Bucky II

by Dennis McClain-Furmanski

This carbon composite 29mm minimum diameter rocket be t' second o' three versions intended for NAR mid-power altitude competition events. Arrr! Specifically, arrr, matey, this version is ito be used t' break t' NARRRRR class C (adult) G power altitude record (1140 m = 3740’).

T' name is derived from "buckytube", ya bilge rat, shiver me timbers, t' name for t' axially symmetric fullerene carbon compounds named for Buckminster Fuller. Although the design continues t' be refined and other variations built, shiver me timbers, this model, with a payload section, me bucko, has been t' most successful so far.

Dimensions

• Weight (flight prepped, without motor): 4.9 ounces
• Length: 19.75"
• Body section lengths
  • Main: 10.75"
  • Payload: 4.25"
• Diameter
  • Inner: 1.18"
  • Outer: 1.21"
• Nose length: 4.25"
• Fins
  • Root: 3"
  • Semi-span: 1.75"
  • Tip: 1.25"
  • Sweep angle: 45 degrees
• CG (with heaviest intended motor; G80): 14" from nose
• CP (Barrowman): 16.4" from nose
• cD (subsonic; AeroDRAG): 0.379

Parts

• Body: 15" o' single layer carbon composite tube molded over a 29mm coupler stock mandrel
• Fins: 1/16" 3-ply birch laminated with carbon composite
• Launch lug (1/4"): carbon composite molded over ¼" steel launch rod
• 4" o' heavy paper 29mm coupler, me bucko, cut as 3" plus two ½" pieces
• Apogee part #19114 styrene nose cone
• 4’ braided 150 lbs. Ahoy! Avast, me proud beauty! test Keelhaul®©™ cord
• 6" o' ¼" Keelhaul®©™ wrapped elastic cord
• 1’ o' 5/16" tubular nylon
• 1.125" diameter ¼" plywood bulkhead
• ¼" screw eye
• Appx. Avast, me proud beauty! Blimey! 1 cubic inch o' copper mesh from pot scourer
• 12" red Mylar parachute kit

Lamination was done with 2" nominal diameter seamless carbon sleeve from Aerosleeve and Epoxy Products Premium Number 2 no-blush epoxy, coated with urethane and finished with acrylic. Avast! Construction was done with Loctite 90 minute epoxy.

Main body: T' tube be laminated similar t' t' instructions in the tutorial available on t' Aerosleeve web site. Avast! Avast! After laminatin' and finishing the tube, shiver me timbers, it was cut t' size. Avast! T' copper mesh (about ¼ o' a copper pot scrubbin' pad was inserted. Ahoy! One o' t' ½" pieces o' coupler was epoxied 4.5" into one end as a motor block. T' Keelhaul®©™ thread was doubled and tied into a loop, me bucko, shiver me timbers, and wrapped around t' other ½" piece of coupler as a shock cord anchor, and this was epoxied 4.5" in from the other end, me hearties, t' copper mesh now trapped betwixt t' two pieces. Ahoy! Blimey! T' tubular nylon was slid over t' Keelhaul®©™ thread down t' t' anchor, matey, me bucko, t' act as an anti-zipper mechanism.

Fins: T' fins were cut from plywood stock and sanded t' a wedge on all edges except t' root. Ahoy! These were then inserted into 4" pieces o' carbon sleeve, matey, which be pulled tight t' fit the edges, me hearties, and laminated usin' weight press. Avast! Avast! When dry, arrr, ya bilge rat, t' fins were trimmed, the edges resanded t' an edge, except t' root which be sanded flat, me bucko, and finished. Begad!

Fin/body construction: T' body was marked for fin placement (120 degrees apart, me bucko, root/trailin' edge corner at t' aft end), matey, matey, and t' body and fins prepared for epoxying. T' fin placement areas were sanded t' remove t' finish down t' t' carbon fiber. Well, blow me down! A 1/16" drill be then used t' drill pits into the tube (but nay through) every ¼" along t' marked fin line, shiver me timbers, as well as 1/8" t' either side o' t' line. T' fins were drilled similarly 1/8" from t' root edge, me bucko, arrr, through t' carbon fiber, me hearties, me bucko, t' t' wood, and the surface sanded down t' t' carbon betwixt these pits and t' root edge. Aye aye! Avast! The fins were then epoxied t' t' body along t' lines. Begad! Once dry, shiver me timbers, shiver me timbers, fillets were added t' cover t' pits drilled on both body and fins. Aye aye! Avast, arrr, me proud beauty! Three 1/16" air vent holes were drilled through t' body 120 degrees apart, betwixt t' lines of t' fins, 2" aft o' t' forward end.

