Purpose - The tips, designs, articles and
other information here has been compiled to help
rocketeers get up to speed on contest flying.
It is recommended that you check out the
Competition
Rocketry page on the NAR website. Try other
links there as well, such as the Competition
Events page and the Plans
page.
Also check out the Competition
Consortium's Competition Primer by Lee
James.
And read the Guide
to Competiton for the Casual Competitor by
Jennifer Ash-Poole.
There are more
Contest Tips near the bottom of this page.
The NAR's competition rule book is officially
called the "U.S. Model Rocket Sporting Code". But
since it has usually had a pink cover, it's more
commonly referred to as the Pink
Book.
The Pink Book has a lot of rules in it, and some
people feel overwhelmed by them. A lot of the rules
cover things as to how to run contests, or
calculating contest points, which you realyl do not
need to wade through in order to compete. So, each
of the individual event tips pages posted here have
their own short description and the basics for each
event. However, if you want to really understand
the finer points of the rules or are considering a
design that may skirt the boundaries of the rules,
by all means you should consult the Pink
Book. For off-line access, a PDF
version of the Pink Book is available.
Getting Started - Everyone has to start
somewhere. It may be useful to identify a few
events that you yourself find interesting to you,
and concentrate more effort into preparing for
those events over the other events.
Just Fly it - Try some of the other
events too, devoting less effort than some other
ones you are keying on, but try none the less, and
fly them. A lot is learned by just trying, and a
lot is learned by competing for real, so the more
experience you get now can pay off later.
Adaptability 101 - If you just can't make
up contest models for many of the events, you can
draft some of your sport models that can be adapted
or pressed into use. A lot of 18mm models can be
flown in B Streamer Duration. Others can be pressed
into use for eggloft with the addition of an egg
capsule. Of course, performance potential may be
compromised. In some duration events, reduced
performance potential could be considered a "good
thing" - if a contestant loses their first model
and needs to make sure they get their second model
back. Although with this year's NARAM event
selection, having specific "return flight" models
is not as critical. At least not involving adapting
sport models, since only the glider events and
possibly helicopter event might make use of some
low-performing "return" models.
Reliability 101 - In the long run,
reliable models of lesser performance usually beat
unreliable high performance ones. The fanciest
high-concept model that is theoretically capable of
outperforming everyone else's models means little
if it can not perform reliably. For the new flier,
it is better to go with something of a proven
reliable design or competitive kit than try
something more advanced or complex. Even advanced
competitors fall victim to trying to squeeze
performance too far, but when/if such models do
fail, they understand that it is a gamble they
chose to take.
Reliability 102 - Recovery Systems often
fail. Kit type shock cords in general do not work
well for most parachute/streamer recovery contest
models. Do not glue shock cord anchors inside of
body tubes (at least not the common kit types that
are attached inside of the tube wall). These
anchors are likely to make the recovery system jam
inside the body tube and after a few flights the
shock cords tend to break at the anchor and are
impractical to fix. The most useful
parachute/streamer shock cord system for most
lightweight contest rockets is to use 100 pound
Kevlar cord. For models with any significant
weight, elastic shock cords are useful to absorb
shock. Single egglofter type models can use 1/8"
elastic, as can some not-too-heavy plastic models.
Beyond that, 3/16" to 1/4" elastic can be employed
to absorb shock in larger/heavier models such as
plastic and scale models. For heavier rockets the
parachutes should be strong enough. Over-the-top
shroud line reinforcement is one method to
strengthen a plastic parachute (See the Eggloft,
Scale, or Plastic model articles on how to do
this). In Scale, some modelers use fabric type
chutes, but only if they have adequate room to
store and safely eject the chute, since they take
up more room for any given body tube storage space
when compared to plastic chutes.
Reliability 103 - Wherever possible,
test/practice fly your models. This might not be a
solid requirement for kits or some designs built
from a plan. However the more out of the ordinary
something is to you, the more you should consider
flying it at your home field to see how it
performs. If you have designed your model yourself,
absolutely test fly it. This can be a double edged
sword, you want to fly it to see how it performs,
but you do not want to lose your rocket if it
performs well. You might want scale back on the
engine power, but don't under power it to the point
of crashing before ejection. Some full power
testing might be needed though. A B Rocket Glider
flown on an A does not prove the wing is strong
enough for a B. However, if you have confidence the
model (wing in that case) is built strong enough,
then that might do. A really nice way to test,
where possible, is to fly shortly after dawn, when
the winds tend to be light. That only does you any
good if you can fly at a site on short notice
though.
