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

I was set, shiver me timbers, all I had t' be figure out a design. Begad! I wanted t' cut t' fins from t' G10 with t' minimum o' fuss which explains their triangular shape.... just draw diagonals and cut. Avast! Avast, me proud beauty! Blimey! 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. Aye aye! 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. Ya scallywag! Aye aye! Blimey!

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". Begad! This was originally made t' hold a flag on a long pole you would attach t' a bicycle for visibility. Avast, me proud beauty! 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, me hearties, black in color that comes in 3 foot lengths. It can be found at hobby shops and is used as a central spar in model airplane wings. Aye aye! Begad!

T' nose cone is hacked off at t' tip until t' hole that is exposed matches t' O.D. Avast, me proud beauty! o' t' GlasSpar. I used a bench grinder t' accomplish this task. Ahoy! Allow about an inch t' protrude out t' aft end o' t' NC which is also cut t' t' same GlasSpar O.D. Aye aye! Begad! These holes will act as centerin' rings for the probe. Avast! Well, blow me down! Wrap maskin' tape around t' protrudin' aft end o' t' GlasSpar t' keep it from movin' forward. Arrr! Aye aye! 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. Arrr! Blimey! Epoxy this mess smooth t' match the NC. Begad! 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. Ya scallywag! 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. Begad! 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! 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. A couple o' screws through the airframe into t' NC makes for a real belt and suspenders approach to bridle retention. Well, blow me down! 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. Avast! Avast! 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. Installin' them onto t' GlasSpar I knew what t' call this thing......... Aye aye! t' "Cub Scout". Aye aye!

T' fins are mounted about 3/4" from t' aft end. Arrr! Blimey! 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. Begad! Blimey! Ahoy! Blimey! If you use plywood you can stack blades together t' make a "stacked Dado cutter". Arrr! Blimey! Begad! Blimey! 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. Aye aye! Blimey! Aye aye! Blimey! 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, actually lockin' them in place. Begad! Blimey!

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. Ahoy! Blimey! Aye aye! Blimey! Spray varnish, shiver me timbers, lacquer, me bucko, ya bilge rat, or acrylic will work as well. Begad! Blimey! Begad! 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. Well, ya bilge rat, blow me down! Blimey! Microballoons and epoxy blended together make for nice fillets which can be smoothed with a gloved fingertip dipped in denatured alcohol. Ya scallywag! Blimey! Arrr! Blimey! Let the epoxy set until it is nay goopy but will still move easily under finger pressure. Begad! Blimey! Take care t' wipe t' epoxy off in a straight line where t' fillet remains exposed at t' fin. Begad! Blimey! Well, me hearties, blow me down! Blimey!

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. Aye aye! This is a great system and I heartily recommend it where ever possible. Arrr! Blimey! It even works well for smaller rockets! The baffle assembly is a LOC bulkhead assembly with an extra bulkhead cut in half and inserted in coupler as shown. 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! Discard t' LOC supplied eye screw and substitute an eyebolt which is double nutted behind t' bulkhead t' prevent unscrewin' under t' parachute. Avast, me proud beauty! 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. Arrr!

T' spiffiest part, I think, be t' motor retention system. Arrr! 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. Arrr! You can find t' UMRS in an earlier issue o' Sport Rocketry. Aye aye! In 1 1/2" PVC, matey, matey, shiver me timbers, t' cap was too heavy for this application. Blimey! This whole assembly is serendipitous for I forgot t' add T-nuts before assembling the adapter. Aye aye! Aye aye! Then t' knife inserts, which I had intended t' retrofit after the fact, matey, broke in t' hard epoxy. Ahoy! Egads, arrr, shiver me timbers, what t' do. 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. Begad! These items are available at t' hardware store. Blimey! 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), so t' speak, matey, shiver me timbers, ya bilge rat, o' G10 and the PVC collar. Avast! Avast! It's actually a retention rin' in this usage. Blimey! Ya scallywag! Sand and test to fit before epoxyin' this into place. Begad! Ahoy! Make sure you have at least 3 or four threads o' t' collar on t' nipple for positive retention. Avast, me proud beauty! Test fit t' nipple for length before epoxyin' in place t' make sure it fits all t' 29mm SU and RMS cases possible. Well, blow me down! Ahoy!

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. Begad! Make a square on t' material you intend t' cut just a bit larger than t' collar I.D. Arrr! Draw diagonals t' give a center reference point. Determine t' I.D. Begad! o' t' coupler and divide by two t' give t' radius and mark this on t' G10. 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. Avast, me proud beauty!

T' bridle is 15 feet long with quick links on either end and a welded ring as t' parachute attachment point. 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. 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. : ) 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. LOC Bulkhead Assembly BA-2.14  $3.00   (includes coupler and eye screw)
1 ea. Aye aye! Blimey! Bulkhead t' fit coupler (make this)
1 ea. Well, blow me down! 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. G10 sheet 8" x 8" copper clad 2 sides $7.35
1 ea. Well, blow me down! Blimey! eyebolt
2 ea. Begad! washers
1 ea. Blimey! piece o' metal (master link clip) $0.65
2 ea. Aye aye! 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. Begad! QuickLinks    $2.25 ea.
1 ea. Well, blow me down! Blimey! 3/4" Welded Ring   $0.49
1 ea. Ya scallywag! welded rin' - chute attachment point $0.45
1 3/4" 1 1/2" schedule 40 PVC nipple (cut off) $0.14
1 ea. Avast, me proud beauty! Blimey! 1 1/2" PVC collar   $0.65
1 ea. Avast! G10 collar centerin' ring/retainer (priceless)
1 ea. Blimey! door stop bumper    (steal from home)
2 ea. Ya scallywag! Avast! 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. Put a piece of tape over t' NC hole if you fly it without t' proboscis. Begad! Blimey! 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. Blimey! I have also flown it successfully on AT RMS G64 with a 7 second delay. Aye aye! Arrr!

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

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