Scratch Leif Erickson Original Design / Scratch Built

Scratch - Leif Erickson {Scratch}

Contributed by John Thompson

Manufacturer: Scratch
(Contributed - by John Thompson - 11/09/08)

Brief:
My entry for t' EMRR 2008 Design this Spaceship contest. Blimey! I would rate this as a skill level three model. It is nay a complicated build, but t' modeler must use CA and epoxy t' adhere different materials t' each other. Begad! Avast! T' modeler must form shrouds from cardstock, shiver me timbers, ya bilge rat, and this build requires usin' a power drill which a beginnin' modeler might nay have the skills t' use.

Construction:
Parts list:

Name Quantity Length Part Number
Engine Tube 1 2.75 inches BT-20J
Body Tube 1 9.75 inches BT-50H
Fuselage 1 6.5 x 4 inches Plastic Bottle
Nose cone 1 2.75 inches PNC-20A
Launch Lug 1 2 3/8 inches LL-2AM
Shroud Sheet 1 8.5 x 11 inches PS-001
Decal Sheet 1 8.5 x 11 inches DS-001
Balsa Sheet 1 4 x 6 inches BS-001
Keelhaul®©™® Cord 1 10.75 inches KV-001
Parachute 1 12 inch PK-12A
Centerin' Rings 2 CR-2050 CR-2050

Construction begins with t' usual engine tube assembly. Aye aye! Well, blow me down! Usin' a pencil, make a mark on t' 2.75 inch BT-20 body tube ½ inches from one end. Begad! Make a second mark ½ inches from t' other end. Avast! Glue t' thrust rin' into one end o' t' engine tube, ya bilge rat, matey, makin' sure t' thrust rin' is flush with t' end o' t' tube.

Next, run a bead o' glue around t' outside o' t' engine tube behind one o' t' marks you made in t' earlier step. Ahoy! Blimey! Take one o' t' CR 20/50 centerin' rings and slide it onto t' engine tube from t' opposite end o' t' glue bead. Slide t' centerin' rin' through t' glue up t' t' pencil mark. Well, blow me down! Arrr! Blimey! Take t' other centerin' rin' and slide it onto the engine tube past t' second mark. Begad! Run a bead o' glue around t' engine tube behind t' second pencil mark and slide the second centerin' rin' through t' glue up t' t' second pencil mark. Blimey! Apply fillets t' both centerin' rings.

Wrap t' Keelhaul®©™® thread around t' engine tube, behind t' centerin' ring, me hearties, shiver me timbers, that is on t' same end as t' thrust ring. Spread some thin CA over t' Keelhaul®©™® wrap t' give it a strong bond t' t' engine tube. Avast, me proud beauty! Blimey! Next, usin' your hobby knife, cut a groove in t' top o' the centerin' ring. Avast! Blimey! Aye aye! Blimey! Blimey! Blimey! T' Keelhaul®©™® thread will rest in this groove and will make it easier t' glue t' engine mount assembly into t' main body tube. Begad! Set the assembly aside and allow it t' dry.

Glue t' engine mount assembly into t' main BT-50 body tube by placin' wood glue on a small dowel and spreading it around t' inside about 2.5 inches from one end o' t' BT-50 tube. Blimey! Run t' exposed Keelhaul®©™® thread through t' thrust rin' o' t' engine mount assembly, arrr, and out t' other end. Blimey! You do this so t' Keelhaul®©™® thread won't interfere with installin' t' engine mount. Slide t' engine mount partly into t' main body tube. Run wood glue around t' exposed centerin' rin' then slide t' mount t' rest o' t' way into t' tube. Ya scallywag! T' aft end o' the mount should be flush with t' aft end o' t' body tube.

Use a sharp knife or a saw t' cut off t' threaded portion o' t' plastic bottle. Avast, me proud beauty! Take your drill and drill a pilot hole in t' bottom o' t' bottle as close t' t' center as possible. Well, ya bilge rat, blow me down! Widen t' hole in t' bottom usin' bigger bits (or a spade bit) until t' BT-50 body tube can slide easily through t' hole. Aye aye! Blimey! Remove all paper labels and adhesive from t' outside o' t' bottle. Finally, take some heavy grit sandpaper, ya bilge rat, 150 or 180 grit, and sand every inch o' the outside o' t' bottle. Ahoy! T' sandpaper marks will allow better epoxy and primer adhesion t' t' plastic.

Use t' supplied template and cut out t' two main fins, ya bilge rat, t' two upper, matey, and t' two lower winglets. Round all edges except t' root edge with sandpaper. Arrr! Take one o' t' large main fins and place a couple o' drops o' thin CA on the fin root then attach t' fin t' t' aft o' t' plastic fuselage, makin' certain t' fin is on t' center mold line that runs t' perimeter o' t' fuselage. Ya scallywag! T' aft o' t' fin that angles outward should extend beyond t' aft o' the fuselage. Avast, me proud beauty! Repeat usin' t' second main fin on t' opposite side. Avast! Mix up enough 5 minute epoxy t' make fin fillets on both main fins, and apply t' epoxy fillets.

