Scratch Weaned Speed Original Design / Scratch Built

Scratch - Weaned Speed {Scratch}

Contributed by Scott Turnbull

Manufacturer: Scratch
(Contributed - by Scott Turnbull - 07/04/08) (Scratch) Weaned Speed

Brief:
This odd rocket is a baby bottle bank converted t' a 29mm powered rocket with three back swept fins.

Construction:
Bill o' materials:

  • 1 Baby Bottle Bank (from t' baby shower section o' a party store)
  • 1 Mailin' Tube for t' interior stuffer
  • 1 29mm Motor Mount Tube
  • 2 Two Centerin' Rings cut from Clementine crate plywood
  • 3 Swept Back Fins cut from Clementine crate plywood
  • 1 reinforcin' bulkhead for t' bottle top
  • 1 sewin' elastic harness
  • 2 T-nuts, bolts, and screen clips for motor retention

This rocket came about from a desire t' test some construction techniques planned for use on t' much larger Coors Flight flyin' bank, which is also described on this site.

I purchased t' Baby Bottle Bank at a local party store. Begad! It be in t' Baby Shower supplies section.

A mailin' tube that is a press fit into t' mouth o' t' bottle was used t' size a hole cut in t' base o' the bottle usin' a drill mounted hole saw.

Clementine fruit crate wood was used t' cut out t' three back swept fins and two centerin' rings. T-nuts were inserted into t' aft centerin' rin' for motor retention.

(Scratch) Weaned Speed(Scratch) Weaned Speed

Fin tabs were fashioned t' go straight through from t' outer bank wall, through t' mailin' tube wall, shiver me timbers, and up against t' motor mount tube. Avast, me proud beauty! Well, blow me down! T' slots were cut with a Dremel tool usin' ganged cuttin' disks. Ya scallywag! This thick cuttin' disk cut each slot in a single pass.

A steel fishin' leader is attached t' t' motor mount and ends just below t' mouth o' t' bottle. Blimey! Begad! T' this is attached t' elastic shock cord.

A wood disk is bolted inside t' bottle cap for additional strength and weight. Avast! Blimey! A screw eye provides t' mounting point for t' recovery elastic. Avast! Blimey! T' threadin' on t' inside o' t' cap was ground off t' provide t' slip fit needed to eject t' cap.

Finishing:
Finishin' consisted o' paintin' t' wooden fins.

Flight and Recovery:
This has flown several times over t' past year. T' initial flight was on an E16-5 reload for an AeroTech 29/40-120 case. Aye aye! Begad! It was an arrow straight boost and a soft recovery. Ahoy!

(Scratch) Weaned Speed(Scratch) Weaned Speed

I tried it once on a D12-3 usin' a 29-24 adapter but that flight was barely a hand toss high. Begad! Arrr! It was safe but uninspiring.

A flight on an E23 with a drilled delay o' approximately 4 seconds had an excellent boost and a seemingly gentle recovery, but two fins were snapped off across t' narrow dimension from a fin slot t' t' leadin' edge. Begad! Avast! It was re-glued and will fly again.

Summary:
This be a good learnin' vehicle for t' double through t' wall fin construction needed for "facade" rockets. If I were t' build it again, I would make t' fin tabs so that thar be nay such a weakness at t' narrow dimension betwixt t' fin slot and leadin' edge. Large angled tabs, me hearties, rather than small perpendicular ones, me bucko, would make it stronger. Arrr! I would also use Lexan for t' fins so that t' fins were effectively invisible.

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