Brief:
Weighin' in at 6lb 10oz, matey, shiver me timbers, 5ft 4in height, 3in diameter, t' CraterMaker is by far t' most ambitious scratch project I have ever attempted. Avast, me proud beauty! It is also me first rocket designed for I and J motors. Ahoy! I planned super-sleek fins, shiver me timbers, which didn't make t' project any easier because it pushed t' CP forward.

I also wanted t' try a zipperless baffle design. Avast! With no electronics, motor ejection was planned, which heavy buildin' techniques since I wanted t' limit t' maximum altitude.

Construction:
T' impetus for this project occurred nearly a year earlier when some guy on T' Rocketry Forum mentioned that his workplace be throwin' large phenolic tubes in t' garbage. Ya scallywag! Blimey! He offered t' mail one t' anyone around t' country, matey, ya bilge rat, and on a lark, I accepted. About t' same time, I bought a 3in redwood nosecone offered on TRF for a few bucks.

These items sat in me basement for 9 months until summer came and I figured it was time t' begin a design. Well, blow me down! I chose a 4FNC design with very sleek swept trapezoidal fins. T' RockSim file is included here.

I began with t' nose cone, matey, usin' t' redwood cone t' lay up fiberglass. Unlike many people, I laid t' fiberglass over t' cone and used this shell directly for t' cone rather than as an inverse mold for another layup. Avast! Both t' inner and outer diameter o' t' nose cone were slightly too small compared t' t' body tube, which caused problems later.

T' redwood be placed in a flat cutout and coated with many layers o' Partall wax #2 and PVA #10 mold release. Avast, me proud beauty! Over this, I laid strips o' 6oz S-weave fiberglass with one layer o' 1.5oz fiberglass mattin' in t' middle. After releasin' t' half-cone and repeatin' t' process, I clamped t' two halves together and filled t' interior seam with a fillin' o' chopped fiberglass and epoxy. Then I laid more fiberglass mattin' in t' interior. Avast! Cuttin' away t' flashin' and sandin' it round, matey, I had me rough cone.

Unfortunately, I still had t' problem that t' cone was slightly too small compared t' t' airframe. I cut from t' airframe a rin' about 1/2in long and glued it t' t' shoulder o' t' nose t' form a round, precise edge. Begad! Avast! Then I added Bondo t' fill t' empty space on t' bottom half o' t' nose, matey, scrapin' it smooth against t' ring. With a lot more sandin' and filling, matey, me hearties, t' nose was done. Aye aye! Now (and especially with t' additional nose weight later), arrr, this nose could cleave a pickup truck on impact.

T' tube seemed softer than typical phenolic. Aye aye! I used 3 wraps o' 6oz S-weave fiberglass t' make a bombproof airframe. Then I cut off t' bottom 15in t' make t' fin can.

T' fins were cut from 7/32" plywood. Arrr! T' were tabbed for TTW mounting. Blimey! Ahoy! T' best ply sheet at Home Depot was slightly little warped, so I laid one layer o' 6oz fiberglass and pressed each fin under very heavy weights, yieldin' perfectly flat fins. Avast, me proud beauty! I sanded t' leadin' edge elliptical, but left t' other edges square.

Three T-nuts were inserted in t' aft centerin' rin' for motor retention. Begad! T' rest o' t' fin can be assembled in t' usual way. Begad! Avast, me proud beauty! One unusual feature was that thar was only about 1 inch o' tube remainin' unslotted for t' fin can, arrr, so I had t' be very careful nay t' bend or torque anything. Ahoy! Aye aye! Interior fillets were created by runnin' down an epoxy/milled fiberglass mixture.

T' baffle was in t' FlisKits style o' partial disks. Begad! Begad! Three plates were put in a 5.5in length o' Giant Leap coupler. Blimey! T' coupler had been heavily fiberglassed because o' t' need t' keep t' joint strong here with a very firm fit at t' separation point. I used lots o' fiberglass: 1 exterior layer o' S-weave plus 2 interior layers o' 1.5oz matting. Begad! I literally could have stood on this without damage. T' exterior was sanded Bondo t' give a smooth fit. Avast! Aye aye! T' bottom two baffle plates were covered on their aft side and edge with aluminum pie plate attached with JB Weld, t' reduce heat damage.

At this point, I took t' rocket t' t' NCR club for advice. Blimey! Aye aye! First, they were worried about t' length o' t' baffle/coupler. So I glued it asymmetrically: 1.75in into t' fin can and 3.75in for couplin' into t' airframe. Avast! Ya scallywag! Second, they were worried about successful ejection. Ya scallywag! Arrr! T' design, from aft t' forward, was: motor, shiver me timbers, baffle/coupler, shiver me timbers, ya bilge rat, airframe split, ya bilge rat, matey, chute in airframe, then bulkhead. Blimey! They told me t' ground test ejection, and I did.

