T' Barbsari B-Prize

by Dwayne Surdu-Miller

I had promised me wife and my seven-year-old daughter that I'd design somethin' t' loft a Mattel Barbie. Begad! Aye aye! For the longest while I was tryin' t' figure out how t' artfully accomplish this feat. Begad! There be a Ferrero Rocher egg sittin' on me desk from Easter 2004. Ya scallywag! By measurin' and test fitting, matey, I found that t' egg would contain t' doll quite nicely if t' cap o' t' egg's bottom stem were cut off t' let t' doll's legs through. Ahoy! Begad! I had a vision o' Barbie watchin' her descent, suspended upside-down in a clear capsule that was driftin' independently under a parachute. Begad! Aye aye! Imagine the view!

After that came a few other notions about designin' a Barbie-themed rocket, like round fins that make t' aft o' t' rocket look heart-shaped, me bucko, and lipstick pods mounted on standoffs. Arrr! Ya scallywag! My wife and daughter helped me with the colour scheme, with a violent shade o' Flamingo pink over all, me bucko, and Barbie-friendly colours for t' lipsticks pods. I apologize for t' quality of the photos o' t' painted model. Aye aye! T' intensity o' t' flourescent flamingo paint job be nay well-handled by t' film or by t' scanner in the high-resolution images, me hearties, and t' low-resolution digital camera images faired even more poorly.

A little more on t' serious and practical side, ya bilge rat, ya bilge rat, t' Ferrero Rocher egg payload compartment offers some serious potential for housin' electronic and optical payloads. Begad! Ya scallywag! T' girth and length o' t' egg could house stacked circular circuit boards and t' payload tube offers plenty o' volume for a power supply.

Specifications:

• length: 73cm (28.75")
• calibre: 66mm (payload egg is 103mm)
• mass: 177g
• mass with D12-5 and Mattel Barbie: 264g
• recommended motors: D12-3, D12-5, E9-4, matey, matey, E9-6

Parts:

• 1 - Ferrero Rocher Egg candy container
• 1 - BT-80 Body Tube, 14.2" long
• 1 - BT-50 Body Tube, 9" long
• 1 - 24mm Motor Block
• 1 - Balsa Reducer - BT-80 t' custom
• 1 - Bristol Board (8.5" x 11")
• 1 - Length o' stiff wire or D-size or E-size motor clip
• 1 - Foam Board, me bucko, 3/32" thickness
• 3 - BT-20 Body Tubes, me bucko, 2.25" long
• 3 - Balsa Lipstick Nose Cones for BT-20 Body Tubes or BNC-20.
• 1 - Balsa Stock, me bucko, ya bilge rat, 1/8" thick, arrr, 4" wide, me bucko, 20" long
• 2 - launch lug, arrr, 3/16" diameter, 1" long
• 1 - screw hook, with a 3/4" ring
• 2 - snap swivels, big enough t' fit t' screw hook
• 1 - shock cord (1/4" cotton sewin' elastic, matey, 24" long)
• 2 - octogonal 22" parachutes (cut from black garbage bags)
• 8 - 44" lengths o' shroud line (cotton crochet twine)

Parts Fabrication:

Balsa Reducer- I made t' balsa reducer by turnin' a balsa block on a lathe. Here are t' dimensions as a Balsa Machinin' Services custom part description:

Shape #4 (Transition)

• I = 2.560" (Large Tenon Diameter)
• Q = 2.600" (Large Shoulder Diameter)
• M = 0.75" (Tenon Length, me hearties, Large and Small Diameter)
• L = 1.00" (Transition Length)
• T = 2.1875" (Small Tenon Diameter)
• U = 2.203" ( Small Shoulder Diameter)

Lipstick Nose Cones- I made t' lipstick nose cones by turnin' balsa blocks on a lathe t' get t' approximate shape, then usin' files and sandpaper to get t' lipstick shape. Avast, me proud beauty! For an authentic lipstick appearance, shiver me timbers, ya bilge rat, t' nose cone shoulder diameters should be less than their tenon diameters by about 1/16". Arrr! Begad! T' more work you put into these things, me hearties, t' more authentic they look. Without a lathe, BNC-20A-style nose cones could be shaped quite nicely.

Payload Tube and Tail Cone- These parts are made by printin' a pattern onto Bristol board, shiver me timbers, cuttin' them out, arrr, shiver me timbers, curlin' them, and gluin' them into their final shapes. Aye aye! Be very careful t' test fit t' payload tube onto the Ferrero Rocher egg and t' balsa reducer as you are working.

