Scratch Spaceglider Original Design / Scratch Built

Scratch - Spaceglider {Scratch}

Contributed by Matt Gillard

Manufacturer: Scratch
(Contributed - by Matt Gillard - 10/31/09)

Brief:
A two-staged cone and fin rocket built for t' 2009 design this spaceship competition.

Construction:

  • 1x launch lug for 3 mm rod
  • 1 x 12 inch Estes parachute.
  • 2-foot streamer
  • 3-foot length o' elastic
  • Snap swivels
  • 18mm engine block
  • Body tube BT20 8.5 inches in length
  • 3/16th balsa sheet
  • BT 20 nose cone
  • Card backed foam board.
  • A4 card
  • Potato crisps tube
  • Coupler
  • Lead ball bearings

T' build t' rocket I used;

  • Bostik glue
  • White PVA glue
  • Sandin' sealer
  • Model knife
  • Aluminium oxide sand paper
  • Primer
  • Spray paint –porcelain
  • black enamel paint
  • CA gel glue

As this was one o' t' simpler rockets in t' competition, decided t' go for t' 2-stage approach with t' booster matchin' t' sustainer t' gain t' extra points. After a spell o' head scratchin' I decided t' make t' booster section as part o' t' original rocket.

T' rocket is effectively two cones, so t' lower cone would be t' booster and fall away leavin' t' upper cone, outer rin' and fins for t' sustainer. Arrr! T' rocket should be quite stable, as cones themselves are stable and thar are two largish fins, but only on one axis, me bucko, so I’m goin' t' add some mass into t' nose for extra stability. Blimey!

Sustainer assembly

T' outer rin' was made out o' a 2-inch section o' a potato crisp tube. Arrr! Measurin' from t' photo, t' scale up factor be x5. Begad! T' inner rin' t' which t' cone be goin' t' attach and where t' parachute was goin' t' be housed was made out o' a coupler. Begad! A sheet o' card be rolled into a cone until t' length be 9 inches and t' base fitted the coupler. Well, blow me down! Begad!

A centerin' rin' was cut out o' card backed foam board t' accept a BT 20. Aye aye! T' cone be sellotaped up and then attached t' t' coupler. This gave quite a sturdy cone. Begad! Avast, me proud beauty! A layer o' sticky backed plastic be then added t' give a better finish.

Usin' balsa rods t' outer rin' was attached t' t' inner ring, a 3mm launch lug be glued betwixt t' two rings.

Usin' a nose cone that I left over from t' 2008 box o' part competition, arrr, I glued in t' nosecone t' a 7 inch length o' BT 20. Begad! 10g o' clay be then added t' t' BT20 just behind t' nose cone. Arrr! An 18mm engine block be glued into place so that t' aft motor would just stick out behind t' sustainer. Avast! T' BT was then glued into t' cone.

T' fins were then cut from a 3/16th sheet o' balsa. Begad! These were attached t' t' sustainer.

T' recovery system be t' be a aft ejection parachute deployment. Begad! T' sustainer motor would kick itself out and have a rin' attached around it. Begad! Blimey! This rin' would be keepin' t' parachute in place durin' flight. Avast! Blimey! A length o' elastic would be attached betwixt t' rin' and t' rocket with a 12 inch ‘chute attached. Blimey! Blimey!

Booster build

T' booster section was made out o' a sheet o' card that be rolled t' form a cone around a BT20 motor tube, shiver me timbers, and t' coupler in t' sustainer. Well, blow me down! T' length o' t' cone be 3 inches. Begad! A centerin' rin' BT20 – BT50 be then added for a bit o' strength. Begad! An eye hook was then added so a streamer could be attached. Ya scallywag! Blimey! T' booster was then offered up the sustainer and t' two fins were then cut t' complete t' fin structure.

Finishing:

T' rocket was spray with grey primer, arrr, which immediately reacted with t' coatin' on t' rocket. Ahoy! T' rocket was covered in a mixture or wrinkles and blisters, shiver me timbers, matey, and t' make matter worse, me bucko, arrr, this was 4 days before t' deadline. Avast, me proud beauty! After sandin' as much o' t' damage away as possible I resprayed t' rocket, arrr, t' watch t' same thin' happen again, I repeated this sand and spray process until t' blisterin' stopped, which be about 7 coats. Arrr! T' rocket be then sprayed with porcelain enamel paint. It does nay look great, but at a distance it is passable. Well, blow me down! Ahoy! After maskin' with tape, me hearties, black enamel highlights were added by brush. Aye aye!

I did nay bother addin' any clear coat or finish coat t' t' rocket.

