Aerotech Model Rocket Kit Modifications

Overview Aerotech model rocket kits are designed with a hook for motor retention, a block in the motor tube that acts as an internal thrust ring and the motor mount tube is recessed in the airframe. These kits are well designed and without modification should work with Roadrunner motors. However, the longest Roadrunner motors will protrude slightly from the rocket. Accordingly, the CG/CP relationship should be checked to make sure it is appropriate for stable flight and positive motor retention in addition to the motor hook will likely be required.

If you are familiar with model rocket construction, you can make the following modifications when building your Aerotech kit in order to allow the use of longer motors.

Modifications

Do not put the internal thrust ring assembly in the motor mount tube.
Do not install the hook for motor retention.

NOTE: Motor retention is still required! There are numerous retention methods. Roadrunner Rocketry motors have a built in thrust ring; masking tape can be used to build an effective thrust ring on other motors. Masking tape should be wrapped around Roadrunner motors to achieve a tight fit in the motor tube in combination with a positive motor retention method.

The location of the plastic fin rings is very important, as they must line up with the fin slots in the airframe. To determine the desired location, put the fin rings on the motor mount tube, without gluing them in place, each ¾” closer to the forward end (nose cone end) of the motor tube than the instructions indicate. Slide the motor tube into the airframe until the fin rings are lined up with the fin slots on the airframe. Make any adjustments to the location of the fin rings until they are aligned in the fin slots, the fins fit properly into the fin rings while the motor tube is in the airframe, and the motor tube protrudes the desired distance. Be patient and make sure all parts fit together properly, then mark their location and follow the kit’s build instructions. Don’t forget to glue the fin rings in place!

Before gluing the motor tube in the airframe, check to see if the centering ring location prevents the lower launch lug from being installed flush (Aerotech launch lugs fit in small slots in the airframe). Use a hobby knife to carefully cut the centering ring (or the launch lug) to allow a flush installation.

That is it!