India Class Helpful Information for Teams and Teachers
Speedfest organizers have compiled some additional information that
India Class teams may find useful. Expect this page to be updated
as questions arise.
mentors, and team members must make sure they are working and operating
their aircraft safely. It is recommended that advisors and
mentors ensure that the teams always comply with the Speedfest Safety
Requirements and General Aircraft Requirements. Even when not at
Additional learning ideas for team advisors
How to be more competitive
you begin! Read the complete India class rules page from top to
bottom carefully. Then, read the instructions for the kit from
cover to cover carefully. We receive multiple questions
about the rules, procedures, and the kits, that need not have been
asked if the team would have done some careful reading beforehand.
construction, consider making full size copies of the plans, or at least tracing kit parts to make templates. That
if you want to build another airframe, or if you need to make major
repairs, all you need to do is buy wood, and not another complete kit.
This will be significantly less expensive, and eliminate the need
to rely on the continued availability of the kit (which are
manufactured in small batches). It will also allow for
mistakes, or the opportunity to have different teams build multiple
you have a large class and want to get more people involved.
There are plenty of places to buy wood for building RC airplanes.
Here is one example. Here is another.
source of useful information is "build threads" which are forums where
people share their experiences building a particular plane. It is
often a nice way to supplement the instructions. Also, you may
submit questions and comments yourself, and people are often eager to
help. Note that there are different ways of doing things, and all
of the information may not be appropriate, but many find it helpful .
Here is a build thread on the Dazzler
http://www.rcgroups.com/forums/showthread.php?t=1403724 and here is another for the Uproar: http://www.rcuniverse.com/forum/kit-building-121/9228805-tower-hobbies-uproar-40-build.html
you are new to building RC airplanes, you may like to search for images
of different types of covering schemes for the Great
Planes Dazzler or the Uproar, to give you some ideas. Remember to keep it simple
until you have some experience covering.
Tips for using Monokote covering can be found here.
You can also find some very helpful videos on how to apply
coverings such as Monokote. If you would like a good DVD for purchase, I recommend this one: "Secrets of Great Covering with Top Flite Monokote" If
you are applying covering properly, there should be very little need
for a heat gun. By gently stretching the film when applying it,
and properly using the iron (with sock), the film can be stretched
appropriately. Be careful when applying covering film, that you
do not warp your wing or tail structures. The fact that the film
shrinks makes this possible. Also note that if you leave your
airplane in a hot car, the covering can sag, and possibly warp.
For larger teams
you may want to consider splitting the team up into subgroups.
For example, wing, fuselage, tail, propulsion. This will
allow things to be completed more efficiently, while allowing more
people to get involved. Just make sure there is good
communication between the teams.
cylinder engines create a great deal of vibration. This can
cause problems for the mounting of the engine. When attaching the
engine to the mount, and the mount to the firewall, use Locktite on the
mounting threads to prevent vibration from loosening the mount.
Blue Locktite which is the type that can be more easily removed,
will usually be sufficient.
Carefully read the complete manual for the 46LA engine. There are directions for every aspect of engine mounting, break-in, starting, operating, tuning, and troubleshooting.
Some additional learning ideas for team advisors
Speedfest India Class project can be considered scalable. Small
teams can compete working after school, and also teachers could
incorporate the project into their curriculum as an aerospace
engineering project for larger teams. Small teams may have the
time to just complete the kit and perform some basic flight testing
before competing. Teachers of larger teams may want to
incorporate more supplemental learning activities appropriate for their
classes. This section is intended to provide some ideas for
subjects that will enhance student understanding as well as possibly
assist the team with competitiveness.
word of advice: Within the RC hobby world, there is a wealth of
information. Unfortunately there are also a lot of myths,
legends, and inaccurate science and engineering. Consider this
when searching for information.
The Academy of Model Aeronautics (AMA) has an education section
on their website that contains useful information for teachers and
students. The information include such topics as; the basics
of flight, scholarship opportunities, grant opportunities, educator
technique that we have found to be very useful to teams working on
competitive projects like this, is to conduct a rules test prior to
commencing the project. A lot of time is saved, mistakes reduced,
and team communication improved, when all team members are equally
aware of the requirements for the project.
subjects in propulsion are key for the India Class planes: engines, and
propellers. The engines being used are examples of 2-stroke, glow
ignition engines. The advantages of these type of engines are:
excellent power to weight ratio, simplicity, reliability, and cost.
The only real disadvantage of these engines are that they are not
as efficient as 4 stroke engines, and because the lubrication oil is
mixed with the fuel, the exhaust is a bit messy. Neither of these
play any factor in racing, and in this they excel. The propellers
that are used are examples of fixed, constant pitch propellers.
There are a several manufacturers of propellers, and a variety of
materials used in their construction.
combustion (IC) engines operate very differently than electric motors.
