2 ©2006
MadCow
Rocketry™
Momba™
Assembly
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.
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
sure you have the motor assembly facing the right way! (The shock cord goes
