• Applicable to model rockets with an engine mount kit. Follow the engine mount assembly instructions.

A model rocket engine mount is the portion of the model rocket kit that houses the model rocket engine. This can range from a simple engine hook to a full engine mount kit.

The typical engine mount kit consists of three pieces

• The engine tube which houses the model rocket engine.
• The centering rings which center the engine tube in the center of the model rocket body tube.
• The engine hook which keeps the engine in place.

In it's most basic form, the model rocket engine mount consists of only a engine hook (no centering rings needed). This type of rocket uses the body tube of the rocket as the engine tube for the model rocket engine, since the diameter of the engine and the diameter of the rocket are the same. This type of design gets the most out of the engine, as there is not the added extra weight of a full engine mount kit.

Prior to assembly, the body tube must be marked for accurate placement of the rocket fins and the launch lug, at a minimum. Other marking may be necessary depending on the rocket being built.

To mark the body tube for the rocket fins, first a location mark should be made at the end of the body tube to indicate the spacing of the fins. To assist in this, there is usually a guide in the instructions, or the Estes Rocket Marking Guide (est302227) may be helpful. Once the initial markings are done, they must be extended up the side of the body tube approximately as far as the rocket fins will go. This line is to help align the rocket fins during assembly, since mis-aligned fins could cause an unstable flight. A door frame, book, or the Estes Marking Guild, can assist in extending these lines up the body tube.

To mark the body tube for the launch lug, follow the instructions for correct marking placement. Make sure that this mark is between two of the rocket fin marks, and not in line with one of the fin marks, to allow space for the fins to clear the launch rod during launch.

Balsa fins require preparation before the assembly phase begins. For plastic fins, this step may be skipped.

All fins should be sanded to assure smooth consistent surfaces, especially the one that connects to the body tube. The fins can be fine-tuned to minimize aerodynamic drag and increase the height the rocket can fly. To tune the rockets fins, the leading edge (the edge facing upward toward the nose cose) should be rounded like the forward edge of an airplane wing. The trailing edge, the one opposite the leading edge, should be tapered (NEVER ROUNDED) to a point to allow for smooth air flow. The root edge of the fin, the on that is glued to the body tube, should never be tuned as this must maintain a strong bond with the body tube.

To assist in attaching the shock cord to the inside of the body tube, a shock cord mount is used. Basically, the shock cord in glued to, and folded inside, of the shock cord mount. The advantage of this system is that shock cord mount has a large surface area to form a strong bond when glued to the body tube. The folding of the shock cord mount gives the system mechanical strength to hold up the the pull from the nose cone when the nose cone is ejected by the model rocket engine.

Some model rocket nose cones come in two pieces that must be glued together. Before gluing the pieces together, make sure to double check the instructions to see if any weight is supposed to be added inside the nose cone for this model rocket kit.

If weight is needed, you must add the weight prior to assembling the nose cone.

The key to secure engine mount installation is to have the centering rings glued tightly to the body tube. To do this, first insert the engine mount kit into the fin-end of the body tube to estimate where the upper centering ring will end up. About 1/2" below this location, on the inside of the body tube, place a ring of glue using a toothpick, q-tip, finger, or other implement. This location guarantees that the upper centering ring must pass though this glue before coming to rest in its final position. For the lower centering ring, the end with the engine hook on it, simply put glue on the centering ring just before inserting the engine mount kit into the body tube.

Once in place, make sure to spin the engine mount kit to make sure that the glue is spread around the inside of the body tube and against both centering rings.

To attach the fins, apply a bead of glue to the side of the fin that connects to the body tube. Using the fin markings placed on the body tube, firmly press the fin against the body tube, lining it up with the marking lines and hold in place until the glue sets enough to hold the fin in place. Repeat for the remaining fins.

Once the glue has dried, place a bead of glue along the edge where the fin meets the body tube. Do this on both sides of the fin. A sponge, paper towel, or finger can be used to smooth the bead of glue down since this is on the outside of the rocket which you will want to try to keep neat and clean.

Attach the launch lug to the body tube where indicated to in the directions, using a liberal amount of glue. Make sure to align the launch lug in the same direction as the body tube, and that is is not in line with any fins as this may cause the rocket not to fit onto the launch rod.

First, place the nose cone into the top of the body tube to determine how far down the body tube the shock cord mount must be placed to the nose cone can still be installed properly.

Now place glue on one side of the shock cord mount and firmly press it inside the body tube far enough down from the top to allow for the nose cone. Since you are having to bend the shock cord mount to make it conform to the curved surface of the body tube, it is critical to hold this in place long enough for the glue to set. If, when you take your finger off the shock cord mount, the mount comes off the body tube, you must then wipe off all glue from both the mount and the body tube and start over.

Tie the loose end of the shock cord to the nose cone.

The parachute or streamer is then connected to the nose cone.