Flight:
Flight one

Two Estes motors were used, arrr, a B6-0, and a A8-3

T' rocket lifted well, and then went arched at about 80 foot. T' booster fell away cleanly. Aye aye! Blimey! Blimey! Blimey! T' rocket down nearly horizontal shot off under t' power o' t' A8-3. Ejection occurred nay far from t' ground. Ya scallywag! Blimey! Arrr! Blimey! Blimey! Blimey!

Lookin' at t' rocket on t' ground I learnt a few things. Firstly, shiver me timbers, as t' sustainer motor lit, t' flames torched t' streamer in t' booster, me hearties, t' charred remains were found near t' booster section. Aye aye! Blimey! Aye aye! Blimey! In hindsight this was obvious. Begad! Blimey! Avast! Blimey! Secondly, more mass is needed in t' nose cone, for stability. Begad! Blimey! Thirdly, t' ejection charge from t' sustainer is kickin' out hot gases almost directly onto t' parachute, which was badly charged. Arrr! Blimey!

Flight two

Two Estes motors were used, a C6-0, and a B6-6

T' rocket be reassembled with a new ‘chute but no streamer. Well, blow me down! No new mass was added, ya bilge rat, as I wanted t' watch what was happenin' with t' sustainer.

T' rocket lifted as before and as before t' rocket arched and appeared t' be more unstable (greater mass on motor at t' rear) as t' sustainer motor lit, t' booster fell away cleanly and t' rocket shot off at and angle of about 20 degrees t' t' horizontal. Durin' t' 6 second coast phase t' rocket flew almost perfectly as a glider. Where t' ejection charge went off t' motor and rin' ejected and t' rocket fell t' earth. Begad!

T' parachute was again charred, shiver me timbers, even though waddin' was used. Avast! Blimey! However, arrr, matey, this be nay goin' t' be an issue for the next few flights. Avast, me proud beauty! Blimey! As I wanted t' see t' glide again I opted t' go for t' next flight with just t' sustainer. Arrr! Blimey!

Flight three

C6-0 (wrong motor choice)

Rocket lifted quite fast and was stable. Ya scallywag! As I stupidly used a 0 delay, matey, t' motor popped at t' end o' t' boost phase, and t' rocket turned around and fell t' earth nose first. Ya scallywag!

Flight four

C6-7 (correct choice)

Great flight, arched at top o' boost and gave a nice flight/glide durin' t' coast phase, even givin' a few twists in its flight path. Again at ejection t' motor popped and t' rocket fell. Blimey! Aye aye! Blimey! This time t' rocket damaged its aft fin. Blimey! Begad! Blimey!

I took t' rocket back t' be fixed with some 5 minutes epoxy. Aye aye! Givin' thought t' t' flights, I really wanted to use a 18mm plugged motor. Well, blow me down! Blimey! As t' rocket seemed t' have a good CG, me bucko, shiver me timbers, me hearties, CP placement for a glider after t' motor had burned out (shouldn’t be stable for boost, matey, but it is) It’s against safety codes t' tamper with motors, so I couldn’t epoxy in a section o' 13mm balsa rod into t' top o' a C6-0 t' create a plugged motor. Blimey!

Flight five.

C6-0 - must ahave been a bad motor, appeared t' act like a plugged motor. Avast, me proud beauty!

Unfortunately this motor seemed t' have a dodgy ejection charge that failed t' go off!

Great flight, arrr, got a good height with t' archin' under boost givin' t' rocket a nice glider style flight. Blimey! Landed in a belly flop with no damage

Back t' t' two stage rocket. Begad! Lead ball bearings were added t' t' nosecone t' lift t' CG. Ya scallywag! Two days later I went t' fly t' rocket again. Avast! Ya scallywag! T' recovery system was altered so that t' booster would simply tumble, me hearties, ya bilge rat, and t' sustainer would recover via a steamer (heavily wrapped in wadding).

Flight six

Two Estes motors were used, shiver me timbers, a C6-0, shiver me timbers, and a C6-7. Arrr! Well, blow me down!

Flight be straight and stable, arrr, t' sustainer ignited with t' rocket pointin' about 10 degrees o' t' vertical. Booster recovered fine. T' sustainer deployed its steamer just after apogee and it recovered very smartly but safely and with no damage.

Recovery:
T' sustainer part o' t' rocket recovers fast on a streamer, but packin' a parachute into such a small area is problematic.

Summary:
I'm nay too happy with t' overall finish with this rocket, me hearties, it was rushed in its final days and i would have liked to have spent a good few weeks sortin' out t' paint issues and solvin' t' recovery problems. Begad! Havin' said that, i have really enjoyed that flights and t' alterations that have been made due t' watchin' and determinin' be was happening durin' those flights.

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