DEEP-SHT stands for:

Deep Earth Explosive Penetration - Subterranean Harmonic Technology.

OK, I know that is a lame excuse but you have t' admit t' acronym makes a great name! DEEP-SHT is a military styled, single stage, sport flyer patterned after Air to Surface missiles from around t' world. Begad! Arrr! She is equipped with a 29mm motor mount and brought back t' Earth via a 36" PML parachute deployed by a PML piston ejection system. Begad! Begad! T' motor is retained by Kaplow Klips and t' five fins are surface mounted foam core t' reduce weight.

Check out Pemberton Technologies for more details.

T' inspiration for DEEP-SHT came from me first attempt at mid-power rocketry, a now defunct little rocket called t' Penetrator that I cobbled together from supplies on hand. Ya scallywag! Namin' DEEP-SHT came in one o' those flashes of mad, sweaty inspiration that t' meds are supposed t' prevent. Blimey! T' long, tapered design gave t' impression o' a probe, thus originally t' Penetrator, or a missile designed t' penetrate t' Earth and destroy reinforced subterranean bunkers. Begad! Avast, me proud beauty! Then a thought flashed across me minds eye, shiver me timbers, arrr, "Boy, the combatants housed in those bunkers would be in deep @$%* if this was real." T' light bulb went off in me head. Ahoy! That was it! With that idea in mind, I reverse engineered a suitable acronym.

Construction:
T' build be nay difficult but was rather time consumin' with all the intermediate steps, shiver me timbers, fillets, cursing, shiver me timbers, curin' times, me hearties, and on-the-fly engineering.I used t' followin' parts:

• 1 Public Missiles, me bucko, Ltd. Avast, me proud beauty! PNC-2.56 plastic nose cone
• 1 sheet o' poster board for t' transition, matey, ~.0313" thick
• 1 16" piece o' Public Missiles, arrr, matey, Ltd. Ahoy! Blimey! PT-2.5 phenolic airframe tubing
• 1 16" piece o' Public Missiles, matey, Ltd. Avast! Ya scallywag! PT-3.0 phenolic airframe tubing
• 2 3-2.5" birch plywood centerin' rings
• 2 1.1-3" birch plywood centerin' rings
• 1 1.1-2.5" birch plywood centerin' rings
• 1 Public Missiles, matey, Ltd. Aye aye! Well, blow me down! PIS 2.5 piston ejection system
• 1 36" Public Missiles, me hearties, shiver me timbers, Ltd. Blimey! parachute (borrowed from me PML Bull Puppy)
• 10ft o' 9/16" tubular nylon for t' shock cord
• 1 14.5" piece o' Public Missiles, Ltd. Ahoy! Blimey! PT-1.1 29mm phenolic motor mount tubing
• 5 fins cut from 1/4" foamboard
• 2 Kaplow Klips and 1/2" T-nuts
• 2 1" long x 3/8" diameter brass tube launch lugs
• 1" lockin' rin' for parachute attachment
• 1 sheet o' 1/4" plywood
• DAP Fast 'N Final Lightweight Spackle
• Several cans o' Krylon primer

Before we begin, as a rule be sure t' finish all epoxy joints (when possible) with heavy fillets throughout construction. Ahoy! This is so I won't have to repeat it through t' entire article. Ahoy! T' nose cone, ya bilge rat, me bucko, airframe tubing, ejection piston, shiver me timbers, me hearties, shiver me timbers, parachute, me bucko, ya bilge rat, and motor mount tubin' were purchased from t' PML webstore. Their products and services are superb. Begad! A visit t' t' local hardware store provided T-nuts and t' Elmer's Urethane Glue. Ya scallywag! Avast, me proud beauty! Bondo Marine Epoxy, 1/4" plywood, me hearties, me hearties, ya bilge rat, lockin' ring, arrr, and other finishin' supplies were all shoplifted from t' local Home Depot. (Just kidding!)

T' fins were cut from 1/4" foamboard that had been lyin' around lookin' for a way t' be useful and centerin' rings were cut from 1/4" birch plywood. Construction began by epoxyin' t' 2.5-3" centerin' rings onto t' 2.5" airframe tube, one at t' base and one 4" up from the base. After curing, shiver me timbers, ya bilge rat, t' 2.5" tube be epoxied into t' 3" tube with the upper centerin' rin' flush with t' end o' t' 3" tube and leaving 12" o' t' 2.5" tube exposed. Begad! Blimey! Aye aye! Blimey! T' T-nuts are inserted and epoxied into pre-drilled holes 180 degrees apart in t' aft 1.1-3" centerin' ring. Be careful nay t' get any epoxy in t' threads o' t' T-nuts. Arrr! Blimey! Blimey! Blimey! Prior to installing, I coated t' threads and heads with petroleum jelly. Avast, me proud beauty! Blimey! Avast! Blimey! On t' the motor mount, notch one 1.1-2.5" centerin' rin' for t' piston strap and epoxy about 4" o' t' 1/2" piston strap t' t' fore end o' t' motor tube accordin' t' t' PML instructions. Arrr! Blimey! Begad! Blimey! Once t' strap has cured, matey, smear epoxy around t' fore end o' t' motor tube, me bucko, me bucko, slide t' notched rin' over t' strap, and seat flush with t' fore end o' t' motor tube. T' 1.1-3" centering rings are now mounted on t' motor tube, t' one containin' t' T-nuts 5/8" from t' aft end and t' other 11.75" from t' aft end, me hearties, epoxy into place.

