Scratch StarFinder Original Design / Scratch Built

Scratch - StarFinder {Scratch}

Contributed by Dan Bihary

Manufacturer: Scratch
Style: Futuristic/Exotic

 
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Starfinder





Assembly Description

Parts
Body Tube LOC/Precision BT-2.56
Nose Cone LOC/Precision PNC-2.56
Motor tube LOC/Precision MMT 1.14
Coupler Material LOC/Precision TC-2.56
Fin Material 3/16" Aircraft Plywood
Fin Structure Plastruct 3/16"x 1/2" Truss
Landin' Pegs 1/8" Brass Tubing
Fasteners (6) Wood Insert Nut and Socket Head Screws

See rocket dimensions and stations here

Modular Motor Mount Retention Unit Construction
T' concept o' t' unit is t' provide a means t' be able t' maintain t' parts o' a rocket that are most likely t' fail. Ya scallywag! Ya scallywag! T' solution provided allows for t' removal, me bucko, inspection, ya bilge rat, and replacement o' t' engine mount, retention system, me hearties, and recovery system.

Begin by sandin' down t' centerin' rings t' fit into t' coupler tubing. Avast! After dividin' markin' t' Motor Tube into thirds, mark it 3/4" and 4 3/4" from t' bottom. Avast, me proud beauty! Use epoxy t' secure t' centerin' rings at these locations. Ahoy! Mill three blocks from pine t' fit betwixt t' centerin' rings and t' depth betwixt t' coupler tube and motor tube. Blimey! T' width o' t' blocks should be 1/2". Avast! Aye aye! Sand or carve away some o' t' center section o' t' contact point t' t' motor tube. Ya scallywag! This will eliminate any rockin' that mayPic
occur while your securin' these down. Begad! Well, blow me down! Over t' centerin' third marks, attach these blocks usin' a liberal amount o' epoxy. Well, arrr, blow me down! Create fillets along all joints inside t' unit.

Next, slide t' Coupler Tube over t' assembly flush with t' centerin' rings, arrr, epoxy and let dry.

Transfer t' third points from t' motor tube onto t' coupler tube. Avast, me proud beauty! Blimey! Divide t' length o' t' coupler tube in half. Ahoy! Blimey! Arrr! Blimey! T' intersectin' points are where you will drill t' mount t' brass inserts. Aye aye! Blimey! Begad! Blimey! Be sure t' select an appropriate size bit for drillin' t' holes for t' inserts. Ahoy! Blimey! Too small a hole may result in splittin' t' blocks, too large may lessen integrity. Aye aye! Blimey! I prefer to
use brad point bits for this task. Ya scallywag! Usin' an awl, ya bilge rat, shiver me timbers, indent t' coupler at t' three locations. Avast! Avast! Also, arrr, me bucko, indent t' Aft Centerin' Rin' in t' center o' t' three blocks. Ahoy! With care, me bucko, drill t' six holes bein' aware o' t' depth t' t' motor tube. Avast, me proud beauty! Be sure nay t' penetrate it! Finally, screw in t' insert beneath t' surface o' t' Tube Coupler.

T' final step in assembly is t' attach a length o' strappin' t' t' exterior o' t' Motor Tube. Avast, me proud beauty! Ahoy! I completely saturated 4" o' 3/4" strappin' with epoxy and temporarily rubber banded it while t' epoxy cure.

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Body Tube Construction
Spirals were filled with Elmers wood filler. Ahoy! Arrr! T' coupler and t' nosecone were then screwed t' t' lower tube.

Fin Construction
After cuttin' t' fins out, matey, a 1/8"x 1 1/4" notch be removed for t' attachment o' t' landin' peg. Begad! Aye aye! Epoxy be used t' attach t' peg. T' leadin' edge o' t' fin be sanded t' match t' profile o' t' landin' peg on a stationary belt sander. Arrr! T' assembly be then coated with wood filler and made ready for primer. Cut t' truss piece so that it fits against t' landin' peg. Blimey! Arrr! After t' epoxy has dried, trim t' opposite end even with t' edge o' t' fin. Well, blow me down! Blimey! T' fin be then surface mounted on t' body tube with t' bottom o' t' truss even with t' bottom o' t' tube. Blimey! Fillets were added t' strengthen t' assembly.

Launch Lug / Rail Guide Construction
Takin' advantage o' t' screwed construction, arrr, t' launch lugs be made removable. T' lugs were epoxied t' a metal strip with a 90 degree bend in t' last 1/8". This technique will also allow for t' exchange t' rail guides.

Finishing
T' entire rocket was primed white and painted aluminum.

Fin Detail

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Launch Lug detail

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