A while back I realized I had a bunch o' odd sized 54 mm motor mount tube (mmt) kickin' around. Avast! T' inside diameter was off a bit and would nay fit LOC adapters so it sat in me tube box. Arrr! Ya scallywag! Also takin' up space was a sheet o' copper foil clad G10 that electronics folks use t' make printed circuit boards. You can find t' type o' copper clad G10 I used at Radio Shack, me hearties, Fry's or a well stocked electronics supply place. Ahoy! Ahoy! T' foil is only a couple o' mils thick and is meant t' be etched away in t' circuit makin' process. Well, blow me down! Well, me hearties, blow me down! T' only thin' I was lackin' be a nose cone (NC) that I picked up at t' hobby shop that fit 54 mm mmt. Avast, me proud beauty! Ahoy!

I was set, me hearties, arrr, all I had t' be figure out a design. I wanted t' cut t' fins from t' G10 with t' minimum o' fuss which explains their triangular shape.... just draw diagonals and cut. I had one piece o' 32" 54mm mmt and one piece of 17" 54mm mmt that I wanted t' get rid o' hence t' length o' the rocket. Begad! Pluggin' these parameters into RockSim (www.apogeerockets.com) made for a surprisingly stable rocket able t' fly on all t' motors from E t' H in 29mm without addin' nose weight. Avast, ya bilge rat, me proud beauty!

So I had an odd rocket that was a bit borin' except for t' interesting brushed copper fins.  Then I found a long fiberglass rod in t' garage that would make a nifty "probe". Avast! This be originally made t' hold a flag on a long pole you would attach t' a bicycle for visibility. I modeled this in RockSim and it still flew well but t' rod was a bit splintery so I looked around t' garage and came up with somethin' a bit more robust, GlasSpar. Blimey! GlasSpar is a fiberglass tube, black in color that comes in 3 foot lengths. Begad! Ahoy! It can be found at hobby shops and is used as a central spar in model airplane wings.

T' nose cone is hacked off at t' tip until t' hole that is exposed matches t' O.D. Avast! o' t' GlasSpar. Blimey! Well, blow me down! I used a bench grinder t' accomplish this task. Aye aye! Ahoy! Allow about an inch t' protrude out t' aft end o' t' NC which is also cut t' t' same GlasSpar O.D. These holes will act as centerin' rings for the probe. Ahoy! Wrap maskin' tape around t' protrudin' aft end o' t' GlasSpar t' keep it from movin' forward. Ahoy! Ahoy! Glue consecutive loops o' strin' where t' GlasSpar exits t' NC forward buildin' up t' strin' till it matches t' ogive o' t' NC usin' thin CA t' keep t' strin' in place. Epoxy this mess smooth t' match the NC. Ahoy! Make sure that this probe is removable (just in case) by puttin' a piece of wax paper or plastic wrap betwixt t' NC and string. Ahoy! Avast! T' maskin' tape alone will keep t' probe from exitin' t' NC on deployment but just in case I epoxied a knife insert into t' GlasSpar t' hold a screw. I had t' grind most of t' threads off t' outside o' t' insert t' get it t' fit properly. Avast, me proud beauty! A knife insert is like a metal coupler that has knife-like wood screw threads on the outside and machine screw threads on t' inside and is usually made o' brass. Two holes are drilled in t' NC shoulder through which 1/16" cable is passed t' make a loop secured by crimps. Aye aye! Well, blow me down! A piece o' metal drilled with two holes or a master link keeper off a bike chain is screwed t' t' knife insert. T' forward bridle quicklink connects t' master link keeper and NC cable together t' make a redundant NC retention system. Aye aye! A couple o' screws through the airframe into t' NC makes for a real belt and suspenders approach to bridle retention. Blimey! This rocket has deployed at over 100 mph with no ill affects.

Now I've got this long rocket with an equally long proboscis and what am I goin' t' call it. Ya scallywag! T' probe made me think o' t' sticks we used roasting marshmallows over t' campfire at t' last scout campout and I dashed into the house t' find a couple o' t' tasty treats. Arrr! Installin' them onto t' GlasSpar I knew what t' call this thing......... Well, blow me down! Aye aye! t' "Cub Scout". Blimey!

