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. Avast, me proud beauty! T' solution provided allows for t' removal, inspection, and replacement o' t' engine mount, ya bilge rat, matey, me hearties, retention system, ya bilge rat, and recovery system.

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

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

Transfer t' third points from t' motor tube onto t' coupler tube. Avast! Divide t' length o' t' coupler tube in half. Avast, me proud beauty! Avast, me proud beauty! T' intersectin' points are where you will drill t' mount t' brass inserts. Arrr! Be sure t' select an appropriate size bit for drillin' t' holes for t' inserts. Aye aye! Too small a hole may result in splittin' t' blocks, matey, ya bilge rat, too large may lessen integrity. Well, blow me down! Blimey! I prefer to
use brad point bits for this task. Ahoy! Avast, arrr, me proud beauty! Usin' an awl, matey, indent t' coupler at t' three locations. Ya scallywag! Also, ya bilge rat, indent t' Aft Centerin' Rin' in t' center o' t' three blocks. Aye aye! With care, drill t' six holes bein' aware o' t' depth t' t' motor tube. 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. I completely saturated 4" o' 3/4" strappin' with epoxy and temporarily rubber banded it while t' epoxy cure. Ahoy!

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

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

Launch Lug / Rail Guide Construction
Takin' advantage o' t' screwed construction, me bucko, t' launch lugs be made removable. Well, blow me down! Ahoy! T' lugs were epoxied t' a metal strip with a 90 degree bend in t' last 1/8". Blimey! Arrr! 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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