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Purpose - The tips, designs, articles and other information
here have 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 Primers by Lee James.
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 really 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 egg loft 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 egg lofter 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
Egg Loft, 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 its 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 Egg Lofters,
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 Egg Lofting 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.
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