Cricket™
Assembly
©2008
MadCow
Rocketry™
3
Test fit each of the fins into the pre cut fin slots. The fin should seat firmly
against the motor tube - sand each fin if necessary. When you are satisfied
with the fit, apply some epoxy to the end of the fin tang that will contact the
motor tube as well as the fin root that will contact the body tube. Also, spread
a thin layer of epoxy on each side of the fin tang.
Slide the fin into place and check the alignment. Continue rechecking the fin
alignment until you are sure the epoxy has set. Clean any excess epoxy from
around the fin joint. Repeat for the remaining fins.
Next, apply epoxy fillets to both sides of each fin. Carefully smooth the epoxy
fillets with your finger before the epoxy sets. Allow each fillet to set before
rotating the airframe for the next fillet.
Step 3 – Fin Assembly
Using a door jam or small section of angle stock, pencil a line halfway between
two of the fins that extends from the front to the back of the body tube. This
line will be used later to align the rail buttons.
Step 2 – Insert Motor Tube Assembly into Body Tube
Wrap the shock chord into a small bundle and stuff it inside the motor tube for
this next step. Test fit the motor tube assembly into the body tube to ensure a
snug fit. Sand the centering rings if necessary.
When you are satisfied with the fit, spread some epoxy on the inside of the
body tube and slide the forward centering ring of the motor assembly into the
body tube.
Make sure you have the motor assembly facing the right way!
Spread some more epoxy on the inside edge of the body tube before sliding
the rear centering ring into the body tube. Continue sliding the assembly inside
the body tube until the aft end of the motor tube is even with the aft end of the
body tube. It’s a good idea to test fit a fin in each slot here before the epoxy
sets. Hold the body tube with the motor tube assembly down until the epoxy
sets. Make sure the weight of the motor assembly doesn’t cause it to slide out
of alignment.
Make sure the eyebolt doesn’t interfere with any of the fin
slots.
Ensure centering rings are clear of the fin slots