General Build Instructions for Mach 1 BT50 and BT55 Single Fin Kits 60-80 grit sandpaper Hobby knife Tape measure Scissors CA Super glue 30-minute epoxy 5-minute epoxy Masking tape 1/16 drill bit Needed Items for Assembly General Instructions for All Fiberglass Rockets Fiberglass is a great material due to its strength and rigidity. However certain techniques must be used that are different than cardboard or phenolic tubing. 1. Fiberglass is covered with mold release agents. This must be removed to allow epoxies to bond properly. Wash all fiberglass parts thoroughly with a grease cutting dish soap and warm water. After it is dry it is a good idea to use isopropyl alcohol to finish cleaning the parts, paying special attention to the inside of the airframe where the motor assembly will mount, and the outside of the airframe where the fins will attach. 2. Fiberglass is very smooth. Smoothness in this case means non-porous. Everywhere epoxy is to be applied, the tubing should be roughed up with 60-80 grit sandpaper, and in the case of fins, scored lightly with a hobby knife. 3. A variety of slow cure epoxies are best to bond fiberglass, provided the surface has been properly prepped. Quick cure epoxies are fine for tacking and for certain portions of the kit that will not be subjected to a lot of stress. CA super glues should only be used where polypropylene plastic will be bonded to fiberglass. The same rules of roughness apply.
Step 1. Make sure all parts are in the kit. If there is something missing, email Steve@mach1rocketry.com and we will send out the part immediately. Parts list: BT 50-55 airframe tube 4 G10 Fins 1-18mm or 24mm Motor tube 2-3/32 Centering rings (1 slot for Kevlar) 1/16 Kevlar Shock Cord 2-Mini or Micro Rail Buttons (3-piece) 1-3/16 launch lug Step 2. Mark Fins Using the downloaded Universal fin marking guide found at http://www.mach1rocketry.com/how-to.html Note: Use the guide according to the number of fins provided in the kit. 2.a Once Fins are Marked you will need to rough the tube where fins will attach with 60-80 grit sandpaper. Rough tube approximately ¼ on each side of the fin marks. It also a good practice to score an X pattern around ¼ on each side of the fin marks. This increases epoxy adherence dramatically.
2.b Also score each side of the root edge of each fin as shown right. 4. Gluing on the fins There are several ways to attach fins and keep them straight. We recommend using a 5-minute epoxy to tack the fins on. Use a very thin layer and allow to set for about a minute. After fins are tacked they may easily be knocked loose, so careful handling until thoroughly dry is needful. 4.a After the 5-minute epoxy has set and dried for each fin. Tape the body leaving ¼ exposure adjacent to the fin and ¼ of the fin exposed adjacent to the body as shown right.
4.c Use your favorite 30-minute epoxy to run a fillet between the tape securing the root edge of the fin to the body tube. After a few minutes it will be necessary to remove the tape. Do one side at a time and allow each side to dry before turning. Fillets should be smooth as shown right 5. Motor Assembly. Test fit your motor retainer now. Sand if Necessary. There are two centering rings with your Mach 1 BT Rocket. You will notice that one has a slot cut in the inside. (On the 18mm motor assembly the are 2 slots on the rear ring. 1 allows for the ring to be inserted over the Motor hook, the other is for Kevlar to go through.) This is to allow for the provided Kevlar shock cord to be inserted and epoxied straight to the 18mm or 24mm motor tube. 5.a Make sure to rough the tube at all attachment points for both the centering rings and the shock cord. Insert the Kevlar cord through the slot and tie a single knot. Also tuck the shock cord in the tube to keep it out of the way
5.b Measure 3/8 from the aft end and that is where the aft centering is epoxied. Measure ¼ from forward end that is where the forward centering ring is epoxied. 5c. Use 30-minute epoxy and glue the centering rings and the shock cord to the Motor Tube. Set upright to dry. 5d. After the 30-minute epoxy has dried, flip the motor tube and repeat on the other side of the rings. 6. Insert the Motor Assembly. Test fit the Motor assembly into the Airframe of the rocket. Use 60-80 grit sandpaper to rough the inside to the airframe at the points where the two centering rings will seat. Note: The motor tube should be flush with the aft end of the airframe. 6a. Apply 30-minute epoxy just aft of where the forward most centering ring will seat. Insert the Motor assembly into the rocket making sure the motor tube is flush with the aft of the airframe. Set upright to dry. 6b. After forward epoxy has dried flip the rocket over and stand upside down. Apply epoxy to the aft centering ring. Also, this is a good time to epoxy in your retainer.
After all epoxy has dried thoroughly, It s time to sand your fillets. To help fill any imperfections, use spot putty or your favorite sandable filler. Nose Cone Notes. Plastic likes to bind with the fiberglass. The Nose cone should be somewhat loose. Sand as need or apply tape as needed. To test fit, insert nose cone into the rocket and blow through the motor tube. If the cone pops off, you re good. Finally, Attach the parachute and Kevlar shock cord to the nose cone and your rocket is ready to fly, but you re not done! Note we provide enough shock cord to get you out of the rocket and then some. You may want to consider adding a length of shock cord, as this will help with hard deployments. Paint your favorite color. The graphics pack is solid vinyl. Make sure your paint is completely dry before applying decal. Thank you for purchasing a BT Fiberglass rocket from Mach1 Rocketry. The only makers of BT fiberglass kits in the world!