Brief:
Weighin' in at 6lb 10oz, 5ft 4in height, 3in diameter, t' CraterMaker is by far t' most ambitious scratch project I have ever attempted. It is also me first rocket designed for I and J motors. Begad! Well, blow me down! I planned super-sleek fins, me bucko, 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, me bucko, ya bilge rat, 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. Aye aye! Blimey! Blimey! He offered t' mail one t' anyone around t' country, arrr, me hearties, matey, and on a lark, ya bilge rat, I accepted. Blimey! 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. Well, blow me down! I chose a 4FNC design with very sleek swept trapezoidal fins. Arrr! T' RockSim file is included here.

I began with t' nose cone, shiver me timbers, matey, usin' t' redwood cone t' lay up fiberglass. Ya scallywag! 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. Both t' inner and outer diameter o' t' nose cone were slightly too small compared t' t' body tube, ya bilge rat, 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. Over this, matey, me hearties, ya bilge rat, I laid strips o' 6oz S-weave fiberglass with one layer o' 1.5oz fiberglass mattin' in t' middle. Begad! Blimey! 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. Arrr! Then I laid more fiberglass mattin' in t' interior. Arrr! Cuttin' away t' flashin' and sandin' it round, matey, I had me rough cone.

Unfortunately, me hearties, 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, ya bilge rat, precise edge. Then I added Bondo t' fill t' empty space on t' bottom half o' t' nose, arrr, scrapin' it smooth against t' ring. Ahoy! With a lot more sandin' and filling, t' nose was done. Now (and especially with t' additional nose weight later), ya bilge rat, 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. 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, me hearties, yieldin' perfectly flat fins. Aye aye! Arrr! Blimey! 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. Avast, me proud beauty! Begad! T' rest o' t' fin can was assembled in t' usual way. Ahoy! One unusual feature was 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 be in t' FlisKits style o' partial disks. Avast! Three plates were put in a 5.5in length o' Giant Leap coupler. Begad! 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. Begad! I used lots o' fiberglass: 1 exterior layer o' S-weave plus 2 interior layers o' 1.5oz matting. Well, arrr, blow me down! I literally could have stood on this without damage. T' exterior be sanded Bondo t' give a smooth fit. Begad! Ahoy! 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, shiver me timbers, I took t' rocket t' t' NCR club for advice. First, me hearties, ya bilge rat, they were worried about t' length o' t' baffle/coupler. Aye aye! Blimey! So I glued it asymmetrically: 1.75in into t' fin can and 3.75in for couplin' into t' airframe. Avast, me proud beauty! Blimey! Second, they were worried about successful ejection. Avast, me proud beauty! Blimey! T' design, from aft t' forward, was: motor, shiver me timbers, baffle/coupler, shiver me timbers, airframe split, chute in airframe, then bulkhead. Well, blow me down! 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. Aye aye! Avast, me proud beauty! These calculations proved worthless. Well, blow me down! T' first ground test used 1.5g powder, me hearties, equal t' what is given with an I or J motor. T' rocket separated but t' chute was nay pulled out. With 2.5g, me bucko, I had t' same result. Avast, 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, me hearties, separated t' airframe, me hearties, but still did nay pull t' chute out. I learned by experience that 3.5g o' powder is way too much, and I realized I that had t' maroon t' zipperless design.

After repairin' t' fin can, ya bilge rat, I cut t' nose off t' airframe and ground it back down t' t' shoulder. Next I had t' remove t' bulkhead, shiver me timbers, which was 11in from t' nearest tube end. Ahoy! What a dusty, bloody knuckle, 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. Well, blow me down! It be 72in diameter, me bucko, 12-gore semi-elliptical in t' Nakka design. Begad! Blimey! 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, me hearties, with an eye bolt through t' middle and attached with epoxy and a screw through t' shoulder wall. Blimey! 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, matey, and wood filler, shiver me timbers, interrupted with interminable periods o' sanding. Ahoy! Arrr! Blimey! You can see t' final red, me hearties, white, matey, arrr, and black paint scheme. Well, blow me down! Begad! Blimey! All t' paint be Krylon gloss, me hearties, many coats, matey, ya bilge rat, with clear over t' top. Ahoy! Blimey! T' CraterMaker sticker was provided by Mike Fisher at Binder Designs. He does first rate work, as I'm sure you can see. Avast! Blimey! 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. Blimey! Blimey! Havin' simmed a variety o' motors, it looked like t' best choices t' keep t' rocket low and visible would be I285R, me hearties, I300T, shiver me timbers, matey, or I366R, simmed t' 1616, me bucko, 1795, and 2446ft, respectively. Ahoy! I opted for t' I300T.

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

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