38 Bare Minimum Diameter Retainer
Attach the Retainer
The kit comes with everything you need except the eyebolt and lock nut. The size of this hardware will vary depending upon your motor preference. The disk comes with a 1/4" hole (Loki compatible), but also has a shallow 5/16 recess that ensure center drilling if you need to open the hole up for an AT compatible eyebolt. If you do need to drill out the hole, do so with a piece of scrap wood backing to prevent tear out. Using your chosen eyebolt and lock nut prepare a disk-sandwich using the included fender washers and tighten...this is what will attach your motor to your airframe.
Locating your Mounting Holes
Screw your retainer into the largest motor you plan to fly in your rocket, and lay this next to your rocket to mark the height at which to drill your mounting holes. You can drill multiple sets for multiple motors, but that would be creating a lot of vent holes as you moved aft, so I recommend using a coupling nut and threaded rod should you want to fly smaller motors in your rocket...I don't know why you would ever do this, but hey, it's your rocket.
Using the Drill Guide
Slide the included drill guide down to the mark you made previously, and drill a single hole (#43 or 3/32") then tap for 4-40. Insert one of the set screws through the guide and airframe to ensure you don't lose reference. It is a good idea to do a check to ensure this first hole is in the correct location before drilling anymore, so line that motor back up to be sure. If everything looks good proceed to drill the next hole, and repeat tapping and insertion of a set screw before drilling and tapping the third hole.
Inserting the Retainer
The easiest way to install the retainer is to push it into place attached to that longest motor. Then insert the 4-40 set screws, and unscrew the motor. The next time you put the motor in it should screw right into place.
NOTE: We do not recommend permanently "glueing" this retainer in place. Epoxy does not stick well to PETG, and there is no great way of positioning the retainer without the motor in place until the epoxy hardens.