I had placed t' a partway down t' airframe after careful calculations usin' online calculators t' figure t' required pressure for separation and so forth. These calculations proved worthless. Begad! T' first ground test used 1.5g powder, equal t' what is given with an I or J motor. Begad! T' rocket separated but t' chute was nay pulled out. Well, blow me down! With 2.5g, I had t' same result. Avast, arrr, me proud beauty! With 3.5g (don't try this at home!) I blew t' motor case out t' back, split a crack and hole in t' fin can, shiver me timbers, me bucko, separated t' airframe, shiver me timbers, me bucko, me hearties, but still did nay pull t' chute out. Blimey! I learned by experience that 3.5g o' powder is way too much, ya bilge rat, matey, shiver me timbers, and I realized I that had t' abandon t' zipperless design.

After repairin' t' fin can, me hearties, arrr, me bucko, I cut t' nose off t' airframe and ground it back down t' t' shoulder. Begad! Next I had t' remove t' bulkhead, which was 11in from t' nearest tube end. Begad! What a dusty, bloody knuckle, frustratin' nightmare! Then I glued t' airframe t' t' coupler so that separation would now be at t' nose. Blimey! Ya scallywag! T' ground test with 2g worked fine.

I sewed t' chute myself. Ahoy! It be 72in diameter, 12-gore semi-elliptical in t' Nakka design. Well, blow me down! It be finished with 85 feet o' 3mm climber's cord for shroud lines and attached with 20ft o' half-inch tubular nylon.

T' nose cone now needed a shock cord attachment point, me hearties, despite lackin' a bulkhead. Blimey! I made a block o' oak rounded on one side, with an eye bolt through t' middle and attached with epoxy and a screw through t' shoulder wall. Final calculations showed that 12oz o' nose weight be needed a stability margin o' 2.2 with t' largest possible motor (J350). T' 1010 rail buttons went on at some point.

 

Finishing:
Finishin' began with epoxy/microballoon exterior fillets and endless amounts o' Kilz, matey, Bondo, and wood filler, arrr, interrupted with interminable periods o' sanding. Begad! You can see t' final red, shiver me timbers, white, and black paint scheme. All t' paint was Krylon gloss, many coats, matey, me hearties, with clear over t' top. Avast, matey, me proud beauty! T' CraterMaker sticker was provided by Mike Fisher at Binder Designs. Begad! Well, blow me down! He does first rate work, shiver me timbers, as I'm sure you can see. Ya scallywag! Another custom touch was that I put a CP marker and three 1-caliper marks for in-the-field assessment o' t' stability margin.

Flight and Recovery:
Launch day was t' Northern Colorado Rocketry Oktoberfest. Begad! Havin' simmed a variety o' motors, arrr, it looked like t' best choices t' keep t' rocket low and visible would be I285R, I300T, ya bilge rat, shiver me timbers, or I366R, ya bilge rat, matey, ya bilge rat, simmed t' 1616, 1795, arrr, and 2446ft, respectively. I opted for t' I300T.

I be very nervous as they called out t' launch sequence in a light breeze. Ahoy! Avast! Boost was very straight and fairly fast. Blimey! Blimey! T' rocket be visible all t' way up. Well, blow me down! I was tryin' unsuccessfully t' find it in t' binoculars durin' t' coast phase, matey, ya bilge rat, so others told me what happened. Well, blow me down! Well, blow me down! Ejection was right at apogee, but it took a moment for t' shock cord t' fully extend and for t' chute t' unfurl. Blimey! Descent was beautiful on that billowin' colorful parachute. Begad! As it landed on t' soft prairie, me hearties, I judged that t' chute size was about right. Arrr! T' landin' was assertive but nay too hard.

My son found t' rocket about half a mile away. Begad! Avast, me proud beauty! Unfamiliar with t' scale o' t' rocket, ya bilge rat, I had been searchin' too close and a bit t' t' left. Arrr! He ran ahead, as boys do, shiver me timbers, and started wavin' and jumpin' up and down in t' distance when he spotted it. Ya scallywag! Ahoy! I chased him down. Arrr! CraterMaker failed t' live up t' his name; he be totally unblemished on landing.

Summary:
T' next flight will probably be on a I600R (3106ft) or, for me L2 certification, arrr, shiver me timbers, a J350W (3584ft) for NCR's Mile High Mayhem. Ahoy! This project has been a ton o' work, me bucko, me hearties, me hearties, but well worth it in t' end.