Scratch Jupiter II Original Design / Scratch Built

Scratch - Jupiter II {Scratch}

Contributed by Glenn Roth

Manufacturer: Scratch
(Contributed - by Glenn Roth - 03/21/09)

Brief:
11 "Finned" rocket that can be launched on a single "E" or staged (D12-0, arrr, matey, D12-3) with a parachute recovery.

Prototype:
I built a protoype o' me choice o' rockets for t' EMRR "Rockets o' t' Future." I choose t' t' do an 18mm version first. Begad! I gathered some cardboard, me hearties, ya bilge rat, posterboard, arrr, and second hand parts, ya bilge rat, etc. Avast, me proud beauty! Ahoy! It would have been ten times harder without t' EMRR "Calculators", for shrouds, ya bilge rat, shiver me timbers, etc. Avast, me proud beauty! I chose cardboard figuring, "If I can get this t' fly without a cad program, from t' heaviest material, I surely will be able t' build one in t' 24 MM scale. Ya scallywag! Also, cardboard a little easier t' work with than "foamboard."

My 1st test flight be a disaster. (Remember, I have no software t' determine where t' CP & CG Is and if it will fly.) After givin' it some thought, me bucko, cut open nosecone and added some clay t' move CG forward. Blimey! Blimey! Last Saturday flew it again and success! Blimey! It only went 50 ft up but successfully deployed chute right before landing. Ya scallywag! Arrr! Blimey!

Prototype Prototype 2

What I've learned is,"use t' material in your prototype, that u intend t' use on your final version." Mine did fly but, would have saved a lot o' aggravation and speeded up t' build. Well, blow me down! Blimey! Also, ya bilge rat, matey, Highly recommended buildin' a prototype, especially in me case. Arrr! Blimey! Begad! Blimey! My submission for t' "rocket o' t' future" has 12 fins! Blimey! Never came close t' design such a complex rocket before. Ahoy! Blimey!

Construction:

PARTS LIST:

  • 24mm engine block
  • 1 engine hooks
  • 1 sheet o' foam board, 20x30x1/4"
  • 2 sheets o' poster board, 20x30"
  • 1 (priority mailin' box)
  • 2 BT-55's (15" long)
  • 1 BT-55 coupler
  • 18"x24mm Body tube for "engine Mounts"
  • Shock cord; ¼"x 24+"
  • 3, 4"x"36"x1/8 balsa sheets/basswood
  • 1 "quest" egglofter nosecone
  • 1 (18") parachute, matey, arrr, & shroud line
  • "non-hardening" clay
  • (8) bic pen caps t' "simulate 8 motors"
  • 2 spent "D" engines
  • Templates (will be loaded shortly)

Just wanted t' interject for a moment. Hope you find this rocket as much o' a challenge t' build as I found to design it, without t' help o' any "Cad software." If anyone cares t' "plug" these measurements into a cad program, I would be very curious as t' t' result. Well, blow me down! I did use EMRR "Calculators" for t' shrouds and centerin' rings. Begad! Begad! I thank Nick for makin' available because without them, matey, me hearties, couldn't have made this design. Well, blow me down! Well, me hearties, blow me down!

This design is for "Personal use only" and nay for resale, with express permission o' myself, Glenn Roth.

I stated in "parts" section that t' balsa is very fragile. Just discovered Tech Report # 29, from www.apogeerockets.com; "Take your rocket t' Supersonic Speeds. Ahoy! " This is a compromise t' replacin' entire fin with basswood or ply. Ahoy! You can download this free report and make these large fins MUCH STRONGER! I tried this on 3 of me fins and they are NOTICEABLY stronger.

ASSEMBLY:

Read thru all instructions before proceeding. Avast, me proud beauty! Blimey! Blimey! Blimey! Options exist. Ya scallywag! Blimey! Blimey! Blimey! Blimey! Blimey!

