Space Grant Consortium - University of Wisconsin - Green Bay

ejection charge from the motor fires. This was accomplished by hand sanding both the inside of
the body and the shoulders of the cone.
Top and bottom of transition cone, prototyper machine
Phenolic tubing was used for the body of the booster stage. For a rational as to why this was
chosen please see the “Body” paragraph of section 2.2.2.
The fins were custom built by Giant Leap Rocketry using G-10 fiberglass. The fins were beveled
on both the leading and trailing edges in order to provide better aerodynamics. A thickness of
3/32” was used per recommendations by Giant Leap. 1/8” could have been used; however, a
thicker material was used to err on the safer side. The fins were in the “clipped delta” shape as
per recommendations by [1]. The G-10 fiberglass was chosen as the construction material
because is has been widely used and tested in the HPR field. It is lighter and cheaper than almost
any feasible metal to be used. Additionally, it can be easily epoxyed to the body of the rocket, as
opposed to needing to weld or rivet metal fins. In the rare case that it would crack, it could also
be repaired quickly and easily with epoxy.
Custom G-10 fiberglass fins
A custom tail-cone was purchased through Public Missiles Limited. The tail-cone, or boat-tail,
that PMI sells happened to fit the rocket design perfectly. It was rough 12 inches long and went
from a four inch diameter to a one and a half inch diameter. The only custom parts of the cone
were the three slots that were cut for the fins to fit in. This was extremely helpful as there was
much less work needed when trying to epoxy the fins in place and one could assume that they
would be almost exactly straight.
A combination of friction fitting and a simple screw and washer will hold the motor in place
during ejection charge firing. The design for this was found in the motor retention device FAQ
found here [2]. In order to increase the strength of the entire booster stage, the lower half of the
transition cone was filled with a two part expanding foam. This provided exceptional rigidity to
the already strengthened lower section that was fortified with 30 minute epoxy. The surface of
the entire rocket was sanded down using 600 grit sand paper. Adding a paint coat to the rocket
would only add extra unnecessary weight. Ultimately, the surface is still extremely smooth
without a paint coating.
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