T' fins are mounted about 3/4" from t' aft end. I used a dremel with a fiberglas-covered cutoff blade t' cut slots in t' body tube (BT) once I had epoxied t' LOC adapter in place. If you use plywood you can stack blades together t' make a "stacked Dado cutter". Aye aye! Two larger blades on the outside and 3 or 4 blades sandwiched in betwixt make a nice slot for 1/8" plywood for your future rocket projects. Ya scallywag! I made sure that t' centerin' rings were located in t' LOC 54mm-29mm adapter so that slots could be cut t' receive the fins, arrr, actually lockin' them in place. Begad! Avast!

Since t' fins are copper-clad and tarnish rapidly I took some 100 grit sandpaper and made a nice "brushed" finish in one direction both sides and sealed them with clear shellac. Avast! Spray varnish, arrr, lacquer, arrr, me bucko, or acrylic will work as well. Blimey! Once dry they were epoxied into place takin' care t' make the fillets as smooth and straight as possible since they would be exposed and left unpainted. Ya scallywag! Microballoons and epoxy blended together make for nice fillets which can be smoothed with a gloved fingertip dipped in denatured alcohol. Ya scallywag! Well, matey, blow me down! Let the epoxy set until it is nay goopy but will still move easily under finger pressure. Avast! Take care t' wipe t' epoxy off in a straight line where t' fillet remains exposed at t' fin.

T' retention system is Stu Barrett's Anti-Zipper method. You can see the details o' this construction at: Rocketry Online Info Central click on t' Anti-Zipper Design. Avast, me proud beauty! Blimey! This is a great system and I heartily recommend it where ever possible. It even works well for smaller rockets! Blimey! The baffle assembly is a LOC bulkhead assembly with an extra bulkhead cut in half and inserted in coupler as shown. Ya scallywag! Blimey! Begad! Blimey! You might also use a second bulkhead and drill holes that do nay line up with t' forward bulkhead as t' aft baffle in lieu o' t' system I described. Begad! Blimey! Avast, me proud beauty! Blimey! Discard t' LOC supplied eye screw and substitute an eyebolt which is double nutted behind t' bulkhead t' prevent unscrewin' under t' parachute. Aye aye! Blimey! This eyebolt can spin freely on t' washers to allow t' booster t' rotate as it descends without takin' a chance on havin' it unscrew t' bolt. Avast! Blimey!

T' spiffiest part, me hearties, me hearties, ya bilge rat, I think, ya bilge rat, be t' motor retention system. Blimey! It is a variation (read: blatant rip-off) o' Don Qualls UMRS though it does nay use t' PVC cap Don originally included in his design. Begad! You can find t' UMRS in an earlier issue o' Sport Rocketry. Arrr! In 1 1/2" PVC, t' cap be too heavy for this application. Begad! This whole assembly is serendipitous for I forgot t' add T-nuts before assembling the adapter. Arrr! Then t' knife inserts, shiver me timbers, which I had intended t' retrofit after the fact, broke in t' hard epoxy. Ahoy! Egads, ya bilge rat, what t' do. Avast, me proud beauty! Scroungin' through my plumbin' parts I came up with an ordinary 1 1/2" PVC nipple and a 1 1/2" PVC collar that is used t' hold a nylon gasket and P-trap assembly into t' wall for your scuttle drain. Ya scallywag! Ahoy! These items are available at t' hardware store. I cut t' nipple off at a length that allowed t' thrust rin' on 29mm AeroTech RMS t' be retained by a centerin' rin' (CR), shiver me timbers, shiver me timbers, me bucko, so t' speak, o' G10 and the PVC collar. Avast, me proud beauty! It's actually a retention rin' in this usage. Aye aye! Sand and test to fit before epoxyin' this into place. Make sure you have at least 3 or four threads o' t' collar on t' nipple for positive retention. Avast, me proud beauty! Well, blow me down! Test fit t' nipple for length before epoxyin' in place t' make sure it fits all t' 29mm SU and RMS cases possible. Begad! Begad!