An electric motor will continue to draw whatever power is
necessary to drive the load while trying to maintain a constant rpm.
Conversely, the power of an internal combustion engine is based
on the rpm which will vary significantly with the load. So, on an
electric propulsion system, increasing propeller size will increase the
power draw, but on an IC engine, increasing propeller size beyond a
certain point will actually decrease
power. This is why it is so critical to run a variety of tests in
order to select the optimum prop for a particular mission. The
propellers provided with the Uproar kits from Speedfest II were a
general purpose propeller, more optimized for aerobatics than racing.
For a given specific
propeller, rpm is a direct indicator of power. As you make adjustments to
the engine, measure rpm with a device like this which is called a tachometer or "tach". More
rpm = more power. See the propeller section for more details.
Do not use the tach in a room with fluorescent lighting or you
will get inaccurate readings.
have an rpm operating range. At the lower limit, the engine
cannot continue to turn and develop power. The high end of the
rpm range is the redline limit. This is the mechanical limit of
the engine. Operation of the engine above this limit will result
in engine damage.
Fuel: 2-stroke glow ignition engines
require a special fuel The fuel has a base of methanol, and
contains a percentage of nitromethane to increase power. The fuel
must also contain oil to lubricate the engine. Without this, the
engine would overheat and seize. The oil in the fuel is the
reason for the residue that comes out of the exhaust, and covers parts
of the plane. It is harmless, but should be cleaned off of the
airplane after each flight. This can be done with paper towels
and a general purpose spray cleaner like 409. The fuel provided during Speedfest contains 15% nitromethane as well as 17% synthetic lubricant, so no additives are necessary or allowed.
Break-in: Start with the engine manual. Properly breaking
in the engine is very important and can give you an advantage.
Dont be afraid to run through several tanks of fuel with your
engine. As long as you are not running too lean and overheating the engine, it will help further break in the engine.
Engine Tuning: Start with the engine manual.
a small engine test stand to test engines. This can be a very
useful diagnostic as well as teaching tool. A test stand can be
as simple as a wooden frame on which to mount a motor for testing, to
as complicated as a full dyno that will measure power. Examples
of simple test stands that you see online, usually are made to measure
thrust. Unfortunately, static thrust is not very useful in
determining the power output of the engine. To measure engine
power, you need to measure torque. This may be done by mounting
the engine on a spindle that is free to rotate. An arm is then
connected from the spindle to a scale. Knowing the force and
moment arm, torque may be calculated. Then by measuring the rpm,
power output of the engine is simply calculated.
are relatively inexpensive. It may be useful to purchase one to
take apart to learn how it operates, and then learn how to reassemble.
propeller is one of the most complicated and nonlinear devices on the
airplane. Small changes in propeller can have very large effects
on thrust and power. For example:
safety, it is a good idea to paint both sides of the tips of the
propeller a bright color. This will significantly increase the
visibility of the propeller when spinning, and reduce the chances of
someone inadvertently putting thier fingers through the blades.
a given propeller, the power draw from the engine is proportional to
the cube of the rpm. When using a given propeller to
evaluate power changes as the engine is adjusted and tuned, the ratio
of change in power can quickly be estimated by : (rpm new / rpm old ) ^
3 So doubling the rpm (for a given propeller),
results in an increase in power of a factor of 8!
power needed to turn a propeller is proportional to the diameter to the
5th power. So a propeller that is twice as large as another, can
require 32 times more power to turn at a given rpm. So very small
changes in propeller diameter will result in significant changes to
- Thrust of a propeller is proportional to rpm squared, and diameter to the 4th power.
pitch of a propeller indicates how steeply the blades are twisted, and
is usually specified in inches. If you think of a propeller as
an air screw, then if you were to rotate the propeller one turn it
would pull itself through the air an amount equal to the pitch.
In air, there is slippage of course, so it will not work exactly
like a screw. The reason why the inner part of the blade is
twisted more than the outer is that it is a constant pitch propeller.
The outer parts of the blade are moving faster, so the blade angle does
not need to be as large to move the specified pitch, as the inner parts
of the blade.
a rule of thumb, a propeller is near its most efficient cruise
operating point, when the speed of the airplane is equal to the pitch
of the propeller*rpm. That is called the "pitch speed" of
the propeller, and it is the theoretical speed that the prop would pull
itself through the air when spinning at a given rpm. Propeller
pitch is usually given in inches, so pitch*rpm would give a "pitch
speed" in units of [inches/minute]. The actual
speed the airplane will fly however, depends not only on the
pitch of the prop, but on the power of the engine, and the drag of the
"unload" with forward speed. That means that the power required
to turn them changes with speed. So the amount of power required
to turn a propeller statically, will be different than the amount it
takes when flying. That is why you will notice the rpm increase when the plane is in a dive.
sure you balance your propellers using some type of balancer. An
out of balance propeller can cause excessive vibration, and can be
are a wide
range of propellers available for radio control airplanes. They
also made of different materials including; wood, nylon, glass fiber,
and composites. Do NOT use propellers made for electric airplanes
the India class. They can not handle the vibrations and
power pulses of an internal combustion engine. At least they will
less efficient due to deformation. At worst, they will
while spinning, and can be very dangerous. Here is a link that
includes 26 pages of propellers for RC airplanes that you can purchase:
At this scale, even the more expensive composite propellers cost
less than $3 each. Test a variety of propellers made by different
manufacturers and different materials. Start with the propeller
recommended in the manual which is an 11x6 (That is 11 inches in
diameter, with a pitch of 6). Test different 11x6 props.
