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, shiver me timbers, 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. Aye aye! I gathered some cardboard, posterboard, me bucko, and second hand parts, shiver me timbers, etc. Begad! It would have been ten times harder without t' EMRR "Calculators", for shrouds, me hearties, etc. Aye aye! Begad! 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. Also, cardboard a little easier t' work with than "foamboard."

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

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, matey, arrr, would have saved a lot o' aggravation and speeded up t' build. Arrr! Also, Highly recommended buildin' a prototype, especially in me case. Ahoy! Begad! My submission for t' "rocket o' t' future" has 12 fins! Never came close t' design such a complex rocket before. Begad!

Construction:

PARTS LIST:

  • 24mm engine block
  • 1 engine hooks
  • 1 sheet o' foam board, me bucko, 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, shiver me timbers, 4"x"36"x1/8 balsa sheets/basswood
  • 1 "quest" egglofter nosecone
  • 1 (18") parachute, arrr, ya bilge rat, matey, & 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. Well, blow me down! Begad! 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, shiver me timbers, me hearties, me hearties, I would be very curious as t' t' result. Well, blow me down! I did use EMRR "Calculators" for t' shrouds and centerin' rings. Aye aye! I thank Nick for makin' available because without them, me hearties, couldn't have made this design.

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

I stated in "parts" section that t' balsa is very fragile. Avast, me proud beauty! Just discovered Tech Report # 29, from www.apogeerockets.com; "Take your rocket t' Supersonic Speeds. Well, blow me down! Begad! " This is a compromise t' replacin' entire fin with basswood or ply. Avast, me proud beauty! Well, blow me down! 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. Aye aye! Options exist. Avast!

**Not happy with way main "body shroud" turned out. Well, blow me down! Avast! 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, t' keep smooth.**

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

Main Engine Tube

  1. Glue t' BT55 centerin' rings on main engine tube. Blimey! Begad! Blimey! Let dry. Blimey! Blimey!
  2. You'll want t' "dry fit" main engine mount and make sure "spent engine" recessed inside BT55 about ¼". Ahoy!
  3. Mark Bt55 where "engine Hook" will be, matey, and cut a slot 1/8" x3/8". Avast! Aye aye!
  4. Glue main engine mount with engine hook lined up with slot in BT55. Arrr! Aye aye!