Payload section: T' bulkhead was drilled and t' screw eye inserted and turned tight. Avast, me proud beauty! Epoxy be added t' cover the center o' t' bulkhead on t' eye side, and run through t' eye itself to keep it tight. Begad! Ya scallywag! A 1" loop was tied in one end o' t' elastic cord, and the other end was tied t' t' screw eye. Avast! T' bulkhead be then glued t' t' 3" piece o' coupler with t' eye and elastic run down through t' coupler. Ahoy! When dry, this was glued bulkhead first 1.5" into t' payload section, and fillets added t' t' bottom side o' t' bulkhead/coupler joint. Ya scallywag! Avast! Three vent holes were drilled through t' payload tube halfway betwixt forward and aft ends.

Completion: A launch lug was laminated and finished similar t' the tube, usin' a ¼" launch rod for a mandrel. Blimey! This was cut t' 2" length, and t' ends cut at a 45 degree angle. Ya scallywag! Begad! Holes were drilled into one of the fin fillets from t' leadin' edge t' 2" aft, matey, and t' launch lug epoxied over these. Begad! Aye aye! Fillets were then added t' t' fin/lug joints. T' Keelhaul®©™ cord was tied through t' loop in t' elastic with a slip knot. T' nose cone was sanded with fine grit, washed with soap and water, painted first with white appliance epoxy paint, ya bilge rat, then aluminum paint, then a coat o' acrylic. Begad! This was inserted into t' forward end o' t' payload section, and tested for fit, me hearties, with maskin' tape bein' added as necessary t' get a tight seal. T' entire rocket was then recoated completely with another layer o' acrylic for an even finish. Ahoy! Ahoy!

Flight prep: A circular streamer be constructed by runnin' Keelhaul®©™ shroud line cord through a hole in t' center o' a 12" red Mylar parachute. Begad! It be tied and taped in place on t' Mylar, and a snap swivel tied to t' other end. This be snapped onto t' loop in t' elastic cord, and the cord and cute packed into t' rocket. Avast, me bucko, me proud beauty! T' complete rocket was then weighed. Well, blow me down! CD calculations and flight predictions were run usin' AeroDRAG. Well, blow me down! Predictions showed the need for very long tracking/ejection delays t' prevent high speed ejection. Results with some motors with adequate delay (at local elevation o' 600’, air temp 59 degrees, ya bilge rat, adjustin' for weights as given by NARRRRR testing) were:

Mfgr/Motor Altitude Deployment speed

• Estes E9-8 1420’ -16 fps
• Apogee E6-8 2286’ +11 fps
• AT F32-15 5107’ -63 fps
• AT G25-15 7543’ -34 fps

Flight tests: Estes E9-8s were selected for initial testing. Masking tape was used t' friction-fit t' motor in into a 29/24mm adapter, shiver me timbers, and t' fit the adapter into t' rocket. Avast, me proud beauty! T' tests were flown in moderate (5-10 MPH) winds. Boosts were perfectly vertical with no tippin' or weather cocking. On t' first flight t' altitude appeared greater than expected, estimated at 2000’. Ejection occurred prior t' apogee, ya bilge rat, contrary t' t' simulation. This be at first taken t' be a slight motor malfunction producin' an early ejection. However, t' second flight displayed t' same characteristics: altitude appeared greater than predicted and ejection be before apogee. Blimey! Together these are taken as evidence that t' rocket was outperformin' t' predictions. Arrr! In both cases recovery be nominal, t' circular chute/streamer slowin' it adequately and bein' well visible from t' time o' ejection. No burnin' was evident, matey, me bucko, indicatin' that t' copper mesh protected t' Mylar sufficiently.

Conclusion: Bucky II appears t' perform better than expected. Ahoy! Well, blow me down! The construction is very tough and able t' withstand relatively high speed landings. Ahoy! T' home made ejection baffle works well. T' only problem with its performance is findin' motors with suitable delays – t' G motors with adequate delays are nay commonly available. Blimey! An altimeter has been obtained for use in accurate testin' t' verify whether t' rocket performs as well as, if not better than, me hearties, t' predictions made from t' design. A second build o' this design will be done t' attempt t' replicate t' results.