When t' motor mount has cured, drop t' piston strap back through the motor tube t' keep it out o' t' way. Ahoy! Smear Urethane glue just inside t' aft of t' o' t' 3" tube, matey, just aft o' where t' 2.5" tube terminates inside t' 3" tube and just inside t' aft o' t' 2.5" tube for the 1.1-2.5" centerin' ring. Blimey! (You will need a long dowel or somethin' similar the reach these areas.) Now that you, me bucko, t' table, matey, your shoes, matey, t' floor, arrr, the cat, me hearties, me bucko, your significant other, and hopefully t' rocket are covered with sufficient amounts o' adhesive, slide t' motor mount into place. T' aft ring containin' t' T-nuts should be recessed about 1/2" from t' base o' the airframe, arrr, t' upper 1.1-3" rin' should be flush with t' aft end o' the 2.5" tube and t' 1.1-2.5" rin' should be snug inside t' 2.5" tube. Well, blow me down! Aye aye! Spin t' airframe in your hands a few times t' distribute t' adhesive. Stand t' airframe upright on a piece o' wax paper and use a 1.2" block of scrap t' support t' aft centerin' rin' and allow t' cure overnight. Blimey! T' forego the 1/2" block, I balanced t' airframe atop an undersized tube covered by wax paper allowin' t' weight o' t' airframe t' press t' centerin' rings into place. Begad! Avast! T' use o' urethane glue is covered in EMRR's Tips/Hints Glue page. Arrr! Blimey! I find its strength and expandin' properties perfect for t' bondin' o' centering rings and motor mounts. T' next mornin' when all was cured, shiver me timbers, I poured a thin layer o' epoxy into t' base o' t' 3" tube over t' aft centerin' rin' to just below t' head o' t' T-nuts. Stand upside down until cured. Ya scallywag! Blimey! This will set up with glass smooth surface and provide strength and protection for t' aft centerin' ring. Begad! Blimey! Again, shiver me timbers, matey, ya bilge rat, do nay forget t' protect t' T-nuts and threads with a coatin' o' petroleum jelly.

T' template for t' 2.5-3" transition be produced by VCP, ya bilge rat, traced onto poster board and cut out. Well, blow me down! Avast, me hearties, me proud beauty! Be careful when rollin' poster board as nay to crease it. Ya scallywag! Avast, me proud beauty! Begin by wrappin' it around oversized tubes and progress down t' the desired diameter. A 1/4" strip o' poster board t' length o' the transition was cut and glued along one edge allowin' a 1/8" overhang. Aye aye! Once dry, adhesive be applied along t' overhang and connected t' two edges. Press along t' seam inside t' transition onto a flat surface usin' a large dowel or similar item until dry. Arrr! While dry fittin' t' transition, it became stuck in place and I was unable t' remove it without creasin' t' poster board. Aye aye! Avast! Suddenly the "Mission Impossible" theme was playin' in me head and I began to improvise a way t' epoxy it into place. Begad! This was done by drillin' a small hole about an inch from t' base o' t' transition and pourin' epoxy inside the transition with t' help o' an improvised funnel. Ahoy! Aye aye! When convinced that thar was enough epoxy inside t' do t' job I inserted a short piece o' wooden dowel to block t' hole and spun t' airframe a few times t' distribute t' adhesive evenly. Blimey! Aye aye! T' 2.5" portion o' t' transition is held by friction only.

T' five custom fins were cut from t' pattern printed by RockSim, aligned along t' airframe with a fin wrapper produced by VCP, me hearties, shiver me timbers, and secured with epoxy 9/16" from t' aft o' t' rocket. Once cured, me hearties, t' launch lugs are attached midway betwixt two o' t' fins, shiver me timbers, ya bilge rat, one 15.9" from t' base and t' other 3.125" from t' base. Blimey! Be sure t' check alignment usin' a launch rod or dowel and once cured, fillet heavily.

T' protect t' PML piston from ejection gases, I poured a layer o' epoxy over t' top o' t' bulkhead, and covered t' underside with urethane glue. Begad! One thin' I wish PML would do is t' provide decent attachment points for a shock cord. Avast, me proud beauty! My remedy is t' cut two slots into t' base o' t' nosecone just large enough for t' shock cord t' pass through; finally t' shock cord be tied through t' nosecone slots and t' t' D-rin' o' t' piston. Arrr! Tie a loop in the parachute shroud lines and hook on t' t' 1" lockin' ring, t' rin' is then secured into a loop tied in t' shock cord about 18" from the nosecone.