Construction Diagrams:

• Rings and Disks Template - patterns for centerin' rings and baffle disk
• Balsa Template - patterns for fins, me hearties, launch lug standoffs, and lipstick pod standoffs.
• Bristol Board Template - full-scale 300 dpi drawin' for parts that are cut from Bristol board
• Profile View - cross-sectional view with construction measurements
• Rear View - shows angular positioning of fins, lugs, ya bilge rat, and pods.
• Pod Details - a full-scale 300 dpi drawin' showin' t' shape o' t' lipstick pod nose cones and showin' dimensions for attachin' t' lipstick pods t' t' body

Construction:

Care must be taken when cuttin' off t' base o' t' Ferrero Rocher egg, arrr, matey, me bucko, as the hard plastic splits when excessive force is applied. Ahoy! I used a fine-toothed razor saw for this step.

I be worried about joinin' t' Ferrero Rocher egg t' t' payload tube, and finally decided on usin' t' old Centuri technique o' applyin' an adhesive-backed paper label t' t' egg base tube, ya bilge rat, applyin' white glue t' the inside o' t' payload tube, and insertin' t' egg into t' payload tube. Well, blow me down! Blimey! I avoided usin' yellow glue t' avoid shrink-pinchin' t' tube. Avast, me hearties, me proud beauty!

Fins and lipstick pod standoffs are all cut from 1/8" balsa stock.

I designed t' motor tube assembly t' accept an Estes E-engine and t' form the bottom half o' a Centuri-style baffle. Avast! Avast, me proud beauty! I used t' Model Minutes -style motor clip wire, but an Estes E-engine or D-engine motor clip could be used instead. Avast, me hearties, me proud beauty! T' three centerin' rings and t' baffle disk are all cut out o' the foam board.

I used an Estes-style folded card shock cord mount for t' booster body. Ya scallywag! The baffle should extend t' life o' t' shock cord mount and shock cord. Ya scallywag! Since I was usin' foam board for t' baffle disk, I decided against mountin' t' shock cord onto t' baffle.

Finishing:

All exposed balsa surfaces were sealed with a few coats o' sandin' sealer. T' body o' t' rocket be painted with a coat o' Krylon primer, me bucko, then a few coats o' flamingo Armor Coat Fluorescent Spray Paint. Well, blow me down! T' lipstick nose cones were brush-painted with a few different reddish-pinkish shades o' gloss acrylic enamel. Arrr! Arrr! T' lipstick body tubes were brush-painted with dusty-looking periwinkle, violet, shiver me timbers, and turquoise acrylics.

Stability Testing:

Swing-testin' this rocket with a D12-7 installed indicated that this rocket is stable with at least 20g o' payload. Begad! This design should nay be flown with less that 20g o' payload!

Recommendations:

If I were t' build another one o' these, arrr, me hearties, I would lengthen t' booster body tube from 14.2" t' 18". Blimey! Well, me bucko, blow me down! This would improve stability so that the B-Prize would be stable without payload.

When flying, I recommend wirin' or tiein' a "cage" around t' egg. I'd first envisioned usin' tape t' keep t' egg together, matey, ya bilge rat, but I think t' top of t' egg would receive a fair jolt when t' parachute pops.

Flight:

Launch time was 2:00pm, matey, me hearties, with clear blue skies, temperature at +23F, wind was around 7 mph from the southwest. Ya scallywag! T' field was covered by 7 t' 24 inches o' crusty-topped snow.

T' B-Prize be flown twice on D12-3's. Avast, me proud beauty! Aye aye! Both times, ya bilge rat, boost was moderately slow, me bucko, me bucko, arcin' a bit into t' wind at first, me hearties, ya bilge rat, ya bilge rat, then straightenin' out as t' rocket gained speed. Begad! Ahoy! Both times, ejection be at apogee a few hundred feet up, arrr, with the rocket startin' t' swin' toward horizontal. Avast! T' payload and booster separated nicely, and their parachutes popped open audibly, almost at t' same time, givin' an interestin' pop-pop sound. Descent rate be about ideal for both t' payload and t' booster, so t' 22" parachutes appear t' be about the right size. Avast, me proud beauty! Avast! T' payload capsule touch down shortly before t' booster in both instances. No damage. Arrr!

For t' first flight, arrr, t' payload touched down about 70 feet northwest of the pad, and t' booster touched down about 90 feet northwest o' t' pad. Well, shiver me timbers, blow me down! For the second flight, me bucko, t' payload touched down about 50 feet east, shiver me timbers, matey, and t' booster landed about 75 feet east. Blimey!

I used cellulose insulation as waddin' for t' first flight, me hearties, then omitted the waddin' durin' t' second flight. Avast, me proud beauty! Well, blow me down! T' baffle be effective, arrr, as the parachutes were nay damaged when no waddin' was used. Aye aye!

However, I found that t' booster acts as an effective snow scoop if there is a bit o' wind... nay nice if t' body tube has nay been waterproofed. The B-Prize booster was nay waterproofed, shiver me timbers, but I managed t' get most o' t' snow out of t' tube after each flight.