Brief:
Weighin' in at 6lb 10oz, 5ft 4in height, me bucko, me hearties, 3in diameter, me hearties, t' CraterMaker is by far t' most ambitious scratch project I have ever attempted. Avast! It is also me first rocket designed for I and J motors. 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. Ya scallywag! With no electronics, motor ejection was planned, me hearties, 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. Begad! Blimey! He offered t' mail one t' anyone around t' country, and on a lark, arrr, I accepted. Aye aye! Avast! Blimey! About t' same time, ya bilge rat, 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. Ahoy! Blimey! I chose a 4FNC design with very sleek swept trapezoidal fins. Ya scallywag! Blimey! T' RockSim file is included here.

I began with t' nose cone, usin' t' redwood cone t' lay up fiberglass. Unlike many people, arrr, I laid t' fiberglass over t' cone and used this shell directly for t' cone rather than as an inverse mold for another layup. Blimey! Both t' inner and outer diameter o' t' nose cone were slightly too small compared t' t' body tube, matey, 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, me proud beauty! Over this, I laid strips o' 6oz S-weave fiberglass with one layer o' 1.5oz fiberglass mattin' in t' middle. Well, blow me down! Begad! After releasin' t' half-cone and repeatin' t' process, matey, I clamped t' two halves together and filled t' interior seam with a fillin' o' chopped fiberglass and epoxy. Blimey! Aye aye! Then I laid more fiberglass mattin' in t' interior. Blimey! Cuttin' away t' flashin' and sandin' it round, me bucko, me bucko, shiver me timbers, I had me rough cone.

Unfortunately, arrr, ya bilge rat, I still had t' problem that t' cone was slightly too small compared t' t' airframe. 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, precise edge. 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. Avast! With a lot more sandin' and filling, t' nose was done. Aye aye! Now (and especially with t' additional nose weight later), me hearties, me hearties, 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. Ya scallywag! 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! 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, matey, ya bilge rat, yieldin' perfectly flat fins. Arrr! I sanded t' leadin' edge elliptical, shiver me timbers, 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. Arrr! Begad! One unusual feature was that thar was only about 1 inch o' tube remainin' unslotted for t' fin can, arrr, arrr, so I had t' be very careful nay t' bend or torque anything. Blimey! Aye aye! Interior fillets were created by runnin' down an epoxy/milled fiberglass mixture.

T' baffle be in t' FlisKits style o' partial disks. Ahoy! Three plates were put in a 5.5in length o' Giant Leap coupler. Ahoy! 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. Aye aye! I used lots o' fiberglass: 1 exterior layer o' S-weave plus 2 interior layers o' 1.5oz matting. Ahoy! Arrr! I literally could have stood on this without damage. Aye aye! T' exterior be 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, me hearties, t' reduce heat damage.

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

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

I sewed t' chute myself. Blimey! Blimey! It be 72in diameter, 12-gore semi-elliptical in t' Nakka design. Begad! Arrr! 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. I made a block o' oak rounded on one side, matey, with an eye bolt through t' middle and attached with epoxy and a screw through t' shoulder wall. Well, blow me down! Final calculations showed that 12oz o' nose weight was 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, Bondo, me bucko, me hearties, and wood filler, interrupted with interminable periods o' sanding. Avast! You can see t' final red, me bucko, white, arrr, and black paint scheme. Avast! All t' paint be Krylon gloss, many coats, me bucko, with clear over t' top. Ya scallywag! T' CraterMaker sticker be provided by Mike Fisher at Binder Designs. Begad! He does first rate work, ya bilge rat, as I'm sure you can see. 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. Aye aye! Havin' simmed a variety o' motors, it looked like t' best choices t' keep t' rocket low and visible would be I285R, I300T, or I366R, simmed t' 1616, arrr, 1795, me bucko, and 2446ft, me bucko, respectively. Ya scallywag! I opted for t' I300T.

I be very nervous as they called out t' launch sequence in a light breeze. Blimey! Boost be very straight and fairly fast. Well, blow me down! T' rocket be visible all t' way up. Well, blow me down! I be tryin' unsuccessfully t' find it in t' binoculars durin' t' coast phase, so others told me what happened. Ya scallywag! Ejection was right at apogee, shiver me timbers, 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. Begad! Avast, me proud beauty! As it landed on t' soft prairie, I judged that t' chute size be about right. Avast! T' landin' be assertive but nay too hard.

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