Brief:
Easy TTW single-stage rocket designed to be flown on D-F motors. The fins and strakes take a little time if you want the rocket to look great.

Construction:
Two standard diameter body tubes with TTW fin design.

List of Parts (all Semroc numbers)

• BNC-60X nosecone
• BT-60DS body tube
• BT-60BB body tube
• JT-60C coupler
• BT-50FE engine tube
• 2 RA-5060 centering rings
• EH-28 engine hook
• CD-12 12" Parachute
• Balsa
• Launch lugs
• small screw eye

Nothing too tricky in this build. I began with the motor mount. Make certain you place the centering rings as per the Rocksim plan (.25" from rear and .50" from front) so you will allow correct space for the fin tabs. I tied the shock cord (Kevlar®) around the engine tube and then slid the forward ring on over it. Then apply generous fillets to both sides of the centering rings making certain the Kevlar® loop had ample glue too. The design uses no engine block and I even left off the engine hook to allow more engine choices. Motor retention is up to you!

The fins were my step two. If you print the fin design from the Rocksim file, you can of course omit the TTW fin design to simplify things. I built mine with TTW design.

I like to rubber cement the fin patterns on cardboard and cut it out before marking the balsa. Once the fins and strakes are cut and sanded, I papered the fins and set them aside. Because the strakes are thin, I decided to seal these with Fill 'n Finish.

The design calls for the shorter body tube to be on bottom. I did this to make installing the motor mount easier. Glue the motor mount so the bottom of the motor tube is even with the end of the body tube. When dry, fillet both ends. (that's why the shorter tube)

Next, mark the coupler at its midpoint and glue it into the lower body tube. Let it dry!

Next, glue the two body tubes together. When this dries, use Fill 'n Finish on that seam and all the spirals.

While all this is drying is a good time to add the eye hook to the nosecone and fill it with Fill 'n Finish. I like to put the wet nose cone through a piece of hangar wire and hang it to dry.

Make the parachute and set aside.

Sand the body tubes being careful not to rough up the cardboard too much and then mark the tube for 3 fins. These lines will need to travel the entire length.

Next I would check to make certain the strake angle matches the fins they will connect with.

Mount the fins and the strakes and when dry, fillet everything.

As for finishing, I use Rustoleum Sandable primer first, then sand most of it off, check for problems, prime again, and then wet sand till very smooth. This design is not a scale model so I went for the hi-visibility orange and flat (Army) green.

I put a loop in my shock cord and attach the chute with a leader line and snap-swivel. I think this helps prevent the chute from tangling.

Finishing:
After first coat of sandable primer I checked for imperfections, repaired those and then sanded everything smooth. After second primer coat I did a finish sanding. First coat of enamel applied and left to dry 24 hours. Light sanding before second coat. That coat looked good so I went ahead with final coat. A ring of tape was wrapped just above the body strakes and everything below that was wrapped before applying two coats of nose color. This all made for a highly visible and simple paint job.

Flight:
I use "dog barf" for my wadding. A couple wraps of masking tape at nozzle end prevents motor front kicking forward. A little wrap around that and the bottom of the rocket keeps it from kicking out.

Estes D12-3 for first flight. Good straight flight. Around 100 ft, ejection just after apogee, rocket landed within 10 feet of where it was launched.

Rocksim shows D12-5 has too long a delay so I didn't try that one.

Aerotech E11-4 gets it to about 170 ft. Rocket landed safely about 50 yds upwind

Aerotech E-18-4 gets it around 225 ft. Rocket drifted about 50 yds downwind

I'm anxious to try other motors.

Rocksim results show F12J-2 ejecting at very near apogee but no greater altitude than the E's

F39T-6 looks great in the computer - 260 ft.

Recovery:
The use of 100lb Kevlar® attached to motor mount presented no problems. On all my flights the ejection was late (well after apogee). This isn't all bad because the rocket landed close to launch pad. No zippering, burning or damage after three flights.

Summary:
I'm happy with this one. It flies great and the body strakes make for a very strong airframe.