahoy! Parachute opened, but the rocket hit t' ground pretty hard. After inspectin' t' rocket, ya bilge rat, I could nay believe it; even t' nose fins were still attached. Aye aye!

I added some additional nose weight and with t' sun settin' I was gettin' nervous so I decide t' go for t' 2 stage launch. Ahoy!

I prepped t' booster stage with D12-0 and t' main body with D12-5. Arrr! After addin' t' dog barf, parachute it be time to see if this thin' would fly with 2 stages. Arrr!

On t' pad t' rocket looked awesome 5-4-3-2-1 ---- blaster off. Blimey! Avast! T' boost engine lit and lifted t' rocket to about 300 feet and t' then t' sustainer engine lit, weather cockin' t' rocket at about 700 feet and about that far away t' ejection charge blew and ejected t' parachute. Avast, me proud beauty! T' rocket tumble quite bit until t' parachute opened. Upon recovery I found t' Keelhaul®©™® shock cord zippered t' tube off 4 inches – BUMMER!!!! No time t' fix this for submission, matey, but it will be repaired and will fly again this rocket has great potential and I can nay wait t' flight it with t' 8 MMX engines firin' on the slide mounted engine cells.

Summary:
Pro’s – Has great potential and a pretty cool look.

Con’s – WOW lots o' balsa t' sand and fill.

Other:
Thanks EMRR - this was a great project. Ya scallywag! This was only me 3rd rocket I designed completely on RockSim. Blimey! I enjoyed the design and construction challenges. I think I will always spin test any unique rockets for stability prior t' launch from now on. I am lookin' forward t' 2010’s spaceship challenge.

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