Usin' sandpaper, bevel one side o' one o' t' upper winglets root edge. Begad! Blimey! This will allow t' upper winglet to attach t' t' main fin at an acute angle. Begad! Blimey! Place a couple o' drops o' thin CA t' t' winglet root and attach it t' the tip o' t' main fin. Ahoy! Blimey! Use t' supplied angle template t' achieve t' proper angle. Repeat t' attach t' second winglet. Ya scallywag! Blimey!

Take one o' t' lower winglets and attach t' t' bottom o' one o' t' upper winglet usin' standard wood glue. Aye aye! Ya scallywag! Blimey! The lower winglet will be at an angle as well. Repeat usin' t' second lower winglet on t' other side. Well, blow me down! Avast, me proud beauty! Blimey! Cut out t' laser gun mounts usin' t' supplied template from t' balsa. Avast, me proud beauty! Blimey! Place a drop o' CA on t' root o' one mount and place it on the main win' approximately 1 inch from t' fuselage. Arrr! Repeat for t' other laser cannon mount. Ya scallywag! Blimey! Mix up epoxy t' make fillets on all t' attachment points for t' upper and lower winglets and t' laser cannon mounts. Aye aye! Ahoy! Blimey! Fill any gaps betwixt t' main win' and winglets usin' epoxy or wood filler.

Take t' body tube and slide it into t' plastic fuselage. T' aft end o' t' body tube should stick out o' the aft end o' t' plastic fuselage approximately 0.5 inches. Avast! Begad! Mix up enough epoxy t' create fillets around t' fore and aft ends o' t' body tube. Apply t' fillets and set t' assembly aside and allow it t' cure. Once t' epoxy has cured, sand all epoxy fillets smooth.

Cut out t' nosecone shroud from t' supplied template on heavy card stock. Avast, me proud beauty! Ya scallywag! Make t' shroud curl by pullin' it across an edge o' a table. Cut a small strip from t' card stock or paper and glue it t' t' bottom on one straight side o' t' shroud. Well, blow me down! Take t' other side o' t' shroud and butt it up t' t' first side so that t' shroud forms a cone. Set aside t' dry. Ya scallywag! Avast, me proud beauty! Next cut out t' large shroud used for t' “neck” and glue it together just as you did t' nosecone shroud. Begad! Set aside t' dry.

Usin' heavy grit sandpaper, sand t' entire nosecone smooth. Begad! Make certain t' smooth out t' mold line that runs along t' perimeter o' t' nosecone. Well, blow me down! Do nay sand t' shoulder. Blimey! Blimey! Sandin' t' plastic nosecone will ensure good adhesion of t' nosecone shroud t' t' nosecone. Well, blow me down! After t' nosecone is sanded, me bucko, arrr, you can attach t' nosecone shroud one o' two ways. Aye aye! You can either use epoxy or you can use CA. Ya scallywag! Begad! Epoxy would be t' better choice because it adds nose weight, and you have some time t' adjust t' shroud t' get it centered and have even gaps across t' circumference o' t' cone. Attach the nosecone shroud t' t' nosecone and place it on a scrap length o' BT-50 body tube, if available. Ahoy! Otherwise, me bucko, hang the nosecone from a piece o' strin' and allow t' CA or epoxy t' cure.

Use scrap balsa t' create t' bridge and bridge platform. Begad! Ahoy! Glue two pieces o' 3/16 inch balsa scrap together and allow t' dry. Arrr! Blimey! Cut out t' bridge platform usin' t' supplied template. Avast, me proud beauty! Ya scallywag! Wrap a piece o' sandpaper t' a pencil and sand a half-circle in t' wide, shiver me timbers, front edge. Begad! Begad! T' bridge will sit inside this half-circle. Avast! Avast, me proud beauty! Glue t' t' nosecone usin' either CA or epoxy. Aye aye! T' aft o' t' bridge platform should extend over t' “neck” approximately ½ an inch.

Shape t' balsa that you glued earlier into a cylinder with a rounded top, usin' heavy grit sandpaper. This will form t' bridge. Ahoy! Ahoy! Trim t' cylinder down t' a length o' approximately ¾ inch. Avast, me proud beauty! Avast! Next, matey, glue t' cylinder betwixt the nosecone shroud and t' bridge platform usin' CA or epoxy. Avast, me proud beauty! T' bridge should sit inside t' half-circle sanded into the bridge platform.