**Not happy with way main "body shroud" turned out. This "posterboard" is hard t' keep smooth without "kinking." You might want t' A) shorten t' about half t' length; b) wrap it around a smooth form of some kind while gluing, shiver me timbers, t' keep smooth.**

  1. Gather parts, matey, shiver me timbers, make templates, shiver me timbers, ya bilge rat, ya bilge rat, and gather followin' tools: sharp razor knife, metal ruler, arrr, me bucko, scissors, carpenters square, arrr, 2 "spent D" engines, shiver me timbers, ya bilge rat, adhesive spray, (worn out windshield wiper. Well, blow me down! Blimey! For engine hooks)., protractor, and compass. Blimey! Blimey! Avast, me proud beauty! Blimey!
  2. Cut two engine mounts from 24mm body tube. Avast, me proud beauty! Main 2 " long and "booster" 3 1/2" long.*****note: Now that t' rocket is half done, t' shroud looks too short. Well, blow me down! Avast, me proud beauty! I have increased length from 3 t' 3 ½ inches or longer, in instructions. Well, blow me down! Begad! You'll have increase length o' shroud accordingly.****
    • *** OPTION: I've since elected t' use a "friction fit", instead o' an engine hook, me bucko, matey, on main motor. Avast, me proud beauty! I'm sure you can use one but, ya bilge rat, ya bilge rat, have t' "dry fit" b 4 assembly.*** I've discovered that with t' aft "body panels", extendin' an inch, it's very difficult t' use an engine hook. Begad! I've since elected t' slip "main motor" into booster engine mount, and tape. Aye aye! T' tape will require a "slit" into it, so makes easy separation. Avast!
  3. Glue 24mm engine block into end o' engine tube w/engine hook stickin' into it.
    • Option*** This designed as a "two stage". Avast, me proud beauty! If you want an easier conversion t' single stage, matey, me hearties, you may want t' insert "booster engine tube" in a section o' BT-55. Ahoy! Avast! Then usin' a BT-55 coupler, matey, fasten t' engine tubes together. Arrr! Ya scallywag! (skip 1st /main engine tube.) It is much easier buildin' booster shroud separately. Ahoy!

Main Engine Tube

  1. Glue t' BT55 centerin' rings on main engine tube. Blimey! Avast! Let dry. Ya scallywag! Avast, ya bilge rat, me proud beauty!
  2. You'll want t' "dry fit" main engine mount and make sure "spent engine" recessed inside BT55 about ¼". Well, blow me down! Begad!
  3. Mark Bt55 where "engine Hook" will be, me hearties, and cut a slot 1/8" x3/8".
  4. Glue main engine mount with engine hook lined up with slot in BT55.

