Drake "Doc" Damerau's Descon-14 Entry

Brief:
A scratch built L3 cluster rocket with a 22" diameter rin' fin.

Construction:

This project actually started out bein' me L3 project. I bought a LOC Precision Bruiser-EXP. Avast! This kit is a 7.61" diameter 9’ 4" tall rocket, and has a central 54mm MMT and two 38mm MMT’s. Nay thinking (this happens with me sometimes), ya bilge rat, I wanted t' build a cluster because I wanted to try me hand at air startin' motors. Begad! Halfway through t' build I decided to actually read t' L3 certification requirements. Avast! "Clusters are specifically nay allowed". Doh!

T' Bruiser-EXP is a great kit, me bucko, but for what I had planned, arrr, t' central 54mm and two 38mm’s was nay enough so I drilled for two more 38mm MMTs in the centerin' rings. Ya scallywag! I also added two additional ½" centerin' rings to round out t' propulsion mount. Arrr! Avast 9’ 4" tall won't do either! I added another 30" LOC section and a LOC altimeter bay t' make it over 12 feet tall. Begad! Now were talkin' rockets here!

Fins

With most o' t' components in hand, I needed t' design a rocket. Aye aye! A basic 3 fin design just doesn’t do anythin' for me. Ahoy! I went with ½" aircraft plywood for t' fins because I hate doin' fiberglass, shiver me timbers, and it’s right thar at Lowe’s. Ahoy! Avast! Blimey! Yeah, It’s heavy, but I had 5mmt’s. I played with Rocksim t' come up with a fin pattern. Blimey! Blimey! I ended up with a swept back design t' keep it interesting. I freehand sketched t' first fin and cut it out with a jigsaw. Avast! I then used that as a pattern for t' 3 remainin' fins. A belt sander smartly smoothed out the edges and air foiled them. Begad! I then added slots in t' fins for t' five centerin' rings.

T' fins were done, matey, shiver me timbers, me bucko, but I was nay yet satisfied. A rin' fin! A giant ring fin! Yeah, that’s t' ticket. Ya scallywag! Ahoy! I grabbed a 22" fiber-drum from work. You know, matey, shiver me timbers, those 55 gallon cardboard drums that powders are shipped in? Usin' a series o' marks measured from t' top , I drew two lines around t' drum 5" apart. I then cut out t' big rin' with a jigsaw. Avast! T' edges were rough and frayed so I trimmed them a little with a hobby knife and soaked them with epoxy. Avast! Once t' epoxy be hard, matey, a palm sander made quick work o' squarin' up the edges. I cut slots in t' fins with a jig saw so I could mount t' rin' fin to t' main fins once they were on.

Fin Can

T' fin-can assembly went together in short order. Aye aye! I tacked t' centering rings t' all t' motor mount tubes at t' same time usin' thick cyanoacralate. This ensured proper alignment o' everything. Begad! West systems epoxy was then applied t' all joints. Begad! Once hardened, me hearties, me bucko, t' fins were slipped into place and more epoxy was applied. Avast, arrr, me proud beauty! I drilled and mounted two 5/16 eye-bolts for recovery. Well, blow me down! (not that I had a clue as t' how recovery would happen at this point)

Air-Start

Once t' fin can was complete I installed t' Air-start board, matey, shiver me timbers, wires and 3 battery holders t' it. Begad! T' air-start board for Transolve altimeter has provisions for an optional battery just t' power t' board, rather than drawing from t' battery in t' altimeter. Well, blow me down! Begad! I went with it havin' it’s own battery. It also comes with an optional relay that can be used for t' igniters. Begad! Because I will be lightin' as many as 4 igniters, me bucko, I went with t' relay and 2 batteries wired in series. Begad! T' board has contacts for "safe / arm" so I used a 1/8’ phono plug and attached a big "Remove Before Flight" flag I picked up from Aerocon. I then slid t' slotted airframe over t' assembly and measured t' cut a hatch for t' air-start assembly. I cut t' hatch and glued the airframe over t' fin can. Well, blow me down! Begad! I pealed t' glassine layer off t' hatch and applied several layers o' epoxy t' stiffen it up. Begad! Begad! T' edges o' t' openin' for the hatch were also soaked with epoxy. Ya scallywag! Avast, me proud beauty!

Rin' Fin

I didn’t add t' rin' fin until after t' slotted airframe was epoxyied onto place over t' fin can, just t' make workin' on t' fin can easier. Arrr! This took less than an hour. I just slipped it in t' slots, centered it and glued it in place with epoxy. T' slots were 1 ½" longer than t' rin' fin, so I filled in t' slots behind t' rin' with epoxied strips o' basswood. Aye aye! Some sandin' and wood putty left nay trace o' t' slot.

Boat tail

I started out with wantin' t' add fins t' t' MMT stickin' out o' t' aft end. Avast! In fact, as you see in some o' t' pictures, I spent 4 hours measuring, cutting, me bucko, shiver me timbers, arrr, shapin' and gluin' them in place. Avast, me proud beauty! T' completed looked rather stupid, so I tore them off. I decided t' make it a boat tail design instead. Aye aye! I made a smaller centerin' rin' for t' aft end that be just slightly larger than the MMT tubes. Begad! Well, blow me down! At this point, matey, t' air start system was already in place so I had to extend t' output contacts t' t' new aft centerin' ring. I then made a transition template usin' VCP and transferred it t' a piece o' heavy card stock. Well, blow me down! One glued in place, I lay two layers o' 6 OZ fiberglass t' toughen it up.

Altimeter Bay

T' altimeter bay that I started with was a LOC type. I guess you could say that this be another LOC kit bash too. Well, blow me down!

