Items with an "R" beside them are rules, not
- R-Minimum thrust to weight of 4 to 1. 5 to 1 for I
- R-Use a launch rail, tube or tower. Rods are prohibited do to
past bad experience.
- R-The ball must be drilled through to retain
it. Or a tapered hole may be drilled, larger on inside, and filled with
epoxy. Weld the eyebolt.
- Test fly in the actual configuration to be
used. Motor, altimeter, recovery, launch system.
- If using a barometric type altimeter and a
large diameter change there may be problems with
turbulent airflow and false readings. Such as the ball
for a nose cone and a smaller body tube. Test fly.
- Question-What if the ball is incorporated into the
airframe and not be weighed? A-We will be on an honor
system. If there is a protest the ball will be weighed.
And then only if the rocket wins. The ball must be
drilled to retain it.
- R-The ball may not be cut up to fit is a
- The ball does not have to have the finger
holes. A new BB has to be drilled for the owners fingers.
No need to pay for this if it not to be used.
- R-Also the rules for real bowling apparently
state no minimum diameter for the balls, only
maximum. For this event the ball shall be minimum
- The Aerotech K458 has been certified by
TMT as an L. It is over 2560NS. So do not plan to use it
unless it is recertified in the interim as a K.
- Q-What are the grounds for a DQ flight?
- The RSO may DQ a rocket if he feels it is
not safe. The rocket must be recovered safely. A striped
chute would be a DQ, but a zipper would not. If it is a
" good flight" it will be OK.
- Other reasons may come up, I will keep you
- Kevlar for parachute attachment has been
found to be prone to breakage. This is due to Kevlar
having little stretch. It will fail before nylon of
similar strength in a shock load situation. It is however very
good in the hot places near the ejection charge.
There are three
schools of thought on the design of bowling ball rockets.
shown are K Bowling Ball Lite entries.
||Ball on a stick
Ball is exposed forming the nose
cone and all or part of the transition to the main body.
Various sized tubes have been used, minimum 54, as seen
here, up to 7.5". Some designs have a conical section aft of the
ball to reduce base drag.
Least streamlined, unless tail cone is placed aft of the ball. A spherical nose is OK at
low velocity. For launching, lug stand offs or a
special tower are required.
Winners of BB lite have
all been this design.
|Exposed ball with cone
Ball is exposed only at its
maximum diameter. A separate cone forms nose. A short
cone is seen here but long and pointed one is used in
some other designs.
- Advantage- Lower drag if rocket
is going to approach mach.
than ball on stick. For launching, lug stand offs
or a special tower are required.
Design has shown
potential, but no winners.
||Ball totally enclosed
The ball is enclosed entirely in
the airframe. It may be retained for recovery or have a
- Advantage- most
heavier, no commercial available cones that are
Enclosed design works
best with higher power rockets, M and above. Here with
mach plus velocities the lower drag of a pointed cone will offset the
weight penalty. All the Unlimited class rockets with O and P motors were
The number one thing to improve
performance is to reduce weight.
Pounds of airframe will hurt
more than pounds of drag.
A safe structure is number one.
For Bowling Ball
- The ball weighs 8 pounds; this is less
than a LOC magnum. Use adequate construction but do not
- For recovering just the 8 pound ball a 6
foot parachute is minimum.
- Heavy balls may be drilled to lighten, but the outside
that is exposed and the diameter may not be altered. You
can get 8lb. balls at K-Mart.
- It has been brought to my attention
the difficulty of finding 8 pound balls. Several
have requested to use a heavier ball that has been
drilled to reduce the weight. This will be
acceptable, but the ball will be weighed.
For Bowling Ball
- Minimum parachute size for
ball alone is 8 feet.
- 16 pound balls are
available at Goodwill, Salvation Army for a few dollars.
Often come with a bag. And sales tax is not charged
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