2 ©2007
MadCow
Rocketry™
Mozzie™
Assembly
Mozzie™ Assembly
©2007 MadCow Rocketry™
3
Please make sure you read all directions and understand how to assemble your model
before you start construction. It is also a good idea to test fit each part before assembly
– some manufacturing tolerances may require light sanding before final assembly.
Laser cut parts will exhibit varying amounts of charring on the edges depending on the
density of the plywood. The charred edges do not interfere with bonding and do not
need to be cleaned before assembly. In most cases the charring will be cleaned up
during sanding for finishing and painting.
Step 1 – Motor Mount Assembly
Test fit the centering rings over the motor mount tube and sand if necessary. The
rings should have a snug fit but loose enough to move the ring over the motor tube
without deforming it. Also test fit the centering rings in the body tube and sand if
necessary. One of the rings will have a notch for the shock cord - this will be the
forward ring. Spread some epoxy on the outside of one end of the motor tube and
slide the ring (without the notch) until there is approximately 1/8” of motor tube exposed.
IMPORTANT:Make sure you clean the motor tube of any epoxy so as not to interfere with
the fin tangs later.
After the aft ring is dry, make a mark
2” from the other end of the motor
tube. Spread some epoxy on the motor
tube and slide the forward ring (with
the notch) until it aligns with the mark.
NOTE: After this assembly cures, you
may want to cut off any excess motor
tube in front of the forward centering
ring to make more room for the
recovery components.
Step 2 – Shock Cord Attachment
The shock cord in this kit consists of a shorter section of Kevlar and a longer section of
nylon cording. The two sections should be tied together using a single overhand, ring
bend or double fisherman’s knot. The Kevlar section will be attached to the motor mount
and the nylon section will be attached to the nose cone.
Wrap the end of the Kevlar shock
cord around the forward end of the
motor tube and tie a square knot or
bowline knot near the notch in the
forward centering ring. Apply some
epoxy to the knot to make sure it
doesn’t come loose later. Make
sure the Kevlar loop is seated against the
forward centering ring so that it will not
interfere with the fin tangs later. You can tack with epoxy or CA to hold in place.
1/8” Exposed
2” Exposed
Forward Ring Notch
Fin
Fin Tang
Apply CA or
Epoxy to knot
Push cord in corner and
tack with epoxy
Step 3 – 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. Make sure the cord passes over the notch in the forward centering ring. 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
Ensure rings are clear of the fin slots
Step 4 – Fin Assembly
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 5 – Launch Lug Attachment
Mark the CG point along the launch lug line you made in the previous step. Make sure
you measure the CG point from the tip of the nose cone and NOT the end of the body
tube. Apply a small amount of epoxy on the launch lug line about ¾” long on the CG
mark. Press one of the launch lugs into the epoxy and ensure that it is aligned with the
launch lug line previously drawn on the body tube. You can site down the tube and look
through the launch lug to make sure it is straight. Similarly epoxy the second launch lug
about 1/2” from the aft end of the body tube. Site down both launch lugs and make sure
they are both aligned. If you have a ¼” launch rod, you can use this to ensure that both
lugs are aligned properly.
sure you have the motor assembly facing the right way! (The shock cord goes
over the forward centering ring)
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.
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 launch lugs.
Step 6 – Nose Cone Assembly
At this point, pack the chute and assemble the rocket. Insert the largest motor that you
intend to fly (or simulate the weight with an appropriate substitute) and ensure the CG is
forward of the point defined in the specifications on the first page. The CG is measured
from the tip of the nose cone. If the CG is behind the specified point, add weight inside
nose cone until the CG is forward of the specified point. You can also choose to fly a
lighter motor.
When you are satisfied with the balance of your model, tie some knots in the end of the
nylon section of the shock cord and stuff the shock cord into the hole in the base of the
nose cone. Fill the hole with some epoxy to secure the shock cord.
Your model is now ready to paint.
