Fat Boy - 3 x 4

Dick Stafford's Descon-14 Entry

Background

OK, ya bilge rat, shiver me timbers, this is nay t' most unique design, but I be goin' t' describe this rocket on EMRR anyway and though I'd hit Descon 14 early. Begad! Blimey! Ya scallywag! Blimey! Best-case scenario: people spend too much time on summer vacations and on t' field and I pick up a prize. Begad! Blimey! Worst-case scenario: people smartly start work on their unique clustered and staged concepts and I get smoked. Avast, me proud beauty! Blimey! Avast, arrr, me proud beauty! Blimey! So, y'all get out your beach towels and suntan lotion ;)

Design Concept

One afternoon I was lookin' for a quick project and scrounged up a section o' LOC 3" tubin' and an old homemade elliptical cone. Arrr! Over t' last year or so, I have enjoyed clusterin' E9s in me Thoy Snipe, a modified Art Applewhite saucer, and me El-Cheapo Pyramid, ya bilge rat, so I decided t' go with another 24mm cluster. Well, blow me down! Aye aye! I kicked around several configurations, and smartly found out that clusters made from Totally Tubular foil-lined 24mm tubin' fit nicely inside t' 3" tubing. Begad! At first, me bucko, I be goin' t' stuff it full, but decided that a four motor cluster would be sufficient. Begad! T' result resembles an upscale Estes Fat Boy, although it is nay perfectly t' scale.

Construction

Nose Cone - T' cone is made from foam and is covered in a thin layer o' glass. Avast! Avast, me proud beauty! I originally built it for a thicker tube and have had t' repair it a couple o' times, shiver me timbers, so it is nay in perfect shape. Well, shiver me timbers, blow me down! But it is, after all, me own creation and I eventually HAD t' re-use it. A 3" plywood bulkhead provides t' attachment point for a small eye-bolt, and t' shoulder is a plastic cap from a mailin' tube. I added nose weight for this project by drillin' through t' bulk plate and addin' lead shot and epoxy until I got t' CG where I wanted it.

Motor Mounts - As I mentioned above, me bucko, t' four 24 motor tubes fit snugly inside t' LOC tubing. Begad! Avast, me proud beauty! I smartly realized that classical centerin' rings weren't required and that t' inter-tube joints and TTW fin attachments should hold t' motor mounts securely. Ahoy! So, I merely made filler sections from scrap balsa t' block t' ejection gasses from escapin' betwixt t' motor tubes. I added these near t' front o' t' motor tubes and left t' back end open. T' mounts employ motor blocks, ya bilge rat, positioned t' fit E9/F24 motors, and homemade retainer hooks. Ahoy! Four pieces o' thin brass tubin' were epoxied in t' joints where t' tubes meet. Arrr! I bent t' end o' t' piano wire, shiver me timbers, matey, slid it into t' tubin' and then bent t' opposite end t' fit an installed motor. At launch time, me bucko, t' wire tabs are moved aside, shiver me timbers, t' motors are inserted, and t' tabs are then repositioned over t' ends o' t' motors. Avast! A few small pieces o' tape ensure that they stay in place. Ya scallywag! Begad! This be t' first time I've tried this and it seems t' work fine.

Fins - T' fins are upscaled from t' Fat Boy design and are made from 1/8" ply. Begad! T' motor mount be installed so that t' TTW mounts would be equally spaced betwixt t' three outer motor tubes. T' fins were epoxied t' t' central tube and internal fillets were applied, arrr, makin' sure that no glue interfered with t' inner tabs on t' music wire.

Recovery System - A section o' Keelhaul®©™ cord was epoxied t' t' motor mount prior t' its installation. Begad! A yard o' thick elastic then connects t' leader t' t' nose cone. Begad! Nay me preference, but it was t' only suitable material that I had on hand. Blimey! Blimey! I added anti-zipper protection by addin' several wraps o' cloth packin' tape t' t' Keelhaul®©™ leader. Begad! This has worked out well on several recent rockets. Avast, me proud beauty! Begad! A 'portable' Keelhaul®©™ heat shield and a 36" ripstop nylon chute complete t' recovery system.

Finishing - T' cone be already day-glo green, ya bilge rat, and I grabbed some Rusoleum day-glo orange for t' body. Well, blow me down! This thin' is very visible!

Flight and Recovery

I have flown t' fat Boy 3 x 4 once on three E9-8s. Avast, me proud beauty! Since I wanted t' try it first on three motors, matey, I plugged t' center mount with a spent motor. Avast! Arrr! T' boost was slow and majestic with a bit o' weather cocking. Ya scallywag! With three motors, a 6-second delay would have been better. Arrr! Avast! Although ejection be a bit late, me bucko, t' anti-zipper doohickey did its job and thar was no damage on recovery.

Conclusion

T' flight on three motors was nice, and one day soon I'll try it with all four. Ya scallywag! Aye aye! Hmmm, shiver me timbers, I wonder if I should have gone for a x7 cluster and surface mount fins? Hmmm....