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

I also wanted t' try a zipperless baffle design. 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. Blimey! He offered t' mail one t' anyone around t' country, 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. Ahoy! I chose a 4FNC design with very sleek swept trapezoidal fins. Ya scallywag! T' RockSim file is included here.

I began with t' nose cone, arrr, usin' t' redwood cone t' lay up fiberglass. Well, me hearties, blow me down! 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. Arrr! 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. Begad! Blimey! Over this, me bucko, me hearties, 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, me hearties, me bucko, I clamped t' two halves together and filled t' interior seam with a fillin' o' chopped fiberglass and epoxy. Begad! Blimey! Avast, me proud beauty! Blimey! Then I laid more fiberglass mattin' in t' interior. Well, arrr, blow me down! Blimey! Cuttin' away t' flashin' and sandin' it round, arrr, I had me rough cone.

Unfortunately, arrr, I still had t' problem that t' cone be slightly too small compared t' t' airframe. Aye aye! Avast, me proud beauty! I cut from t' airframe a rin' about 1/2in long and glued it t' t' shoulder o' t' nose t' form a round, matey, precise edge. Aye aye! Begad! Then I added Bondo t' fill t' empty space on t' bottom half o' t' nose, ya bilge rat, scrapin' it smooth against t' ring. Avast, me proud beauty! With a lot more sandin' and filling, t' nose be done. Avast, me proud beauty! Blimey! 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. Begad! 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. Well, me hearties, blow me down! T' best ply sheet at Home Depot be slightly little warped, so I laid one layer o' 6oz fiberglass and pressed each fin under very heavy weights, yieldin' perfectly flat fins. Ahoy! Aye aye! I sanded t' leadin' edge elliptical, arrr, but left t' other edges square.

Three T-nuts were inserted in t' aft centerin' rin' for motor retention. Avast, me proud beauty! T' rest o' t' fin can was assembled in t' usual way. One unusual feature be that thar was only about 1 inch o' tube remainin' unslotted for t' fin can, 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 was in t' FlisKits style o' partial disks. Three plates were put in a 5.5in length o' Giant Leap coupler. 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. Well, blow me down! Blimey! 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. Aye aye! T' exterior was sanded Bondo t' give a smooth fit. Begad! 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, me bucko, I took t' rocket t' t' NCR club for advice. Blimey! Blimey! First, they were worried about t' length o' t' baffle/coupler. Well, blow me down! So I glued it asymmetrically: 1.75in into t' fin can and 3.75in for couplin' into t' airframe. Second, me bucko, they were worried about successful ejection. Begad! Arrr! T' design, matey, from aft t' forward, was: motor, baffle/coupler, airframe split, chute in airframe, me hearties, then bulkhead. 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. Begad! These calculations proved worthless. T' first ground test used 1.5g powder, me hearties, me bucko, equal t' what is given with an I or J motor. T' rocket separated but t' chute was nay pulled out. Ahoy! With 2.5g, I had t' same result. Begad! 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, separated t' airframe, but still did nay pull t' chute out. I learned by experience that 3.5g o' powder is way too much, ya bilge rat, me hearties, and I realized I that had t' abandon 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. Ahoy! Next I had t' remove t' bulkhead, which was 11in from t' nearest tube end. Well, blow me down! What a dusty, me bucko, shiver me timbers, bloody knuckle, matey, frustratin' nightmare! Then I glued t' airframe t' t' coupler so that separation would now be at t' nose. Begad! T' ground test with 2g worked fine.

I sewed t' chute myself. Aye aye! It be 72in diameter, me bucko, 12-gore semi-elliptical in t' Nakka design. Ya scallywag! Avast! It was 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. Avast! 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. Ahoy! Final calculations showed that 12oz o' nose weight was needed a stability margin o' 2.2 with t' largest possible motor (J350). Aye aye! T' 1010 rail buttons went on at some point.

 

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

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

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