Booster Engine Mount

  1. Take 3" piece o' 24mm BT; then cut 1/8"x 3/8" slot in one end. Blimey!
  2. Lay "flat" side o' hook inline with slot and tape. Avast, me proud beauty! Arrr! *** I used a long piece o' old wiper blade for hook and cut t' length later.
  3. Cut out 3 "rear shroud centerin' rings. ***Tip: when I cut out middle o' rings FIRST, arrr, ya bilge rat, I then took a spent engine and inserted and twisted t' check for a tight fit. Ya scallywag! Then inserted engine in tube for support. Ahoy!
  4. Take largest aft rin' and glue over aft engine mount WITHOUT coverin' slot in t' mount. Be careful nay t' get glue on motor!!
  5. Glue middle and end centerin' rings and remove spent motor and let dry.
  6. While drying, me hearties, ya bilge rat, cut out aft shroud. Ya scallywag! Arrr! (You will see I include pattern, showin' a "saw tooth design" on inside radius o' shroud. Aye aye! Ahoy! Cut design in shroud. Aye aye! Blimey! Much easier t' glue.)
  7. Shape shroud, tape together on inside. Avast, me proud beauty!
  8. Fold "teeth" over t' inside and make a sharp crease. Arrr! Straighten out.
  9. After center rings on engine tube have dried, shiver me timbers, arrr, me hearties, take some glue and apply t' edges o' rings. Arrr!
  10. Take shroud and slip over engine assembly. Aye aye! Be sure t' get completely in. Ya scallywag!
  11. Spread some glue on smallest centerin' rin' and fold shroud "teeth" down, holdin' till set. Well, blow me down! Begad! You may only be able t' do a few @ a time. Blimey! Let dry Thoroughly.
  12. Put a spent engine in "Main and aft " engine mounts. Blimey!
  13. Slide together, me bucko, linin' up "slots" in engine tubes. T' aft engine tube should slide over t' Main engine about ½" and stay in place. ***Make sure aft Booster engine is as far forward as it will go WITHOUT disengagin' t' booster.
  14. Mark t' aft engine hook , cut and bend t' correct size.
  15. Cut shock cord mount and glue shock cord t' it. Ya scallywag! Avast! Blimey!
  16. Slide "loose" end o' shock cord thru a BT55 coupler.
  17. Glue Shock cord mount t' inside o' BT55 containin' engine mount far enough inside t' be able t' glue BT55 coupler. Aye aye! Glue Bt55 coupler and let dry. Well, blow me down!
  18. Cut other BT55 t' length so when t' two r put together , you have a rocket body 23" long, "without" aft shroud. Begad!
  19. Cut out Main Body centerin' rings. Avast, me proud beauty! Avast! (u can take spare piece o' BT55 t' check fit). Avast, me proud beauty! Ahoy!
  20. Take t' "fin template" and mark 3", me bucko, 3.5" rin' where it will engage each fin. Well, blow me down! Ya scallywag! Blimey! ****Note: you can mark 4" rin' but, because o' size, it won't line up with other two rings. Blimey! You will have t' do slots on this rin' once it is mounted. Begad! Ahoy! Blimey!
  21. Take care, me bucko, cut a ¼" deep slot x 1/8" wide into each ring. Aye aye!
  22. Mark 1st slot on each rin' with a #1 for reference. Ahoy!
  23. Make a fin from 1/8" "Basewood/plywood" as a guide t' check fit o' fins. Blimey! Begad! It will also b used t' as guide for slots, matey, and cut initial fin slots in 4" ring.
    • ***You may want t' fasten up aft shroud again w/spent motors t' check placement o' centerin' rings and fins.***

Fins and Body:

