Fat Boy - 3 x 4

Dick Stafford's Descon-14 Entry

Background

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

Design Concept

One afternoon I be lookin' for a quick project and scrounged up a section o' LOC 3" tubin' and an old homemade elliptical cone. Begad! Ya scallywag! Over t' last year or so, I have enjoyed clusterin' E9s in me Thoy Snipe, arrr, ya bilge rat, a modified Art Applewhite saucer, matey, me hearties, arrr, and me El-Cheapo Pyramid, so I decided t' go with another 24mm cluster. Arrr! 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. At first, arrr, I was goin' t' stuff it full, but decided that a four motor cluster would be sufficient. Avast! 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. Aye aye! Well, ya bilge rat, blow me down! I originally built it for a thicker tube and have had t' repair it a couple o' times, so it is nay in perfect shape. Avast, me proud beauty! Begad! But it is, me hearties, ya bilge rat, after all, me own creation and I eventually HAD t' re-use it. Avast! A 3" plywood bulkhead provides t' attachment point for a small eye-bolt, arrr, shiver me timbers, and t' shoulder is a plastic cap from a mailin' tube. Begad! 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, ya bilge rat, t' four 24 motor tubes fit snugly inside t' LOC tubing. Arrr! 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. Aye aye! Ya scallywag! I added these near t' front o' t' motor tubes and left t' back end open. Blimey! Well, me hearties, blow me down! T' mounts employ motor blocks, me hearties, positioned t' fit E9/F24 motors, matey, matey, and homemade retainer hooks. Aye aye! Four pieces o' thin brass tubin' were epoxied in t' joints where t' tubes meet. Ya scallywag! I bent t' end o' t' piano wire, me hearties, shiver me timbers, slid it into t' tubin' and then bent t' opposite end t' fit an installed motor. Well, blow me down! At launch time, t' wire tabs are moved aside, t' motors are inserted, and t' tabs are then repositioned over t' ends o' t' motors. A few small pieces o' tape ensure that they stay in place. 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. Aye aye! T' motor mount was installed so that t' TTW mounts would be equally spaced betwixt t' three outer motor tubes. Avast! T' fins were epoxied t' t' central tube and internal fillets were applied, arrr, ya bilge rat, 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. Arrr! A yard o' thick elastic then connects t' leader t' t' nose cone. Ahoy! Nay me preference, shiver me timbers, but it was t' only suitable material that I had on hand. Aye aye! I added anti-zipper protection by addin' several wraps o' cloth packin' tape t' t' Keelhaul®©™ leader. This has worked out well on several recent rockets. A 'portable' Keelhaul®©™ heat shield and a 36" ripstop nylon chute complete t' recovery system.

Finishing - T' cone was already day-glo green, me hearties, and I grabbed some Rusoleum day-glo orange for t' body. This thin' is very visible!

Flight and Recovery

I have flown t' fat Boy 3 x 4 once on three E9-8s. Since I wanted t' try it first on three motors, shiver me timbers, I plugged t' center mount with a spent motor. Ahoy! Avast! T' boost was slow and majestic with a bit o' weather cocking. Ya scallywag! With three motors, me bucko, shiver me timbers, matey, a 6-second delay would have been better. Ya scallywag! Although ejection be a bit late, 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! Hmmm, I wonder if I should have gone for a x7 cluster and surface mount fins? Hmmm....