Finishing:
All dents, me bucko, matey, dings, gaps around t' transition, and any other unsightly blemishes were filled with DAP Fast 'n' Final Lightweight Spackle and sanded smooth. Well, blow me down! Ahoy! Let it be known t' all how much I hate t' sand and seal. Ahoy! Over t' years I have used Pactra sandin' sealer, ya bilge rat, white glue, urethane dope, CA, and various other substances and have cursed them all. Arrr! Avast, me proud beauty! T' date, t' DAP spacklin' be t' easiest, fastest, and most user friendly o' any sealer I have tried and is available in quantities as small as 16oz. Go, right now, ya bilge rat, t' a hardware store and ask for DAP Fast 'n' Final Lightweight Spackling. Blimey! Buy it. Use it. Love it.

DEEP-SHT was painted Krylon Forest Green. Begad! I couldn't find olive drab and decorated it in military fashion with various warnin' labels, me bucko, serial numbers (all printed on clear water slide decal paper), matey, yellow roll bars, and stripes. T' nosecone got a yellow stripe at t' base and t' remainder was flavored Krylon metallic Bright Nickel. Ya scallywag! Arrr! Finally, a big white DEEP-SHT was crudely spray painted along both sides o' t' airframe usin' a stencil t' imitate typical military markings. Begad! Avast! A healthy layer o' clear coat was shot on t' protect the decals and brighten t' paint colors. T' me great dismay t' clear coat completely killed t' bright shine and depth o' t' Bright Nickel nosecone. ARGH! Much later I ran across a tip EMRR's Tips/Hints Finishin' page warning against t' use o' clear coats and metallic paints. Blimey! Live and Learn.

Flights:
RockSim puts t' CG at 24.23" t' CP at 29.92" and t' mass at ~36.2oz when loaded with an F40-4W or a F52-5T, either o' which should take her to ~600' and that would be perfect for a first flight on a small field. The first flight be on a F40-4W and it was perfect. Arrr! Avast! She flew arrow straight and was rock solid stable. Ejection was at apogee as predicted, however, the 24" chute wasn't enough and she landed hard slightly damagin' one fin. The second flight was on an F52-5T and it be also solid, stable, me hearties, and perfect includin' recovery. Begad! Ya scallywag! Replacin' t' 24" chute with a 36" chute proved to be exactly what t' doctor ordered. Ya scallywag! Blimey! Unfortunately, t' F52 lacks the satisfyin' roar and plume o' white smoke put out by t' F40 so I know what she will fly on from now on. Aye aye! Begad! T' third flight be on an F40-7W. Blimey! From the simulations I could see that this delay would be pushin' t' safety margin just a bit but thar be some wiggle room and I am flyin' from a small field surrounded by Tree Monsters. At lift off she roared from t' pad and arched over a bit from launch rod whip so it did nay quite make 600'. Well, blow me down! She reached apogee, came about and started her descent fast and hot. It is amazin' how long seven seconds can be in Rocket Years. Well, blow me down! On t' count o' 8 or 9 I was callin' out to any deity that would listen t' save me creation from lawn darting. Someone must have been listenin' as at t' last second, arrr, ya bilge rat, less than 100 feet from the ground, shiver me timbers, t' nose cone popped, me hearties, me bucko, me hearties, chute deployed, and she landed light as a feather without any damage. Whew!

On t' next wind free day I will stuff her with a G64 and see what happens.

My experience with Copperhead igniters has nay been a pleasant one. So far I have had a 50% failure rate even usin' t' tips on EMRR's tips/hints page. Well, blow me down! No matter how much I scraped or even when I separated t' leads thar was still a 50% failure rate. Out o' frustration I ordered two packs o' FirstFire igniters from redarrowhobbies.com. T' igniter failure rate then dropped t' zero, however, arrr, t' thought o' payin' almost three dollars for an igniter makes be break out in hives.

Summary:
This design is solid, ya bilge rat, stable, ya bilge rat, and loves t' fly, but a lot o' extra mass came with all that epoxy. Well, blow me down! Bein' stranded in t' outback o' Arkansas, I have yet to gain me Level One certification so I designed DEEP-SHT with a 29mm motor mount which will loft her nay very far. Aye aye! Begad! Had I been sane at t' time, me hearties, matey, I would have built in a 38mm motor mount and used a 29mm adapter until such time as I gained my Level One certification, which is what I have done with all me heavy designs since. Ahoy! Usin' foam core as fin material may seem questionable, but at t' time it appeared t' be a good idea. Well, blow me down! Ahoy! T' point be t' save weight off t' aft end of the airframe eliminatin' t' need for nose weight while still havin' an acceptable CP-CG relationship with a mass compatible with mid power 29mm motors. T' save t' fins from damage, me hearties, I mounted them up t' airframe from the base so they wouldn't take t' shock o' recovery. Blimey! They are still in place but already show creases, arrr, bends, and signs o' wear. Avast, me proud beauty! Avast! T' next DEEP-SHT build will be DEEP-SHT Lite with a reduced mass, matey, matey, matey, a 38mm motor mount, and sturdier fin material.