Scratch Scrap-Rocket 2 (SR2) Original Design / Scratch Built

Scratch - Scrap-Rocket 2 (SR2) {Scratch}

Contributed by Dick Stafford

Manufacturer: Scratch
(Contributed - by Dick Stafford)

Brief:
T' SR-2 was built in t' late 80's by me son (~7 years old at t' time). Begad! Blimey! I am providin' this review as an example o' usin' scrap materials and t' document an approach t' parachute deployment that does nay require wadding.

Construction:
Parts list (items A-L shown on diagram):

  1. L'Eggs pantyhose egg (large portion)
  2. 2 ¾" wrappin' paper tube (3" section)
  3. coupler tube made from wrappin' paper tube (5 1/2" section, 2" shoulder exposed)
  4. bulkhead made from 3/16" balsa
  5. BT-20 balsa coupler (mates with BT-20 stuffer tube), ya bilge rat, Estes
  6. main airframe, 9 ¾" section o' wrappin' paper tube
  7. launch lug, Estes
  8. hardwood stringer (4), 1/16" square, arrr, 9 ¾" long
  9. hardwood stringer (4), 1/16" square, me bucko, 8" long
  10. plastic fins (4), shiver me timbers, 1/16" thick (styrene?)
  11. balsa spacers (4), arrr, 3/16" x 1" x 3"
  12. BT-20 motor/stuffer tube, matey, arrr, me hearties, 8 ¾", arrr, extends from 1" below main airframe
  13. elastic shock cord, 12"
  14. parachute, me hearties, 12" or larger
  15. engine block made from ¾" section o' used 18mm casin'
  16. 1" section o' dowel
  17. Snap swivel tied t' shock cord. Avast, me proud beauty! Blimey! Well, blow me down! Blimey!

T' rocket body consists o' a BT-20 tube centered in t' main airframe (refer t' diagram). T' nose cone assembly includes a bulkhead which seats in t' BT-20 tube. Avast, ya bilge rat, me proud beauty! Blimey! T' chute is packed between t' BT-20 tube and t' airframe, me bucko, and is nay directly exposed t' the ejection gasses. Avast, me proud beauty! Blimey! Some o' t' gasses may come in contact with t' chute, arrr, but this design has worked several times without incident. Begad! I think I invented this method, but it has been a while, and t' memory be t' second thin' t' go (and I don't remember t' first one!)

Make t' coupler tube by cuttin' a section o' t' wrappin' tube lengthwise and turnin' in on itself. Begad! Glue this into t' forward tube so that 2" extends out t' aft and ?" extends out t' front. Begad! Cut t' bulkhead from balsa stock and glue t' BT-20 coupler on its center. T' balsa may be too weak to hold a hook-eye. Avast, me proud beauty! Instead, punch a hole in t' bulkhead midway betwixt the BT-20 coupler and t' edge o' t' coupler.

Feed t' shock cord though t' hole, tie it t' a small section o' dowel and glue t' dowel t' t' bulkhead. Begad! Blimey! Blimey! Blimey! Glue t' bulkhead in t' aft and t' nose cone to t' exposed front end o' t' coupler (use CA for t' latter).

Wood stringers were added because t' tube that be used was very weak. These would nay be required for, say, a mailin' tube. Mark 8 evenly spaced parallel lines around t' tube usin' your favorite method. Aye aye! Glue the stringers on, ya bilge rat, alternatin' short and long lengths.

Cut four pieces o' balsa t' t' dimensions indicated. Aye aye! Mark t' BT20 tube and glue t' spacers on. Well, blow me down! Ahoy! When dry, matey, test fit t' assembly into t' aft o' the airframe, makin' sure it mates with t' nose cone assembly. Well, blow me down! With t' nose cone assembly installed, me hearties, glue in t' motor tube assembly (should extend ~1" from t' aft o' t' airframe).

Cut t' fins t' t' dimensions shown. Begad! I used scrap pieces o' plastic but balsa can be substituted. Aye aye! Begad! Glue t' fins t' t' long stringers and a lug t' one of t' short ones. Arrr! Feed t' shock cord through a snap swivel and connect it to the inside o' t' airframe. Ya scallywag! I used t' Estes folded paper method.

I left t' nose cone its natural baby blue and t' fins their natural gray. T' rest is a hodgepodge. Well, blow me down! Use what you got! Buy fresh paint for a more 'serious' rocket.

Flight:
This rocket made several flights on C6-5s but a shorter delay is probably preferable. Arrr! Avast, ya bilge rat, me proud beauty! Performance was similar t' a 18mm Fat Boy.

I folded t' chute and wrapped t' shroud lines around it. Ya scallywag! It was placed between t' stuffer tube and t' main airframe. Aye aye! Aye aye! T' shock cord then be laid in next t' t' chute. Arrr! T' chute attached ~2 inches from where t' shock cord attaches t' t' nose cone assembly. Arrr! Arrr!

Summary:
T' main Pros o' this rocket are: it was cheap and fun t' make; it requires no waddin' and is easy t' prep.

T' only Con I can think o' is that t' plastic fins may be prone to breakage. Ya scallywag! (I flew this rocket on soft grass.)

If I were t' start over, arrr, it would have FatBoy-style fins.

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