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

I also wanted t' try a zipperless baffle design. Arrr! With no electronics, motor ejection was planned, shiver me timbers, matey, 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 was throwin' large phenolic tubes in t' garbage. Ahoy! Ahoy! He offered t' mail one t' anyone around t' country, and on a lark, me hearties, I accepted. About t' same time, me hearties, 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 be time t' begin a design. Begad! Blimey! I chose a 4FNC design with very sleek swept trapezoidal fins. Avast! Blimey! Begad! Blimey! T' RockSim file is included here.

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

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

T' tube seemed softer than typical phenolic. 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. T' were tabbed for TTW mounting. Begad! Blimey! T' best ply sheet at Home Depot was slightly little warped, shiver me timbers, matey, so I laid one layer o' 6oz fiberglass and pressed each fin under very heavy weights, yieldin' perfectly flat fins. Begad! 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. Blimey! T' rest o' t' fin can was assembled in t' usual way. Begad! One unusual feature was that thar be only about 1 inch o' tube remainin' unslotted for t' fin can, me hearties, so I had t' be very careful nay t' bend or torque anything. Interior fillets were created by runnin' down an epoxy/milled fiberglass mixture.

T' baffle be in t' FlisKits style o' partial disks. Begad! Avast! Three plates were put in a 5.5in length o' Giant Leap coupler. Avast! 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. Begad! I used lots o' fiberglass: 1 exterior layer o' S-weave plus 2 interior layers o' 1.5oz matting. Well, blow me down! Ahoy! I literally could have stood on this without damage. Aye aye! Avast! T' exterior was sanded Bondo t' give a smooth fit. Avast! T' bottom two baffle plates were covered on their aft side and edge with aluminum pie plate attached with JB Weld, matey, t' reduce heat damage.

At this point, I took t' rocket t' t' NCR club for advice. Avast, me proud beauty! First, shiver me timbers, they were worried about t' length o' t' baffle/coupler. Ya scallywag! So I glued it asymmetrically: 1.75in into t' fin can and 3.75in for couplin' into t' airframe. Avast, me proud beauty! Second, they were worried about successful ejection. Ya scallywag! T' design, me bucko, from aft t' forward, was: motor, ya bilge rat, baffle/coupler, airframe split, chute in airframe, then bulkhead. Avast, me proud beauty! Arrr! 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! Begad! T' first ground test used 1.5g powder, equal t' what is given with an I or J motor. Ya scallywag! T' rocket separated but t' chute was nay pulled out. Avast, me proud beauty! Blimey! With 2.5g, ya bilge rat, I had t' same result. Begad! With 3.5g (don't try this at home!) I blew t' motor case out t' back, shiver me timbers, split a crack and hole in t' fin can, separated t' airframe, arrr, but still did nay pull t' chute out. Aye aye! I learned by experience that 3.5g o' powder is way too much, me hearties, shiver me timbers, and I realized I that had t' maroon t' zipperless design.

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

I sewed t' chute myself. Ya scallywag! It was 72in diameter, shiver me timbers, 12-gore semi-elliptical in t' Nakka design. Ahoy! 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, despite lackin' a bulkhead. Begad! 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. Avast, me proud beauty! Blimey! Final calculations showed that 12oz o' nose weight be needed a stability margin o' 2.2 with t' largest possible motor (J350). Avast, me proud beauty! Blimey! 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, interrupted with interminable periods o' sanding. Arrr! You can see t' final red, me hearties, white, ya bilge rat, and black paint scheme. Begad! All t' paint be Krylon gloss, arrr, me hearties, many coats, arrr, with clear over t' top. Ahoy! T' CraterMaker sticker was provided by Mike Fisher at Binder Designs. He does first rate work, as I'm sure you can see. Avast! 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 be t' Northern Colorado Rocketry Oktoberfest. Avast! Blimey! Havin' simmed a variety o' motors, it looked like t' best choices t' keep t' rocket low and visible would be I285R, matey, I300T, ya bilge rat, matey, or I366R, simmed t' 1616, me hearties, 1795, me hearties, and 2446ft, respectively. Ya scallywag! Blimey! Blimey! Blimey! I opted for t' I300T.

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

My son found t' rocket about half a mile away. Avast, me proud beauty! Unfamiliar with t' scale o' t' rocket, I had been searchin' too close and a bit t' t' left. Well, blow me down! He ran ahead, as boys do, me bucko, and started wavin' and jumpin' up and down in t' distance when he spotted it. Avast! I chased him down. 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, me bucko, me hearties, for me L2 certification, a J350W (3584ft) for NCR's Mile High Mayhem. Begad! This project has been a ton o' work, shiver me timbers, me hearties, but well worth it in t' end.