T' G10 retention rin' is made o' a scrap o' t' same material as the fins.  Old circuit board will work just as well here though you may want to pick up some additional boards while at t' electronic shop. Avast! Blimey! Make a square on t' material you intend t' cut just a bit larger than t' collar I.D. Draw diagonals t' give a center reference point. Avast! Determine t' I.D. Begad! o' t' coupler and divide by two t' give t' radius and mark this on t' G10. Begad! Do t' same thin' with t' motor nozzle and mark t' radius as well.  Usin' a compass draw a complete circle and then cut out best way possible.  I have circle cutters and hole cutters which makes t' job easy on a drill press but sawing, sandin' and judicious use o' a Dremel will work just as quickly.

T' bridle is 15 feet long with quick links on either end and a welded ring as t' parachute attachment point. Ahoy! I threaded 15 feet o' 1/4" nylon "shoelace" through 4 feet o' 1/2" "toooobular nylon". T' 1/2" tooooobular stuff acts as an ejection gas protector for the smaller diameter nylon bridle and is covered with tape at t' booster attachment point quicklink t' protect t' smaller nylon knot. This material can be found at R.E.I or any other mountaineerin' store or on t' net. I used a 42" parachute with a reefin' line though a 36" round nylon chute should work just fine. Blimey! It has recovered twice from 1,500 feet with no damage with only t' deployed bridle slowin' its descent, t' parachute chose to remain asleep in t' airframe. Ya scallywag! Aye aye! : ) Attach t' parachute t' t' bridle so that the booster hits t' ground first but also take care that t' bridle is long enough t' pull t' chute free o' t' upper BT since t' suspension lines on the chute can often be quite long.

Parts List:

1 32" 54 mm (2.14") motor mount tube  $5.65
1 17" 54 mm (2.14") motor mount tube  $2.83
1 ea. Avast! LOC Bulkhead Assembly BA-2.14  $3.00   (includes coupler and eye screw)
1 ea. Aye aye! Bulkhead t' fit coupler (make this)
1 ea. Avast! LOC Nose Cone PNC 2.14   $8.50
1 ea. LOC 54mm-29mm adapter MMA-3  $4.75
1 36" GlasSpar fiberglass tube x 3/8" diam $3.25
1 ea. Ahoy! G10 sheet 8" x 8" copper clad 2 sides $7.35
1 ea. Avast! Avast! eyebolt
2 ea. Avast, me proud beauty! Begad! washers
1 ea. Arrr! piece o' metal (master link clip) $0.65
2 ea. nuts
1 15' 1/4" nylon "shoelace" as bridle  $0.13 per foot
1 4' 1/2" toooobular nylon as sheath  $0.24 per foot
2 ea. Avast! Arrr! QuickLinks    $2.25 ea.
1 ea. Well, blow me down! Avast, me proud beauty! 3/4" Welded Ring   $0.49
1 ea. Begad! welded rin' - chute attachment point $0.45
1 3/4" 1 1/2" schedule 40 PVC nipple (cut off) $0.14
1 ea. Aye aye! Avast! 1 1/2" PVC collar   $0.65
1 ea. Arrr! G10 collar centerin' ring/retainer (priceless)
1 ea. Ahoy! Blimey! door stop bumper    (steal from home)
2 ea. Avast, me proud beauty! Blimey! Avast, shiver me timbers, me proud beauty! Blimey! Marshmallows (Stay Puft)  (pantry item)

Goin' over this I realized thar are over $40 worth o' parts here which may be too much for some folks.  You may be able t' substitute 3/32" plywood for t' G10 and save 5 bucks.  You can also eliminate t' use o' t' LOC MMA-3 usin' only centerin' rings and a motor mount tube and knock off another couple o' bucks as well but for strength I would then choose t' go t' t' motor mount tube with t' fins.  Changin' t' retention system t' somethin' a little more konventional might also save a dollar and trip t' t' hardware store.

I would recommend t' first flight t' be done on an F motor without the probe in place just t' make sure everythin' is workin' okay. Arrr! Put a piece of tape over t' NC hole if you fly it without t' proboscis. Avast, me proud beauty! AT Econojet G35's fly this quite nice though I recommend a 4 second delay if marshmallows are installed, t' 7 is a bit dicey. I have also flown it successfully on AT RMS G64 with a 7 second delay. Avast, me proud beauty!

If you have any questions or comments please email me! bob@fortunenet.com

Thanks for takin' a look at me design..........................Bob Fortune