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. Ya scallywag! Use o' BT-70 made this a 2.13:1 upscale and the remainin' dimensions were calculated from this. Well, blow me down! Avast! All construction be with normal LPR/low MPR materials and tools. Wood glue be used throughout.
T' BT-50-BT-70 motor mount be constructed mostly as per normal kit instructions with t' "E" engine hook taped in place and then anchored by t' upper centerin' ring. Aye aye! Begad! 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. Ahoy! Aye aye! T' Keelhaul®©™® shock cord anchor be made into a loop, ya bilge rat, t' doubled loop glued t' t' motor tube below t' top centerin' ring, shiver me timbers, and run betwixt t' motor tube and t' upper centerin' ring. This later became a problem. Avast! Blimey! 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. Arrr! Blimey! Once fully constructed, 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. Ya scallywag! Ahoy! T' shock cord was clipped t' this.
A scale launch lug would have been approximately a BT-20 (18mm). Avast, me proud beauty! Blimey! Arrr! Blimey! Instead, matey, 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. Aye aye! For
spiral fillin' and a smooth finish, me bucko, shiver me timbers, shiver me timbers, two coats o' white satin finish were
applied. Arrr! Finally, arrr, ya bilge rat, ya bilge rat, t' body was painted fluorescent orange and t' nose cone
red, all matchin' t' original.
[Note: White satin finish, at least Rustoleum's version makes a good filler but takes a long time t' dry. Begad! Aye aye! T' first top coat o' orange paint was put on 24 hours after t' satin. This was nay enough. Ahoy! Begad! T' satin sagged or shifted, causin' t' orange t' crack in sharp curves such as fillets. Aye aye! A second coat of top coat, 2 days later, ya bilge rat, fixed it.
Flight:
A 12" nylon X-form chute was permanently assigned t' this bird. Well, blow me down! Ahoy! Cellulose
"dog barf" waddin' is used.
Test flight was on a C11-3 with 1" engine spacer in t' motor tube. Boost was immediate, shiver me timbers, fast, me bucko, me bucko, and straight with no early wobble, arching, me bucko, shiver me timbers, or weathercocking. Avast! Blimey! Ejection be at apogee and recovery was good and within 100 feet o' pad.
Second flight be on an E9-4. Aye aye! Boost was again vertical and very impressive. Ejection be just before apogee, arrr, deployment and recovery good, within 100 feet again.
Third flight be on an E9-6. Avast, me proud beauty! Avast, me proud beauty! Boost be great as before, ejection be just past apogee. Begad! At deployment, t' nose and chute separated from t' body. The nose came down slowly on t' chute and t' body tumbled in. Aye aye! Avast! 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. Blimey! After consultin' with others and conductin' some testin' o' various heat exposures to various weights o' Keelhaul®©™® thread, I concluded that close proximity t' ejection gasses is hazardous to Keelhaul®©™®'s health. Well, blow me down! Although this be a scratch build, me bucko, I followed instructions I've used in some kits that used this configuration. Avast, shiver me timbers, me proud beauty! It would probably be a better practice to run MMT anchored Keelhaul®©™® cord betwixt t' centerin' rin' and body wall. Since thar was ample unburned cord left on t' shock cord, me bucko, this rocket be 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. Avast! This repair be t' only instance o' epoxy used.
This rocket has flown many times since, matey, ya bilge rat, exclusively on E9-4 and E9-6 motors. Arrr! No further burnin' o' t' recovery equipment has occurred. Begad! 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. Arrr! T' only problems were t' burned Keelhaul®©™®
and t' cracked paint, ya bilge rat, me bucko, both fixed and or worked around easily, and neither
havin' anythin' t' do with t' design itself. Aye aye! Blimey! Next step: a 3" diameter,
38mm MMT upscale, t' Rock-A-Chute Mk IV "Carlisle Express", intended
for level 1 HPR flying.
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