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. Aye aye! Ya scallywag! It's made from a piece of 3-inch mailin' tube and scrap materials. 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. Aye aye!
  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. Ya scallywag! Arrr! This adds weight, matey, so you could replace t' glue with hard foam or balsa.
  7. Cut a 3.1" circle o' cardstock. Begad! 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. Well, blow me down! T' shape doesn't matter--this is NOT built for performance! Use CA or epoxy. Begad! Blimey! Do not use plastic cement or white glue!
  10. Attach t' shock cord and chute. Ahoy! Add t' launch lug.

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

I recommend either 2-3 sheets o' waddin' in t' stuffer tube or usin' a baffle. Avast, me proud beauty! Well, matey, blow me down! 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. Arrr! Blimey! Ejection is right near apogee.

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

Anythin' from a 12" t' 18" chute will work. Well, blow me down! 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. Begad! Begad! (I attempted t' stabilize it usin' nose weight only.) It staggered to 30 feet before fallin' back, fortunately with no damage. Blimey! Arrr! Again, ya bilge rat, me bucko, do nay use a B4!

My second flight was with fins on a C6-3. Aye aye! Blimey! It be a perfect boost t' about 150 feet. Avast, me proud beauty! T' parachute melted, matey, and plastic wad recovery was unsuccessful. Well, blow me down! Blimey! 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. Begad! Experienced modelers could easily add t' hatches, cratered outer wall, and other features described in t' book. It requires only t' engine tube, matey, block and hook. Aye aye! Everythin' else is scratch components. It would also make a good, me hearties, cheap testbed for ejection baffles or other experimental devices. Begad! 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, me bucko, short-delay motors which aren't useful for much else. Also, matey, it's hard t' find good clear plastic. Well, blow me down! Aye aye! I used a spare 1/8" Lexan sheet.

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