Other testing doesn't necessarily risk losing
the model, but shows that you have learned how to
prep the model and fly well. Packing a chute for
Egg Duration or Parachute Duration is an important
thing to learn. The objective is to pack it in such
a manner that you go with a big chute that deploys
quickly after ejection. Or to test by prepping and
flying models that use a unique method of recovery,
such helicopter and rocket glider models, and the
burn-thread/rubber band activation systems which
many of those designs use.
Testing for events like Sport Scale and Plastic
Model Conversion can be important as well. If you
are making your own scale model, rather than
building from a kit, a boilerplate model can be
very useful. Same for Plastic Model. If you achieve
first place after static judging, but the flight is
disqualified, the static score doesn't count for
anything. Boilerplate testing should include using
the same shock cord and parachute system as you
intend for the real model to use. If you test using
one kind of chute and then use a different chute
type for the actual contest model, then your
testing did not prove out the recovery system. If
there is any doubt as to stability, be sure that if
your boilerplate flew successfully, that the "real"
model has it's CG no further rearward than the
boilerplate's CG location.
Why are some plans so old, or so few? -
Various reasons. Some plans are fairly well proven.
The Rotaroc design for helicopter has not changed
much since 1978. Same for Streamer models and some
Gliders. Some events are not flown very often,
while for other events the rules have changed
significantly over time (B Payload, such as Jim
Cook's 1980 plan for the old 1/2" long lead
payload). Many of the higher performance engines
that used to be available in the past are no longer
produced or contest certified (like Apogee 10.5mm
micro motors and 13mm B7's). Plans for those models
are now moot. Also, simply, the pool of electronic
versions of good plans has not hit critical mass
yet.
The NAR website's competition pages are the
first one to really begin compiling plans, thanks
to the efforts of Wolfram Von Kiparski. Some of the
older plans that were only in print, he scanned and
redrew. This NARAM tips page is a further expansion
of those efforts.
NAR
magazine Back-issues - The NAR's magazine
(Sport Rocketry now, previously named American
Spacemodeling and the Model Rocketeer) has
published articles and plans for contest models,
and scale data. NARTS sells back-issues, and in
cases of originals being out of stock, photocopies.
Check out this magazine
index, compiled by Lila Schmaker, to see what
scale data has been published in the magazine
through 1999.
Some plans have been published in Sport Rocketry
Magazine, and magazines before it, but some of
those plans have not made it to electronic form on
the web yet. Back-issues
are available NARTS. There is a magazine
index, compiled by Lila Schmaker, you can use
to see what contest articles, plans, and scale data
have been published in the magazine through
1999.
It's not a beauty contest (except for the
craftsmanship events) - For Duration and Altitude
events, great finishing and painting can make for
great looking models, but the model's appearance
won't get you any bonus seconds or bonus meters. A
lot of finishing and paint can be detrimental to
many duration type models, because of the extra
weight making the models descend faster than if
they were lighter. A lot of people fly duration
models that are unpainted, or use some magic marker
for coloring. For Altitude models it is a closer
call, since low drag means smooth surfaces. So some
try to hit a balance between a really good smooth
finish without really weighing down the model too
much.
But build them well - Build the models to
fly straight and true. Work towards attaching all
of the fins so they are straight and parallel to
the body. This should translate to a straight
boost, with minimal wobbling that would hurt the
altitude. Even Duration models get better times
when they fly higher than they would if they
wobbled.
To eject, or not to eject? - That is the
question. Very few contest rockets use engine
hooks. So the engines are often friction fitted in,
using tape on the engine to build up the diameter.
Sometimes the friction fit is not enough though,
and the combination of the recovery system,
wadding, and in some events tracking powder, is too
much for the ejection charge to push out forward,
so the engine ejects out the back instead. So, at
the least, be sure to get a good friction fit of
the engine in the tube.
Some designs move the fins up a bit on the body
tube, so the body tube sticks down about 1/4-1/2"
or so below the trailing edges of the fins. This
allows for a second line of defense to be used to
try to keep the engine from ejecting out. A collar
wrap of tape is applied so that half the tape width
is around the end of the body tube, and the other
half is around the engine. You will see several
plans that have this design feature. If you are
using a plan or kit that does not have this
feature, and want to move the fins up, make sure it
is a very stable design or you may need to make the
fins a little bit bigger.
Also, try to not cram things tightly inside the
body to begin with. Test-prep the model without
engine, and using lung power, blow into the engine
mount simulate and ejection charge (of course, do
not do this with tracking powder or you will have a
mess everywhere, including on yourself!). If you
can't get the nose and recovery system to eject
out, or if it was very hard to do so, that will
increase the chances that the engine will eject.
