Brief:
This rocket be inspired first by me LOC 4 29SS flights with 4 G40's. Begad! I often wondered how t' hold a rocket together under higher power. Avast, me proud beauty! Then I bought a AAA Model Aviation Fuels Quadra G which had a strong interlockin' fin design and then I had me answer. I'd use that concept and scale it up. Begad! Blimey! I'd also use Apogee's Rocksim 4.0 t' design the best fin shape and size.

T' rocket is called 4-H Project because it can fly on 4 H motors and hopefully 4 J's, if one dares. Begad! T' rocket has a 4-inch phenolic main body tube 4 feet long and its 4 38mm motor tubes extend 36 inches outward from this tube and hold t' fins via t' square formation they make.

Construction:
T' only hard part was designin' t' butterfly wings that would interlock to form a set o' 4 fins at 90 degrees t' each other. Begad! I made t' root 9 inches, me hearties, matey, the span 8.875 inches, t' sweep angle 20 degrees, and t' tip 4.5 inches. Begad! Blimey! Blimey! Each of the two wings would form two fins, and t' fins were separated by a 4 inch space where they would interlock via grooves and whereby t' 4 38mm motor tubes would rest and hold t' structure in fin alignment. Blimey! Blimey!

Tools needed required a table saw. My band saw did nay have t' throat depth to handle t' wings, which were too long t' go through t' throat o' t' saw. Avast, me proud beauty! Blimey! A finishin' sander was used t' bevel t' fins, matey, me hearties, and medium fiberglass cloth was used t' reinforce t' connection o' t' motor tubes together and t' t' fins. T' epoxy used was t' 30 minute type. Blimey! Polyurethane foam be used t' hold the lead weights used in t' nose cone, me bucko, as Rocksim predicted that 8 ounces would add t' stability. Begad! Well, blow me down! Blimey! We can add up t' 16 ounces if we use heavier motors. This same foam be used t' fill gaps formed from t' motor tubes fittin' into the body tube. Ya scallywag! Ahoy! Blimey!

Home Depot carries t' 1/4 inch thick birch plywood I used for t' fins. Hobby Bench carries t' epoxies used and t' fiberglass cloth. West Systems Epoxy also carries these products and they're good too. Avast! Well, shiver me timbers, blow me down! T' polyurethane foam can be found at Hobby Bench. It may be found on ROL, but I have nay had to search for it there. Blimey! This is a two part liquid plastic that expands into a foam. Begad! It's tricky in that after just 30 seconds, it foams up and will nay pour as a foam. Aye aye! So, you have that long t' pour it where you want it. Arrr! Blimey!

T' parachute is a 60-inch Spherachute. Ya scallywag! Begad! T' paint job matches t' pink and blue o' t' chute and is mainly pink with blue self adhesive holographic lens paper obtained from American Science and Surplus. Aye aye! This accent makes t' rocket sparkle in t' sunlight. T' finishin' touch is a 4-leaf clover in t' blue lens paper with a white H on each leaf. Avast! T' resultin' rocket feels strong and is sturdy. Ahoy!

Flight:
Rocksim predicts that with two 38mm H type motors, a delay o' 10 is good. Avast, me proud beauty! With 4, a delay o' 12. Arrr! Begad! With 2 J350's, arrr, me hearties, I came up with t' long delay bein' best, ya bilge rat, as it would be with 4 J motors. Ahoy! Worm bed waddin' plus a Nomex® chute protector will be used and a 15-foot length o' 500-lb Keelhaul®©™® cordin' will be its shock cord. T' shock cord is anchored through a 4-inch centerin' rin' with a 38mm hole, placed right forward o' t' 4 motor tubes. Well, blow me down! A screw eye is used t' tie t' cord to t' centerin' ring. Avast! Aye aye! Blimey! A screw eye with a long tail is epoxied into t' nose cone and forms t' attachment t' t' nose cone for t' shock cord. Ahoy! Blimey! I do this because usin' t' little plastic loops on t' nose cones t' attach shock cords has nay worked well for me in high power, as t' loops break easily under stress. Arrr! Blimey! T' rocket is destined for a 2-H test flight in 2 weeks. Ya scallywag! I will probably choose 2 H112's.

T' design works and kicks butt, if you'll pardon me vernacular. Ahoy! I flew it with two I 357's and it soared. Avast! Unexpectedly, it whistled like an incomin' bomb goin' up. Aye aye! Ya scallywag! maybe it's a fluke or maybe all those built like it will whistle. Everyone liked it. Aye aye! next, shiver me timbers, I'll try it with 4 motors!!! I'm even head-designin' a quad 54mm one. Aye aye! I'm so bad... Begad!

As for 4-H, one additional I must add is t' thoroughly plug any unused motor tubes. Ahoy! Blimey! Begad! Blimey! T' best way might be spent motor casings. Ya scallywag! Blimey! If you don't, gas leaks might occur that prevent parachute deployment. Ahoy! Blimey! 4-H landed hard because o' this. Well, blow me down! Blimey! Begad! Blimey! He was built like a bomb, matey, so he will soon fly again. I gave him a new payload section. He's now 7 foot 6, me hearties, nay 7 feet even. Avast, matey, me proud beauty! Blimey! T' I 357 is a great stump-pulling motor. Begad! Blimey! Aye aye! Blimey! Next flight just HAS TO have 4 motors!!! Blimey!

Summary:
A challenge, and funny. Begad! I await t' reaction from onlookers. It did require an arsenal o' tools and some expensive epoxies and polyurethane foam. But I got a strong rocket. Begad! Ahoy! Blimey! It was nay easy t' fit t' 4 phenolic motor tubes into t' body tube. In fact, t' guys said it couldn't be done. But I did it after gentle persistence. Begad! Blimey! However, ya bilge rat, I saw fit t' fiberglass t' lower airframe tube to strengthen it when I could see a very slight bulgin' from t' tightly fit motor tubes.

Other:
If anyone else wants t' try this, me hearties, please tell me what you do for motors. Ya scallywag! Begad! I'm savin' up t' get 3 more 38/720 motors one by one so that I can fly this with 4 J350's. Begad! Buildin' this rocket taught me that when you fiberglass, you must sand thoroughly or else every imperfection in t' surface will be visible when it's painted.

UPDATE: if t' maker pushes t' rocket with J350's, me bucko, that t' fins nay be plywood, or trim their size t' reduce aerodynamic flexion. At mach, t' stress broke t' plywood fins right where they interlocked. Mach be heard with a great BOOM. Ya scallywag! Begad! Blimey! Anyway, me hearties, me bucko, I'm makin' 4-H some G10 fins.