I love t' Estes Yellow Jacket. Begad! Begad! I’ve built 2 originals, and many upscales and downscales. I’ve taken t' identifyin' t' YJ’s in me fleet by t' number and size o' t' engines, so me 2.6-inch upscale was t' YJ-324, me hearties, indicatin' a triple cluster mount o' 24mm motors. T' name for this rocket means that a cluster o' two 18mm mounts are installed. Ya scallywag! This be me very first cluster rocket, arrr, me bucko, and after 20 sweet flights on C6-5’s and C6-7’s she’s still goin' strong.

Pictured here be t' YJ-218, shiver me timbers, an original Yellow Jacket in t' middle, and a 13mm downscale, t' YJ-113.

Materials:

• PNC-60 Nose Cone — nay t' Big Bertha or Mean Machine type, it’s 4.75-inches long (not includin' shoulder).
• BT-60 Body Tube — true scale is 21.3-inches long, me bucko, but mine is 24.75-inches t' compensate for t' too-short nose cone.
• TC-60 body tube couplers as needed, me bucko, shiver me timbers, possibly one or two.
• BT-20 Body Tubes — you’ll need 2, shiver me timbers, each around 3-inches long for t' motor mounts.
• Cardboard for t' centerin' rings — I used cereal box cardboard as described below.
• Balsa fin stock — 1/8-inch thick.
• Launch lugs — 3/16-inches or use rail buttons (mine has both)
• Shock Cord — at least 36-inches o' 1/4-inch elastic, more is better.

Also:

• Elmer’s Fill’n’Finish
• Yellow wood glue
• Thin CA

Construction:
Jim Z’s site has t' original Yellow Jacket plans here, me hearties, arrr, and except as noted t' construction be t' same.

What follows aren’t complete construction steps, me bucko, just highlights for t' methods I used here and there.

T' centerin' rings are t' most involved part o' construction. Begad! Avast, me proud beauty! Blimey! Start by layin' out t' diameter o' t' first centerin' rin' on your sheet o' cardboard. Begad! Blimey! Next, me hearties, me bucko, bisect t' circle into four quadrants (make an ‘X’ centered in t' circle). Arrr! Blimey! Holdin' t' two BT-20’s together, shiver me timbers, trace around them so that they are centered along one axis and t' other axis splits them. Ya scallywag! Well, blow me down! Blimey! There are more precise ways o' doin' t' layout, but t' semi-freehand method is what I used, and it works fine.

Use an X-acto knife t' carefully cut out t' inside holes. Well, blow me down! Ya scallywag! Test fit t' motor mounts and sand t' holes as needed. Avast, me proud beauty! T' main thin' is t' nay compress t' motor tubes, or you’ll have trouble gettin' t' motors in or out.

Once t' inner holes are cut, me hearties, use scissors t' cut out t' outer diameter. Ahoy! Blimey! Trim t' fit t' body tube. Begad! Blimey! Ya scallywag! Blimey! Now use this first centerin' rin' as a template t' make 3 more.

When all are cut and fit, matey, glue them together into pairs so you have two double-thick rings. Begad! Begad! Blimey! You can use yellow glue or thin CA. Avast! Once dry, matey, use yellow glue t' attach them t' t' motor mount tubes, ya bilge rat, makin' sure t' tubes ends are even and they’re nay twisted along their length. Arrr! Ya scallywag! Blimey! I usually leave t' front rin' about 1/4-inch back t' make room for a good glue fillet around t' top, ya bilge rat, arrr, and t' back rin' should be glued on about 1/2-inch from t' end.

Print t' fin template from t' original plans, me hearties, then enlarge it 168% on a copier for t' correct sizing. Ahoy! T' fins are simply 1/8-inch balsa, sanded and sealed with Fill’n’Finish. Begad! Ahoy! Airfoil if you want, I just rounded t' leadin' and trailin' edges. Begad! Arrr! After they’re attached t' t' body tube with yellow glue, shiver me timbers, soak t' fins with thin CA for extra strength. Well, blow me down! Begad! You can add tabs t' t' root edges and make t' fins through t' wall, shiver me timbers, but I’ve had nay had any problems with surface mount.

One o' t' couplers is used in front o' t' motor mount t' strengthen t' body tube. Avast, me proud beauty! This area just forward o' t' fins takes a tremendous amount o' stress durin' flight, matey, ya bilge rat, and a coupler here greatly reduces t' possibility o' tube crimps durin' t' boost phase and upon landing.

I used t' standard Estes ‘paper sandwich’ shock cord mount, me hearties, and it’s holdin' up fine. Blimey! There’s plenty o' room in t' body tube for waddin' and lots o' shock cord, matey, shiver me timbers, so be generous with both. This rocket is light enough t' come down on a 4" X 40" streamer, but we recover on soft grass so if your field is harder ground you’ll want t' use a 15" or 18" chute.

If you don’t make your own decals, me bucko, matey, Tango Papa can make enlarged versions for you at a reasonable cost. Aye aye! Or you can forego t' decals and use auto pinstripin' tape for t' stripes. Begad! For t' YJ-218, t' bottom 13.4-inches is painted yellow.

I did nay install motor retention. What I do is insert t' motors, matey, arrr, then use a wrap o' maskin' tape around both t' motor casings and t' motor mount tubes. Arrr! I’ve never had a motor kick usin' this method with black powder motors.

Final ready-to-fly weight, matey, excludin' engines, is around 5 ounces.

Flight:
C6-7’s are t' perfect motor for this rocket, ya bilge rat, but C6-5’s can be used without sacrificin' much altitude.

I fly a lot o' clusters, ya bilge rat, and out o' many, many flights I’ve had exactly 2 motors fail t' ignite. Aye aye! T' key t' success is attention t' detail. Arrr! Make sure t' motor nozzles aren’t clogged with excess clay before installin' them. Use igniters in good condition, with plenty o' pyrogen on t' ends. Carefully twist together one lead from each igniter, then twist together t' other pair before attachin' t' clips from t' launch controller. Blimey! Blimey! If you use clip-whips instead, solder t' connections for reliability. It’s also very important t' make sure that t' battery you’re usin' has enough oomph t' fire all o' t' igniters at once because a standard Estes controller will nay do it reliably.