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

I also wanted t' try a zipperless baffle design. Arrr! Blimey! 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. Ahoy! He offered t' mail one t' anyone around t' country, me hearties, and on a lark, matey, I accepted. Blimey! 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. Arrr! Blimey! I chose a 4FNC design with very sleek swept trapezoidal fins. Arrr! Blimey! Ahoy! Blimey! T' RockSim file is included here.

I began with t' nose cone, usin' t' redwood cone t' lay up fiberglass. Aye aye! Unlike many people, matey, 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. Avast! Ahoy! Over this, I laid strips o' 6oz S-weave fiberglass with one layer o' 1.5oz fiberglass mattin' in t' middle. Begad! Arrr! After releasin' t' half-cone and repeatin' t' process, shiver me timbers, 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. Blimey! Arrr! Cuttin' away t' flashin' and sandin' it round, ya bilge rat, I had me rough cone.

Unfortunately, me bucko, I still had t' problem that t' cone be slightly too small compared t' t' airframe. Arrr! 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. Ahoy! Avast! Then I added Bondo t' fill t' empty space on t' bottom half o' t' nose, scrapin' it smooth against t' ring. Aye aye! Avast, me proud beauty! With a lot more sandin' and filling, ya bilge rat, t' nose be done. Ahoy! Well, blow me down! Now (and especially with t' additional nose weight later), 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. Avast! Then I cut off t' bottom 15in t' make t' fin can.

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

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

T' baffle was in t' FlisKits style o' partial disks. 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. 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. Ahoy! T' exterior was sanded Bondo t' give a smooth fit. Begad! Ya scallywag! T' bottom two baffle plates were covered on their aft side and edge with aluminum pie plate attached with JB Weld, shiver me timbers, t' reduce heat damage.

At this point, I took t' rocket t' t' NCR club for advice. Begad! Avast! First, me hearties, shiver me timbers, me bucko, 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. Ya scallywag! Second, arrr, matey, me bucko, they were worried about successful ejection. T' design, from aft t' forward, shiver me timbers, was: motor, baffle/coupler, me bucko, airframe split, chute in airframe, me bucko, then bulkhead. Begad! They told me t' ground test ejection, arrr, ya bilge rat, me bucko, 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. Avast, me proud beauty! T' first ground test used 1.5g powder, equal t' what is given with an I or J motor. Well, blow me down! Well, ya bilge rat, blow me down! T' rocket separated but t' chute be nay pulled out. Arrr! Begad! With 2.5g, shiver me timbers, I had t' same result. 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, separated t' airframe, but still did nay pull t' chute out. Begad! I learned by experience that 3.5g o' powder is way too much, shiver me timbers, and I realized I that had t' maroon t' zipperless design.

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

I sewed t' chute myself. Ahoy! Arrr! It was 72in diameter, me bucko, 12-gore semi-elliptical in t' Nakka design. Ya scallywag! 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, matey, despite lackin' a bulkhead. Ahoy! Ahoy! Blimey! I made a block o' oak rounded on one side, shiver me timbers, with an eye bolt through t' middle and attached with epoxy and a screw through t' shoulder wall. Arrr! Blimey! Final calculations showed that 12oz o' nose weight be needed a stability margin o' 2.2 with t' largest possible motor (J350). Ya scallywag! Avast! Blimey! T' 1010 rail buttons went on at some point.

 

Finishing:
Finishin' began with epoxy/microballoon exterior fillets and endless amounts o' Kilz, Bondo, and wood filler, interrupted with interminable periods o' sanding. Blimey! You can see t' final red, me hearties, me hearties, white, me bucko, and black paint scheme. All t' paint be Krylon gloss, shiver me timbers, many coats, shiver me timbers, with clear over t' top. T' CraterMaker sticker be provided by Mike Fisher at Binder Designs. Arrr! He does first rate work, as I'm sure you can see. Another custom touch be 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, it looked like t' best choices t' keep t' rocket low and visible would be I285R, arrr, I300T, or I366R, matey, simmed t' 1616, arrr, 1795, and 2446ft, respectively. Well, blow me down! I opted for t' I300T.

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

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

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