Booster Engine Mount

  1. Take 3" piece o' 24mm BT; then cut 1/8"x 3/8" slot in one end. Blimey! Blimey! Arrr! Blimey!
  2. Lay "flat" side o' hook inline with slot and tape. Well, blow me down! *** I used a long piece o' old wiper blade for hook and cut t' length later. Aye aye!
  3. Cut out 3 "rear shroud centerin' rings. ***Tip: when I cut out middle o' rings FIRST, ya bilge rat, I then took a spent engine and inserted and twisted t' check for a tight fit. Then inserted engine in tube for support. Begad! 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, cut out aft shroud. Ya scallywag! (You will see I include pattern, arrr, me bucko, showin' a "saw tooth design" on inside radius o' shroud. Blimey! Cut design in shroud. Begad! Much easier t' glue.)
  7. Shape shroud, matey, tape together on inside. Avast, me proud beauty! Blimey!
  8. Fold "teeth" over t' inside and make a sharp crease. Ahoy! Blimey! Straighten out.
  9. After center rings on engine tube have dried, ya bilge rat, take some glue and apply t' edges o' rings. Arrr! Avast, me hearties, me proud beauty!
  10. Take shroud and slip over engine assembly. Ahoy! Be sure t' get completely in. Avast! Well, blow me down!
  11. Spread some glue on smallest centerin' rin' and fold shroud "teeth" down, holdin' till set. Begad! You may only be able t' do a few @ a time. Let dry Thoroughly. Well, blow me down!
  12. Put a spent engine in "Main and aft " engine mounts.
  13. Slide together, ya bilge rat, linin' up "slots" in engine tubes. Aye aye! T' aft engine tube should slide over t' Main engine about ½" and stay in place. Ya scallywag! ***Make sure aft Booster engine is as far forward as it will go WITHOUT disengagin' t' booster. Well, blow me down! Avast, ya bilge rat, me proud beauty!
  14. Mark t' aft engine hook , cut and bend t' correct size.
  15. Cut shock cord mount and glue shock cord t' it. Begad!
  16. Slide "loose" end o' shock cord thru a BT55 coupler. Begad! Well, blow me down!
  17. Glue Shock cord mount t' inside o' BT55 containin' engine mount far enough inside t' be able t' glue BT55 coupler. Well, blow me down! Glue Bt55 coupler and let dry. Blimey!
  18. Cut other BT55 t' length so when t' two r put together , me hearties, shiver me timbers, you have a rocket body 23" long, "without" aft shroud. Blimey!
  19. Cut out Main Body centerin' rings. Avast! (u can take spare piece o' BT55 t' check fit). Ahoy!
  20. Take t' "fin template" and mark 3", 3.5" rin' where it will engage each fin. Avast! ****Note: you can mark 4" rin' but, ya bilge rat, me hearties, because o' size, it won't line up with other two rings. Begad! You will have t' do slots on this rin' once it is mounted. Well, blow me down! Avast!
  21. Take care, arrr, cut a ¼" deep slot x 1/8" wide into each ring. Avast, me proud beauty!
  22. Mark 1st slot on each rin' with a #1 for reference.
  23. Make a fin from 1/8" "Basewood/plywood" as a guide t' check fit o' fins. Well, blow me down! It will also b used t' as guide for slots, 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, me bucko, and use sealer if desired. Avast, me proud beauty! Ya scallywag! Blimey!
  2. Use fine guide and cut slots in each fin: 1" from aft o' fin, 1x1/4 deep. Next one 7" from end. Ya scallywag! Well, blow me down!
  3. Last slot is 2.5 " from previous slot and only 5/8" deep.
  4. These r initial slots. Well, blow me down! You may have t' widen for proper fit.
  5. Slide center rings on BT one @ a time. ***If seems tight or binds, increase size o' hole slightly. Avast, me proud beauty! Begad! You can use a piece o' BT55 t' "shape" hole. Arrr! Arrr! (you want t' maintain a fairly tight fit). Well, me bucko, blow me down!
  6. Space rings approximately same distance as slots on fin. Avast, me proud beauty! Aye aye!
  7. "Orientate" all 3 rings with #1's lined up. Ya scallywag!
  8. Take your "Guide Fin", me hearties, ( t' one made from plywood), matey, and check slot lineup for first fin.
  9. You'll have t' cut slots deeper in each ring, checkin' fit each time. Blimey! You may nay even need a slots for 4" ring, arrr, till ready t' glue on fins, due t' a "redesign", me hearties, and linin' up o' fin with "center ring slots," I made for simplicity. Blimey! (make recess higher, arrr, about 1 ¼"). Aye aye!
  10. After you get a good fit for t' fine on t' center rings, take a "real" fin and glue in #1 slots of rings. Avast! (I kept breakin' balsa fins, matey, that why I recommended goin' t' a sturdier material, such as basswood or Tims Tech report #29, me bucko, gluin' "notebook paper" t' exterior o' fin first for strength).
  11. Take guide fin and check next set o' slot, adjustin' for correct fit. Ahoy!
  12. Then glue 3 center rings in place. Aye aye! Avast, me proud beauty!
  13. Glue all 8 fins in place, checkin' fit first with "guide fin". Well, blow me down! Begad!
  14. Cut out two "body templates". Ya scallywag! Make a slice at end o' each one ¼-3/4" deep, 1" from end on each side. Fold over @ slices and straighten out. Ya scallywag!
  15. Dependin' upon which set o' fins you start with, will determine what size template t' use, medium or large. Avast! Blimey! Begad! Blimey! Blimey! Blimey!
  16. Lay template betwixt fins, shiver me timbers, and gently push down. It should hang out rear, matey, betwixt fins 1", me hearties, up to "slices."
  17. Check front o' template and mark where template extends past fin. Begad! Blimey! Ahoy! Blimey!
  18. Cut on t' mark, down t' ¼" fold mark on each side. Well, blow me down! Cut a "saw tooth" pattern in sides of body templates. Blimey! Makes for easier gluin' and smoothin' out. Avast! ***see photo"***
  19. Before gluin' fins, I made "fin supports," ½" x 1 ¼", and glue betwixt ends of fins. Begad! Also, shiver me timbers, made a bevel on each end. Ya scallywag! **See photo**
  20. Glue in place and repeat for each set o' fins. Arrr! Avast! ***remember t' check fit! (Center on BT) too. T' aft o' body template should be about ½-3/4" above body and aft shroud.
  21. Cut out "body templates," with "saw-tooth" design on edges and glue betwixt fins. Well, blow me down!
  22. Main Body Shroud: As I stated in beginning, me bucko, ya bilge rat, nay happy with t' way this one turned out. Ya scallywag! You may want t' shorten or find a different material or wrap around a "form" t' keep smooth. Ahoy! Also, use same "saw-tooth" design for edges before gluin' in shape o' cone. Begad! Once glue, shiver me timbers, let DRY THOROUGHLY. Blimey! Well, blow me down!
  23. I fitted over main body tube t' fins. Begad! Blimey! I marked where touched fins and cut slits about 1" long, in shroud. Keep fittin' till you get a tight fit into slots, me bucko, then glue and let dry thoroughly. Avast, me proud beauty!
  24. Now comes a tricky part. Well, blow me down! Well, blow me down! Seams that r formed betwixt "fins, body templates, arrr, me hearties, matey, 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. Arrr! Strong, ya bilge rat, shiver me timbers, light, arrr, and easy t' sand after hardened.
  25. After seams dry, sand till smooth. Blimey!

