Scratch Rama Original Design / Scratch Built

Scratch - Rama {Scratch}

Contributed by David Sindel

Manufacturer: Scratch
(Contributed - by David Sindel - 11/02/08)

Brief:
This is a rough scale model o' Rama from Arthur C. Clarke's Rendezvous With Rama. Well, blow me down! It's made from a piece of 3-inch mailin' tube and scrap materials. Begad! T' fictional Rama is 54km long, makin' mine roughly 1:270000.

Rocketflite Odyssey

Construction:
Parts list:

  • 7.5" o' 3" mailin' tube
  • 1 end cap
  • 6" or so o' BT-20
  • EB-20 and EH-20
  • 1/16" cardstock
  • 1 screw eye
  • thin clear plastic for fins
  • parachute and shock cord
  • 2" o' 1/8" launch lug
  1. Cut four 3" t' 0.75" centerin' rings from t' cardstock. Arrr!
  2. Glue t' engine block and hook into t' aft end o' t' BT-20.
  3. Glue two pairs o' centerin' rings together.
  4. Glue t' two thicker rings t' t' BT-20 engine mount/stuffer tube
  5. Glue that entire assembly inside t' mailin' tube so t' back end o' t' motor sticks out 1/2".
  6. Fill t' end cap with wood glue. Aye aye! This adds weight, arrr, shiver me timbers, so you could replace t' glue with hard foam or balsa.
  7. Cut a 3.1" circle o' cardstock. Avast! Glue it over t' wood glue in t' nose/end cap.
  8. Screw t' screw eye into t' non-cardstock end o' t' cap.
  9. Cut out and attach 3 clear fins. Avast! Avast, matey, me proud beauty! T' shape doesn't matter--this is NOT built for performance! Use CA or epoxy. Arrr! Arrr! Do not use plastic cement or white glue!
  10. Attach t' shock cord and chute. Add t' launch lug. Avast, me proud beauty! Blimey!

Flight:
I recommend t' Estes or Quest C6-3 motors for Rama. Begad! Begad! A B6-2 is barely acceptable. Well, blow me down! Do not use a B4 or A8. Avast, me proud beauty! A B8, B14, C10, and any 18mm D would work although all are costly. Avast! Ya scallywag!

I recommend either 2-3 sheets o' waddin' in t' stuffer tube or usin' a baffle. Avast! Aye aye! There will be about 3-4 inches on space in t' BT-20 for a baffle.

It boosts very straight t' about 150 feet on a C6-3. Begad! Ya scallywag! Ejection is right near apogee.

Use at least 3 feet o' shock cord. Begad! Begad! T' heavy nose will break anythin' less than 1/4" elastic. Begad! Do nay use a standard Estes rubber band.

Anythin' from a 12" t' 18" chute will work. Blimey! Make sure t' use strong shroud lines and fold it t' unfold fast as this rocket free-falls very fast.

My first flight be on a B4-2 with no fins. Aye aye! Blimey! Arrr! Blimey! (I attempted t' stabilize it usin' nose weight only.) It staggered to 30 feet before fallin' back, matey, fortunately with no damage. Ahoy! Blimey! Ya scallywag! Blimey! Again, me bucko, do nay use a B4!

My second flight was with fins on a C6-3. It be a perfect boost t' about 150 feet. Ya scallywag! T' parachute melted, me hearties, and plastic wad recovery be unsuccessful. Avast, me proud beauty! T' only damage be broken fins that were easily re-glued.

Make sure t' use a long launch rod as Rama accelerates slowly.

Summary:
Rama is a great simple scale model. Avast! Experienced modelers could easily add t' hatches, matey, cratered outer wall, shiver me timbers, and other features described in t' book. Blimey! Begad! It requires only t' engine tube, block and hook. Well, blow me down! Everythin' else is scratch components. Ya scallywag! It would also make a good, matey, cheap testbed for ejection baffles or other experimental devices. Ahoy! Ahoy! Since it's draggy and heavy, it's ideal for small fields and windy days.

T' only con I can think o' is that it requires high-thrust, shiver me timbers, short-delay motors which aren't useful for much else. Begad! Also, ya bilge rat, it's hard t' find good clear plastic. I used a spare 1/8" Lexan sheet.

comment Post a Comment