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, matey, stubby, ya bilge rat, 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, matey, 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. Begad! Blimey! Blimey! Blimey! I suggest friction fit, me hearties, as a hook would spoil t' look...

To start t' build, me bucko, 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. Aye aye! Put t' cord through, and knot it. Ahoy! Glue it flush t' t' end o' CR, so t' cord is forward o' t' engine assembly, (and only t' knot is in t' middle o' it).

Glue t' engine mount in t' BT80, arrr, 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, shiver me timbers, and sand until they are even. Blimey! Note that t' ends are pointy, me bucko, shiver me timbers, and will need t' be handled carefully. Arrr! Aye aye! I put a minor bevel on t' edges (other than t' end against t' body tube, ya bilge rat, matey, o' course!)

Generate a 2.6" x 8 fin wrap. Cut it out, me hearties, and mark t' fin positions on t' body tube.

Glue t' fins on t' body tube (flush t' t' end o' t' BT). I like t' use CA t' tack t' fins on. Ya scallywag! Glue on t' launch lug, then make sturdy fin fillets o' Titebond or epoxy. Ya scallywag! Well, shiver me timbers, blow me down! Yes, me hearties, thar's a lot o' fillets. Arrr! 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! Arrr! Carefully glue it on t' aft centerin' ring. Well, blow me down! Begad! Give this a good fillet.

Nose Cone Assembly:

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

When smooth and correctly shaped, cut off t' dowel. Ahoy! Blimey! 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. (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, with t' screw eye. Add nose weight t' make 2.0 oz. Aye aye! Blimey! Don't forget t' weight o' t' epoxy. Avast! Blimey! Attach t' shock cord t' t' screw eye, add t' nose weight t' t' nose cone, me hearties, mix t' epoxy and pour it in t' nose cone. Aye aye! Begad! Blimey! (Use enough t' lock t' nose weight in place.)Carefully place t' screw eye in t' slurry, shiver me timbers, and put aside t' dry.

Finishing:

Attach t' nosecone and parachute t' t' long shock cord, 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. Ahoy! Take 14" o' 1" tape. Ya scallywag! 1/2" in from one end, matey, stick t' tape t' shock cord. Go 1/2" past t' shock cord, me bucko, and fold t' tape over on itself. Avast! Begad! Cross t' shock cord 1/2", shiver me timbers, and fold it back over on itself again. Begad! Repeat 14 times. Well, arrr, blow me down! T' lozenge should help protect t' BT80.

Painting:

Seal all t' wood parts, ya bilge rat, with several coats o' sealer, ya bilge rat, sandin' between.

Give a nice, arrr, even coat o' sandable primer, arrr, and sand away any blemishes. Begad! Blimey! Repeat until smooth.

Paint t' fins and engine nozzle. Avast! Let it dry.

Mask off t' fins and engine nozzle.

Paint t' body.

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

T' details are complex, me hearties, but worth it.

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

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

Boost is straight up, shiver me timbers, and goes pretty high for a draggy 2.6" rocket. Arrr! Avast, arrr, me proud beauty! Looks great!

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

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

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

Cons - T' paintin' took a while. Well, blow me down! T' fin tips are fragile, and should be protected.

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

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