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

T' rocket body consists o' a BT-20 tube centered in t' main airframe (refer t' diagram). Aye aye! T' nose cone assembly includes a bulkhead which seats in t' BT-20 tube. Begad! T' chute is packed between t' BT-20 tube and t' airframe, and is nay directly exposed t' the ejection gasses. Some o' t' gasses may come in contact with t' chute, matey, but this design has worked several times without incident. Begad! I think I invented this method, ya bilge rat, me bucko, but it has been a while, ya bilge rat, 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. Arrr! Cut t' bulkhead from balsa stock and glue t' BT-20 coupler on its center. Well, blow me down! T' balsa may be too weak to hold a hook-eye. Begad! Instead, me hearties, me hearties, 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. 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. Begad! Aye aye! These would nay be required for, say, ya bilge rat, a mailin' tube. Ahoy! Avast, me proud beauty! Mark 8 evenly spaced parallel lines around t' tube usin' your favorite method. Ahoy! Ya scallywag! Glue the stringers on, matey, alternatin' short and long lengths.

Cut four pieces o' balsa t' t' dimensions indicated. Mark t' BT20 tube and glue t' spacers on. When dry, arrr, shiver me timbers, test fit t' assembly into t' aft o' the airframe, makin' sure it mates with t' nose cone assembly. Blimey! Avast, ya bilge rat, me proud beauty! 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. Avast, me proud beauty! Begad! I used scrap pieces o' plastic but balsa can be substituted. Aye aye! Glue t' fins t' t' long stringers and a lug t' one of t' short ones. Feed t' shock cord through a snap swivel and connect it to the inside o' t' airframe. Aye aye! 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. Ya scallywag! 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. Avast! Blimey! It was placed between t' stuffer tube and t' main airframe. T' shock cord then was laid in next t' t' chute. Well, shiver me timbers, blow me down! Blimey! T' chute attached ~2 inches from where t' shock cord attaches t' t' nose cone assembly.

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

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

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

comment Post a Comment