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). Ahoy! Avast! 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), Estes
  6. main airframe, shiver me timbers, ya bilge rat, me hearties, 9 ¾" section o' wrappin' paper tube
  7. launch lug, Estes
  8. hardwood stringer (4), ya bilge rat, 1/16" square, shiver me timbers, 9 ¾" long
  9. hardwood stringer (4), matey, 1/16" square, 8" long
  10. plastic fins (4), arrr, 1/16" thick (styrene?)
  11. balsa spacers (4), 3/16" x 1" x 3"
  12. BT-20 motor/stuffer tube, 8 ¾", extends from 1" below main airframe
  13. elastic shock cord, 12"
  14. parachute, matey, 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! Well, matey, blow me down!

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. Well, arrr, blow me down! T' chute is packed between t' BT-20 tube and t' airframe, ya bilge rat, and is nay directly exposed t' the ejection gasses. Ahoy! Some o' t' gasses may come in contact with t' chute, but this design has worked several times without incident. Well, blow me down! Ahoy! 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. Aye aye! Glue this into t' forward tube so that 2" extends out t' aft and ?" extends out t' front. 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. Instead, shiver me timbers, 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, me bucko, tie it t' a small section o' dowel and glue t' dowel t' t' bulkhead. Arrr! 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 was used was very weak. These would nay be required for, me bucko, ya bilge rat, say, shiver me timbers, a mailin' tube. Ya scallywag! Mark 8 evenly spaced parallel lines around t' tube usin' your favorite method. Begad! Glue the stringers on, alternatin' short and long lengths.

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

Cut t' fins t' t' dimensions shown. Begad! Blimey! I used scrap pieces o' plastic but balsa can be substituted. Blimey! Avast! Glue t' fins t' t' long stringers and a lug t' one of t' short ones. Ahoy! Feed t' shock cord through a snap swivel and connect it to the inside o' t' airframe. Begad! 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. Avast, me proud beauty! 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. Performance was similar t' a 18mm Fat Boy.

I folded t' chute and wrapped t' shroud lines around it. Well, blow me down! Ahoy! It be placed between t' stuffer tube and t' main airframe. T' shock cord then was laid in next t' t' chute. Begad! T' chute attached ~2 inches from where t' shock cord attaches t' t' nose cone assembly. Begad!

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

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

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

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