Sand t' epoxy around t' front o' t' fuselage smooth usin' heavy grit sandpaper. Well, blow me down! Blimey! Ahoy! Blimey! Spread wood glue around the outside o' t' neck 1/8 inch from t' end where t' nosecone will attach. Slide t' neck shroud onto t' neck and butt it up against t' fuselage. Tack t' shroud t' t' plastic fuselage usin' a couple o' drops o' CA. Mix up epoxy and spread epoxy over t' aft edge o' t' shroud and blend t' epoxy into t' existin' sanded epoxy. Avast! Blimey! Ya scallywag! Blimey! Set aside and allow epoxy and wood glues t' cure.

Cut out t' two laser cannon shrouds on t' solid black lines then fold on t' dotted lines. Begad! When folded, the shrouds should make a hexagon shape. Use a sharp hobby knife or a razor blade t' cut a slit on t' top and bottom of the fuselage. Aye aye! Slide one edge o' t' shroud into t' slit on t' top side and slide t' other end o' t' shroud into the bottom slit. Do t' same for t' other shroud. Avast! Tack t' shrouds in place usin' CA.

Use a scrap piece o' thick balsa and cut it t' approximately 1.5 x 0.75 inch rectangle. Round off all four corners o' t' rectangle then round down t' top o' t' fore and aft ends o' t' rectangle. Avast, me proud beauty! Blimey! Place a piece o' sandpaper rough side up onto t' aft end o' t' fuselage. Well, blow me down! Blimey! Place t' rectangle onto t' sandpaper and sand t' bottom so it will conform t' t' shape o' t' fuselage. Arrr! Blimey! Center and attach t' rectangle t' t' aft o' t' fuselage usin' CA. Aye aye! Blimey! Aye aye! Blimey!

Cut two more small rectangles, arrr, me bucko, approximately ¼ x ½ inches from scrap balsa. Blimey! Aye aye! Attach one small rectangle t' each side o' t' larger rectangle made in t' previous step usin' CA. Ya scallywag! T' smaller rectangles should be ¼ inch from t' larger rectangle. Blimey! Cut two 1/8 inch squares from t' same balsa material and attach t' the fuselage 1/8 inch away from t' small rectangles usin' CA.

Center t' launch lug on t' bottom o' t' fuselage and secure with CA or epoxy.

Slide t' Keelhaul®©™® cord back through t' engine mount and body tube and tie it t' one end o' t' elastic cord. Ya scallywag! Tie t' other end o' the elastic t' one o' t' attachment points on t' nosecone. Aye aye! Loop t' parachute shroud lines through t' other attachment point on t' nosecone. Pass t' parachute through t' shroud line loop and pull tight.

Finishing:
Start by sealin' all t' balsa usin' your preferred method. Prime t' entire rocket with an automotive grade primer that can be found at most automotive parts or home improvement stores. Avast, me proud beauty! T' automotive grade primer fills imperfections very well and sands fairly easily.

Once t' rocket has been primed, arrr, "dust" a light coat o' flat black paint over t' entire rocket t' give it a "splattered" look. Avast, me proud beauty! Blimey! T' flat black will show all t' imperfections, ya bilge rat, help you keep track o' where you have sanded, where you need t' sand, me hearties, me hearties, and will ensure t' surface is flat for t' next primin' session. Begad! Blimey! Allow t' primer to fully dry.

Sand all t' flat black paint off with medium-coarse grit sandpaper, me hearties, such as 220 grit. Aye aye! Blimey! Re-prime t' rocket and "dust" t' rocket with flat black paint. After t' primer has dried, sand all t' flat black off again, matey, shiver me timbers, using fine grit sandpaper, me hearties, such as 400 or 600 grit.

Once t' flat black has been sanded off, t' rocket is ready t' paint. Begad! Clean t' entire rocket with glass cleaner, me bucko, matey, such as Windex. Begad! T' glass cleaner has ammonia in it, which will nay only remove t' sandin' dust, but it will also remove t' oils left by your hands, arrr, which cause "fish eyes" in t' paint. Aye aye! Paint t' entire rocket light gray and allow t' dry for several days.

Once t' main color has fully cured, start applyin' t' details like windows, me hearties, me bucko, vents, lettering, and t' outline for t' shuttle bay doors.

Decal templates can be downloaded here.

Flight:
This model will make it difficult t' use t' spin stability method because o' t' odd shaped fuselage, shiver me timbers, however, me hearties, arrr, it can be done. Well, blow me down! T' CG should be directly in front o' t' laser shrouds. Arrr! Well, blow me down! Prep t' model as if you we goin' t' launch it usin' t' largest motor you intend t' use. Tie a long piece o' strin' at t' CG point and perform t' spin test. Begad! Ahoy! Add nose weight until t' model spins correctly.

Recommended engines: Estes B4-4, B6-4, shiver me timbers, shiver me timbers, C6-3

comment Post a Comment