Nosecone Fins:

  1. Looking @ picture o' t' rocket I was copying, shiver me timbers, "upper fins" aren't really in nosecone but, shiver me timbers, I liked this location better. (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, shiver me timbers, about 2" long and 3/16-1/4" wide. Arrr! Blimey! ** b careful nay t' cut all t' way thru t' end o' nosecone**. Ahoy! Blimey! I mounted a piece o' 1" aluminum angle iron t' a piece o' wood and clamped t' me table as a guide. Ya scallywag! Blimey!
  3. Fit fins in slots one @ a time, ya bilge rat, shiver me timbers, me hearties, trimmin' slots till fins fit. Avast! Begad! Remove fins and put a ball o' clay in tip of nosecone and press into place. Begad!
  4. Replace fins 1 @ a time til they "touch" in middle o' nosecone and glue. Aye aye! (I opted for "gorilla glue" type). Avast! It foams up and becomes very strong). Ahoy! Avast! Let dry. Begad!

Nose Cone:

  1. Keep addin' balls o' clay, fillin' void in nosecone, ya bilge rat, and pressin' into place. Avast, me proud beauty! ****remember t' allow room for end o' nose cone t' slide in.****
  2. Also, arrr, arrr, as you r fillin' void, arrr, assemble nosecone and check for CG with motors in main and booster BT's. Ahoy! (goin' to take a few ounces o' clay t' fill and balance rocket so CG approx. Ahoy! Ya scallywag! Blimey! in middle.)
  3. Once clay pressed into place and you r satisfied w/location o' CG, assemble nosecone. Avast! Aye aye!

Finishing:

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


Flight:

My first flight be very successful. I used a E9-4. Aye aye!

Preparation a little different than usual but, shiver me timbers, easy. Begad! Ya scallywag! After loadin' an 18" parachute, arrr, dusted with baby powder, and t' wadding, I loaded t' engine. Begad! 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. Ya scallywag! It flew great! Relatively straight for t' design, arrr, 11 fins, and t' weight. Aye aye! Arrr!

T' shock cord, attached t' rocket, me hearties, was Keelhaul®©™. Begad! Blimey! Then an elastic, arrr, tied t' t' Keelhaul®©™, shiver me timbers, which proved t' b t' weak. (will explain in next flight).

Parachute deployed perfectly and landed about 30 yards away. Ya scallywag!

SECOND FLIGHT

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

Summary:

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

Cons: Very time consuming. Begad! 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. Arrr! Alighnin' body panels betwixt fins a pain!

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

Other:
Highly recommend "apogeerockets" tech report #29, shiver me timbers, "Take your rocket t' supersonic speeds", for durability o' fins. Arrr! Motor stagin' critical! Must b completely in main body so aft shroud close enough t' it. Aye aye! Blimey! Used two 1/4x 2" soda straws on a fin for launch lugs.

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