  1. Cut out 8 fins, and use sealer if desired. Well, blow me down!
  2. Use fine guide and cut slots in each fin: 1" from aft o' fin, 1x1/4 deep. Avast! Next one 7" from end.
  3. Last slot is 2.5 " from previous slot and only 5/8" deep. Aye aye!
  4. These r initial slots. Begad! Aye aye! Blimey! You may have t' widen for proper fit.
  5. Slide center rings on BT one @ a time. Ahoy! ***If seems tight or binds, increase size o' hole slightly. You can use a piece o' BT55 t' "shape" hole. Well, blow me down! (you want t' maintain a fairly tight fit).
  6. Space rings approximately same distance as slots on fin.
  7. "Orientate" all 3 rings with #1's lined up. Blimey!
  8. Take your "Guide Fin", arrr, ( t' one made from plywood), and check slot lineup for first fin. Avast, me proud beauty!
  9. You'll have t' cut slots deeper in each ring, ya bilge rat, me bucko, ya bilge rat, checkin' fit each time. Ya scallywag! Blimey! You may nay even need a slots for 4" ring, matey, me hearties, till ready t' glue on fins, due t' a "redesign", arrr, and linin' up o' fin with "center ring slots," I made for simplicity. Blimey! Blimey! (make recess higher, about 1 ¼"). Avast, me proud beauty! Blimey!
  10. After you get a good fit for t' fine on t' center rings, me hearties, take a "real" fin and glue in #1 slots of rings. (I kept breakin' balsa fins, shiver me timbers, that why I recommended goin' t' a sturdier material, ya bilge rat, ya bilge rat, such as basswood or Tims Tech report #29, arrr, gluin' "notebook paper" t' exterior o' fin first for strength). Avast!
  11. Take guide fin and check next set o' slot, ya bilge rat, arrr, adjustin' for correct fit.
  12. Then glue 3 center rings in place. Avast! Blimey!
  13. Glue all 8 fins in place, ya bilge rat, checkin' fit first with "guide fin". Avast, me proud beauty!
  14. Cut out two "body templates". Arrr! Make a slice at end o' each one ¼-3/4" deep, ya bilge rat, 1" from end on each side. Ya scallywag! Ya scallywag! Fold over @ slices and straighten out. Arrr! Arrr!
  15. Dependin' upon which set o' fins you start with, arrr, will determine what size template t' use, arrr, medium or large. Begad!
  16. Lay template betwixt fins, and gently push down. It should hang out rear, betwixt fins 1", arrr, up to "slices."
  17. Check front o' template and mark where template extends past fin.
  18. Cut on t' mark, me hearties, down t' ¼" fold mark on each side. Arrr! Cut a "saw tooth" pattern in sides of body templates. Begad! Makes for easier gluin' and smoothin' out. Ahoy! ***see photo"***
  19. Before gluin' fins, I made "fin supports," ½" x 1 ¼", and glue betwixt ends of fins. Aye aye! Blimey! Also, made a bevel on each end. Avast! Blimey! **See photo**
  20. Glue in place and repeat for each set o' fins. Well, blow me down! Ya scallywag! ***remember t' check fit! (Center on BT) too. T' aft o' body template should be about ½-3/4" above body and aft shroud. Avast! Avast, me proud beauty!
  21. Cut out "body templates," with "saw-tooth" design on edges and glue betwixt fins.
  22. Main Body Shroud: As I stated in beginning, matey, nay happy with t' way this one turned out. Avast! Avast! You may want t' shorten or find a different material or wrap around a "form" t' keep smooth. Avast! Also, arrr, use same "saw-tooth" design for edges before gluin' in shape o' cone. Once glue, let DRY THOROUGHLY. Ya scallywag!
  23. I fitted over main body tube t' fins. Begad! Avast, me proud beauty! I marked where touched fins and cut slits about 1" long, shiver me timbers, in shroud. Keep fittin' till you get a tight fit into slots, then glue and let dry thoroughly. Well, blow me down!
  24. Now comes a tricky part. Avast, me proud beauty! Seams that r formed betwixt "fins, body templates, main shroud have t' be "filled." I opted t' use "Elmers wood filler" and nay happy with result. Friend recommended these tiny silicone beads you mix w/epoxy. Avast, me proud beauty! Strong, light, and easy t' sand after hardened. Arrr!
  25. After seams dry, sand till smooth. Well, blow me down!

Nosecone Fins:

  1. Looking @ picture o' t' rocket I be copying, "upper fins" aren't really in nosecone but, matey, I liked this location better. Begad! (You can opt t' move out o' nosecone, down body a few inches in "same configuration.)
  2. Cut slits in nose cone ½" from end o' "open" nosecone, about 2" long and 3/16-1/4" wide. ** b careful nay t' cut all t' way thru t' end o' nosecone**. Aye aye! I mounted a piece o' 1" aluminum angle iron t' a piece o' wood and clamped t' me table as a guide. Avast!
  3. Fit fins in slots one @ a time, ya bilge rat, me bucko, trimmin' slots till fins fit. Remove fins and put a ball o' clay in tip of nosecone and press into place. Aye aye! Blimey!
  4. Replace fins 1 @ a time til they "touch" in middle o' nosecone and glue. Ya scallywag! (I opted for "gorilla glue" type). It foams up and becomes very strong). Let dry. Avast, me proud beauty! Aye aye!

Nose Cone:

  1. Keep addin' balls o' clay, me hearties, me bucko, matey, fillin' void in nosecone, and pressin' into place. Aye aye! ****remember t' allow room for end o' nose cone t' slide in.****
  2. Also, as you r fillin' void, assemble nosecone and check for CG with motors in main and booster BT's. Well, blow me down! Blimey! (goin' to take a few ounces o' clay t' fill and balance rocket so CG approx. Begad! in middle.)
  3. Once clay pressed into place and you r satisfied w/location o' CG, matey, assemble nosecone. Well, blow me down!