So, refine the prepping methods and keep testing
till you find a method that ejects easily enough.
And remember to prep that same way when you fly for
real.
Lariat Loop Shock Cord attachment - Ed
LaCroix (creator and former owner of Apogee
Components) has popularized a method that allows a
Kevlar shock cord to be directly attached to the
engine. Tie a slip knot in the end of the Kevlar
shock cord and tighten it around the nozzle end of
the engine. Wrap one layer of 1/2" mylar tape
(available from ASP) around the Kevlar. This keeps
the kevlar in place and also acts as a thrust ring.
The tape in front of the engine will go INSIDE the
body tube so that the bulge in the tape from the
Kevlar becomes the thrust ring. Insert the Kevlar
and engine into the body tube until about 1/4" of
the engine still sticks out. Then wrap the body
tube and engine with another layer of mylar tape.
If the engine should manage to eject, it remains
with the model so a DQ is avoided (as long as some
means of safe recovery deploys).
The above method has some extra benefits. Since
the Kevlar is not attached to the body tube, it can
be easily replaced. It also does not block the
inside of the tube, as some other internal shock
cord mounts used. It has a couple of drawbacks,
though. The Kevlar cord is not easily burned, bit
it CAN be burned apart if exposed to too much of an
ejection charge. 100 pound Kevlar holds up well to
18mm Ejection charges and smaller. But a D12 or E9
ejection charge will definitely burn 100 pound
Kevlar. So for larger engines, use stronger Kevlar,
at least for the first few inches in front of the
ejection charge. Or add some form of protection
such as heat-shrink tubing in the portion of the
Kevlar that is exposed to the ejection charge
heat.
Another drawback is that Kevlar cord does not
absorb shock. For some events this is not too much
of an issue, such as Parachute & Streamer
Duration, as the models are fairly light. But for
others such as Egglofters, Plastic Models, and
Scale Models, it is an issue. Those models usually
need to have their shock cords stretch to absorb
shock at chute deployment. So, the appropriate size
and length of elastic is suggested for most of the
shock cord (Kevlar and elastic can be used together
such as Lariat Loop to run the cord inside the body
then transitioning to elastic outside of the top of
the tube).
Flights per event & scoring - In most
events, you are allowed two flights, weather
permitting.
In Altitude events, your score is based on the
best single flight. If a qualified flight is not
tracked (or the tracking data does not close), you
can get a re-flight.
In Duration events, usually, your score is a
TOTAL of the flights made (the exception being
Eggloft Duration, where the best single flight with
the egg returned intact is your score).
In Multi-Round Duration events, three flights
are allowed, each with a maximum time cap. If there
is a tie for first at the end of three rounds of
flying, then those who are tied enter an additional
flyoff round.
In Craftsmanship events (like Scale &
Plastic Model Conversion), two flights are allowed.
The best qualified flight score of the two is used.
So if your model flies well, and you do not think
it would score better, there is no need to risk
flying it again.
Various other events only allow one flight, like
Spot Landing. And Drag Race is one flight per heat,
but involves multiple heats (if you keep winning),
as with automotive drag racing.
NARAM-50
is not holding Spot Landing or Drag
Race, these are mentioned just for general (and
future) reference.
Models per event - Usually, you are
allowed to use two models in each event.
Events that only allow one model are
Craftsmanship events (like Scale & Plastic
Model Conversion), events that only allow one
flight (like Spot Landing), or Drag Race (one model
for multiple heats). In case of a "catastrophic
failure", which normally means an engine
malfunction, a replacement model is allowed.
Launch Equipment - At NARAMs, a
centralized electrical launch control is used. Each
NARAM pad has a 1/8" rod, and a few 3/16" and 1/4"
rods are available for some pads.
If you want to use your own Launch Pad (i.e.
rod, tower, piston, C-rail, etc), you may. You'll
set it up in the assigned launch lane, hook up the
electrical leads from the NARAM launch control
system and fly.
That's why we fly 'em - Regardless of
performance potential, reliability, and everything
else, it all comes down to flying and seeing what
happens. Some days you'll do well, other days not
so well. And the same goes for your fellow
competitors.
So, keep at it and learn as you go. As you have
time, observe what the other fliers are doing,
model-wise and flying-wise.
Fellow competitors - Fellow competitors
are a good source for learning about designs,
flying, and so forth. Most are happy to give such
advice, and most of them learned the same way from
other competitors. And flying against them is also
a good way to learn.
|