Sport Rocketry

edges. I do not try to add any airfoil on such a thin fin. I can't image it makes much dif- ference. The key to the fins is to make them smooth and flat. 3. Mark the body tube for three fins. I love the Estes "pancakes" and marking tool for this. Make a mark about 6mm (0.25") from the bottom of the tube on each fin line. This is where the trailing edge of the fins will go. 4. The next step is gluing the fins to the body tube. If you have the Art Rose fin jig, or access to one, that is the best method of attaching the fins to insure they are straight. If you do not have a precision fin jig, see the accompanying article for how I attach thin G10 fins. 5. The engine block comes next. Tie the Kevlar shock cord to the engine block ring and glue it at the fin end of the main tube so it is 36mm from the end of the tube (engine should extend 1/4"). That concludes con- struction of the main body tube. 6. The Apogee vacuum formed 13mm to 18mm transition comes with a short 18mm cardboard centering ring that is meant to be glued into the large open end of the transi- tion. Discard that centering ring and instead glue the 20mm long Balsa Machining C20 tube into the open end of the transition. 7. The payload section assembly is next. Follow the same process for finishing the 18mm tube as described for the main tube. Once that is done, glue the nose cone into the payload tube. If the nose cone is a balsa cone, it should be finished to a smooth fin- ish, and the seam between the nose cone and the payload tube should be filled and smoothed as well. The idea is to have the nose cone/payload tube unit be as smooth as possible to keep the airflow laminar down to the transition. Any discontinuities will cause turbulence and drag. Ideally, the airflow will stay laminar until the 18mm/13mm tran- sition, but it's more likely to become non- laminar here, so the payload and altimeter are inserted into the rocket there. 8. The last step in assembly of the pay- load section is to add vent holes in the top of the transition. These can be three pin holes spaced 120 degrees apart around the top of the transition. 9. If building the B engine class version, the booster needs to be built next. Follow steps 1 through 4 to build the booster. Flight Prep 1. To fly, add wadding to the main tube and add the recovery system. 2. Tie the transition attachment cord to the main tube Kevlar shock cord. 3. Insert the payload into the payload tube, all the way to the top. 4. Put the altimeter into the inside of the transition section (don't forget to turn it on first). The dimensions in this design should allow the payload section to hold a 60mm long payload and fit a MicroPe- ak altimeter in the transition section. It is likely that a Firefly or ALTBMP would also fit, but do some testing before cutting the payload body tube. 5. To secure the payload section to the transition section there are a few options. Option 1 is to friction fit the two together. This option may be the most aerodynamic, but also the most risky. Option 2 is once the transition and payload section are con- nected, place a piece of Mylar tape or other thin smooth tape around the joint to insure they are firmly attached. 6. If flying single-stage, secure an Es- tes A3-4T in the rocket, and launch it from your tower and/or piston launcher. 7. If flying two-stage, friction fit an A10-0T in the booster stage so it is tight. Then remove it. Take a piece of cellophane tape and wrap the booster motor to the upper stage motor (Estes staging method). Then carefully push the booster stage up onto the booster motor. 8. Now load it up into your tower and/ or piston launcher and have a great launch. 14 JANUARY/FEBRUARY 2020 SPORT ROCKETRY THE LARGEST SATURN V MODEL - 5 FEET TALL, AND MUSEUM SCALE or call us M-F MST 9am-5pm at 719-535-9335 Visit us at www.ApogeeRockets.com Model Rocketry Resources and Components SATURN V ANNIVERSARY th 50 Continued from page 8.

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