Brief:
T' idea for this rocket be t' create a minimum diameter gap-stager designed for speed and altitude, me bucko, while still flyin' on economical Estes D12-0 and D12-7 motors. Ya scallywag!

Parts

• 1 Estes PNC-50 nosecone
• 28" BT-50 or equivalent (mine came from Totally Tubular, if you use Estes tube, arrr, you'll need t' add a coupler for t' extra length.)
• 2"-3" length o' BT-50 for inner reinforcement
• 24mm engine block
• 1/8" balsa for fins
• shock cord, shiver me timbers, I used 12' o' 1/4" elastic attached with t' Estes 'paper sandwich' method
• 3/16" launch lug or rail button

• 4" BT-50 or equivalent
• 24mm engine block
• 1/8" balsa for fins
• 3/16" launch lug or rail button

Construction

All glue joints are done with yellow wood glue. All body tube grooves were filled with Elmer's Fill 'n' Finish, and then sanded smooth. Ahoy! Fin fillets were done with yellow glue, arrr, shiver me timbers, then another coat with Fill 'n' Finish sanded smooth, and then finally painted with thin CA for extra strength.

See t' attached RocSim file for fin templates. Blimey! Blimey! (above right)

Sustainer Construction

Take t' 2"-3" length o' BT-50 and slit it lengthwise, ya bilge rat, then remove a small sliver. Begad! Blimey! T' idea here is t' create an elongated tube that will slip inside t' main body tube. Begad! Blimey! Glue this reinforcement inside t' main body tube, positionin' it near t' top o' t' sustainer fins and makin' sure it doesn't interfere with t' placement o' t' thrust ring. Aye aye! Blimey! T' reason for this extra tube is that t' area just ahead o' t' fins is where a rocket will often crumple - either under thrust or on landing. Blimey! Blimey! I had t' do this after t' first flight, it'll be easier t' do durin' construction instead o' as a retrofit.

Position t' engine block so that t' inserted D12 motor extends out the back betwixt 1/4"-1/2".

T' rest o' t' sustainer is simple Estes-style construction. Begad! Blimey! Avast, shiver me timbers, me proud beauty! Blimey! For extra strength, you can coat t' inside o' t' body tube with thin CA.

Booster Construction

T' fins are attached even with t' front o' t' body tube. Aye aye! Blimey! This allows about a half inch o' body tube at t' motor end t' accept a wrap o' masking tape for motor retention.

Position t' engine block so that t' inserted D12-0 extends out t' back about ¼". Avast, me proud beauty! Blimey! Just above t' booster engine block, cut three holes in the body tube - betwixt t' fins - t' vent t' ejection gasses that might separate the booster before ignitin' t' upper stage motor. Avast! Blimey! You can use a hole punch to make these holes, arrr, me bucko, or carefully cut them with a hobby knife. Arrr! Blimey! Soak thin CA into the area around t' holes for strength. Begad! Aye aye! Blimey! You can see one o' t' vent holes in the picture.

Paintin' and Finishing

T' entire rocket be primered and painted gloss white. Avast! Begad! Once that be dry, the fin can o' t' sustainer be masked off and painted with fluorescent pink, as was one fin o' t' booster.

Final details were added usin' chrome mylar tape for striping, and then the name and checkerboard patterns were created with a laser printer usin' MS PowerPoint and Papa Tango decal paper.

Empty weight for t' booster was .75 ounce (21.5 grams), and t' sustainer was 1.5 ounces (43 grams). Begad! These seem unusually light t' me, me hearties, and t' only explanation I can think o' is that t' body tubin' I used is from Totally Tubular, shiver me timbers, and doesn't appear t' be as heavy (nor as strong) as standard Estes tubes. Ahoy! T' rocket was weighed on a recently-calibrated postal scale, so I'm confident that t' weights as stated were correct.

Flight Prep

Friction fit a D12-7 into t' sustainer and a D12-0 into t' booster. Ahoy! Fit the stages together, me hearties, ya bilge rat, matey, usin' t' upper stage motor as t' coupler. Ahoy! Begad! It's important that t' fit betwixt stages be smooth and nay too tight. A little light sandpaper used around t' nozzle end o' t' D12-7 might be needed.

Add waddin' o' your choice, matey, me hearties, then t' recovery device. Avast, me proud beauty! Blimey! Because o' t' tight space and expected altitude, we use two pieces o' fluorescent flaggin' tape as streamers, each 1" wide by at least 6 feet long. Arrr! Blimey! Avast! Blimey! Packin' t' streamers can be a challenge, especially if t' wind is actin' up.

Flight History

T' first flight was on BattlePark '02 in Culpeper, me hearties, matey, Virginia. T' boost was great and she staged perfectly (really high too), arrr, but just after separation the sustainer body tube let go a little bit and she wobbled t' apogee. Begad! It looked like t' kick o' t' D12-7 ignitin' was just too much for a weak spot in the body tube and it crimped, matey, turnin' t' sustainer into a banana. Well, blow me down! I cut t' body apart at t' crimp and installed a coupler as reinforcement so she could fly again.

She made three more beautiful single-stage flights, arrr, ya bilge rat, matey, all on D12-7's before bein' lost. Ya scallywag! Estimated altitude for these flights was around 1500 feet.

Summary

This is a fun and simple rocket t' build and fly, and she's definitely light enough t' fly C6's with adapters. You can also adjust t' position o' the sustainer thrust rin' and use an E9 in t' upper stage for even more altitude. Gap stagin' eliminates many o' t' hassles o' multi-stage prep.