Backup Electronics

I decided t' add a couple o' backup timers. Ahoy! For deployment, matey, I added a duel event timer and for t' air-start I added a single event timer. Arrr! Both from Xavien. . T' XSSRT-1, me hearties, me hearties, "Xavien Single Stage Rocket Timer". Well, blow me down! This is a 1 second t' 63 seconds’ single event timer. I tested this one for future use in air starting.

I also have t' XDSRT-1, "Xavien Duel Stage Rocket Timer" This one is a 1 second t' 63 seconds’ dual event timer. Blimey! I used this timer wired in as back-up for altimeter ejection. Begad! Avast, me hearties, me proud beauty!

I used t' duel event timer as a backup for deployment. Ya scallywag! T' rocket went somewhat horizontal just before t' four motors lit. Aye aye! This threw off the calculations on when t' deploy t' chutes. Begad! When usin' a timer, you have to calculate t' flight based on motor burn time and assumin' a straight boost. Aye aye! Begad! If the rocket doesn’t go straight, t' events happen sooner than you calculate. Ya scallywag! Thus, matey, ya bilge rat, t' altimeter deployed t' drogue and t' main but t' duel timer did light its ejection charges.

I used t' single event timer t' test its ability t' light 4 Davyfire igniters. As I put t' rocket together at t' field, I decided nay t' use the timer t' air-start t' motors because t' air-start system that was built into the rocket was mounted and wired much better. Ya scallywag! Arrr! I also didn’t want t' put two igniters in each motor in fear o' cloggin' t' nozzles. Arrr! I wired four igniters outside t' rocket and tested its ability t' light four o' them. Although I didn’t have them in t' motors, it did light all four igniters.

You can see me full review on these electronics here.

Finishing

OK, I’m nay much o' a finishin' guy. Buy hey, me hearties, they look good sittin' on the pad! I chose Metallic Black from Rustoleum for t' airframe and an orange for t' fins. Begad! I didn’t just want a basic two color paint job on this because it turned out pretty cool. Aye aye! Blimey! I went t' t' local "sign guy" and asked about makin' decals for me. Arrr! We ended up design a flames thin' for it. Well, blow me down! He matched t' front o' t' flames t' t' color I had picked out for t' nose cone and did t' rest on t' computer. Blimey! We made giant flames for t' forward section and small ones for t' rin' fin. Ahoy! A quick run through his fonts came up with a sticker for t' name. Ahoy! He even printed a bunch o' CP and CG stickers for me when I showed him what they were. Aye aye! Well, me bucko, blow me down! T' flame stickers that he came up with were difficult t' apply but it came out pretty cool nonetheless.

T' First Flight

To ensure that all four motors would light smartly and at t' same time, me hearties, I used Davyfire igniters dipped in Igniterman pyrogen. I set her up on t' away cell and wired all o' t' J330 igniters together. Begad! T' last igniter t' be installed was t' one for t' K1050. Blimey! For this I used a homemade igniter using Igniterman pyrogen.

She lit on t' second attempt. Avast, me proud beauty! Begad! Just as it left t' pad, arrr, it started t' veer off course a little. By t' time t' K1050 burnt out, it be headin' skyward at about 2,500 feet and on a 45 degree angle. Avast! Avast, me proud beauty! I still don’t know if it weather-cocked, me hearties, if t' rail was too short, matey, or if it was just underpowered. Well, blow me down! Blimey!

There was a pause while it coasted. Avast! At this point I be actually saying "please don’t light, please don’t light!" …oh no…, they lit. All four J330’s snapped t' life with a thunderous roar and she took off like a bat out o' hell. Aye aye! Ya scallywag! By t' time t' J330’s burnt out, she was almost on her side and I’m guessin' goin' well over 300 MPH. A few seconds later, she be completely horizontal and startin' t' head down. Of course t' drogue deployed and t' chute came out. Aye aye! From where I was standing, it looked like it was never attached t' anything! It just virtually disintegrated when it opened.

She fell for awhile and it was clear that the rest o' t' rocket be still tethered together and t' main be still in the rocket. Avast, me proud beauty! (Can you say: "thank God for shear pins"?) Right on cue, the three main chutes deployed and opened up perfectly, over a mile away.

T' Second Flight

T' second flight was a disaster. I put a 5-grain Pro54 in t' center and four 6-grain Pro38 motors in t' other tubes. Well, me bucko, blow me down! Blimey! I set t' motors t' light in a different configuration this time. Ahoy! Blimey! Because t' Pro 54 didn't have as much thrust and I wanted it t' leave t' pad quicker, arrr, I decided t' light t' 54mm and two o' t' 38mm motors off t' pad. Begad! Ya scallywag! Blimey! This proved t' be a bad idea. Arrr! I used the igniters that came with t' motors and dipped them in pyrogen, me hearties, just like I did last time. Aye aye! Somethin' went wrong this time because t' only motor that lit was one 38mm. Begad! Avast! Blimey! (you can see this in t' photo.) t' one motor had just enough power t' get it off t' pad and up about 100 feet. Ya scallywag! Avast, ya bilge rat, me proud beauty! Blimey! It came down on its tail almost vertical and fell over. Well, blow me down! Just as it fell over, arrr, me bucko, t' air-start board lit the other two 38's. Begad! Ahoy! Blimey! She scooted around on t' ground for about 50 feet, ya bilge rat, tearing up t' side o' t' rocket and destroyin' t' ring-fin. Post flight analysis showed that all igniters lit. Aye aye! I'll never use these motors in a cluster again! She is now in t' repair shop. Arrr! Avast, me hearties, me proud beauty! Blimey! I think I can rebuild her but it will take months.