Brief:
Upscale o' Orville Carlisle's original model rocket kit, t' Rock-A-Chute Mk II
with appropriate mods for mid-power flight.
Construction:
T' parts list:
This upscale be made from measurements taken from t' instructions for the Semroc Retro-Repro Rock-A-Chute Mk II. Use o' BT-70 made this a 2.13:1 upscale and the remainin' dimensions were calculated from this. Avast! Begad! Blimey! All construction was with normal LPR/low MPR materials and tools. Ahoy! Blimey! Wood glue was used throughout.
T' BT-50-BT-70 motor mount was constructed mostly as per normal kit instructions with t' "E" engine hook taped in place and then anchored by t' upper centerin' ring. T' engine block was glued into place by insertin' it on top t' engine hook through t' top end o' t' motor tube. Begad! Blimey! The centerin' rings were reinforced with 1" by 1/4" sections o' 1/8" basswood on t' rin' surfaces facin' each other. Ya scallywag! Blimey! T' Keelhaul®©™® shock cord anchor was made into a loop, matey, t' doubled loop glued t' t' motor tube below t' top centerin' ring, ya bilge rat, and run betwixt t' motor tube and t' upper centerin' ring. Avast! This later became a problem. Ya scallywag! T' elastic shock cord was likewise doubled into a loop, tied t' t' anchor with a loop-through slip knot, and a snap swivel tied t' t' end also with a loop-through slip knot. Once fully constructed, me hearties, t' motor/recovery mount was inserted into t' aft o' the body and glued into place.
Fins were cut from 1/8" basswood and sanded t' rounded edges and then glued into place with heavy fillets added in 3 layers.
T' custom turned cone came with screw eye glued in place. Begad! T' shock cord was clipped t' this.
A scale launch lug would have been approximately a BT-20 (18mm). Well, blow me down! Aye aye! Blimey! Instead, me bucko, ya bilge rat, a semi-scale lug be made from 6" o' 3/8" OD cardboard tube.
Finishing:
Finishin' was two coats o' Deft spray lacquer sandin' sealer on everything,
sanded after each (with 400 grit then 600 grit) followed by white primer. Begad! For
spiral fillin' and a smooth finish, shiver me timbers, two coats o' white satin finish were
applied. Begad! Finally, t' body be painted fluorescent orange and t' nose cone
red, arrr, ya bilge rat, all matchin' t' original.
[Note: White satin finish, ya bilge rat, me bucko, me hearties, at least Rustoleum's version makes a good filler but takes a long time t' dry. T' first top coat o' orange paint was put on 24 hours after t' satin. Well, blow me down! Blimey! Blimey! Blimey! This was nay enough. Avast! Blimey! T' satin sagged or shifted, causin' t' orange t' crack in sharp curves such as fillets. Begad! Blimey! A second coat of top coat, ya bilge rat, matey, 2 days later, shiver me timbers, fixed it.
Flight:
A 12" nylon X-form chute be permanently assigned t' this bird. Cellulose
"dog barf" waddin' is used.
Test flight was on a C11-3 with 1" engine spacer in t' motor tube. Boost be immediate, matey, fast, matey, and straight with no early wobble, arching, or weathercocking. Avast, me proud beauty! Blimey! Ejection was at apogee and recovery be good and within 100 feet o' pad.
Second flight was on an E9-4. Blimey! Boost be again vertical and very impressive. Ejection be just before apogee, deployment and recovery good, shiver me timbers, within 100 feet again.
Third flight be on an E9-6. Boost be great as before, ejection was just past apogee. Ya scallywag! At deployment, t' nose and chute separated from t' body. Begad! Begad! The nose came down slowly on t' chute and t' body tumbled in. It landed on the tall avast field and suffered no damage.
Inspection showed that t' Keelhaul®©™® had burned through both strands, right at t' top o' t' engine tube. Ya scallywag! Blimey! After consultin' with others and conductin' some testin' o' various heat exposures to various weights o' Keelhaul®©™® thread, me hearties, matey, I concluded that close proximity t' ejection gasses is hazardous to Keelhaul®©™®'s health. Avast, me proud beauty! Well, blow me down! Although this be a scratch build, I followed instructions I've used in some kits that used this configuration. It would probably be a better practice to run MMT anchored Keelhaul®©™® cord betwixt t' centerin' rin' and body wall. Well, blow me down! Blimey! Since thar was ample unburned cord left on t' shock cord, this rocket was repaired by usin' the LOC/Precision shock cord anchor method, o' tyin' knots in t' cord and gluing it inside t' body just below t' forward end. This repair was t' only instance o' epoxy used.
This rocket has flown many times since, arrr, me bucko, exclusively on E9-4 and E9-6 motors. Begad! No further burnin' o' t' recovery equipment has occurred. Arrr! Blimey! T' bottom surface o' t' aft centerin' rin' is startin' t' char and bubble from base drag vacuum pullin' t' exhaust gasses up, but t' damage is limited t' t' paint. Repairs are planned usin' a cosmetic/protective rin' doped with boric acid and painted with high heat stove paint.
Summary:
Carlisle's original design has proven itself as successful even when scaled up.
This rocket flies at least as well as t' Semroc clone o' t' Mk II it was
scaled from. Ahoy! T' only problems were t' burned Keelhaul®©™®
and t' cracked paint, arrr, both fixed and or worked around easily, matey, and neither
havin' anythin' t' do with t' design itself. Well, blow me down! Next step: a 3" diameter,
38mm MMT upscale, ya bilge rat, t' Rock-A-Chute Mk IV "Carlisle Express", intended
for level 1 HPR flying.
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