Finishing:

  1. FinishedGet 8 "regular" bic pen caps and cut off "pocket clip."
  2. Paint rocket color o' preference. Aye aye! Blimey!
  3. After you r sure you have color o' rocket and finished painting, arrr, sand a flat spot on each "pen cap," and glue in place betwixt each fin above booster shroud. Blimey! Ahoy! Blimey! (These pen caps simulate 8 motors o' rocket).
  4. Prep rocket and you r ready t' fly. Avast! Blimey!
  5. I would rate this build a 5++. Avast, me proud beauty! Very difficult. Begad!


Flight:

My first flight was very successful. Well, blow me down! Ya scallywag! I used a E9-4. Well, blow me down!

Preparation a little different than usual but, easy. Avast! Begad! After loadin' an 18" parachute, me bucko, dusted with baby powder, and t' wadding, I loaded t' engine. Ahoy! Arrr! I loaded it into t' booster from t' "inside." (T' E9 is a much longer motor than t' D.) Then I applied a little maskin' tape t' t' end for a "friction fit," and inserted it into main rocket body. It flew great! Relatively straight for t' design, arrr, 11 fins, arrr, me hearties, and t' weight. Arrr!

T' shock cord, attached t' rocket, was Keelhaul®©™. Arrr! Arrr! Then an elastic, tied t' t' Keelhaul®©™, which proved t' b t' weak. (will explain in next flight). Aye aye!

Parachute deployed perfectly and landed about 30 yards away. Avast!

SECOND FLIGHT

Another story. Avast, me proud beauty! I designed this rocket t' be an optional 2-stage. I prepped t' parachute t' same way. Then taped t' booster, a D12-0, t' t' main motor, me hearties, a D12-3, with scotch tape, and put a small slit in it, shiver me timbers, t' help with separation. Aye aye! Once motors finished, arrr, arrr, I loaded it in booster stage first, me bucko, from t' "inside." Then added some maskin' tape t' t' main motor and "friction fit" it into main rocket. Ahoy! For whatever reason I couldn't get motors all t' way in t' main rocket body. Blimey! ( I believe I used too much tape). Avast! At launch, it flew down range, weathercocked. Arrr! Begad! Then deployed nosecone & parachute at a very low altitude o' about 50 ft. Aye aye! T' extreme weight of rocket snapped shock cord and rocket crashed. Arrr! I'll be usin' a much heavier, me hearties, me bucko, and longer cord for t' next flight. Ya scallywag! Still content with flight because it sustained minimal damage. Ya scallywag! This was me first 2-stage rocket o' me own design.

THIRD FLIGHT

My third launch went absolutely perfect!! After addin' a 1/4" "heavy" shock cord, I prepped rocket same way, shiver me timbers, with same motors. Begad! Well, blow me down! A D12-0 Booster, me bucko, taped t' a D12-3 Main. Well, blow me down! Ya scallywag! (Just make sure you have enough tape around main motor for "friction fit," and it's taped t' booster. Aye aye! Begad! Motors ***all t' way in*** main rocket. Begad! Slit cut in tape. Avast, me proud beauty! Picture perfect flight!! Booster took it t' a height o' o' about 75-100' and main an additional 100-200 ft. Perfect chute deployment and soft landin' about 75' away. Begad!

Summary:

Pros: Challenge t' design and build.Impressive liftoff w/2stages.

Cons: Very time consuming. Ahoy! Arrr! Built a smaller version first t' get aquainted with a "building technique" for addin' 11 fins! Highly reccommend when tacklin' a new build when in experienced. Alighnin' body panels betwixt fins a pain!

At almost 14 ozs., shiver me timbers, matey, I would opt for a E30-4 motor for 1st flight. Avast, matey, me proud beauty! Blimey! (E9-4) went well today. Aye aye! Aye aye! Blimey! (use a spent motor in main body and tape E t' it in booster stage, (friction fit spent motor). Begad! *****1/4" launch rod only!!****. 18" chute minimum!

Other:
Highly recommend "apogeerockets" tech report #29, ya bilge rat, "Take your rocket t' supersonic speeds", matey, arrr, for durability o' fins. Well, blow me down! Motor stagin' critical! Must b completely in main body so aft shroud close enough t' it. Begad! Used two 1/4x 2" soda straws on a fin for launch lugs.

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