Then you can iterate from there by selecting props with smaller
diameter, different pitch, etc. Dont change pitch or diameter too
much at one time. Make sure to check rpm of the engine to make
sure it is not over redline. The only way you will be able to
compare these propellers is to fly with them to see which will give you
the fastest lap time. To make a fair comparison, make sure all
other variables during the flight are held constant. If you are a
returning team, you could actually perform these tests early on with
your Uproar since the airplane is very similar aerodynamically to the
Dazzler. Once you find your optimal propeller, purchase several of them since they can chip or break sometimes.
the kit is fixed, significant aerodynamic changes are most likely not
beneficial. However accuracy and care in construction can have a
should do what they can to reduce drag in order to increase speed.
Properly applying covering material is one way to reduce drag.
Make sure covering is tight with minimal wrinkles.
sanding aerodynamic surfaces and shapes, take care to avoid
discontinuities and other types of bumps or protrusions.
Accurately shape and round the aerodynamic surface leading edges.
Avoid gaps as much as possible.
Aerospace structures are designed to be lightweight and strong.
the materials in a way that takes advantage of the nonhomogeneous
nature of wood. For example, cut the shear webs for the wing spar
such that the grain runs vertical. In this way the structure will
be much more resistant to shear loads with no increase in weight.
instructions carefully when putting parts together. Make sure the
fit together well. Gaps reduce strength of the structure and the
sure epoxy and CA are used properly and cured completely. It is
best to "jig" the structure in some way as the adhesives are curing so
that the structure does not deform.
Flight Stability and Control
sure that the center of gravity (cg) for the airplane is where the
manufacturer recommends. Take care to accurately
measure the CG
location. An aft cg will reduce the stability of the airplane, a
forward cg will reduce turning ability. It is a good idea to mark
the required cg location on the airframe so that it is easy to quickly
"Slop" in control
surfaces make airplanes more difficult to fly, and can even make the
airplane feel unstable to the pilot. Make sure control surfaces
and control actuators are firm.
surface throws have a significant effect on how the plane "feels" to
the pilot. This is called "handling qualities." Control throws
that are too small do not allow the plane to be fully controlled.
Conversely, control throws that are too large, reduce handling
qualities, and make the airplane too sensitive to input. Test
turn rate by decreasing and increasing elevator throw.
Turning faster will reduce lap time. Turning too fast will
increase drag too much and possibly stall the wing and can lead to loss
How to be more competitive
Some basic rules of thumb
your airplane carefully and accurately. Make sure everything is
assembled square and true without twist. This will reduce drag in
a variety of ways, and also make your airplane easier to fly for the
Anything that makes it harder for your pilot to fly your airplane
will take his time away from using his skills to compete, and put more
burden on just keeping the airplane in the air. Simple things
like slop or flexibility in the controls and linkages can have a big
impact on handling qualities.
sure to spend time optimizing the propulsion system.
Although airframes and engines are the same for each team,
significant power differences will be observed based on: engine
break-in care, propeller used, fuel/air mixture setting, etc.
Maximize the power output of your engine (through engine settings
and propeller diameter), and also make sure the pitch selected is
optimized for your cruise speed. Also, measure your fuel burn
rate, and size your fuel tank accordingly. Using a fuel tank that
is too large will just add weight to the airplane and reduce
- Finish your airplane promptly, and well in advance of the contest. Practice, practice, practice.
Not only will this help your pilot but it will also allow you to
find problems with your plane and fix them before contest day.
It will also allow you time to optimize the performance of the
plane. Make sure you conduct your flights only at an AMA-sanctioned airfield.
coordination between your flaggers and your caller before you come to
the contest. We have found that teams that coordinate the
flagging with the caller promptly and efficiently have a significant
advantage over other teams. Loss of even a fraction of a second
requires the airplane to fly a longer distance, and time lost adds up
because there are as many as 15 or more turns during a single heat.
you are only building one airplane, and you have no backup or spares,
you may want to consider "grounding" your airplane at some point before
the contest, so if you have an accident your team has time for repairs
and purchase of spares.
push things to the edge of the envelope too early. There is a
great saying by one of the best race car drivers in history; Rick
Mears: "To finish first, you must first finish."