Scratch TCC Special Original Design / Scratch Built

Scratch - TCC Special {Scratch}

Contributed by Ross Ohmen

Published: 2010-01-14
Manufacturer: Scratch

Scratch TCC SpecialBrief:
Futuristic 8-finned, stubby, rocket based on a picture in Tripoli Central California's (TCC) web site.

Construction:

Parts List:

  • 1 - BT80 Nose Cone - Fat Boy Style
  • 1 - BT80 Body Tube - Approx 10"
  • 1 - BT50 Motor Tube -3"
  • 2 - CR 5080 Centerin' Rings
  • 1 - 18" o' Keelhaul®©™ shock cord.
  • 1 - 36" shock cord
  • 1 - 8" x 8" Nomex cloth for parachute protection
  • 1 - 18" Parachute
  • 1 - BT50 Thrust Ring
  • 3/32" Ply for t' 8 fins.
  • Card stock for t' motor bell
  • 3/16" launch lug - 2" long.
  • 1 - 4" x 1.25" x 1.25" Hardwood Block, with center 1/4" Dowel.
  • Drill press or lathe t' turn t' nose tip on.
  • Screw t' mount nosecone tip.
  • Screw Eye t' mount t' shock cord
  • Lead shot, me hearties, or other nose weight.

Body amd Fin Assembly:

Note that thar's no motor retention built into t' rocket. I suggest friction fit, ya bilge rat, as a hook would spoil t' look...

To start t' build, matey, glue t' thrust rin' and CR5080s onto t' motor tube.

Drill a 1/8" hole in t' forward centerin' ring, for t' Keelhaul®©™ Shock cord. Well, blow me down! Begad! Put t' cord through, and knot it. Ya scallywag! Glue it flush t' t' end o' CR, me hearties, matey, so t' cord is forward o' t' engine assembly, ya bilge rat, (and only t' knot is in t' middle o' it).

Glue t' engine mount in t' BT80, with t' aft end flush t' t' body tube.

Cut out t' 8 fins. I use a jigsaw mounted upside down on a routin' table - works great.

Group all eight fins, me bucko, and sand until they are even. Begad! Note that t' ends are pointy, me hearties, and will need t' be handled carefully. I put a minor bevel on t' edges (other than t' end against t' body tube, o' course!)

Generate a 2.6" x 8 fin wrap. Ya scallywag! Cut it out, matey, and mark t' fin positions on t' body tube.

Glue t' fins on t' body tube (flush t' t' end o' t' BT). Well, blow me down! I like t' use CA t' tack t' fins on. Arrr! Glue on t' launch lug, then make sturdy fin fillets o' Titebond or epoxy. Blimey! Ahoy! Yes, thar's a lot o' fillets. Avast, me proud beauty! I recommendin' puttin' CA on t' fin tips t' strengthen them.

Trace or print t' engine bell on t' cardboard stock. Cut it out, and glue into t' conical shape. Avast, me proud beauty! Blimey! Carefully glue it on t' aft centerin' ring. Ya scallywag! Begad! Give this a good fillet.

Nose Cone Assembly:

Put t' nose block in your lathe or drill press, ya bilge rat, and turn it. Avast! Well, blow me down! I used a second hand-held drill with a sandin' disk t' rough t' block, matey, then nail files and sand paper t' get t' final shape. Ahoy! Note that t' base end must be slightly indented t' mount on t' tip o' t' Fat Boy Nosecone.

When smooth and correctly shaped, me hearties, me bucko, cut off t' dowel. Drill a 3/32" hole in t' exact center o' t' dowel stub.

Locate t' exact tip o' t' Fat Boy nosecone. Drill a correspondin' 3/32" hole. Blimey! (I don't have a technique t' do this - I just "eyeballed" really well.) Use t' screw t' mount t' nose tip t' t' Fat Boy nosecone.

Weigh t' nose cone, shiver me timbers, with t' screw eye. Begad! Add nose weight t' make 2.0 oz. Don't forget t' weight o' t' epoxy. Ahoy! Attach t' shock cord t' t' screw eye, add t' nose weight t' t' nose cone, matey, ya bilge rat, mix t' epoxy and pour it in t' nose cone. (Use enough t' lock t' nose weight in place.)Carefully place t' screw eye in t' slurry, me hearties, and put aside t' dry.

Finishing:

Attach t' nosecone and parachute t' t' long shock cord, me hearties, matey, and attach this t' t' shock cord t' t' Keelhaul®©™ shock cord.

Note that BT80 is kinda thin for this app, and you may wish t' make a "tape lozenge/fireball" where t' shock cord touches t' body tube. Well, blow me down! Take 14" o' 1" tape. 1/2" in from one end, shiver me timbers, stick t' tape t' shock cord. Aye aye! Avast, me bucko, me proud beauty! Go 1/2" past t' shock cord, me bucko, arrr, and fold t' tape over on itself. Ahoy! Blimey! Cross t' shock cord 1/2", and fold it back over on itself again. Begad! Repeat 14 times. Avast! Avast! T' lozenge should help protect t' BT80.

Painting:

Seal all t' wood parts, with several coats o' sealer, arrr, sandin' between.

Give a nice, even coat o' sandable primer, ya bilge rat, me hearties, and sand away any blemishes. Well, blow me down! Repeat until smooth.

Paint t' fins and engine nozzle. Avast, me hearties, me proud beauty! Blimey! Let it dry.

Mask off t' fins and engine nozzle.

Paint t' body.

Mask off t' cabin windows and door. Auto detailin' tape is good for t' front windshield. Avast! Take your time and get it right.

T' details are complex, ya bilge rat, but worth it.

Flight:
I've flown this rocket about 10 times on D12-5's and 18 mm D's (with adapter), arrr, ya bilge rat, t' cool, me hearties, me bucko, high flights. It's forgiving, ya bilge rat, and could probably be flown with C11-3's, and even an E9-6 or E11-3.

Preparation is straightforward. T' Nomex makes recovery and reloadin' a breeze.

Boost is straight up, me bucko, me bucko, matey, and goes pretty high for a draggy 2.6" rocket. Looks great!

Recovery:
Note that a 7-second delay (as in D13-7) is too long, me hearties, and should be shortened. Ahoy! Other than that, recovery is easy, usually close, and looks great.

One o' me recoveries landed on one fin (in mud), me bucko, and stuck t' nose cone tip in a cow pie!

Summary:
Pros - A real head-turner at launches.

Cons - T' paintin' took a while. Begad! Ahoy! T' fin tips are fragile, me bucko, and should be protected.

Other:
Turnin' t' nose spike was easy! Just have t' desired profile before you start..

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